4.1.4 Aggregate
Aggregates shall comply with the requirements of IS
383. As far as possible reference shall be given to
natural aggregate. Aggregates are the important
constituents in concrete. They give body to the
concrete, reduce shrinkage and effect economy. One of
the most important factors for producing workable
concrete is good gradation of aggregates. Good grading
implies that a sample fractions of aggregates in
required proportion such that the sample contains
minimum voids. Samples of the well graded aggregates
containing minimum voids require minimum paste to
fill up the voids in the aggregates. Minimum paste will
mean less quantity of cement and Minimum paste will
mean less quantity of cement and less water, which will
further mean increased economy, higher strength,
lower shrinkage and greater durability. Aggregate
comprises about 55% of the volume of mortar and
about 85% volume of mass concrete. Mortar consists
size of 4.75mm and concrete contains aggregates up to
a maximum size of 150mm.The fractions from 80 mm
to 4.75 mm are termed as coarse aggregates. Those
fractions from 4.75 mm to 150 microns are termed as
fine aggregates. For most work, 20 mm aggregates are
suitable.
Specific gravity of fine aggregate = 2.38
Specific gravity of coarse aggregate = 2.71
4.1.5 Water
Water is an important ingredient of
concrete as it actually participates in the chemical
reaction with cement. Since it helps to form the
strength giving cement gel, the quantity and quality of
water is required to be looked into very carefully.
Water used for mixing and curing shall be clean and
free from materials like oils, acids, alkalis, salts, sugar,
organic materials or other materials that may be
harmful to concrete or steel. pH value of the water used
in concreting shall not be less than 6
4.1.6 Steel
Steel is important ingredient of qualify structure and it
is used to carry out the load easily from the structure to
column and it is having high tensile strength. It is
preferred according IS 800-2007