Tests for Concrete to be performed on site
Tests are held at 28 days, 7 days and 3 days. Constituent of mix should be such that concrete can be transported, placed and finished easily without segregation.
- Workability – it is a property of fresh concrete and affects the finished product as it affects compaction.
- Need for workability – Imparted by the amount of useful internal work necessary to provide full compaction.
Optimum water varies for different methods of compaction
- i.e., more water – hand compaction – lower density
- less water – mechanized compaction – higher density
If we add more water, the workability may increase may increase but core has more voids
- 5% of more voids – reduces strength by 30%
- 2% of more voids – reduces strength by 10%
The voids result due to –
The entrapped air voids are caused by grading of fine aggregate.
Excess water evaporating later excess – (water) voids are due to increase in workability
Aim should be to have maximum density – therefore for maximum compaction, you will have to have optimum water cement ratio, at which both the type voids are at minimum.