Friday, December 9, 2011

Testing Concrete Aggregates

Here after is the specification for concrete aggregate testing in a hi-rise building construction.


Samples of the fine and coarse aggregates approved by the Engineer shall be kept on the Site and shall give a fair indication of the approved quality of the aggregate for comparison with the aggregate delivered during the course of the works.

Should a sample fail to comply with any of tests, the Engineer may at his own discretion reject the batch from which sample was taken, or order it to be washed and/or screened, or permit such to be used with variations in the proportions of the concrete mixes specified, all a the Contractor’s expense. Any batch of aggregate rejected by the Engineer shall be removed from the site forthwith and replaced entirely at the Contractor’s expense.

All sample and testing of aggregates shall be carried out in accordance with ASTM C33.

Preliminary Aggregate Tests

As soon as the source of supply of aggregate have been approved, the Contractor shall instruct the testing agency to carry out the following tests for compliance with “Specification of Concrete Aggregates” (ASTM C33).

Sieve analysis
Tests for clay, silt and dust content
Tests for organic impurities
Tests for salt content (chloride and sulfate ions)
The results of these tests shall be submitted for approval as soon as available. Test (1) and (2) with tests for the moisture content of each aggregate shall be carried out on the sample used for each trial mix.

Testing sampling of Aggregates

The contractors shall carry out such tests on aggregate samples as are necessary for the production of the specified concrete. The minimum incremental frequency of tests on each type of concrete used for the works shall be:

Sieve analysis: at least once weekly
Moisture content: at least once weekly
Tests for clay, silt and dust content: at least once fortnightlu
Tests for organic impurities: at least once monthly
Tests for salt content (chloride and sulfate ions): for every 500 cubic meters of concrete placed.
If for any reason the Engineer is not satisfied with the works concrete, he may instruct the Contractor to further increase the rate of sampling. Conversely, the rate of sampling may be reduce by the Engineer when consistent high quality been well established.


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