AGGREGATES GENERAL REQUIREMENTS
1. Except as may be modified hereunder the aggregate (fine or coarse) for all types of concrete shall comply with BS 882 “CONCRETE AGGREGATES FROM NATURAL SOURCES” & shall also comply with Dubai municipality administrative order no. 143/91.
2. The aggregates used in the permanent works shall be naturally occurring or crushed materials obtained only from approved sources.
3. Before any material from a particular source is used, representative samples of fine & coarse aggregates shall be obtained & necessary tests & analyses shall be carried out to show that the samples comply with the specification. During the progress of the works, the grading & chemical characteristics may be checked at frequent intervals.
4. Before using the material in the works all the tests result shall be approved by the engineer. Part of each sample will be required for concrete trial mixes & part shall be retained for comparison with subsequent deliveries.
5. Sampling for testing & analysis shall be carried out, where applicable, in accordance with BS 812 Part 102.
6. The maximum size of the aggregate shall not be larger than 1/5 of the narrowest dimension between sides of the member for which the concrete is to be used & not larger than 3/4 of the maximum clear distance between reinforcing bars.
7. Fine aggregate shall be natural or crushed sand & beach sand shall not be permitted for use in concrete mixes.
8. Coarse aggregate shall be crushed aggregate obtained from a quarry approved by the engineer.
9. Unless otherwise authorized by the engineer, coarse aggregate shall be delivered to site in separate sizes according to the maximum specified aggregate size for each grade of concrete.
10. Aggregate shall meet the requirements of table I.
11. The frequency of testing of aggregates shall be in accordance with table ii or as directed by the engineer.
12. Aggregates shall contain no harmful material that will adversely affect the strength & durability of the concrete or attack steel reinforcement. Aggregates shall not be composed of or contain any materials likely to cause staining or otherwise to disfigure finished concrete surfaces.
13. The aggregate source shall not contain material that is potentially reactive to alkalis. Potential analysis of aggregates in accordance of ASTM C 294 & C 295 to identify the mineral constituents. Only the aggregate which is not susceptible to alkali aggregate reaction hall be used. These tests made by the Contractor.
14. Fine aggregates shall be natural sand, manufactured crushed rock, sand, or combination of both. Manufactured crushed rock sand does not include crushed rock fines which are by-products of course aggregate production. A combination of natural sand & manufactured crushed rock sand will only be permitted where the two materials are separately batched & where each separate material, with the exception of grading ,complies with the requirements of this specification.
LIMITS FOR PHYSICAL, CHEMICAL &MECHANICAL
PROPERTIES OF AGGREGATES FOR CONCRETE
NOTE 1: THERE IS NO REQUIREMENT OF SHELL CONTENT IN SANDS PASSING 02.36 MM SIZE SIEVE
LIMITS FOR PHYSICAL, CHEMICAL & MECHANICAL PROPERTIES OF AGGREGATES FOR CONCRETE
(TABLE I CONTINUE)
NOTE 2 : AGGREGATES MAY INITIALLY BE STRESSED FOR ITS REACTIVITY IN ACCORDANCE WITH ASTM C 289 & IF POTENTIAL REACTIVITY IS INDICATED, THEN MORTAR BAR TESTS IN ACCORDANCE WITH ASTM C 227 SHALL BE CARRIED OUT
FREQUENCY OF ROUTINE TESTS ON AGGREGATES
NOTE : DRYING SHRINKAGE & POTENTIAL REACTIVITY OF AGGREGATES SHALL BE DETERMINED INITIALLY AT THE START OF THE PROJECT OR WHENEVER THERE IS A CHANGE IN THE SOURCE OF SUPPLY
1. The gradation of fine aggregate shall be in accordance with BS 882 latest edition excluding grading designation F.
2. Each batch of aggregate delivered to site shall be kept separate from previous batches & shall be stored for at least 3 working days before use to allow inspection & tests to be carried out.
3. Fine aggregate shall be clean sharp natural & / or crushed sand & shall be within BS 882 zones c & m only.
4. Aggregate shall be mechanically washed to remove salts & other impurities in order to meet the requirement specified. ( contractor)
COARSE AGGREGATE FOR CONCRETE.
1. Coarse aggregate shall be prepared as single sized aggregate & blended to produce normal size grading. The combined grading shall be within the appropriate grading limits given in BS 882.
2. Aggregates that are deleteriously reactive with the alkalis in the cement in an amount sufficient to cause excessive expansion of concrete shall not be used.
3. Aggregate shall be mechanically washed to remove salts & other impurities in order to meet the requirement specified. ( contractor)
1. Approved coarse aggregate & fine aggregate in each batch shall be combined in proportions as specified in BS 882 & as approved by the engineer. However, in no case shall materials passing the 0.075 mm, sieve exceed 3% by wt. of the combined aggregate.
2. The combined aggregate gradation used in the work shall be as specified except when otherwise approved or directed by the Engineer. Changes from gradation to another shall not be made during progress of the work unless approved by the Engineer.
MATERIALS FOR STONE PITCHING
1. Stone for pitching shall be hard, sound, durable, stones as approved by the Engineer. Samples of the stone to be used shall be submitted to & approved by the engineer before any stone is placed.
2. The requirements for the properties of the stone shall comply with the following values in TABLE I.
3. The size & shape of the stones shall be such to allow for proper placement. The width of the stone shall not be less than one & one half ( 1-1/2 ) times their respective thickness & lengths of not less than two ( 2 ) times their respective widths. The minimum width shall be 100 mm.
1. The stones shall be arranged in such a way that the largest stones are at the bottom of the slope of the sub grade or base which is firm & well compacted. The stones shall be placed on a mortar bed.
Gabion shall consist of furnishing & placing wire mesh boxes rectangular in shape ( galvanized steel fabricated in double twisted woven hexagonal shape with wire diameter of 2.7 mm for mesh size of 8*10cm for boxes & of 2.2 mm of 6*8 cm for mattresses ),filled with clean & uniform rocks larger than the mesh openings in accordance of the following specifications.
1. The rock shall be greater than 150 mm in size
2. The rocks shall consist of clean solid rock non-friable & resistant to weathering & frost action meeting the following requirements:-
METHODS OF SOFT AREA TREATMENT
Alternative methods of soft area treatment which may be directed by the Engineer:-
1. Non friable Boulders of sizes between 150 - 300 mm shall be end dumped over the soft area & rolled until the area is stabilized to the satisfaction of the Engineer. Further stones of 10 - 70 mm size shall be rolled into the area until all the areas are leveled & well blinded.
2. Crushed rock material free from dirt, organic matter, shale & any other deleterious material. The acceptance criteria when graded according to BS812 Part 103 shall be as follows: