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					Lecture No. 06

Subject: Sources of
    Aggregates
     Objectives of Lecture
• To explain the sources of aggregates
  used for making concrete.
                Aggregates
• The total aggregates (fine aggregates + coarse
  aggregates) are used in concrete as filler and
  generally occupy 60 % to 75 % of the concrete
  volume (70 % to 85 % by weight).

• Fine aggregates generally consist of natural sand or
  crushed stone with most particles smaller than 0.2
  in.

• Coarse aggregates consist of one or a combination
  of gravels or crushed aggregate with particles
  predominantly larger than 0.2 in. and generally
  between ⅜ and 1½ in.
Fine Aggregates
Coarse Aggregates
          Sources of Aggregates

• Freshly mixed normal weight concrete (2200 to 2400 kg/m3)
  can be produced using:
• Natural gravel and sand are usually dug or dredged from a pit,
  river, lake, or seabed.

• Crushed aggregate is produced by crushing quarry rock,
  boulders, cobbles, or large size gravel.

• Crushed air-cooled blast-furnace slag is also used as fine or
  coarse aggregate.

• Recycled concrete, or crushed waste concrete, is a feasible
  source of aggregates and an economic reality where good
  quality aggregates are scarce.
• Various light weight materials such as expanded
  shale, clay, slate, and slag are used as aggregates
  for producing lightweight concrete (1350 to 1850
  kg/m3).

• Other lightweight materials such as pumice, scoria,
  perlite, vermiculite, and diatomite are used to
  produce insulating lightweight concretes (250 to
  1450 kg/m3).

• Heavy weight aggregates such as barlite, magnetite
  and iron are used to produce heavy weight concrete
  and radiation-shielding concrete.
      Lightweight Aggregates
• Expanded clay (left)

• Expanded shale
  (right)
        Constituents in Naturally
         Occurring Aggregates
• Naturally occurring concrete aggregates are a mixture of rocks
  and minerals (see Table 5-1)
   – Minerals
       • Silica (ex. Quartz)
       • Silicates (ex. Clay)
       • Carbonate (ex. Calcite, dolomite)
   – Igneous rocks
       • Granite
       • Basalt
   – Sedimentary rocks
       • Sandstone
       • Limestone
       • Shale
   – Metamorphic rocks
       • Marble
       • slate
Range of particle sizes found in
 aggregate for use in concrete
Making a sieve analysis test of
 coarse aggregate in a Lab
• Amount of cement
  paste required in
  concrete is greater
  than the volume of
  voids between the
  aggregates.
Fine aggregate grading limits
Type of aggregate and drying
         shrinkage
Harmful materials in aggregates
• Aggregates can
  occasionally contain
  particles of iron oxide
  and iron sulfide that
  result in stains on
  exposed concrete
  surface.
Cracking of concrete from alkali
        silica reactivity
Influence of Adding mineral admixture on
       alkali-silica reactivity (ASR)
Heavily reinforced concrete is
crushed with a beam-crusher
Recycled-concrete aggregate
     Local Aggregates Sources
    Eastern Province:

Fine aggregates:
• Most of the fine aggregate in the eastern province is dune sands with silica contents
   ranging from 79% to 98%.
Coarse Aggregates:

•  The coarse aggregates are limestone and they contain high content of calcite and
   some quartz.
Central Province:

Fine aggregates:

•  Good quality fine aggregates are available throughout the central province; they
   contain quartz, feldspar, and calcite. In general, the fine aggregates contain 82% to
   99% silica.
Coarse Aggregates:
• The coarse aggregates are limestone, diorite, and amphibolites. These
   aggregates contain calcite, quartz, and dolomite.
Western Province:

Fine aggregates:

• The fine aggregates contain quartz, feldspar, calcite, and
  mica. In general, the fine aggregates in the western
  region contain less silica (60% to 76%) compared to
  sands from eastern and central regions.
Coarse Aggregates:

• The coarse aggregates are amphibolites, hornblende
  diorite, etc. They contain about 50% SiO2.
• Unwashed local aggregate is the
  largest contributor of chlorides in
  concrete in the Gulf region. The local
  aggregate in the eastern region of
  Saudi Arabia is composed of crushed
  limestone which is usually porous,
  absorptive, relatively soft and
  excessively dusty. The dust and fines
  are heavily contaminated with sulfate
  and chloride salts.
 The following Tables present some test results on
          selected local coarse aggregates:
Table 1. Mineralogical composition of the selected coarse aggregates
               determined by X-ray diffraction technique.
  Sample #     Name of quarry     Location     Mineralogical composition, % by weight



                                               Calcium carbonate      Quartz (SiO2)
                                                     (CaCO3)


     1          Al-Suhaimi      Abu-Hadriyah          99.0                 1.0


     2            Al-Osais      Abu-Hadriyah          95.0                 5.0


     3           Al-Moosa          Hofuf              80.0                20.0
     4           Al-Aflaq          Hofuf              75.0                25.0
     5           Al-Muneer      Riyadh road           85.0                15.0


     6          Al-Summan       Riyadh road           75.0                25.0
Table 2.       Materials finer than ASTM # 200 sieve in
             the selected coarse aggregates.

Sample #     Name of      Location     Material finer than   Acceptable
               quarry                    ASTM No. 200           value, %
                                             sieve, %          [ASTM C
                                                               33, Saudi
                                                                Aramco]
   1       Al-Suhaimi   Abu-Hadriyah          0.50              1.0

   2       Al-Osais     Abu-Hadriyah          0.65

   3       Al-Moosa     Hofuf                 0.46
   4       Al-Aflaq     Hofuf                 0.17
   5       Al-Muneer    Riyadh road           0.20

   6       Al-Summan    Riyadh road           0.44
   Table 3.             Specific gravity and water absorption for the
                        selected coarse aggregates.


Sample #      Name of         Location     Specific Absorption,   Acceptable
                quarry                       gravity      %         value, %
                                                                     [Saudi
                                                                    Aramco]
   1       Al-Suhaimi       Abu-Hadriyah    2.52        2.32         2.5

   2       Al-Osais         Abu-Hadriyah    2.53        2.4

   3       Al-Moosa         Hofuf           2.43        1.80
   4       Al-Aflaq         Hofuf           2.45        1.2
   5       Al-Muneer        Riyadh road     2.59        1.06

   6       Al-Summan        Riyadh road      2.6        1.1
 Table 4.             Loss on abrasion in the selected coarse
                             aggregates.

Sample     Name of              Location   Loss on      Acceptable value,
   #         quarry                         abrasion,        % [Saudi
                                               %             Aramco]

  1      Al-Suhaimi     Abu-Hadriyah        32.40              40

  2      Al-Osais       Abu-Hadriyah        33.20
  3      Al-Moosa       Hofuf               35.05

  4      Al-Aflaq       Hofuf               25.89
  5      Al-Muneer      Riyadh road         23.66

  6      Al-Summan      Riyadh road         22.60
Table 5.                Chloride and sulfate concentrations in the
                        selected coarse aggregates.

Sample #    Name of       Location     Chloride     Allowable      Sulfate        Allowable
              quarry                     concen-       chloride    concentratio       sulfate
                                         tration,    concentrati      n, %             conce
                                            %           on, %                            n-
                                                        [Saudi                        tration
                                                       Aramco]                          ,%
                                                                                      [Saudi
                                                                                      Aramc
                                                                                         o]
   1       Al-Suhaimi   Abu-Hadriyah    0.066         0.03         0.206

   2       Al-Osais     Abu-Hadriyah    0.028                      0.059             0.4


   3       Al-Moosa     Hofuf           0.026                      0.083

   4       Al-Aflaq     Hofuf           0.011                      0.035
   5       Al-Muneer    Riyadh road     0.017                      0.059

   6       Al-Summan    Riyadh road     0.022                      0.067
                   In conclusion
• Tests conducted on the selected coarse aggregates indicated that
  the quality of coarse aggregates from quarries on the Riyadh road is
  relatively better than the coarse aggregates from quarries in Hofuf
  and Abu-Hadriyah.

• The quantity of fine materials in all the coarse aggregates was less
  than the allowable value of 1%. However, the quantity of fine
  materials in the coarse aggregates from quarries in Abu-Hadriyah
  was more than that in the coarse aggregates from quarries in Hofuf
  and on the Riyadh road.

• The loss on abrasion in all the coarse aggregates was less than the
  allowable value of 40%. The loss on abrasion in the coarse
  aggregates from quarries in Abu-Hadriyah was generally more than
  that in the coarse aggregates from quarries in Hofuf and on the
  Riyadh road.
               In conclusion
• The water absorption in the coarse aggregates from
  quarries in Abu-Hadriyah was more than that in the
  coarse aggregates from quarries in Hofuf and on the
  Riyadh road.

• The chloride concentration in the coarse aggregates
  from the Al-Suhaimi quarry in Abu-Hadriyah was two
  times the allowable value of 0.03%, while in other
  coarse aggregates, the chloride concentration was
  less than the threshold value.

• The sulfate concentration in all the coarse
  aggregates was less than the value specified by the
  Saudi Aramco specifications.

				
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posted:9/26/2011
language:English
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