Ingredient of Concrete
The main Ingredient of Concrete are cement; fine aggregates, coarse aggregates, water and/or admixtures both chemical & minerals. pozzolanic materials like fly ash, ballast furnace slag & silica fumes etc are called as mineral admixtures, where to increase the work-ability and slump for given w/c ratio is known as chemical admixtures. The chemical admixtures should compatible with cement used. Cement and pozzolanic materials are called mineral admixtures and they are grouped as compendious material and they are listed in updated version of national & international codes.
The following types of cement can be use in pre-stress concrete as the Ingredient of Concrete.
- Ordinary Portland cement
- Portland slag cement but with not more than 50% slag cement.
- Rapid hardening Portland cement
- High strength ordinary Portland cement
The cement should confirm to the approved standard of various countries Is269, Is455, IS8041, and IS 8112 detailed out the specification for the above cement India.
All aggregates got out from igneous and metamorphic formation may be used as coarse aggregate and sediments of above finer particles may be used as fine aggregates but they should specify the requirement IS383 confirm by specific tests.
A national size of 20mm coarse aggregates may mostly satisfies these requirements in pre-stress concrete work.
Coarse aggregate shall be gap graded for proper adhesion of material.
Fine aggregate shall free from dust, lumps, soft flaky materials, mica and other deleterious material and their presences if at tall should be restricted so that they do not reduce the strength & durability of concrete or attach the embedded steel.
Water used in preparation of concrete should be potable and permissible limits of certain ingredients of water which could be use as guide line s in given in the following tables.
Permissible limits for solids in water
|Organic solid||200 mg/l|
|Inorganic solid||300 mg/l|
|Sulphate So4||400 mg/l|
|Chlorides||2000 mg/l for plain concrete and 500 mg/l for reinforced concrete|
|Suspended matters||2000 mg/l|
The PH value shall generally the not less than 6, whenever necessary tests should be done, mixing and curing with sea water shall not be permitted.
For Indian condition admixtures should confirm to IS 9103-1979 and should be with the approval of engineers in charge. The compatibility of the chemical admixtures with cement use is necessary and should be tested before use in construction. The testing should be done against the adverse effect of these admixtures on the basic properties of concrete in harden state. Use of admixtures containing in any form is totally prohibited