Mixing of Ingredients of Concrete:

Various properties of concrete ingredients, factors influencing these properties and the role of these ingredients in governing the property of concrete have been described in detail in the earlier units. The process of manufacturing concrete passes through various stages, that is storing, batching and dry mixing of concrete ingredients, mixing of concrete ingredients with water, transporting and placing of fresh concrete mix, compacting and completing of concrete, etc. In order to produce good quality hardened concrete it is necessary to monitor these operations properly. Here, storing, batching and mixing of concrete ingredients and the associated issues have been discussed.

At any construction project, proper arrangement for storing these ingredients in adequate quantity is the prime requirement. All these ingredients should be so stored as to preserve their quality for use in the work because the quality of concrete is mainly governed by the quality of its ingredients. Batching is the measurement of these ingredients in desired proportion in successive batches. In the design mix concrete it is necessary to take the exact quantity of each and every ingredient so as to maintain the designed proportion of these ingredients.

There are two methods of batching namely, weigh batching and volume batching. Other important operation, in manufacturing of concrete, is mixing of these ingredients so as to ensure good workable concrete mix. The mixing method should be able to produce a uniform and homogeneous mass of fresh concrete so as to produce the good quality hardened concrete.

In this unit, storing, batching and mixing of concrete ingredients are discussed in detail. This includes various arrangements for storing cement and aggregates; batching of cement and water; weigh batching and volume batching of aggregates; hand mixing and machine mixing of concrete ingredients; various operations involved in the case of machine mixing; and finally the types of mixer commonly used for concrete mixing.

Objectives

After studying this unit, you should be able to

• appreciate the importance of storing, batching and mixing operations for manufacturing of concrete,
• list the necessary precautions to be observed during storing, batching and mixing operations,
• get acquainted with the various types of mixers commonly available now-a-days, and
• perform their duties of site engineer within a better way to produce good quality concrete.