Cement Concrete || Constituents Properties and Uses

Table of Contents

What is Cement Concrete?

Portland cement concrete is a mixture of Portland cement, water, coarse and fine aggregates, and admixtures proportioned to form a plastic mass capable of being cast, placed, or molded into forms that will harden to a solid mass. The desirable properties of plastic concrete are that it be workable, placeable, and non-segregating and that is set at the desired time. The hardened concrete should provide the desired service properties such as Strength ( compressive and flexural), Durability ( lack of cracks, resisting to thawing and freezing and resistance to chemical attacks, resistance to abrasion).

Cement concrete is important building material because of the following properties which are listed below:

1. Concrete can be molded into any size and shape.
2. It is possible to control and alter the properties of cement concrete.
3. Concrete possesses adequate plasticity for mechanical work
4. It is possible to mechanize its preparation and placing.

Fig. Cement Concrete

 

Constituents of Cement Concrete

The main constituents of cement concrete are as follows:

1. 1. Cement/Lime :

      Before the introduction of cement, lime was used as a binding material. Nowadays most of the cement concrete works in the building construction are done with Ordinary Portland Cement (OPC). But other special types of cement such as rapid hardening cement, high alumina cement are used under certain circumstances. The cement should compliance with all standard specifications.

   2. Fine Aggregates or Sand :

      When the particles of granular material are so fine that they pass through  4.7625 mm B.S. test sieve, it is called fine aggregate. Usually, natural river sand is used as a fine aggregate in concrete. Places where natural river sand is not available, finely crushed stone may be used as fine aggregates.

   3. Coarse Aggregates :

      Coarse Aggregates are the materials which are retained on 4.7625 mm size B.S. sieve. Broken stone from different sources is generally used as a coarse aggregate. For thin walls and slabs, the maximum size of coarse aggregates should be limited to one third the thickness of the section.

   4. Water :

      Water to be used in the concrete must be free from oils, acids, or alkalies. It should not contain items such as iron, vegetable matters, or other substances which is likely to harm concrete.

• Water acts as a lubricant for fine and coarse aggregate and cement.
• The water causes the hardening of cement through a process called Hydration.
• The water to cement ratio is the most critical factor in deciding the strength of concrete.