Concrete mix design.
The process of selecting suitable ingredients of concrete and determining their relative amount is termed concrete mix design. This is done with the objective of producing concrete of required, strength, durability, and workability and economically as possible. The required performance of the concrete in two states Namely, the plastic state and the hardened state depend on the proportioning of the ingredient. However, the workability property of concrete becomes of a vital importance.
Effect of Concrete Mix Design.
Furthermore, the compressive strength of a hardened concrete is generally considered to be an index of its other properties. It also depends upon many factors. Example of the numerous factors includes quality and quantity of cement. Other factors include water and aggregates, batching and mixing, placing, compaction and curing. Materials, plants, and labour made up of the cost of concrete. The variations in the cost of materials arise from the fact that cement is several times costlier than the aggregates. For this reason, the aim is to produce a lean mix as possible.
Technical point of view of concrete mix design.
From a technical point of view, a rich mix design may lead to high shrinkage and cracking in the structural. Again, the evolution of high heat of hydration in mass concrete may also cause cracking in concrete. Therefore, the actual cost of concrete is related to the cost of the materials required. These materials are for producing a minimum mean strength. This strength is called characteristic strength that is specified by the designer of the structure. This also depends on the quality control measures. But there is no doubt that the quality control adds to the cost of concrete.
The extent of quality control is often an economic compromise and depends on the size and type of job. Labour cost depends on the workability of the mix. For example, a concrete of inadequate workability may result in a high cost of labour. This is due to obtain the degree of compaction with available equipment.
A requirement of concrete mix design.
The requirement which forms the basis of selection and proportioning of concrete mix ingredient are:
- The minimum compressive strength required from structural consideration.
- The adequate workability necessary for full compaction with the compacting equipment.
- Maximum water-cement ratio and maximum cement content to give adequate durability for a particular sit consideration
- Maximum cement content to avoid shrinkage cracking due to temperature cycle in mass concrete