Course aggregate shall be prepared as single sized and blended to produce a normal size grading. The combined grading shall be within the appropriate grading limits laid down in BS 882 and as described below.
Course aggregate shall be prepared as single sized and blended to produce a normal size grading. The combined grading shall be within the appropriate grading limits laid down in BS 882 and as described below.
The gradation of fine aggregate shall be in accordance BS 882 and shall be crushed from Ras Al Khaimah. All-in aggregate shall be permitted for low-grade concrete only.
For normal use, aggregates shall consist of fine aggregates (those passing a 5 mm (3/16") sieve, and coarse aggregates (those retained on a 5 mm (3/16") sieve batched separately which, when combined together, give a grading curve which lies within the following limits:
Sieve Size% Size% Passing by wt.
Grading Percent
The amount of material passing BS 75 micron sieve in the combined aggregates when tested in accordance with BS 812 (wet sieving method) shall not exceed the following limits:-
- Fine aggregate - 3% by weight - Coarse aggregate - 1 % by weight 3000.7.3 COARSE AGGREGATE
All coarse aggregate for concrete shall conform to Standard Specifications for Concrete Aggregate ASTM Designation: C-33. Coarse aggregate shall consist of gravel, crushed gravel, or crushed stone, having hard, strong durable pieces, free from adherents. It shall not contain harmful materials such as iron pyrites, coal, mica, alkali, laminated materials, or any material which may attack the reinforcement, in such a form or in sufficient quantity to affect adversely the strength and durability of the Concrete. If necessary, coarse aggregate shall be washed to remove deleterious substances, and shall conform to the requirements of these specifications.
3000.7.3.1 Deleterious Substances
The amount of deleterious substances shall not exceed the following limits:
Max.Permissible
(length greater than 5 times
average thickness)...………. 4.0 - Other local deleterious
substances ...………. 0
- Shell content ……… 1.0
3000.7.3.2 Percentage of Wear
Coarse aggregate shall conform to the following requirements:
Percentage of wear. Los Angeles test, not more than ...30 30007.3.3 Soundness
When the coarse aggregate is subjected to five alternations of the sodium sulphate soundness test, the weighed loss shall not exceed 10 (ten) percent. In the event of failing to obtain a satisfactory result it shall be subjected to an alternate freezing thawing test.
Coarse aggregate, when tested according to the requirements of ASTM, shall meet the following gradation and shall be uniformly graded within the limits stated in Table I here below:
_________________________________________________________________
ASTM Percentage by Weight Passing
_______________________________________________________________
Grading Grading Grading
Any remedial treatment of surfaces shall be approved from the Engineer following inspection immediately after removing the form work and shall be carried out without delay. ''
Any concrete, the surface of which has been treated before being inspected by the engineer, shall be liable to rejection.
No claim of any sort will be admissible for carrying out any such repair work.
Finishes
All concrete surfaces which are not exposed (sawn form work ) are to be left as struck from the mould, except that any surfaces which are found to be honeycombed shall be made good as soon as they have been inspected by the Engineer.
The making good shall be done with a mixture of fine aggregate and cement in similar proportions to the concrete and as dry as possible.
All exposed concrete surfaces with wrought form work are to have a rubbed finish, which shall mean the application of rubs. The first rub shall be made after the removal of the forms; the surface shall be wetted and rubbed with a No. of 20 carborandum stone to remove all mould marks. The second rub shall be made when finishing the concrete work when the surface shall again be wetted, and rubbed with a No of 24 carborandum stone, excess paste being removed with a we brush.
The final surface shall be free from all irregularities and discoloration and shall be an even level surface.
If any honeycombing is found on exposed faces, the Engineer's decision as to whether the concrete shall be cut and replaced or made good shall be final.
30007.4 Fine Aggregate
All fine aggregate for concrete shall conform to Standard Specification for Concrete Aggregates of ASTM Designation: C-33 and also to the detailed requirements given Table 300A (appended here below). It shall not contain harmful materials such as iron pyrites, coal, mica, shale, alkali, coated grains, or similar laminated materials such as soft and flaky particles, or any material, which may attack the reinforcement, in such a form and in sufficient quantity to affect adversely the strength and durability of the concrete. Fine Aggregate passing sieve No. 4 shall not contain
any voided shells.
Fine aggregates shall be washed with clean water and sieved to remove deleterious substances and shall conform to the requirements of these specifications and as per Dubai Municipality requirements.
Fine aggregate from different sources of supply shall not be mixed or stored in one pile nor used alternately in the same class of construction or mix.
Table 300A two-thirds the intensity of the standard colour solution. (Not darker than Plate 2 as determined by the Standard Method of Test for Organic Impurities in Sands for Concrete of ASTM Designation: C-40.
Silt Not more than 2 percent.
Mortar strength Compression ratio not less than 95 percent.
Soundness Weighted average loss when subjected to 5 cycles of the soundness test using magnesium sulphate, not more than 10 percent.
Shrinkage The mean aggregate shrinkage test shall be of lowest shrinkage category given in category
given in table 1 of BRE Digest 35, 1968.
3000.7.5 Testing of Aggregates
All fine and coarse aggregates shall be imported from sources approved by the Engineer and shall be within the limits laid down in the table below in respect of contamination and reactivity:
Property Method test and Standard Maximum Limit (by %weight)
Fine Aggregates Natural Sand or
Clay Lumps ASTM C 142 Coarse Aggregate 1%
Fine Aggregate 1%
Organic ASTM C 40 Colour standard not darker
Impurities than Plate No. 3
Chlorides AS Cl Acid soluble Coarse Aggregate 0.0002 BS 812: Part 1 1 7 Fine Aggregate 0.0005 Sulphates as S03 Acid Soluble Coarse Aggregate 0.003
BS 812: Part 1 1 8 Fine Aggregate 0.003
Potential alkali If the total amount of potentially
reactivity ASTM C 289 reactive material exceeds 0.5 %
by weight of the total aggregate
the alkali in the cement
shall be restricted to 3 Kg/m3 of concrete
Innocuous
Chemical method ASTM C 289 Innocuous
of Cement
Aggregate ASTM C 227 6 month expansion, 0.1 % max
The tests and the maximum acceptable limits and samples taken for testing in accordance with the relative specified standards shall be as indicated in the table below:
Description Standard Maximum Limit (% by weight) Contamination and As detailed in the table above
Reactivity
Grading BS 812: Part 103 (Dry) As detailed under Aggregates
Surface texture Descriptive, BS 812 Limit not applicable Water absorption Weighing dry & saturated Coarse Aggregate 2 %
ASTM C 128 / C127 Fine Aggregate 2.3 % Soundness 5 Cycles ASTM C 88 MgSO40.12
Na3SO40.12
Drying shrinkage BS 812: Part 120 Shrinkage 0.0005 Shell content
Coarser than 1 0 mm
Size 2.36 & 5 mm BS 812 Part 106 maximum 0.05 Finer than 2.36 mm maximum 0.1 Particle shape
Flakiness index BS 812 Part 105.1 maximum 0.25 Elongation index Part 102.2 maximum 0.25 Specific Gravity ASTM C 128/C 127 Course & Fine aggregate 2.6 Mechanical 1 0% fines, BS 812: Part 1 1 1 Minimum 100 kN Properties Impact Value Part 112 30 %
Los Angeles abrasion test
(ASTM C-1 31 or C-535) 0.3
The contractor shall allow for frequent testing of aggregates as described in the table below. The Engineer might alter the frequency of testing depending on the condition of material delivered to site or at the concrete supplier yard.