Although the terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is basically a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and Portland cement. The aggregates are sand and gravel or crushed stone; the paste is water and Portland cement. Concrete gets stronger as it gets older. Portland cement is not a brand name, but the generic term for the type of cement used in virtually all concrete, just as stainless is a type of steel and sterling a type of silver. Cement comprises from 10 to 15 percent of the concrete mix, by volume. Through a process called hydration, the cement and water harden and bind the aggregates into a rocklike mass. This hardening process continues for years meaning that concrete gets stronger as it gets older.

Curing is one of the most important steps in concrete construction, because proper curing greatly increases concrete strength and durability. Concrete hardens as a result of hydration the chemical reaction between cement and water. However, hydration occurs only if water is available and if the concrete’s temperature stays within a suitable range. During the curing period from five to seven days after placement for convectional concrete the concrete surface needs to be kept moist to permit the hydration process.

Good concrete can be obtained by using a wide variety of mix proportions if proper mix designs procedure

OPC means Ordinary Portland Cement, which contains mixture of Portland clinker and Gypsum ground to a very fine powder.

PPC means Portland Pozzolana Cement. It is manufactured by blending a mixture of Ordinary Portland cement and Pozzolana material such as Fly Ash, in proportions not less than 15% and not more than 35% by weight of cement. The fineness of PPC will be greater than OPC.