CONSTRUCTION - MATERIALS TESTING

Site Tests ~ the majority of materials and components arriving on site will conform to the minimum recommendations of the appropriate British Standard and therefore the only tests which need be applied are those of checking quantity received against amount stated on the delivery note, ensuring quality is as ordered and a visual inspection to reject damaged or broken goods. The latter should be recorded on the delivery note and entered in the site records. Certain site tests can however be carried out on some materials to establish specific data such as the moisture content of timber which can be read direct from a moisture meter.

Other simple site tests are given in the various British Standards to ascertain compliance with the recommendations, such as tests for dimensional tolerances and changes given in BS EN 771-1 and BS EN 772-16 which cover random sampling of clay bricks of up to 10 units. An alternative site test can be carried out by measuring a sample of 24 bricks taken at random from a delivered load thus:-

Site Test ~ apart from the test outlined on page 83 site tests on materials which are to be combined to form another material such as concrete can also be tested to establish certain properties which if not known could affect the consistency and/or quality of the final material.

Typical Example ~ Testing Sand for Bulking This data is required when batching concrete by volume † test made at commencement of mixing and if change in weather

Therefore volume of sand should be increased by 21% over that quoted in the specification NB. a given weight of saturated sand will occupy the same space as when dry but more space when damp

Silt Test for Sand ~ the object of this test is to ascertain the cleanliness of sand by establishing the percentage of silt present in a natural sand since too much silt will weaken the concrete

Obtaining Samples for Laboratory Testing ~ these tests may be required for checking aggregate grading by means of a sieve test, checking quality or checking for organic impurities but whatever the reason the sample must be truly representative of the whole:-

Concrete requires monitoring by means of tests to ensure that subsequent mixes are of the same consistency and this can be carried out on site by means of the slump test and in a laboratory by crushing test cubes to check that the cured concrete has obtained the required designed strength.

The slump cone is filled to a quarter depth and tamped 25 times - filling and tamping is repeated three more times until the cone is full and the top smoothed off. The cone is removed and the slump measured, for consistent mixes the slump should remain the same for all samples tested. Usual specification 50mm or 75mm slump.