Aggregates are generally classifieds in two categories:
Coarse Aggregates for Cement Concrete Works :
- The size of coarse aggregates defined as within range from 100 mm to 4.75 mm. Stone chips or stone ballast for cement concrete (plain or reinforced) shall be sufficiently hard, of uniform in size and fine texture and must be irregular. Free from faults or planes of weakness and free from weathered faces.
- The ballast or chips must be free from loam, clay or any surface coating, free from organic matter or other impurities and screened, free of dust. Stone aggregates from any sources may also be used provided the same is found suitable in the opinion of the Engineer-in-Charge.
- The ballast or chips shall be obtained by breaking from large blocks and must be more or less cubicle in shape.
Size of Coarse Aggregates : For any of the following nominal sizes of graded coarse aggregates, grading shall be in conformity with the requirements laid down with Standards Specification .
Generally 100 mm ,80 mm, 40 mm,20 mm, 10 mm, 5 mm size coarse aggregates is used for constructional work.
- Gravel, for use as coarse aggregates in cement concrete work must be hard, absolutely free from surface coating and on being broken, the fractured surface must indicate a uniform and fine texture free from lamination or planes or weakness. It shall be thoroughly washed and free from any foreign elements.
- Jhama chips for cement concrete work shall be obtained by breaking good quality Jhama bats, must not be spongy or with any coating of foreign materials and should be homogeneous in texture. The chips shall be more or less cubicle in shape.All coarse aggregates for concrete works must be well graded.
Coarse Aggregates for Lime concrete Works
(i) Brick aggregates for lime concrete in foundation or flooring shall consist of approved, clean, hard and well-burnt Jhama khoa. The khoa be well graded and unless otherwise specified shall pass through 32 mm. ring.
(ii) Brick aggregates for Lime Terracing work on roof shall consist of khoa broken from 1st class brick
bats and unless otherwise specified shall pass through 25 mm ring and be suitably graded.
SAND for constructional material
- Sand is generally classified as fine aggregates as size below 4.75 mm.All sand shall be clean sharp and free from clay, loam, organic or any other foreign matter, chemical reagents shall be obtained from approved source.
- The contractor shall get the sample of sand to be used in different kinds of works approved by the Engineer-in-Charge before using the same in work. Sand for all cement concrete work must be coarse. The sand shall pass through a mesh, 4.75 mm.
- Sand shall not be used for concrete works if it contains more than 10% of fine grains passing through a 76 mm mesh sieve as used for cement test, nor should the fineness
- modulus be less than 2.00 mm unless specific permission is obtained from the Engineer-in-Charge.
(iii) Medium sand may be used for cement mortar, for masonry, plaster etc. fineness modulus shall be
between 2 mm and 1.8 mm.