Ordinary Portland Cement

3. Materials

This section will describe the materials that were used in the laboratory experiments that will be presented in this thesis.

3.1 Portland CEMENT

Portland cement is composed of a combination of limestone and either shale, clay, sand, or iron. These materials are ground and blended together and heated in a kiln from 2600o F to3000o F. This causes the materials to fuse together to create clinker. Cooled clinker is then ground with gypsum (CaSO4*2H20). The addition of gypsum controls the aluminate chemistry and the setting time of cement concrete. Portland cement reacts with water to form a paste that binds the aggregate particles together to form concrete.

Ordinary Portland Cement (OPC) of grade 53 is used in the project. The cement

Specific Gravity

3.1

2.

Normal Consistency

31 %

3.

Initial setting time

35 minutes

4.

Compressive Strength

7 days

28 days

29 N/mm2

54.5 N/mm2

3.2 AGGREGATES

3.2.1 Fine Aggregates

Fine aggregates are the aggregates which pass through the sieve of size 4.75 mm. Sand which is locally available and is free from any organic impurities is used. Which is further passed through IS sieve of 4.75 and retained on 150 micron IS sieve is used in the making of the concrete. The physical properties of fine aggregate like fineness modulus, specific gravity and Bulk density are tested in accordance with IS

S.no

Test

Observations

1.

Fineness Modulus

2.73

2.

Specific Gravity

2.65

3.

Bulk Density

1710

3.2.2 Coarse Aggregates

The aggregates whose size is bigger than 4.75mm i.e. which cannot pass through 4.75 mm IS sieve are all coarse aggregates. Coarse aggregates are crushed rocks. The crushed coarse aggregate of maximum size 12.5mm obtained from Gurgaon Crushing zone are used in the present study. The physical properties of coarse aggregate like fineness modulus, specific gravity and bulk density are tested in accordance with IS

S.no

Test

Observations

1.

Fineness Modulus

5.93

2.

Specific Gravity

2.80

3.

Bulk

Silica fume is a by-product resulting from the reduction of high-purity quartz with coal/coke in an electric arc furnace during the production of Silicon metal/Ferro-silicon alloys. The use of silica fume in concrete can achieve a lower permeability, which is good for the durability issues of bridge decks. However, it has a high hydration heat so that it has a higher tendency of plastic shrinkage cracking. Darwin et al. (2007) stated that when cast with a high-absorption coarse aggregate, the addition of silica fume results in a reduction in shrinkage at all ages. Mazloom et al. (2004) studied the replacement of cement with 0%, 6%, 10%, and 15% of silica fume and concluded that the percentage of silica fume replacement did not have a significant influence on the total shrinkage of concrete, but the autogenous shrinkage increased as the increase of silica fume

Silica fumes used in this project are obtained from a local dealer