In my previous post I discussed with you about volume batching of concrete and how it is done in field.
Now let us solve an example, so that you become more confident in the field. In this example I have also tried o show you, how correction for bulking is applied and how correction of any surface moisture is applied.
Data Given
- Relative proportion of cement : sand : coarse aggregate is 1:2:4
- Water-cement ratio is 0.6
- Moisture content in fine aggregate (i.e. sand) is 6% by volume
- Moisture content in coarse aggregate is 1.5% by volume
- Bulking of fine aggregate is 20%
Solution
| Step-1-Calculating Volume of Dry material Required | |
| Ratio of materials by volume | =1:2:4 |
| Volume of one bag of cement | =35 litres |
| Volume of dry fine aggregate required | =35*2=70 litres |
| Volume of dry coarse aggregate required | =35*4=140 litres |
| Water-cement ratio | =0.60 |
| Total water required | =0.60*50=30 litres |
| Step-2-Applying Correction for Moisture Present in Aggregate | |
| Moisture percent in fine aggregate (F.A.) | =6% |
| Amount of moisture present in F.A. | =70*(6/100)=4.2 litres |
| Moisture percent in coarse aggregate (C.A.) | =1.5% |
| Amount of moisture present in C.A. | =140*(1.5/100)=2.1 litres |
| So extra amount of moisture present in C.A & F.A. | =4.2+2.1=6.3 litres |
| Net water to be added | =Total water-extra amount of water present as moisture content=30-6.3
=23.7 litres |
| Step-3-Applying Correction for Bulking of fine aggregate | |
| Bulking of fine aggregate | =20% of total volume of F.A.=70*(20/100)
=14 litres |
| Moist fine aggregate required | =70+14=84 litres |
This is the best according to study for the concrete bulking