Concrete – Definition, Types & Composition in Civil Engineering

Concrete Technology

Concrete is a construction material composed of cement, fine aggregates, and coarse aggregates mixed with water. Concrete is used for the construction of foundations, columns, beams, slabs and also other load-bearing components. There are different kinds of binding material is used other than cement-like bitumen for asphalt concrete which is used for road construction.

Types of Concrete

Concrete is usually used in two types of construction, plain concrete, and reinforced concrete. In plain cement concrete (PCC), it is poured without the use of any type of reinforcement. This is used when the structural member is subjected only to the compressive forces and not for bending.
When a structural member is subjected to bending, reinforcements are required to hold up against tension forces structural member as it is very weak in tension compared to compression.

How to Make Concrete?

Concrete is made or mixed in proportions like 1:1.5:3, 1:2:4, and so on. There are two types of concrete blends nominal mix and design mix. The nominal mix is used for typical construction works such as small projects where a strength test is not needed. Most preferred nominal mix is in the proportion of 1:2:4.

Design mixed concrete are those for which mix proportions are finalized based on different lab tests on cylinder or cube for its compressive strength. This process is also called as mix design. These tests are conducted to find a suitable mix based upon locally available material to get the strength needed based on the structural design. A design mixed deals economy on use ingredients.

When suitable mix proportions are known, then its ingredients are mixed in the ratio as selected. Two methods are used for mixing, i.e. Hand Mixing or Machine Mixing.

Based on the quantity and quality required, a suitable method of mixing is selected. In the hand mixing, the ingredients are placed on a level surface and water is added and blended with hand tools. In machine mixing, various types of machines are used. In this case, the components are added in the required quantity to blend and produce fresh concrete.

When it is mixed adequately it is moved to the casting place and poured into formworks. Different types of formworks are available which as selected based on use. Poured concrete is allowed to be set in formworks for a specified time based on the type of structural member to gain sufficient strength.

After removal of formwork, curing is done by different methods to comprise the wetness loss because of evaporation. Hydration reaction needs wetness which is responsible for setting and strength gain. So, curing generally proceeds for minimum of 7 days after removal of formwork.