Local ready mixed concrete : a critical view

Abstract

Concrete is an important component in the infrastructure and contributes in many different ways to our everyday surroundings. It is the most important building material, and is a mixture of cement, aggregates (gravel or crushed stone with sand), water and other supplementary materials. The ready mixed concrete industry manufactures concrete in small production units, widely dispersed in and around urban and sub-urban centres, and transports it in a freshly mixed, unhardened condition to the job site where it is ready for placing by the builder or contractor. Concrete was traditionally mixed on site, but two conflicting requirements had to be met, namely product, quality and cost. With ready mixed concrete, the industry takes advantage of central storage and bulk handling methods. The handling of materials in bulk has dominated the design of ready mixed concrete plants from the start. Therefore the equipment and labour forces are used in the most cos-effective way. In its ready mixed state, the concrete with a shelf life of only a few hours can only be transported for short distances, rarely more than a few tens of kilometers, before it has to be placed.