Question

In batching of aggregates the moisture content is expected to be in saturated surface dry condition. However, in a concrete production, the actual moisture content of coarse aggregate on the site just before the batching measured as 8%, and its saturated surface dry condition requires 5% moisture content. If 1000kg/m³ of coarse aggregate and 220kg/m³ of free water is needed for a concrete production, how many kg of coarse aggregate and water is to be placed into the mixer for one m³ of concrete production?

Answer 1

Solution:- the values given in the question are as follows:

actual moisture content of coarse aggregate on site just before batching=8%

surface saturated dry condition moisture of coarse aggregate=5%

coarse aggregate used for 1 m^3 of concrete=1000 kg

free water used for 1 m^3 of concrete=220 kg

according to question aggregate use for concreting is surface saturated dry coarse aggregate, but in this case we use the actual moisture content coarse aggregate. so the extra moisture is mixed in concrete.

extra moisture goes into concrete=actual moisture content of coarse aggregate on site just before batching-surface saturated dry condition moisture of coarse aggregate

extra moisture goes into concrete=8%-5%

extra moisture goes into concrete=4%

extra moisture goes into concrete=0.04 of dry coarse aggregate

moisture content=weight of water/weight of dry coarse aggregate

0.04=weight of water/1000

weight of water extra goes into concrete=0.04*1000

weight of water extra goes into concrete=40 kg

total weight of water used in 1 m^3 of concrete=220+40

total weight of water used in 1 m^3 of concrete=260 kg

actual weight of water used in 1 m^3 of concrete=260 kg

actual weight of coarse aggregate used in 1 m^3 of concrete=1000-weight of extra water used

actual weight of coarse aggregate used in 1 m^3 of concrete=1000-40

actual weight of coarse aggregate used in 1 m^3 of concrete=960 kg

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