VOLUME BATCHING OF CONCRETE – WORKED OUT EXAMPLE

In my previous post I discussed with you about volume batching of concrete and how it is done in field.

Concret MIx
Dry Concrete Mix

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

 

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