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					                 CON 251 Lab Notebook

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                        CON 251 Lab #1
                     Measurements Lab Activity



Introduction
      This lab activity is to familiarize students with a variety of
measurement methods and measuring instruments that are used
for testing. Students will use the following measuring devices for
this lab activity:

Tape Measure
Ruler
Dial caliper
Digital caliper
Micrometer
Thread pitch gage
Protractor
Triple beam scale
Pin gages



Procedure:

This lab activity has ten different stations that require
measurements and or calculations that need to be collected.
Start at any station and complete the activity then move to the
next open station. When measurements have been taken at all
stations each group will need to complete the calculations or
summaries away from the stations so others can gain access.
When the lab is completed, keep the report and add it to your
workbook.




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Sample #1
Measure the length of the 2X4 to the nearest 1/16”



Length



Sample #2
Using a dial caliper, measure the diameter and length of the
round piece of aluminum to the nearest .001”.

Diameter

Length



Cross Sectional area

Volume



Sample #3
Using a digital caliper, measure the diameter, inside (ID) and
outside (OD) and the length of the aluminum tube to the
nearest .001”.

Diameter (OD)

Diameter (ID)

Length

Cross Sectional Area of the aluminum only

Volume
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Sample #4
Using a Digital Caliper, what is the length and width of the
rectangular pocket (measure to the nearest .001”) ?

Length                            Width



Sample #5
Using a steel rule, what is the length and width of this blue
aluminum plate to the nearest 1/16” ?

Length

Width

Sample #6
Using a digital caliper, what is the depth and width of the
blue groove in this part to the nearest .001”?

Depth

Width



Sample #7
Using a steel rule and thread pitch gage, what is the nominal
diameter and the thread pitch of this bolt? (nominal)
diameters of fasteners are measured in 1/16” fractions.)

Bolt Diameter

Threads per inch (thread pitch gage)


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Sample #8
Using a micrometer, measure the width and thickness of the
square tool to the nearest .001”.

Width

Thickness



Sample #9
Using pin gages, determine the diameter of holes A, B, & C.



Diameter A

Diameter B

Diameter C



Sample #10
Using a Digital caliper, measure the width and thickness of
this block. Also measure the diameter of the round hole and
the length of the slot above the hole to the nearest .001”.



Width

Thickness

Diameter of the hole

Length of the slot


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Sample #11
Using the adjustable protractor, measure all three angles to
the nearest degree.

Angle A

Angle B

Angle C



Sample #12
Using the test procedure provided on the last following page
to calculate the Relative Density of samples A, B, and C.



A

B

C




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                           Relative Density
                            ASTM D-792

Density=               A -       B
                    (A-B) - (C-D)

Where:
A = mass of the specimen +Wire in Air

B=    mass of wire in air (.58 g)

C=    mass of wire & specimen immersed in water



D=    mass of wire with end immersed in water (.54 g)

Sample A mass in air (A)
Sample A mass in water (C)

Sample A Relative Density

Sample B mass in air (A)
Sample B mass in water (C)

Sample B Relative Density

Sample C mass in air (A)
Sample C mass in water (C)

Sample C Relative Density




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                         CON 251 Lab #2
                Metallic Tensile Testing Lab Activity



Introduction:

The tensile test is a common test performed on metals, wood,
plastics, and most other materials. Tensile loads are those that
tend to pull the specimen apart, putting the specimen in tension.
They can be performed on any specimen of known cross-sectional
area and gage length to which a uniform tensile load can be
applied.
Tensile tests are used to determine the mechanical behavior of
materials under static, axial tensile, or stretch loading. Data and
calculations for these tests include tensile stress, tensile
strength, elastic limit, percent elongation, modulus of
elasticity, proportional limit, percent reduction in area, yield
point, yield strength, and similar properties.
ASTM standards for common tensile tests may be found in
sections E8 (metals), D638 (plastics), D2343 (fibers), D897
(adhesives), D987 (paper), and D412 (rubber).



Tensile Testing – Procedure:

Tensile tests are used to determine the tensile properties of a
material, including the tensile strength.

In order to conduct a tensile test, the proper specimen must be
obtained. This specimen should conform to ASTM standards for
size and features. Prior to the test, the cross-sectional area may
be calculated and a pre-determined
gage length marked on the specimen (usually 2”). This gage
length is used to determine the amount of elongation that has
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taken place on the test specimen. The specimen is then loaded
into a machine set up for tensile loads and placed in the proper
grippers. Once loaded, the machine can then be used to apply a
steady, continuous tensile load.
Data is collected at pre-determined points or increments during
the test. Depending on the material and specimen being tested,
data points may be more or less frequent. Data include the
applied load and change in gage length. The load is generally read
from the machine panel in pounds or kilograms. The change in
gage length is determined using an extensometer. An
extensometer is firmly fixed to the machine or specimen and
relates the amount of deformation or deflection over the gage
length during a test.
While paying close attention to the readings, data points are
collected until the material starts to yield significantly. This can
be seen when deformation continues without having to increase
the applied load. Once this begins, the extensometer is removed
and loading continued until failure. Ultimate tensile strength and
rupture strength can be calculated from this latter loading.
Once data have been collected, the tensile stress developed and
the resultant strain can be calculated. Stress is calculated based
on the applied load and cross-sectional area. Strain is the change
in length divided by the original length.
Principal properties determined through tensile testing include
yield strength, tensile strength, ductility (based on the
percent elongation and percent reduction in area), modulus of
elasticity, and visual characteristics of the fracture. For brittle
materials, which do not show a marked yield or ductility, data is
collected for tensile strength and type and condition of fracture.
Expected Results
The results of tensile testing can be used to plot a stress-strain
curve that illustrates the tensile properties of the material.
Stress (in pounds per square inch or Pascal’s) is plotted on the
vertical axis while strain (inches per inch, millimeters per
millimeter, or unit less) is plotted along the horizontal.
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As the load is applied, the curve is proportional and this period of
linearity is termed the elastic region. Once the curve deviates
from a straight line and begins to yield, the material has reached
the proportional limit. Once the material has yielded, it exhibits
plastic behavior or plasticity. Brittle materials do not exhibit
much yield and are, therefore, less curved than ductile materials.
Ductile material curves have marked areas of yield and curvature
illustrates the degree of ductility. At the top of the curve is the
ultimate tensile strength of the material. Once the curve has
peaked, stress continues to decline while strain continues to
increase. This condition continues until failure.
As with any testing situation, please observe caution and wear
proper safety equipment.

Text References:

Chapter 14 – Tensile Testing

Appendix 2C pg. 479

Also see pages 474 & 475 for Stress Strain curves




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                          CON 251 Lab #2

                        Tensile Testing Data



Sample # 1

*Thickness

*Width

*Peak Load                                 lbs.

**Load at Yield                            lbs.

*Peak Load at Rupture                                   lbs.

   * Measured or observed values

   ** Interpreted from Plot



 (Ultimate Tensile strength )

 σ=          Load at Peak       =                 psi
         Cross Sectional Area



(Strain at Peak load)


   elongation*
                                  Strain* =
        2
Strain* = (final length – starting length)/ starting length

*At peak load




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(Modulus of Elasticity)
   
E
   
Modulus of Elasticity = Stress/ Strain



Percent Elongation =



Per Cent Elongation = final length*- starting length           X 100
                             Starting length

* final length after break



Sample # 2

*Thickness

*Width

*Peak Load                                 lbs.

**Load at Yield                            lbs.

*Peak Load at Rupture                                   lbs.

   * Measured or observed values

   ** Interpreted from Plot

(Ultimate Tensile strength )

 σ=          Load at Peak       =                 psi
         Cross Sectional Area




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(Strain at Peak load)


   elongation*
                                  Strain* =
        2
Strain* = (final length – starting length)/ starting length

*At peak load




Modulus of Elasticity
   
E
   
Modulus of Elasticity = Stress/ Strain



Percent Elongation =



Per Cent Elongation = final length*- starting length     X 100
                             Starting length


   *final length after break

Problem:
We want to use #3 rebar to pre-stress a concrete beam.

How much load must be applied to the rebar to stress it to
80 % of its ultimate tensile strength?

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Procedure:
   1.  Reduce a middle section of the rebar sample on the
       engine lathe. (Turn until cleaned up)

   2.    Measure the smallest diameter of the turned area.



   3.    Using the Vega Tester, apply a load until the sample
         ruptures.



   4.    Calculate the ultimate Tensile Strength



   5.    Use a value of 80% of the calculated ultimate tensile
         strength to determine pre-stress value.



   6.    Use a value of 80% of peak load to approximate
         pre-stress load.



Turned Diameter                 Cross Sectional Area

Load at Rupture                                   lbs.

Ultimate Tensile Strength                            psi.
( Ultimate Tensile Stress = Load at Rupture / Area )

Pre-stress Load                                   lbs.
(80% of load at Rupture)

Pre-stress value                           psi.
(80% of Ultimate Tensile Stress)
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                      CON 251 Lab #3
         Hardness Testing Heat and Treatment of Steel



Introduction      (Chapter reference Chapter’s 4 & 19)

      One of the most desirable characteristics of steels is
the ability to easily change the hardness and strength the
material. This process of changing the hardness is referred
to as heat treatment. Steels are classified as carbon steels,
alloy steels or special steels. This activity will focus only on
carbon steels.
The classifications of steels was established by the Society
of Automotive Engineers (SAE) and later adopted by the
American Iron and Steel Institute (AISI) and is now referred
to as the SAE-AISI system of steel classification.

      Carbon steel is an alloy of iron and carbon, without
significant amounts of other elements. Therefore the carbon
content plays the most important role in determining the
properties of carbon steel. About 85% of all steel is carbon
steel. About 130 different grades of carbon steel are
produced today to meet the growing needs of modern
technology. Carbon steels are classified as low carbon,
medium carbon or high carbon steels. The amount of carbon
content determines which classification the steel is in. Low
carbon steels contain between 0.08% and 0.35% carbon. In
terms of tonnage produced, low carbon steels constitute the
larges volumes with the extensive use as structural members
in buildings and bridges. These steels can be easily welded,
formed and forged, but have poor machining properties. Due
to their low carbon content cannot be hardened through
conventional heat treatment. Medium carbon steels are those
with carbon content between 0.35% and 0.50%. Because of
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relatively high carbon content, these steels can be hardened
by water quench and tempered. Medium carbon steels are
considered the most versatile of all carbon steels because
they can be hardened, easily welded and machined. High
carbon steels are those with carbon content over 0.55%. The
outstanding characteristics of these steels are that they can
be heat treated more readily than any other carbon steels.
However, because of the high carbon content these steels are
relatively difficult to machine, form and weld. They are used
for springs, hand tools, cutting tools and agricultural
implements such as plow shears and cultivating shoes.

OBJECTIVES: To introduce those solid-state transformations of

material structures, known as “heat-treatments”. More

specifically, define “heat treating” as the controlled heating and

cooling of metal alloys in the solid-state. The process starts by

heating the steel above its critical temperature or austenitic

temperature range. (Between 1333F and 1666F), which
transforms the iron into austenite . The slow cooling of steel

from its critical temperature over several hours or days is called

“Annealing”. Annealing leaves the steel in its softest possible
condition with the least amount of internal stress and maximum

malleability. “Normalizing” involves heating the metal into its

critical temperature then letting it cool in still air at room

temperature. Normalizing forms even grain size that makes them

easier to machine. “Quenching” is the process used to harden

steel through out (through hardening) and is performed by


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heating the metal into its critical temperature then rapidly cool it

back to room temperature. This rapid cooling causes the

austenite to form into “Martensite” which is very hard and

brittle. This will form the hardest and highest strength steel but

is extremely brittle and has a high amount of internal stress.

Depending on the carbon and alloying content, different

quenching media are used. The most common media are, water,

brine (salt water), oil and air. Water or brine provides the most

rapid quenching. Oil is slower than water with air quenching being

the slowest. “Tempering” is also referred to as drawing, is a

process by which a hardened part is reheated to 400F to 800F

and quenched in water. This process will relieve stress, reduce

hardness and increase toughness of the processed part. “Case

hardening” is also referred to as surface hardening and is used on
such parts as gear teeth, axles and other parts and tools. These

case hardened parts represent a compromise between the hard,

wear resistant brittleness of high carbon steels and the softer,

more ductile, less wear resistant low carbon steels.

      The purpose of this lab activity is to familiarize the

student with the terminology and methods used for steel

classification and heat treatment. The lab activity will involve

hardening, annealing, case hardening, tempering and Rockwell

hardness testing.


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Procedure:     You must wear safety glasses for this lab
   1. Each group will get one sample each of O-1 tool steel

      5/16” X3” round and 5/16”X3” round 1018 Cold Rolled

      Steel (CRS).

   2. Using the Rockwell hardness tester, measure the

      hardness of each sample. (take two readings for

      accuracy and record)

   3. Using the oxy-acetylene torch heat approximately 1” of

      each sample until it is orange, then quench quickly in

      water. (Use pliers to hold samples)

   4. Bead blast the ends of the samples that were

      hardened. This will remove oxides and scale from the

      samples.

   5. Repeat step 2. Making measurements in the middle of

      the hardened section. (take two readings for accuracy

      and record)




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                           CON 251 Lab#3

           Heat Treatment and Hardness Testing Data



5/16” Round O-1 untreated            RC



5/16” Round O-1 hardened            RC



5/16” Round O-1 tempered            RC



5/16” Round *CRS untreated          RC



5/16” Round *CRS hardened           RC



* Note CRS stands for Cold Rolled Steel



Briefly explain what occurred when a sample of O-1 was hardened

and then held in a vise and hit with a hammer.



Briefly explain the advantages and disadvantages of through

hardening and Case hardening.




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                     CON 251 Lab #4
          Masonry Screw Anchors Testing Lab Activity



Introduction:

Fasteners are a essential component used in the construction
industry for connecting a variety of hardware or accessories to
rigid structures such as walls, stone or brick. There are
numerous fastening devices and systems that are used for
numerous different applications. With so many choices, it is
often times difficult to determine what fastener is best suited
for a particular application. In many instances specifications and
or callouts will specify precisely what fastener must be used.
Most of the time a sub-contractor will use what is most familiar
to him or her or what can be purchased at the best price.

The application that we will examine is that of the holding
strength of a variety of different screw anchors. Two types of
loading can occur with a screw anchor mounted on a vertical wall.
The first is downward shear caused by the loading similar to a
shelf bracket screwed to a wall. As loads are placed on the shelf,
the downward force creates a downward shear between the
bracket holding the shelf and the wall. The second is the pullout
force applied as a result of the cantilever of the bracket pulling
away from the wall. While both forces are at issue, most concern
is usually with the forces applied from the cantilever more than
the downward shear. This is because the shear forces are the
greatest closest to wall and will increase the force on the
cantilever as the load moves further from the wall. The tests will
be conducted using #10 or 3/16” diameter fasteners. Typically
wood screws, sheet metal screws and machine screws are used
for these applications, depending on the type of anchors used.



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Procedure:

 Each group will test two different screw anchors. Holes will be
drill according to the diameter specified for that type of anchor.
Location of the holes is centered on the edge of the brick and 2-
3/4” in from either end. Both edges of the brick will need to be
drilled. One edge of the brick will be used to test the shear
strength of the fastener and anchor. The other edge will be used
to test the pullout force necessary to dislodge the fastener and
anchor from the brick. This test will emulate a cantilever load
being applied to the fastener and anchor. The pullout force test
will be performed on the AST digital tester located in the
metrology lab. The shear tests will be performed on the
Testmark Compression Testing machine. The instructor will
demonstrate both testing machines and procedures.




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The anchors that can be tested are as follows:

   1. Tapcon masonry screws (drill 5/32” hole 1” deep)

   2. Flanged Conical Plastic Screw Anchor (drill ¼” hole 1-1/14”
      deep)

   3. Flanged and Grooved Conical Screw Anchor (drill ¼” hole 1-
      1/14” deep)

   4. Caulking Bolt for #10 Machine Screw (drill 3/8” hole 1”
      deep)



Insert the anchors into drilled holes and tap with a hammer to
insure that the anchor is fully seated. Only put screw and
anchors in one edge of the brick at a time. On the edge that will
be used for the pull out test, leave about 5/8” of the screw
sticking out of the brick. When you perform the shear test,
screw the 3/8” steel plate to the brick but do not over tighten
the screw. Shear each screw separately moving the plate to the
opposite end of the brick to perform the second shear test.




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                          CON 251 Lab #4

           Masonry Screw Anchors Testing Lab Activity

Shear Test             Type of Anchor          Force Applied
                                               To Failure


Anchor # 1                                                 lbs.


Anchor # 2                                                 lbs.




Pullout Test    Type of Anchor             Force Applied
                                           To Failure


Anchor # 1                                                 lbs.


Anchor # 2                                                 lbs.




Based on your test results, briefly explain which fastener and
anchor proved to withstand the greatest shear and which
fastener and anchor proved to withstand the greatest pullout
force? Which combination was the best buy?




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                       CON 251 Lab #5
                Holding Strength of Framing Nails



Introduction:

One of the most widely used fasteners in the construction
industry is the ordinary nail. Below is a brief history of the nail
that is quite interesting.

A Two-Bit History of Nails by Paul Fourshee Copyright © 1992

   The lowly nail’s history goes back several thousand years.
While the nail has almost always been produced for fastening and
joining, historically some other fairly imaginative applications
have been made of this versatile product, such as mayhem and
punishment.
   Bronze nails, found in Egypt, have been dated 3400 BC. The
Bible give us numerous references to nails, the most well known
being the crucifixion of Christ. Of course we should not forget
that model wife in Judges who in 1296 BC drove a nail into the
temple of her husband while he was asleep, “so he died.” (Thelma
and Louise where is your imagination?)
   Exactly what do we mean when we refer to nail sizes by
“penny?” You’re in good company if you have no idea.
   With 2,200 varieties of nails being manufactured today and
everyone using them from the hobbyist to the professional
builder, one would think, if it is such a good idea, that somebody
would know what the term “penny” means and who started it. At
long last an answer to the question you never asked.
   The term “penny”, as it refers to nails, is thought to have
originated in medieval England to describe the price of 100 nails.
(e.g. 100 3-1/2” nails would cost 16 pence, while 100 2-1/2” nails
could be bought for 6 pence.) This system of classifying nails by
size according to price was in place by 1477 AD.
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The letter “d”, which means penny, stands for the Latin name
given to Roman Coins, Denarius.
   The size of the nail is determined by measuring its length.
Nails start at 2d, which is 1” in length, and range up to 60d which
is 6” in length. From 2d to 16d the penny length increases by
quarter inches. Above 16d, the size increases by half inches. Nails
longer than 60d or shorter than 2d are described in inches or
fractions thereof.
   Just prior to the American Revolution, England was the largest
manufacturer of nails in the world. Nails were virtually impossible
to obtain in the American Colonies so it was quite common for
families to have a small nail manufacturing setup in their homes
by the fireplace. During bad weather and at night, entire families
made nails not only for their own use but also for barter.
   This was not a practice restricted to the lower classes,
Thomas Jefferson was quite proud of his hand made nails. In a
letter he wrote, “In our private pursuits it is a great advantage
that every honest employment is deemed honorable. I am myself
a nail maker.” From the president to the pioneer, nail making was
an important facet of life. Jefferson was among the first to
purchase the newly invented nail-cutting machine in 1796 and
produce nails for sale.
   Such value was placed on nails that it was common practice,
when moving, to burn one’s home in order to retrieve them.
   The invention of the nail cutting machine rapidly put the
United States in front in the manufacturing of nails and has lead
the world ever since.
   In the 1850’s several manufactures were established in New
York which made wire nails. These machines were most likely
imported from France. The earliest wire nails were not made for
construction but for the manufacture of pocket book frames and
cigar boxes. It was not until after the American War Between
the States that wire nails began to gain acceptance in
construction. Even through the 1890’s many builders preferred
using cut nails because of their holding power.
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It was well into the twentieth century before wire nails became
the dominate type and only then because they were so much
cheaper.
   It is because of the tremendous holding power and hardness
that cut nails are still used today for specific functions such as
flooring nails, boat nails and masonry nails.
   The Tremont Nail Company of Wareham, Massachusetts was
established in 1819 and has manufactured cut nails continuously
under several owners and names ever since. This company, now
owned by Maze Nails, still makes 20 different types of cut nails
with 100 year old machines. Their nails are still packaged in 100 #
wooden kegs.
   Did you know that the holding power of common nails drops by
half within two days after being driven? After about a month the
holding power will increase slightly as the wood fibers straighten
out and grip the nail.
   Cement coated nails hold more securely than common nails but
wet wood will loosen the cement coating in a matter of days.
Threaded or ring shank nails loose their holding power when
subjected to sudden pressure (e.g. staircases) which can cause a
thread to pop with each shock. Therefore a twist or spiral shank
nail will have the best holding power.




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Procedure:

Each group will use a 2X4X12 long and drive one each of the
following nails into the edge of the 2X4 at the locations shown
below.




The nails to be driven are as follows:

      16d Smooth
      16d Cement Coat
      16d Ringed Shanked
      16d Spiral shank
      16 Cement Coat pneumatic nailer
       2”x 7/16“ Crown Stapler

All nails should be seated with ¾ “to 1” of the head above the 2X4
so that they can be secured in the AST universal tester. Using a
crosshead speed of .5 to 1 inch per minute, pull each nail until
maximum force is displayed then move on to the next until all
have been tested. Use spacer blocks provided for setting nails
from the nail gun and stapler.

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                          CON 251 Lab #5

                   Holding Force of Framing Nails

               Type of Nail                Force Applied to Pull out


Nail # 1                                                    lbs.


Nail # 2                                                    lbs.

Nail # 3                                                    lbs.

Nail # 4                                                    lbs.

Nail # 5                                                    lbs.

Nail # 6                                                    lbs.



   1. Based on your test results, briefly explain which Nail proved
      to withstand the greatest pullout force?




   2. Why do you believe this is the best fastener?




   3. Setting the nails into the wood can cause splitting, how can
      this affect holding force of the nails?



   4. How can moisture content and type of wood affect holding
      force of the nails?


96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                           Page 28
                     CON 251 Lab #6
          Impact Strength of Flooring & Underlayment



Introduction:


Subfloor versus Underlayment

The terms "subfloor" and "underlayment" are often used
interchangeably, but there is a world of difference between the
two. A subfloor is a layer intended to provide structural support.
Underlayment, on the other hand, is installed over a subfloor to
create a smooth, durable surface upon which finish flooring is
installed.

Resilient floor coverings demand a lot from underlayments. These
underlayments must be hard, smooth, dimensionally stable and
stiff. Hardboard, plywood and at least one OSB product offer
smooth, hard surfaces that are considered safe for thin resilient
flooring. Other popular choices are particleboard and American
Plywood Association's (APA) Sturd-I-Floor, a hybrid system that
combines subflooring and underlayment functions in a single panel
product.

Particleboard

Particleboard is smooth, knot-free, and hard. It has no core voids
and has great impact resistance. Sounds like a winner! But the
RFCI doesn't recommend its use for fully adhered sheet vinyl or
tile floors.

Thickness edge-swelling is the number one complaint when it
comes to particleboard installed under resilient flooring.
Particleboard soaks up moisture at its edges first, creating
ridges in the finish flooring.

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 If vinyl tiles are used, they create a finish floor with many
seams. These seams can expose particleboard underlayment to
wetting and swelling when the floor is washed. Here, wood fibers
will swell and tiles will lift around their edges. Particleboard is not
a strong candidate for underlayment in moist locations like
basements and bathrooms.

Rich Margosian, general manager with National Particleboard
Association (NPA) claims, "The biggest problems are usually
related to installation." Examples leading to failure include laying
particleboard underlayment:

      before the structure is weathertight
      over unvented crawlspace
      over crawlspace without a groundcover
      improperly stored on site (store flat & keep dry)
      before plaster and concrete have cured dry

If particleboard is used, a glue-nail fastening system will produce
the best results. White carpenter's glue, not subfloor adhesive,
is recommended by NPA. Spread the glue onto the subfloor with a
paint roller and then nail down the panels.

OSB

While there are over a dozen APA-approved oriented strand
board (OSB) subfloor and sheathing products, there are no APA-
approved OSB underlayment products. Only one manufacturer,
Weyerhauser, seems to be seeking APA approval for their 1/4-
inch OSB underlayment, Structurwood. The lack of APA approval
for Structurwood appears to be a procedural technicality based
on the fact that APA just hasn't developed a standard for non-
plywood underlayment yet. APA and Weyerhauser promise a
standard is in the works. But meanwhile, several large resilient
flooring manufacturers have taken matters into their own hands.


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Some companies have tested and approved Structurwood for use
under fully-adhered and perimeter-bonded floors. Weyerhauser
backs its product with a one-year warranty.

Surface smoothness can be a problem with OSB underlayment
because strands lying next to each other in the panel's matrix
may shrink and swell differently. The irregular surface will
telegraph through thin resilient flooring. Weyerhauser claims to
have solved this riddle with a proprietary stabilizing and
conditioning process.

APA Plywood

Tried-and-true is appealing in an environment where everyone
wants to blame the other guy for problems that might arise.
Plywood gets a clean bill-of-health from everyone. All resilient
flooring manufacturers approve the use of appropriately-graded
APA plywood under all types of resilient flooring, provided it is
installed correctly

>Approved plywood underlayments for resilient floor coverings
have the following characteristics noted in their grade standards
or stamp markings

      "underlayment" or "plugged crossbands"
      exposure classification
          o Exposure 1 - limited exposure to moisture
          o Exterior - repeated exposure to moisture
      fully sanded face (not PTS, plugged and touch-sanded)




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96fbc762-1fd3-440a-88bf-c394dc96a26a.doc   Page 32
                               Procedure

The purpose of this lab activity is to do relative comparison of
the impact strength of three different sub-flooring and
underlayment materials. The materials used for this test are:
19/32” OSB (oriented Stranded board), 19/32” particleboard,
and 19/32” CD plywood. There are several ASTM test standards
for impact testing of wood-based floor and roof sheathing. The
two standard tests are ASTM E-661-88 and E-695-79. Both of
these tests are conducted with a leather bag filled with lead or
steel shot to a weight of 30 lbs. Both tests are rather
complicated and the apparatus for the tests are not really
practical to build. We will use ASTM D-143 A modified Hatt-
Turner Test. This test is a flexural impact test normally used for
solid wood samples. (refer to page 542 in text for more
information) We will use a falling dart that weighs 5 lbs. And will
be dropped from .5 feet to up to 9 feet which will generate a
total of 45 lbs of impact.

Procedure:

         1. Place sample in steel holding fixture.

         2. Raise falling dart to .5 feet and release rope allowing
            dart to impact test specimen. (note any permanent
            deformation of fracture)

         3. Repeat test raising dart in .5 foot increments until
            fracture or permanent deformation occurs.

         4. Examine failure location on specimen and note any
            internal voids or defects that may have contributed to
            the specimen failure. Record impact failure value and
            comments.


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         5. Repeat the above test procedures to the other
            specimens.


  Specimen Type                 Impact Load            Comments




                          Food for Thought

A Traditional king sized waterbed is 6’ X 7’ and approximately 12”
deep. The pedestal base under the waterbed is recessed 6” on all
sides, and supports the weight of the waterbed. The weight of
water is approximately 62.42 lbs per cubic foot. And contains
approximately 7.48 gallons per cubic foot.

   1. How many gallons of water are in the waterbed?




   2. What is the load per square foot that the waterbed is
      exerting on the floor?




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 An upright 22 cubic foot freezer located in a kitchen is
approximately 24” X 24” X 6’ high. You recently purchased a
whole Angus beef and had it cut and wrapped. The total weight
of the beef was 750 lbs cut and wrapped. The weight of the
freezer empty was 150 lbs. Screw casters on the bottom of the
freezer are located on the corners and are 1-1/2” in diameter.
What is the load in lbs per square foot of the freezer on the
kitchen floor?



A homemaker wearing ½” diameter high heel shoes weighs 150 lbs.
The homemaker reaches for a bowl on a top shelf, raising one leg
to stretch is supported only by one heel. What is the load that is
being applied to the floor in lbs per sq. ft.



A snowstorm in spring of 2003 dropped 28” of snow in Ft. Collins.
The moisture content of the snow was 4:1 (4” of snow yields 1” of
water.) A newly constructed 40’ X 60’ metal building with a
relatively flat roof collapsed. What was the total weight load on
the roof, and what was the load per sq. foot? (Reference
information is in the first problem)

                   Total load               Load per sq. foot.




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                        CON 251 Lab #7
     Holding Strength of Construction Adhesive on Sub-flooring



I.               Introduction

Construction adhesive refers to a broad range of similar
products used to bond common materials used in the construction,
renovation and finishing of homes. Of course, if you have
shopped in a hardware store you know that some companies have
adhesives they have named "construction adhesive". In the
context of this article, I am speaking of a class of adhesives that
share certain properties. The basic characteristics of these
products are:
Available in cans, squeeze tubes, and caulking tubes
Thick pasty consistency; applied with putty knife or notched
trowel
Water or solvent based
Can fill gaps and imperfections in materials
Will adhere to a wide range of building materials
Tend to remain flexible after drying
Waterproof or water-resistant
Usually dry within 24 hours
Choosing the correct construction adhesive product can be
confusing, since there is lots of functional overlap among them.
Fortunately, the manufacturers are pretty good about listing the
uses of their products on the labels. Some of them are quite
specific... "For ceramic tile only", for example. Others label their
products for broader uses... the more generic and well-known
"construction adhesive", a generalist that can be used for wide
range of adhesive tasks.
Some construction adhesives that work wonderfully on indoor
wood will not stand up to the moisture and temperature changes
of exterior work. You only get to choose once, so choose wisely.


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There are two ways construction adhesive is applied. These are
in beads or full coverage. Beads are lines of adhesive that are
applied to a surface with the use of a caulking gun. This is the
most economical use of construction adhesive and is used for the
gluing of large, flat materials to large flat surfaces. Some
common uses for the bead method are in the installation of
plastic tub surrounds over drywall or ceramic tile, wood paneling
to any smooth wall, attaching drywall to studs and securing sub
flooring to floor joists.
Full coverage is used where the material to be glued is small, such
as floor tiles or ceramic tile, or where an absolutely solid surface
is required, which includes virtually all flooring applications with
the exception of carpet over padding and some types of vinyl
flooring.
All full coverage adhesive jobs require the use of a notched
trowel to apply the adhesive. You may be tempted to just slather
the adhesive on with a putty knife... and you might get away with
this for a small repair. But there are five sensible reasons for
doing it right, though the product labels won't tell you why... they
just say to do it their way or else! In a nutshell,...
Saves adhesive... using a notched trowel can save you up to 50%
on the adhesive used over a flat trowel or wide putty knife!
Consistent thickness of adhesive... Remember that most
construction adhesives tend to stay flexible. Applying too thick
an application can cause a soft spot in the floor, producing
movement in the material. This may not be as critical with
interlocking wood parquet flooring but it can be a disaster with
ceramic tile!
Shortens drying time... those little grooves flatten when the
material is pressed into the adhesive giving a thinner glue film.
Thinner coats mean less drying time. An overly thick adhesive
coat can take weeks to dry properly.
Better adhesion... the "peaks" produced by troweling increase
the chance that the material will grip firmly to the adhesive.


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Less shrinkage... as the adhesive dries, it will shrink. This is not
an issue with a thin coat. But if a thick layer is applied, the
material you are gluing may noticeably move or settle! This is why
you should never build up a depression in a floor or wall with
adhesive alone... use a floor leveler or wallboard compound to
flatten the surface before your gluing effort!
Be careful when choosing a construction adhesive!! Certain
applications and materials require special construction adhesives.
Plastics are especially sensitive to poor adhesive choices! So
when installing products such as tub surrounds and vinyl cove
base, be sure to use an adhesive recommended by the
manufacturer. Otherwise, you may find that the adhesive's
solvent will actually migrate through the plastic, causing
noticeable staining on the surface! This solvent "creep" can be a
sneaky process... it could take weeks to occur, long after the job
is done. Needless to say, you will not be a happy camper!
Note the drying times on the packaging! Construction
adhesives in many cases do not reach full strength for a week; so
if you want the job to last give them plenty of drying time!
One of the more popular lines of construction adhesive is
manufactured by the PL Company. Their line includes the old
favorite PL200 general-purpose construction adhesive, as well as
special formulations for plastics and foam and an exterior wood-
flooring adhesive purported to be as "strong as nails"! Another
major player in this area is Macco, manufacturer of Liquid Nails, a
full line of construction adhesives for virtually all materials,
indoor and out.




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Recommended Application of construction adhesive:

      1. Surface must be clean, structurally sound and free from
         excessive water. Can be applied in temperatures as low
         as 10°F depending on type of adhesive. Should be
         conditioned to 40°F before use.
      2.
      3. Cut nozzle at 45° to the desired bead diameter, usually
         ¼” to 5/16”.

      4. Puncture inner seal with nail or wire.

      5. Run adhesive beads slightly past the length and width of
         the sheet of sub flooring. Do not lay more adhesive than
         can be covered in fifteen minutes. (Scrape off any
         adhesive that has set for more than 15 minutes or that
         has skinned over.)

      6. Where sheets butt along the joist, lay adhesive in a
         zigzag pattern to include both sheets.

      7. Space the adjoining sheet the thickness of a putty knife
         to allow for expansion.

      8. Nail sheets in place with 8d-ringed shank or spiral
         shanked nails, spaced 12” on center of each joist.

      9. Sub-flooring must be under roof within six weeks.

Testing procedures:

Set up AST testing machine with the appropriate fixtures. Set
crosshead speed at .5 inches per minute and pull sub-flooring
from joists. Record maximum load for each sample withstood at
failure.

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  Adhesive Brand         Type/Grade        Solvent   Load        Load     Load    Load   Remarks
                                            Base     0 min      15 min   30 min   Wet




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   1. From the tests, what can be concluded about the delayed set
      time of construction adhesives?




   2. How can this failure be minimized in the field?




   3. What effects can moisture have in the adhesive properties of
      construction adhesives?




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                         CON 251 Lab #8
                Threaded Fasteners and Shear Strength



I.               Introduction
      Threaded fasteners comprise a majority of the assembly
techniques used in the manufacturing and construction industries.
While specifications of some of the fasteners vary between the two
industries, the end result is the same, the joining of materials. In the
manufacturing industries, typical fasteners used for assembly of
components of subassemblies include but are not limited to bolts, nuts
and bolts, machine screws, self-tapping machine screws and sheet
metal screws. While the list is quite extensive, fasteners in
manufacturing can be categorized in two main categories. They are
machine screws and machine bolts.
       Machine screws are typically less than ¼” in diameter and are
sized by a number such as a # 10 machine screw which happens to be
3/16” in diameter. Sizes range from 0-80 to #10. There are also
special sizes on either end of this spectrum such as a 00-96 or #12.
The other criteria used for sizing machine screws are whether they
are a course or fine pitch thread. For each # size there exists a fine
and course thread. These thread pitches are identified as Unified
National Fine or Unified National Course thread. Usually referred to as
UNC or UNF. An example would be #10-32 UNF or 10-24 UNC. The
head configuration of machine screws can be slotted; Phillips, Torx, or
socket headed Allen. Other specialty head configurations are also
available for tamper resistant fasteners found in restrooms and other
public places.
      Machine bolts are listed by there nominal diameter as a fraction,
such as ¼” or ¾” Bolt and also have both course and fine thread
configurations. Examples of these configurations are, ¼”-20 UNC or ¼”
28- UNF. Head configurations also vary with machine bolts. Most
fasteners will be either hex head, socket head Allen, or Torx. Other
specialty fasteners may have different head configurations. The
standards for these mechanical fasteners is established by SAE and
96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                    Page 42
ANSI (Society of automotive engineers and American National
Standards Institute.) These fasteners are made in different grades
from grade 2 to 8, which corresponds to their tensile strength and
material type. Specific grades and their representative symbols will be
listed later in this document.
      Fasteners used for structural applications in the construction
industry are categorized differently than machine bolts. The
standards for the construction industry are established by ASTM
(American Society of Testing Materials) While there is some cross
over in classifications, the markings are distinctly different that
standard machine bolts. Specific grades and their representative
symbols will be listed later in this document. Regardless of the type of
fastener, there are similar stresses that are applied the fasteners
when they are used. The first example is that fasteners can be
subjected to tensile loads in which they are pulled apart or elongated.
Bolts can also be subjected to Torsion or twisting loads, and they can
also be subjected toe shear stresses in which they are sheared at
right angles to their central axis. The shear stresses can be
categorized as either a single or double shear depending on the type of
application. See the illustration below for examples of each.




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                    Page 43
              Modes of Failure in Bolted Shear Connections:
                a. Failure of the fastener
                                   fv = P/A (single shear)
                                   fv = P/2A (double shear)




   In structural steel applications, the fasteners used are typically of one
of two types. They are either standard hex headed bolts with structural
nuts and washers, or they are Tension controlled bolts that are pre-
torqued with a pneumatic or electric drive tool. Upon tightening, the bolt
is not tightened by the head, but by a spline on the end of the bolt. When
the maximum amount of torque is applied to the bolt, the spline separates
from the bolt. Standard bolts and nuts must be tightened with a torque
wrench to a specific load. Applying maximum torque to the bolt insures
that its maximum clamping force will be applied to the assembly.




  96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                      Page 44
                       Hex Head Bolt Markings
The strength and type of steel used in a bolt is supposed to be
indicated by a raised mark on the head of the bolt. The type of mark
depends on the standard to which the bolt was manufactured. Most
often, bolts used in machinery are made to SAE standard J429, and
bolts used in structures are made to various ASTM standards. The
tables below give the head markings and some of the most commonly
needed information concerning the bolts. For further information, see
the appropriate standard.




                           SAE Bolt Designations

 SAE                        Tensile
Grade          Size        strength,                             Head
 No.          range           ksi              Material         marking

  1      1/4 thru 1-1/2        60           Low or medium
                                             carbon steel
  2       1/4 thru 3/4         74
         7/8 thru 1-1/2        60

  5        1/4 thru 1         120           Medium carbon
          1-1/8 thru 1-       105               steel,
               1/2                           quenched &
                                              tempered

 5.2       1/4 thru 1         120            Low carbon
                                           martensite steel,
                                             quenched &
                                              tempered




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  7       1/4 thru 1-1/2      133           Medium carbon
                                             alloy steel,
                                             quenched &
                                              tempered

  8       1/4 thru 1-1/2      150           Medium carbon
                                             alloy steel,
                                             quenched &
                                              tempered

 8.2        1/4 thru 1        150            Low carbon
                                           martensite steel,
                                             quenched &
                                              tempered


                           ASTM Bolt Designations

                              Tensile
 ASTM            Size        strength,                            Head
standard        range           ksi             Material         marking

  A307        1/4 thru 4         60         Low carbon steel



 A325        1/2 thru 1         120          Medium carbon
 Type 1     1-1/8 thru 1-       105              steel,
                 1/2                          quenched &
                                               tempered

 A325        1/2 thru 1         120           Low carbon
 Type 2     1-1/8 thru 1-       105         martensite steel,
                 1/2                          quenched &
                                               tempered




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 A325        1/2 thru 1         120        Weathering steel,
 Type 3     1-1/8 thru 1-       105          quenched &
                 1/2                          tempered

  A449       1/4 thru 1         120         Medium carbon
            1-1/8 thru 1-       105             steel,
                 1/2             90          quenched &
            1-3/4 thru 3                      tempered

 A490        1/4 thru 1-        150           Alloy steel,
 Type 1          1/2                          quenched &
                                               tempered

 A490        1/4 thru 1-        150        Weathering steel,
 Type 3          1/2                         quenched &
                                              tempered


Often one will find "extra" marks on a bolt head--marks in addition to
those shown above. Usually these marks indicate the bolt's
manufacturer.
ASTM A325 Type 2 bolts have been discontinued, but are included
above because they can be found in existing structures. Their
properties can be important in failure investigations.
While the bolts shown above are among the most common in the U.S.,
the list is far from exhaustive. In addition to the other bolts covered
by the SAE and ASTM standards, there are a host of international
standards, of which ISO is perhaps the most well known.




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                       Page 47
                               Specifications

                           Tension Control Bolts
                Available from Textron Fastening Systems




                    Nucor® Tru-Tension® Assemblies
                 Features
-     Preassembed bolt and washer
      packaged with heavy hex nut
-   Installed with lightweight, electric
                 drive tool
-   Bolt is calibrated so the spline tip
     twists off when the proper bolt
            tension is achieved
    Supplied as ASTM A325 or ASTM
            A490 Grade bolts
-            Made in the USA
                 Benefits
-            Speeds assembly
-    More ergonomic installation over
          pneumatic wrenches
- Easier traceability than components
            sold separately
- Visual inspection is normally all that is
  required to determine proper tension




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      Performance and Technical Data: View a tech data sheet from Nucor
      Fastener Division
                       Material Surface Identification Head Available Available
Type Description
                      Description Finish  Marking* Styles Diameters Lengths
       F1852
       splined    carbon
     bolt, heavy   steel,
                                                                                   3/4" to 1-
A325 hex nut and quenched               plain                           round                 up to 6"
                                                                                     1/8"
        F436        and
       washer    tempered
      assembly
       F1852
                   medium
       splined
                    carbon
     bolt, heavy
                 alloy steel,                                                      3/4" to 1-
A490 hex nut and                        plain                           round                 up to 6"
                  quenched                                                           1/8"
        F436
                     and
       washer
                  tempered
      assembly


      F593, F594 - ASTM F593 is a specification for stainless hex head cap screws:
      ASTM F594 is for stainless nuts. Compared to regular (18-8) stainless fasteners,
      F593 and F594 call for: (a) tensile requirements about 20% higher than that of
      commercial 18-8 or stainless hex caps and nuts to MS Specifications (MS35307-8,
      MS34649-50); (b) both a minimum and a maximum tensile and hardness
      requirements while commercial and MS fasteners do not have a maximum; (c)
      chemical requirements that (eliminate) many commonly used mixtures of 300 or 18-
      8 stainless while allowing others. (courtesy Star Stainless Screw)
                                                                              Machined Specimen
                                                   Full Size Tests
                                                                              Tests
                           Alloy                                                                 Elon-
     Stainless                                 Tensile Yield              Tensile Yield
                           Mechanical Nominal                    Rockwell                        gation
     Alloy       Condition                     Strength Strength          Strength Strength
                           Property   Diameter                   Hardness                        in 4D
     Group                                     ksi c    ksi c/d           ksi d    ksi c/d
                           Marking                                                               %
     303, 304,                                     100 to            B95 to
               CW1        F593 C      1/4 to 5/8            65                95       60        20
     305, 384,                                     150               C32
     XM1,                             3/4 to1-     85 to             B80 to
     XM7,302Se CW2        F593 D
                                      1/2          140
                                                            45
                                                                     C32
                                                                              80       40        25




      96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                                         Page 49
                             CON 251 Lab #8

               Double Shear Test of Threaded Fasteners

Shear Strength =                Load @ Rupture
                            2X Cross Sectional Area of Bolt


(Note 1: The shear strength of a fastener is equal to

approximately 80% of its rated tensile strength value.

Note:2     Cross sectional area thru the threads are:

          Stress area of a ¼-20 UNC is 0.0318 sq. in.

          Stress area of a ¼-28 UNF is 0.0364 sq. in.)

Sample # 1 Type and Grade          1 & 2 or A307 Carriage Bolt

Diameter

Peak Load at Rupture

Shear Strength                                psi.

Listed Tensile Strength of this fastener                         ksi

Approximated shear strength value                                ksi



Sample # 2 Type and Grade           1 & 2 or A307 Bolt

Diameter

Peak Load at Rupture

Shear Strength                                psi.

Listed Tensile Strength of this fastener                         ksi

Approximated shear strength value                                ksi



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Sample # 3 Type and Grade         5 or A325

Diameter

Peak Load at Rupture

Shear Strength                                  psi.

Listed Tensile Strength of this fastener                     ksi

Approximated shear strength value                           ksi




Sample # 4 Type and Grade           8 or A490

Diameter

Peak Load at Rupture

Shear Strength                                  psi.

Listed Tensile Strength of this fastener                     ksi

Approximated shear strength value                           ksi



Sample #5 Type and Grade            F593 SS

Diameter

Peak Load at Rupture

Shear Strength                                  psi.

Listed Tensile Strength of this fastener        100 - 150    ksi

Approximated shear strength value                           ksi




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Sample # 6 Type and Grade           Allen Socket Cap Screw

Diameter

Peak Load at Rupture                           (Thru the threads)

Shear Strength                                psi. (Thru the threads)

Peak Load at Rupture                           (Thru the body)

Shear Strength                                psi. (Thru the body)

Listed Tensile Strength of this fastener      180                ksi

Approximated shear strength value                              ksi




Type and Grade            Grade 5

Diameter & Pitch          ¼-20 & ¼-28

Listed Tensile Strength of this fastener                         ksi

Approximated shear strength value                              ksi

Fine thread Peak Load at Rupture

             Shear Strength                             psi.

Course Thread Peak Load at Rupture

             Shear Strength                             psi.




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                       Page 52
                           CON 251 Lab #9
                      Concrete Compression Testing



I.               Introduction

Concrete (construction), artificial engineering material made from a
mixture of Portland cement, water, fine and coarse aggregates, and a
small amount of air. It is the most widely used construction material in
the world.
Concrete is the only major building material that can be delivered to
the job site in a plastic state. This unique quality makes concrete
desirable as a building material because it can be molded to virtually
any form or shape. Concrete provides a wide latitude in surface
textures and colors and can be used to construct a wide variety of
structures, such as highways and streets, bridges, dams, large
buildings, airport runways, irrigation structures, breakwaters, piers
and docks, sidewalks, silos and farm buildings, homes, and even barges
and ships.
Other desirable qualities of concrete as a building material are its
strength, economy, and durability. Depending on the mixture of
materials used, concrete will support, in compression, 700 or more
kg/sq cm (10,000 or more lb/sq in). The tensile strength of concrete is
much lower, but by using properly designed steel reinforcing, structural
members can be made that are as strong in tension as they are in
compression. The durability of concrete is evidenced by the fact that
concrete columns built by the Egyptians more than 3600 years ago are
still standing.



II.   Composition

The two major components of concrete are a cement paste and inert
materials. The cement paste consists of portland cement, water, and
some air either in the form of naturally entrapped air voids or minute,
96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                    Page 53
intentionally entrained air bubbles. The inert materials are usually
composed of fine aggregate, which is a material such as sand, and
coarse aggregate, which is a material such as gravel, crushed stone, or
slag. In general, fine aggregate particles are smaller than 6.4 mm (.25
in) in size, and coarse aggregate particles are larger than 6.4 mm (.25
in). Depending on the thickness of the structure to be built, the size of
course aggregate particles used can vary widely. In building relatively
thin sections, a small size of coarse aggregate, with particles about 6.4
mm (.25 in) in size, is used. At the other extreme, aggregates up to 15
cm (6 in) or more in diameter are used in large dams. In general, the
maximum size of coarse aggregates should not be larger than one-fifth
of the narrowest dimensions of the concrete member in which it is
used.
When portland cement is mixed with water, the compounds of the
cement react to form a cementing medium. In properly mixed concrete,
each particle of sand and coarse aggregate is completely surrounded
and coated by this paste, and all spaces between the particles are
filled with it. As the cement paste sets and hardens, it binds the
aggregates into a solid mass.
Under normal conditions, concrete grows stronger as it grows older.
The chemical reactions between cement and water that cause the
paste to harden and bind the aggregates together require time. The
reactions take place very rapidly at first and then more slowly over a
long period of time. In the presence of moisture, concrete continues to
gain strength for years. For instance, the strength of just-poured
concrete may be about 70,307 g/sq cm (1000 lb/sq in) after drying for
a day, 316,382 g/sq cm (4500 lb/sq in) in 7 days, 421,842 g/sq cm
(6000 lb/sq in) in 28 days, and 597,610 q/sq cm (8500 lb/sq in) after 5
years.
Concrete mixtures are usually specified in terms of the dry-volume
ratios of cement, sand, and coarse aggregates used. A 1:2:3 mixture,
for instance, consists of one part by volume of cement, two parts of
sand, and three parts of coarse aggregate. Depending on the
applications, the proportions of the ingredients in the concrete can be
altered to produce specific changes in its properties, particularly
96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                     Page 54
strength and durability. The ratios can vary from 1:2:3 to 1:2:4 and
1:3:5. The amount of water added to these mixtures is about 1 to 1.5
times the volume of the cement. For high-strength concrete, the water
content is kept low, with just enough water added to wet the entire
mixture. In general, the more water in a concrete mix, the easier it is
to work with, but the weaker the hardened concrete becomes.
Concrete can be made to have any degree of water tightness. It can be
made to hold water and resist the penetration of wind-driven rains. On
the other hand, for purposes such as constructing filter beds, concrete
can be made porous and highly permeable. Concrete can also be given a
polished surface that is as smooth as glass. By using heavy aggregates,
including steel fragments, dense concrete mixtures can be made that
weigh 4005 or more kg/cu m (250 or more lb/cu ft). Concrete that
weighs only 481 kg/cu m (30 lb/cu ft) can be made by using special
lightweight aggregates and foaming techniques. Forms consisting of
such lightweight aggregates can be floated on water, sawed into pieces,
or nailed to another surface.
For small jobs and minor repairs, concrete can be mixed by hand, but
machine mixing ensures more uniform batches and, therefore, superior
performance. For most home repairs and improvements—for example,
floors, walks, driveways, patios, and garden pools—the recommended
proportion is a 1:2:3 mix.
After exposed surfaces of concrete have hardened sufficiently to
resist marring, they should be cured by sprinkling or ponding (covering)
with water or by using moisture-retaining materials such as waterproof
paper, plastic sheets, wet burlap, or sand. Special curing sprays are
available. The longer concrete is kept moist, the stronger and more
durable it will become. In hot weather, it should be kept moist for at
least three days. In cold weather, drying concrete must not be allowed
to freeze. This can be accomplished by covering the cement with a
tarpaulin or some other material that helps trap the heat generated by
the chemical reactions within the concrete that cause it to harden.




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III.                         Construction Techniques

Concrete is poured into place in a number of ways. For the footings of
small buildings, the wet concrete is poured directly into trenches dug
into the earth below frost level. Concrete for foundations and certain
types of walls is placed between supporting wood or metal forms, which
are removed after the concrete has hardened. In lift-slab
construction, floors and roof slabs are cast at ground level and then
raised by hydraulic jacks and fastened to columns at the desired
elevation. Slip forms are used to produce vertical shafts for silos and
the cores of buildings. They are moved upward at a rate of 15 to 38 cm
(6 to 15 in) per hour while concrete and reinforcements are put in
place. The tilt-up method of construction is frequently used for one-
and two-story buildings. Walls are cast in place on the ground or on the
previously laid concrete floor and tilted into position by cranes. The
walls are joined at the corners or between panels with cast-in-place
concrete columns. To pave a highway or road with concrete, a slip-form
paver is used. Two metal side forms are connected to a slip-form paver.
A layer of concrete is poured between the side forms as the paver
slowly moves forward on its treads; the side forms keep the concrete
in position as it dries. Slip-form pavers can lay continuous strips of one
or two lanes of concrete pavement.
For certain applications, such as the construction of swimming pools,
canal linings, and curved surfaces, concrete may be applied by the
shotcrete method. In shotcreting, concrete is sprayed under pneumatic
pressure rather than placed between forms. Often the use of
shotcrete eliminates the need for formwork and permits placement of
concrete in confined areas where conventional forms would be difficult
or impossible to construct.
Air-entrained concrete is concrete in which minute air bubbles are
intentionally trapped by the addition of an admixture to the cement,
either during its manufacture or during the batching and mixing of the
concrete. The presence of a properly distributed amount of these
bubbles imparts desirable properties to both freshly mixed and
96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                     Page 56
hardened concrete. In freshly mixed concrete, entrained air acts as a
lubricant, improving the workability of the mix, thereby reducing the
amount of water that needs to be added. Entrained air also reduces
the need for fine material (sand).
Entrained air in hardened concrete dramatically reduces the scaling
that might otherwise result from the use of chemicals to melt ice on
roads and streets. It also prevents damage to pavements caused by
freezing and thawing. The air bubbles function as minute safety valves
by providing room for the free water in concrete to expand harmlessly
as freezing occurs.

IV. Concrete Masonry

Concrete masonry is block and brick building units molded of concrete
and used in all types of masonry construction. Concrete masonry is used
for load-bearing and nonload-bearing walls; piers; partitions; fire walls;
backup for walls of brick, stone, and stucco facing materials;
fireproofing over steel structural members; firesafe walls around
stairwells, elevators, and other enclosures; retaining walls and garden
walls; chimneys and fireplaces; concrete floors; and many other
purposes.
About 60 percent of all concrete masonry units, such as cinder blocks,
are made with lightweight aggregates. Processed clays, blast-furnace
slag, shales, natural volcanic aggregates, and cinders are the
lightweight aggregates most commonly used. The size of the masonry
unit most commonly used for walls, both below and above ground, is 20
by 20 by 40 cm (8 by 8 by 16 in). Masonry units are laid horizontally,
and are cored to reduce weight and to provide an insulating air space
within the block. New types of concrete masonry, such as split and
slump block, are being used as facing in homes, commercial buildings,
schools, churches, and municipal facilities.
Basic block types are fairly well standardized today. Specific types can
usually be supplied for any construction without cutting or fitting.
Special molds are available for the production of patterned shadow


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effects on exterior and interior block walls. It is possible to supply
virtually any color or type of texture.

V.    Reinforced Concrete

Concrete used in most construction work is reinforced with steel.
When concrete structural members must resist extreme tensile
stresses, steel supplies the necessary strength. Steel is embedded in
the concrete in the form of a mesh, or roughened or twisted bars. A
bond forms between the steel and the concrete, and stresses can be
transferred between both components.
Prestressing concrete has removed many limitations on the spans and
loads for which a concrete structure can be economically designed. The
basic function of pre-stressing is to greatly reduce the tensile
stresses to which crucial areas of concrete structures are subjected.
Prestressing is accomplished by stretching high-strength steel to
induce compressive stresses in concrete. The strengthening effect of
compression in concrete acts like horizontally squeezing a row of books.
When you apply sufficient pressure to the books at each end, you
induce compressive stresses throughout the entire row; thus, although
the center volumes are unsupported, you can lift the books and carry
them horizontally.
Compressive stresses are induced in pre-stressed concrete by either
pretensioning or post-tensioning the steel reinforcement. In the
pretensioning process, the steel is stretched before the concrete is
placed. After the concrete has hardened around the tensioned
reinforcement, the stretching forces are released. The steel shortens
somewhat, and because of the bond between the steel and concrete,
the compressive stress in the concrete increases. In post-tensioning,
the concrete is cast around, but not in contact with, un-stretched
steel. The steel is stretched after the concrete has hardened by
anchoring one end against the concrete and using hydraulic jacks to pull
the other. After stretching, the second end is also anchored,
compressing the concrete.


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Test Procedures:

Each class made three samples of three different aggregate sizes. All
samples we fully cured for 28 days to achieve optimal strength. The
significances of this test is to demonstrate how aggregate size impacts
the compressive strength of concrete.
Test procedures will be the same for all samples.

 In the test data, record the load at failure of the three different
samples of each aggregate size. Average the load at failure and then
calculate the average compressive strength of each aggregate size.




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                   Page 59
                             CON 251 Lab #9

                Compression Testing Concrete Cylinders


                               Test Data
     Slump             Slump                 Slump       Slump
                       0” – 1”             1-1/2” – 3”   6” – 9”
    Load at
Failure Sample
      #1
    Load at
    Failure
  Sample #2
    Load at
Failure Sample
      #3
Average Load
  at Failure

    Cross
Sectional Area

   Average
 Compressive
 Strength psi



Compressive Strength =              Load at Failure
                                          Cross Sectional Area

Cross Sectional Area = π X R2




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      1. What is the significance of the size, shape and texture of
         aggregate as compared to the strength of the concrete?




      2. What is the significance of the slump as compared to the
         strength of the concrete?




      3. Why is there a decrease in strength of concrete if it is
         allowed to freeze during curing?




      4. What is hydration and how does it effect the curing of
         concrete?




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                           CON 251 Lab #10
                      Flexural Strength of Concrete



Introduction

Flexural Strength is the ability of a beam or slab to resist failure in
bending. It is measured by loading concrete beams with a span three
times the depth. The flexural strength is expressed as “Modulus of
Rupture” (MR)

Flexural Strength is about 10 to 20% of compressive strength.
However, the best correlation for specific materials is obtained by
laboratory tests.



Sample Preparation

 Flexural strength specimens shall be rectangular beams of concrete
cast and hardened with long axes horizontal. The length shall be at
least 2 in. greater than three times the depth as tested. The ratio of
width to depth as molded shall not exceed 1.5. The standard beam shall
be 6 in. in cross section, and shall be used for concrete with maximum
size coarse aggregate up to 2 in.. When the nominal maximum size of
the coarse aggregate exceeds 2 in. , the smaller cross sectional
dimensions for the beam shall be at least three times the nominal
maximum size of the coarse aggregate. Unless required by the project
specifications, beams made in the field shall not have a width or depth
of less than 6 in.




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1.    Scope:

      This test is for determining flexural strength of concrete with
      third point loading.




2.    Procedure:

            a.    Turn the test specimen on its side, with respect to its
                  position as molded, and center on the bearing blocks.

            b.    Bring the load-applying blocks in contact with the
                  surface of the Specimen.

            c.    If full contact is not obtained at no load between the
                  specimen and the load-applying blocks, grind the
                  contact surfaces of the specimen or shim with leather
                  strips.

            d.    Load at a rate of 125 to 175 psi/min

            e.    Measure the beam at the breaking point to obtain the
                  width and depth to nearest 1/16" (1 mm) with respect
                  to its position when tested.

            f.    Record the load in lbs.




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3.    Report:

            Calculations for (modulus of rupture)

                        R = Pl/bd2

            Where:

            R = modulus of rupture, psi

            P = maximum applied load indicated by the testing
            machine, lbs.

            l   = span length, in., (or mm),

            b = average width of specimen, inches

            d = average depth of specimen, inches



            Report the flexural strength to the nearest 10 psi.




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5.    References: ASTM C 78-02




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc   Page 65
                              CON 251 Lab #10

                       Flexural Strength of Concrete
                             (Flexural modulus)

                 Un-           Reinforced
                 Reinforced    Below
                               Neutral
                               Axis
P (load)
l   (span)
b (width)
d (depth)
R ( MR)
psi

                                     R = Pl/bd2

             Where:

             R = modulus of rupture (MR), psi

             P = maximum applied load indicated by the testing
             machine, lbs.

             l    = span length, in., (or mm),

             b = average width of specimen, inches

             d = average depth of specimen, inches




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc               Page 66
         1. What were the results of loading the unreinforced beam?




         2. What were the results of the sample with the rebar located
            below the neutral axis?




         3. What results would you expect to see if rebar were placed
            above and below the neutral axis in the specimen?




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                         CON 251 Lab #11
       Flexural Properties of Laminated and Solid Floor Joists




I.               Introduction


      Trus Joist’s Silent Floor® System continues to set the standard
for engineered solutions to residential framing challenges. At the
heart of the system is the TJI® joist, which was created and
marketed by Trus Joist more than 25 years ago as the first
commercially available wood “I” joist. Over the past quarter century,
we have continued to test, develop and improve our product line with
more than 400 refinements in order to better serve our customers,
while more efficiently utilizing forest resources.

      A healthy future for the building industry depends on sustaining a
predictable supply of wood fiber—fiber Trus Joist uses to develop
structural building products. In the face of a diminishing supply of
quality structural lumber and changing forest resources, Trus Joist is
dedicated to giving you top quality products that optimize wood fiber
utilization. Our goal is to provide you with the best possible products
today, through advanced manufacturing technology and resource
utilization that also assure you the best possible products tomorrow.


Understanding Floor Noise
     Any homeowner knows there are many sounds that
emanate from a house’s walls and floors: boards creak
and squeak, ductwork flexes and nails rub. In many
cases, these noises are difficult to prevent and should
be expected.

However, there is a cure for the most common cause
of floor squeaks—the inconsistent size of sawn lumber.
96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                    Page 68
Floor joists of sawn lumber are unlikely to be the same
depth when they’re installed, and subsequent drying
can magnify unevenness. When floor sheathing flexes over these joists,
squeaks occur.
      The Silent Floor® Joist, on the other hand, is manufactured to
precise specifications to ensure that all joists are the same
depth and won’t shrink after installation. The natural defects found in
sawn lumber are engineered out, and dimensional
stability is manufactured in. Using the Silent Floor® Joist virtually
eliminates floor noise caused by dimensional instability.
A builder that uses the Silent Floor® Joist has made a significant
effort to eliminate annoying floor squeaks. While it won’t
prevent all the normal sounds that come from a structure, homes built
with the Silent Floor® Joist are much quieter than
those framed with sawn lumber.
3 Changing the Way You Build™




                              ASTM D 198-84

Scope of Flexure Test

      These test procedures cover the determination of the flexural

properties of structural members made of solid or laminated wood.

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The test method is intended primarily for beams of rectangular

cross section but is also applicable to beams of round and irregular

shapes, such as round posts, I-beams, or other special sections.

Summary of Test Methods

      The structural member, usually a straight or slightly

cambered beam of rectangular cross section, is subjected to a

bending moment by supporting it near its ends, at locations called

reactions and applying transverse loads symmetrically imposed

between these reactions. The beam is deflected at a prescribed

rate, and coordinate observations of loads and deflection are made

until rupture occurs.




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                  Page 70
                            CON 251 Labs #11

       Flexural Properties of Laminated and Solid Floor Joists


Procedures for conducting flexural test on TJI laminated joists and

solid dimensional members. Place specimen in Test fixture.

Applied load to cross head at the rate specified. Observe

indicator for deflection measurements and simultaneously record

load values. Take for deflection and load measurements. Continue

loading until rupture occurs. Record Peak load value. Repeat the

same procedures for other sample.




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                 Page 71
                 Sample #1                        Sample #2


     TJI          Deflection      Volts    Load   Deflection   Volts   Load

      #1

      #2

      #3

      #4

 Peak Volts       --------                        -------



     Solid

      #1

      #2

      #3

      #4

 Peak Volts       --------                        --------



LVL/Microlam

      #1

      #2

      #3

      #4

 Peak Volts        -------                        -------

96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                    Page 72
Calculations for Modulus of Rupture Sr (two point loading):

      Sr = 3Pa ÷ b(h2)

    Modulus of Rupture for TJI =
    Modulus of Rupture for Solid =
Where P = Peak Load at Rupture

         a = ½ shear span

         b = width of beam          TJI= .943     Solid= 1.5

         h = depth of beam          TJI= 11.875   Solid= 11.25
                                    t
Calculations for Shear Stress        m
t
m = 3P ÷ 4 (bh)
(bh) for Solid     16.875     (bh) for TJI 11.200
Shear Stress for TJI =
Shear Stress for Solid =




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This test was to examine and compare the Shear Strength and

flexural properties of two different floor joists. Sample one was

the solid Douglas Fir 2X12 joist and the second a Engineered TJI

2X12 joist.

(these questions pertain only to the comparison of TJI, Vs. Soild)


From the test results, which joist withstood the greatest loading

before rupture?




From the test results, which joist displayed the best load to

deflection ratio?




If defects were present in each sample, what significance did the

defects have on the test results?




What is the advantage and disadvantage of each type of joist?




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                  Reference Materials




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc   Page 75
               Carbon Steel              10XX       Plain carbon steel , Mn 1.00% max
                                         11XX            Resulphurised free cutting
                                         12XX   Resulphurised - Rephosphorised free cutting
                                         15XX        Plain carbon steel, Mn 1.00-1.65%
              Manganese Steel            13XX                    Mn 1.75%
               Nickel Steel              23XX                     Ni 3.50%
                                         25XX                    Ni. 5.00%
           Nickel Chromium Steel         31XX             Ni 1.25%, Cr 0.65-0.80%
                                         32XX               Ni 1.75%, Cr 1.07%
                                         33XX             Ni 3.50%, Cr 1.50-1.57%
                                         34XX               Ni 3.00%, Cr 0.77%
             Molybdenum Steel            40XX                  Mo 0.20-0.25%
                                         44XX                  Mo 0.40-0.52%
        Chromium Molybdenum Steel        41XX         Cr 0.50-0.95%, Mo 0.12-0.30%
     Nickel Chromium Molybdenum Steel    43XX      Ni 1.82%, Cr 0.50-0.80%, Mo 0.25%
                                         47XX      Ni 1.82%, Cr 0.50-0.80%, Mo 0.25%
          Nickel Molybdenum Steel        46XX      Ni 1.05%, Cr 0.45%, Mo 0.20-0.35%
                                         48XX         Ni 0.85-1.82%, Mo 0.20-0.25%
              Chromium Steel             50XX               Ni 3.50%, Mo 0.25%
                                         51XX                  Cr 0.27-0.65%
                                        50XXX                  Cr 0.80-1.05%
                                        51XXX              Cr 0.50% C 1.00% min
                                        52XXX   Cr 1.02%, C 1.00% minCr 1.45%, C 1.00%
         Chromium Vanadium Steel         61XX          Cr 0.60-0.95%, V 0.10-0.15%
          Tungsten Chromium Steel        72XX               W 1.75%, Cr 0.75%
     Nickel Chromium Molybdenum Steel    81XX         Ni 0.30%, Cr 0.40%, Mo 0.12%
                                         86XX         Ni 0.55%, Cr 0.50%, Mo 0.20%
                                         87XX         Ni 0.55%, Cr 0.50%, Mo 0.25%
                                         88XX          Ni 0.55% Cr 0.50% Mo 0.35%
            Silicon Manganese Steel      92XX    Si 1.40-2.00%, Mn 0.65-0.85% Cr 0.65%
     Nickel Chromium Molybdenum Steel    93XX         Ni 3.25%, Cr 1.20%, Mo 0.12%
                                         94XX         Ni 0.45%, Cr 0.40%, Mo 0.12%
                                         97XX         Ni 0.55%, Cr 0.20%, Mo 0.20%
                                         98XX         Ni 1.00%, Cr 0.80%, Mo 0.25%




96fbc762-1fd3-440a-88bf-c394dc96a26a.doc                                        Page 76
Approximate Tensile Strength for Rockwell "C" scale
 Diamond    Approximate      Diamond       Approximate
   Brale      Tensile          Brale         Tensile
 150 kg C   Strength 1,000   150 kg C   Strength 1,000
  Scale          PSI          Scale          PSI
   65                          33              154
   64                          32              150
   63                          31              146
   62                          30              142
   61                          29              138
   60                          28              134
   59            326           27              131
   58            315           26              126
   57            304           25              124
   56            294           24              122
   55            287           23              118
   54            279           22              116
   53            269           21              113
   52            261           20              111
   51            254           18              107
   50            245           16*             102
   49            238           14*             98
   48            232           12*             92
   47            225           10*             90
   46            219            8*             87
   45            211            6*             83
   44            206            4*             79
   43            202            2*             77
   42            198            0*             74
   41            191                           73
   40            185                           70
   39            181                           67
   38            176                           65
   37            171                           62
   36            168                           60
   35            163                           58
   34            159                           56




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                  Concrete Cores and Beam Preparation

Purpose of this activity is to prepare concrete core and beam
specimens in accordance with ASTM C31. During this lab activity 4’X8”
cylinders will be molded to compare relative compressive strength of
different aggregate sizes. Concrete beams will be molded to test for
flexural strength. After molding cylinders and beams the specimens
will cure for a full 28 days at which time they will be tested for there
compressive strength and flexural modulus.

A slump test is prepared in accordance with (ASTM C 143). It has
been determined that a slump of less than ½” may not be adequately
plastic and concretes having slumps greater than 9” may not be
adequately cohesive. In adequate amount of water will not allow full
hydration of the cement and excessive amounts of water will dilute the
cement. Both extremes will significantly weaken the strength of
concrete. Under laboratory conditions with strict control of all
concrete materials, the slump is generally found to increase
proportionally with the water content of a given concrete mixture, and
thus to be inversely related to the concrete strength.

Three sets of 4” X 8” concrete test cylinders will be prepared by the
class. Each set of concrete cylinders will be molded using three
different water to cement ratios determined by a slump test. After 28
days testing of these cylinders should indicate a change in compressive
strength as the water to cement ratio changes.

   1. Three cylinders will be molded out of a standard Quikrete mix.
      With a slump of 0” to 1”. (approx. 32 oz. water)
   2. Three cylinders will be molded out of a standard Quikrete mix.
      With a slump of 1-1/2” to 3”. ( approx. 50 oz. water)

   3. Three cylinders will be molded out of a standard Quikrete mix.
      With a slump of 6” to 9”. (approx. 60 oz. water)


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   4. Each cylinder shall be properly labeled on its lid stating, class
      section number and mix or slump and oz. of water.

Adequate water must be added to insure complete plasticizing but not
excessive enough to exceed a 9” slump. Each plastic cylinder mold will
be filled ½ full then rodded 25 times with a rounded end rod. The
cylinder will then be filled to the top and rodded an additional 25
times. Using a rod or trowel, the cylinders should be leveled off and
made smooth. Cylinders should then be capped with a plastic lid and
labeled. This process will be repeated for all nine cylinders. They then
will b e placed on a plywood panel and stored for 28 days.

Design mixes will be mixed by hand in a wheel barrow:

   1.    Measure our six quarts of Quikrete for each batch of three
         cylinders. (3- heaping 2qt. buckets)
   2.    Start by adding no more than 2 pints (1 quart or 32 oz.) of
         water.
   3.    Mix thoroughly with shovel or hoe.
   4.    Perform Slump test and add additional water to achieve
         desired slump. (No design mixes should contain more than 4
         pints (2 quarts or 64 oz.) of water.
   5.    Record the actual total amount of water added to the mix on
         the lid.




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Procedures for ASTM C-143 (Slump Test for Hydraulic Cement)

1.   Start the test within 5 min. after obtaining the final portion of
the mixed concrete sample.

2.    Dampen the mold (inside) and place on the dampened base plate.



3.   Hold the mold firmly in place during the filling and rodding
operation (by the operator standing on the two foot pieces).

5.   Fill the mold in three layers, each approximately one-third the
volume of the mold.



5.   Rod each layer with 25 strokes of the tamping rod. During filling
and rodding the top layer, heap the concrete above the mold before
rodding is started.



6.   Strike off the surface by a screeding and a rolling motion of the
tamping rod



7.   Remove the mold immediately by raising it in a vertical direction.
(Steps 2 through 7 should be completed in less than 2.5 minutes).

8.   Place the empty mold (inverted) adjacent to the concrete sample
and measure the vertical difference between the top of the mold and
the displaced original center of the sample. This is the slump.




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The concrete beams will be 6”X6”X20” in length. They will be molded
using a standard Quikrete mix with a slump of between
 2” and 3”.
(2- 80lb. bags of Quikrete 5000 High Early Concrete Mix will make two
beams and 3 compression cylinders))

   1. One beam will be molded with no reinforcing bar.



   2. One beam will be molded with a #3 reinforcing bar located below
      the neutral axis of the beam.

All beam molds will be filled half full then rodded 25 times. The mold
will then be filled completely and then rodded an additional 25 times.
Using a trowel or bar, level the top surface even with the top of the
mold. Place molds in storage to cure for 28 days.

Be sure to rinse and clean all tools and equipment before returning to
storage.

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          Sub-flooring Adhesive Testing Sample Preparation


This test is designed to simulate a variety of different conditions in

which construction adhesives are applied in the construction industry

as it pertains to the installation of sub-flooring. There are a variety of

different variables that will be discussed during this lab that are

dependent upon the type of adhesives used, and the conditions in which

they are applied. Some or all of these variables may or may not affect

the bonding properties (holding strength) of the adhesive. Four

samples will be prepared to simulate some of these variables. Each

sample must be properly labeled with the following information:



   1. Class Section Number

   2. Brand Name of the adhesive, i.e. Liquid Nails, Locktite, etc.

   3. Type or grade, i.e. Pl 200, Sub-Flooring etc.

   4. Solvent Base, either water base or Petroleum based.

   5. Time or condition variable.



Each group then will need 2- precut 2X4 and 4- precut pieces of sub

flooring. The procedures are as follows:

   1. Lay bead of adhesive on one edge of the 2X4 and immediately

      place sub flooring on adhesive and nail at each end. Label that

      edge “0 Minutes”.


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   2. Turn over and lay a bead of adhesive on the edge of 2X4. Do not

      install sub flooring until 15 minutes has elapsed. Label that edge

      “15 Minutes”. After 15 minutes has elapsed the sub flooring can

      be installed and nailed at each end.

   3. The second 2X4 is one that has one edge soaking in water. Shake

      off excess water and apply adhesive to the wet edge.

      Immediately place the sub flooring on the adhesive and nail at

      each end. Label this edge “Wet”.

   4. Turn over and lay a bead of adhesive on the edge of the 2X4. Do

      not install sub flooring until 30 minutes has elapsed. Label that

      edge “30 Minutes”. After 30 minutes has elapsed the sub flooring

      can be installed and nailed at each end.

   5. Store samples on bench for one week before testing.




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