Concrete has long been specified by nominal mixing (mixtures of fixed proportions that ensure sufficient strength) and applied arbitrarily with respect to the required strength of the concrete with water to ensure workability Was. But there are three modifiable factors to be considered for the desired strength mix:
- Water Cement Ratio and Stability of Fresh Concrete
- cement paste or cement aggregate ratio
- upgrade set
These above three inter-related factors should not be manipulated. Usually some of these factors are specified and others are adjusted to give maximum practicality and economy.
1. Water Cement Ratio and Consistency of Fresh Concrete
The water cement ratio dilutes the paste and the cement content varies directly with the amount of paste of the given dilution. The stability is established by the requirements of having and is not subject to manipulation of the ratio. This is given in terms of deceleration and it is recommended that mixtures of rigid consistency, which are effectively kept, can be adopted.
2. cement paste
Effort should be made to use minimum amount of paste in concrete. The paste volume ensures smoothness of the concrete mass when fresh and binds the aggregates and fills the gaps in them when hardening. An overdose of paste will result in:
- increased cost
- Greater drying shrinkage
- more likely to leak
- attack by weather action
3. upgrade set
To keep the paste used to a minimum, the classification of the aggregates used should be such that the spacing between them is relatively small. Although ideal grading is not possible, efforts should be made to mix fine and coarse aggregates in a ratio that requires minimal paste.