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Brick Masonry ConstructionTechnical Issue No TIS

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Brick Masonry ConstructionTechnical Issue No TIS Powered By Docstoc
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                                      Brick Masonry Construction
                                                  TECHNICAL ISSUE NO. TIS-002

Mortars for Brickwork
       The following information relates to the construction of brick walls to meet ASTM C270, the design
and aesthetic requirements.
 
INTRODUCTION 
           Mortar is the bonding agent that integrates brick into a masonry assembly. Mortar must be strong,
    durable and capable of keeping the masonry intact, and it must help to create a water-resistant barrier.
    Also, mortar accommodates dimensional variations and physical properties of the brick when laid. These
    requirements are influenced by the composition, proportions and properties of mortar ingredients.

            Because concrete and mortar contain the same principal ingredients, it is often erroneously as-
    sumed that good concrete practice is also good mortar practice. In reality, mortar differs from concrete in
    working consistencies, methods of placement and structural performance. Mortar is used to bind masonry
    units into a single element, developing a complete, strong and durable bond. Concrete, however, is usually
    a structural element in itself. Mortar is usually placed between absorbent masonry units and loses water
    upon contact with the units. Concrete is usually placed in non-absorbent metal or wooden forms, which
    absorb little if any water. The importance of the water/cement ratio for concrete is significant, whereas for
    mortar it is less important. Mortar has a high water/cement ratio when mixed, but this ratio changes to a
    lower value when the mortar comes in contact with the
    absorbent units.
Mortar Cements 
            Mortar cements are hydraulic cements, consisting of a mixture of Portland or blended hydraulic ce-
    ment, plasticizing materials such as limestone or hydrated or hydraulic lime, and other materials intended
    to enhance one or more of the properties of mortar. In this respect, mortar cement is similar to masonry
    cement. However, ASTM C1329, Standard Specification for Mortar Cement includes requirements for
    maximum air content and minimum flexural bond strength that are not found in the masonry cement speci-
    fication. Because of the strict controls on air content and the minimum strength requirement, mortar ce-
    ment and Portland cement-lime mortars are treated similarly in the Building Code Requirements for Ma-
    sonry Structures (ACI 530-05/ASCE 5-05/TMS 402-05).

           Three Types of mortar cements are specified in ASTM C1329: Types M, S and N. Physical require-
    ments vary depending upon mortar cement Type. Air content for all three Types must be a minimum of 8
    percent. The maximum air content is 14 percent for Types M and S and 16 percent for Type N. Flexural
    bond strength, as measured by the test method in ASTM C1072, Standard Test Method for Measurement
    of Masonry Flexural Bond Strength, is also specified. The minimum flexural bond strength for these mortar
    cements is 115 psi 0.8 MPa) for Type M, 100 psi (0.7 MPa) for Type S and 70 psi (0.5 MPa) for Type N.
Aggregates 
    Aggregates (sand) act as a filler material in mortar, providing for an economical mix and controlling shrink-
    age. Either natural sand or manufactured sand may be used. Gradation limits are given in ASTM C144,
    Standard Specification for Aggregates for Masonry Mortar. Sometimes the most feasible method requires
    proportioning the mortar mix to suit the available sand, rather than requiring sand to meet a particular gra-
    dation.
    Water 
    Water that is clean, potable and free of deleterious acids, alkalis or organic materials is suitable for ma-
    sonry mortars.
 


Admixtures 
Admixtures are sometimes used in mortar to obtain a specific mortar color, increase workability, decrease
setting time, increase setting time, increase flexural bond strength or act as a water repellent. Admixtures to
achieve a desired color of the mortar are the most widely used. Although some admixtures are harmless,
some are detrimental to mortar and the resulting brickwork. Admixtures also should be examined for their
effect on the masonry, masonry units and items embedded in the brickwork.




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                          Brick Masonry Construction (continued)
                                                  TECHNICAL ISSUE NO. TIS-002


Colored Mortar
        The mortar color can dramatically affect the overall look. The color of mortar is influenced by the
 color of the cement and the aggregates (sand). Many pigments are also available ranging in color through
 red, yellow, brown, green, blue and black (mainly oxides but carbon black can be used to give black mor-
 tar). The cheapest
 way of coloring mortar is to use colored sand. White and yellow sands are commonly available but red
 and brown sands are also available. Sands are normally natural materials which vary considerably even
 in the one deposit. To ensure color consistency, sufficient sand from the one batch should be set aside
 for the whole job. Where color is crucial to the look of the masonry, before accepting the sand, a trial wall
 should be built (4 bricks x 10 courses). After the mortar dries assess the color. Where oxides or carbon
 black are used as colors never use more than 10% by weight of the cement content.
        Colors are additive in their effect and it is possible to get different shades and tones of mortar using
 different combinations of cement, sands and oxides.
 Use as little pigment as is needed to produce the desired results; an excess may seriously impair
 strength and durability. The maximum permissible quantity of most metallic oxide pigments is 10 percent
 of the cement content by weight. Although carbon black is a very effective coloring agent, it will greatly
 reduce mortar strength when used in greater proportions. Therefore, limit carbon black to 2 percent of the
 cement content by weight.
         For best results, use cement and coloring agents premixed in large, controlled quantities. Premix-
 ing large quantities will ensure more uniform color than can be obtained by mixing smaller batches in the
 field. A consistent mixing sequence is essential for color consistency when mixing smaller batches in the
 field. Further, use the same source of mortar materials throughout the project.
 Color uniformity varies with the amount of mixing water, the moisture content of the brick when laid and
 whether the mortar is retempered. The time and degree of tooling and cleaning techniques also will influ-
 ence final mortar color. Color permanence depends upon the quality of pigments and the weathering and
 efflorescing qualities of the mortar.


                                   Table 1: Typical Colored Mortar Components
          Mortar Color                   Cement                                  Sand                Oxide
              Red                         Grey                      White or Yellow or Red            Red
             Yellow                Off-white or Grey                            Yellow           Yellow & Brown
             Cream                       Off-white                              Yellow               None
              Tan                          Grey                          White or Yellow             Brown
             Black                        Grey                                  Yellow               Black

 Br
 Note: The color of mortar can be severely degraded by incorrect or poor brick cleaning.


SPECIFYING MORTAR
       Masonry mortars are classified by ASTM C270 into four Types: M, S, N and O. Each mortar Type
 consists of aggregate, water and one or more of the four cementitious materials (Portland or hydraulic
 cement, mortar cement, masonry cement and lime) listed in the previous section.

       There are two methods of specifying mortar by Type in ASTM C270: proportion specifications and
 property specifications. A cement-lime mortar, a mortar cement mortar, or a masonry cement mortar is
 permitted. The type of cementitious material desired should be specified.
        




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                           Brick Masonry Construction (continued)
                                                TECHNICAL ISSUE NO. TIS-002


Proportion Specifications
       The proportion specifications require that mortar materials be mixed according to given volumetric
 proportions. If mortar is specified by this method, no laboratory testing is required, either before or during
 construction. Table 1 lists proportion requirements of the various mortar Types. Note that masonry ce-
 ment and mortar cement may be used alone to produce Type M, S, N or O mortars. Additionally, Type N
 mortar cement or masonry cement may be combined with Portland cement to produce a Type M or Type
 S mortar.

                              TABLE 2: Proportion Specification Requirements

 Note: Two air-entraining materials shall not be combined in mortar




       The volumetric proportions given in Table 2 can be converted to weight proportions using assumed
 weights per cubic foot (cubic meter) for the materials as follows:
 Portland cement                                94 lb (1506 kg)
 Masonry, mortar and blended cements            Varies, use weight printed on bag
 Hydrated lime                                  40 lb (641 kg)
 Lime putty                                     80 lb (1281 kg)
 Sand, damp and loose                           80 lb (1281 kg) of dry sand




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                             Brick Masonry Construction (continued)
                                                TECHNICAL ISSUE NO. TIS-002


 
Property Specifications
          The property specifications require a mortar mix of the materials to be used for construction to meet
    the specified properties under laboratory testing conditions. If mortar is specified by the property specifi-
    cations, compressive strength, water retention and air content tests must be performed prior to construc-
    tion on mortar mixed in the laboratory with a controlled amount of water. Table 2 lists property require-
    ments of the various mortar Types. Properties of field-mixed mortar cannot be compared to the require-
    ments of the property specifications because of the different amounts of water used in the mortars, the
    use of different mixers and the different curing conditions. Field sampling of mortar, where specified, is
    typically performed for tracking project consistency from beginning to end. It is not to be used for compli-
    ance with property specifications.  
     
                                                  TABLE 2
                                     Property Specification Requirements




    1. Laboratory prepared mortar only.
    2. When structural reinforcement is incorporated in cement-lime or mortar-cement mortar, the maximum
      air content shall be 12 percent.
    3. When structural reinforcement is incorporated in masonry-cement mortar, the maximum air content
      shall be 18 percent.
                                                              

Proportion vs. Property Specifications

          The specifier should indicate in the project specifications whether the proportion or the property
    specifications areto be used. If the specifier does not indicate which should be used, then the proportion
    specifications govern by default. The specifier also should confirm that the mortar Types selected and the
    materials indicated in the project specifications are consistent with the structural design requirements of
    the masonry.

           Mortar prepared by the proportion specifications is not to be compared to mortar of the same Type
    prepared by theproperty specifications. A mortar that is mixed according to the proportion specification
    will have a higher laboratory compressive strength than that of the corresponding mortar Type under the
    property specification.




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                          Brick Masonry Construction (continued)
                                              TECHNICAL ISSUE NO. TIS-002


Joint Types
       The type of joint can dramatically affect the overall look of brick masonry. Joints can be used to
 create a casual, rustic or formal look to brickwork. There are many different joints; the most common
 ones used are shown below.


                                                          IRONED JOINTS
                                                          10mm round bar create half round
                                                          grout neck



                                                          THIN IRONED JOINTS
                                                          Wheeled nail is for thin grout neck
                                                          with uniform depth



                                                          STRUCK JOINTS
                                                          Combination steel create uniform
                                                          depth of grout neck



                                                          RAKED JOINTS
                                                          10mm rectangular bar create a flat
                                                          depth grout neck



                                                          WEATHERED JOINTS
                                                          10mm steel square bar create a
                                                          triangular grout neck


           Terminology and joint preference differs in different countries and within thr Kingdom. Where
   there is any confusion, always use a drawing or physical sample to avoid misunderstandings.
          Shallow ironed joints are recommended in areas requiring exposure grade bricks and mortar.
   produces a dense smooth surface which sheds water and dirt better than other types of joint. Ironed
   and struck joints should always be used for bricks with straight sharp edges.
          Raked joints may be used with any type of brick but they tend to retain dirt and may lead to
   streaks down the masonry in dirty environments. Raking must not come closer than 5 mm to any core.
   This usually limits raking toeless than 10 mm, however it is best to check the bricks that are being used
   before raking.
           Flush joints or flat to surface joints may be used with any type of brick. However, flush joints are
   particularly effective with rumbled bricks as flush joints make the joints look to be of variable thickness
   that gives a pleasing rustic look.




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                             Brick Masonry Construction (continued)
                                                 TECHNICAL ISSUE NO. TIS-002


Brick bonds and other decorative effects

           A bond is the pattern in which bricks are laid. The most common bond is Stretcher Bond which con-
    sists of
    courses of full bricks where every course is offset half a brick from the course below. When following the
    mortar joint, stretcher bond has the longest vertical pathway and therefore the best bend strength.

           Stretcher bond is used in walls one brick wide. Where walls are two or more bricks wide then
    stretcher bond needs ties to hold the leaves together to give it a monolithic action. To avoid the use of
    ties traditional practice has been to lay some of the bricks sideways. This has usually been either full
    courses of headers with full courses of stretcher (English) or courses of alternating header and stretcher
    (Flemish). A variation of Flemish Bond is Garden Wall Bond where courses are made of a header and
    three stretchers alternating.

          Corner treatment can be different in these bonds. English corners end in full stretchers or full head-
    ers, and any part brick required to make up the course is set inside the corner. Dutch corners end in the
    part bricks.

          Variations on these bonds are common in particular a header course every three or six courses
    with stretcher courses between. Although these bonds have traditionally been developed for thick walls,
    they can be used in single leaf walls asa decorative effect using cut bricks for the headers. Such walls are
    usually non-load bearing. Cutting costs are high but not excessive as the headers have the cut side
    turned in and the bricks can be bolstered.

          Other decorative bonds may be used in non-load bearing applications, particularly in the form of
    panels. The limitations are strengths lower than Stretcher Bond and the cost of cutting and slower brick
    laying. The decorative effect of bonds is highlighted by using a mortar in a contrasting color to the brick.

    Other bonds include:
       • Stack Bond – Bricks laid horizontally in vertical columns so all vertical joints align.
       • Soldier Stack Bond – Bricks laid vertically in vertical columns so all vertical joints align.
       • 1/3 Bond – Every course is offset by 1/3 of a brick.
       • Zigzag Bond, Vertical Zigzag Bond, 45˚ Stretcher Bond, Chevron Bond,
          Basket Weave Bond, 45˚ Basket Weave Bond and virtually any pattern that tessellates
           
 
Other decorative effects are available such as:
    •   Laying bands of bricks of the same color with different textures eg smooth faced and rock faced;
    •   Laying bands of bricks with different (contrasting or complimentary) colors;
    •   Corbelling (bricks set out from the wall);
    •   Racking (bricks set back into the wall);
    •   Quoining (corner bricks in different colors or set out from the wall);
    •   Soldiers above openings or as a single course;
    •   Copings on piers and parapet walls;
    •   Sills in different colors or textures, using sill bricks, etc.; or,

          In the late 1800’s bricks of contrasting colors were laid in patterns such as diamonds or crosses. A
    more subtle effect can be made by laying bricks with different textures or corbelling the bricks in these
    patterns.

    Combinations of the above effects can be used. Eg. An American Architect specified a corbelled course
    with the course on the next page to be laid in the darkest bricks selected from the packs delivered. The
    darker band accentuated the shadowing effect from the corbelled course.




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                         Brick Masonry Construction (continued)
                                            TECHNICAL ISSUE NO. TIS-002


Brick bonds and other decorative effects




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                             Brick Masonry Construction (continued)
                                                TECHNICAL ISSUE NO. TIS-002




Brick Coursing Height
 




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                         Brick Masonry Construction (continued)
                                            TECHNICAL ISSUE NO. TIS-002




Blending
       Blending refers to the process of mixing the bricks or pavers to evenly distribute the prod-
 uct colors across the entire finished wall or pavement. This is an important step whether the
 products you have delivered are a single color or are multi-colored.

       Our bricks and pavers are partially blended during the packing process in the factory. This
 is not sufficient to ensure a well blended job. Bricklayers and paving contractors must always
 blend or mix the product as it is being laid.

     1.Work from at least three open packs.
     2.Select the top brick or paver from the left of each pack.
     3.Work progressively from a corner across and down each pack in a diagonal pattern.
      Don’t unpack the bricks or pavers in horizontal layers.

      Be sure to inspect the product before laying. Product liability transfers to the purchaser
 once the units are installed.




  Well blended: These are the same bricks selected according to the blending instructions.
  This brick walll are beautifully blended.


Brick Storage
        Bricks stored on site should be covered and kept off the ground. Bricks may absorb ground water
 containing salts or colored minerals creating subsequent problems with staining. Bricks when laid satu-
 rated usually produce excessive efflorescence as the masonry dries. Saturated bricks may also adversely
 affect the mortar bond strength. Moving bricks around the site may cause chipping and excessive move-
 ment of packs should be avoided.




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                            Brick Masonry Construction (continued)
                                                TECHNICAL ISSUE NO. TIS-002


Laying Practices
Hand tools required and technique for Installing facing bricks
        Installing facing bricks needs extra care . It will be the final surface of your project. Creativity is also
a plus factor yet not really a vital. For your guidance, our gallery and brochure and catalogs images are
very helpful as reference. Otherwise you can ask our technical team for any technical support.

        The following tools can help and guide you to achieve a very nice finished project:




   Steel Knife                          Hand Brush                                  Steel Bar
   for grout neck trim-                 for stain removal and                       5 – 10mm round r
   ming and cleaning                    grout neck cleaner.                         square to keep uni-




             Rough rug                                                   Strong Brush
             for polishing wet mor-                                      For finishing, the sur-
             tar and tough stain.                                        face must be almost

Control Joints
Control joints must not be bridged by mortar or render. After laying the bricks or rendering, the joint must be
cleaned. Lumps of mortar or render can transfer forces across the closing joint and will cause the bricks to
crack (or spall). Control joints are usually constructed with a highly compressible material (in the form of a
sheet or rod) inserted to keep dirt and moisture from penetrating to the cavity. For aesthetic reasons a com-
pressible caulking material, matched to the mortar color, is usually applied on the outside. As the joint
closes, compressible caulking compounds may be extruded from the joint but incompressible ones may
damage the bricks. If extruded caulking compound is considered unsightly, it can be cut out and replaced or
the compound can be recessed during construction. Care must be taken when choosing a caulking com-
pound to ensure it is a highly compressible type that will survive for the design life of the building and not
discolor significantly. There are numerous suitable materials available and manufacturer’s recommenda-
tions should be sought.
Where a control joint has flexible masonry ties built in, a piece of the compressible material must be re-
moved to accommodate the tie.




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