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WHAT ARE THE EFFECTS OF MAXIMUM SIZE OF AGGREGATE ON THE STRENGTH OF CONCRETE



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WHAT ARE THE EFFECTS OF MAXIMUM SIZE OF AGGREGATE ON THE STRENGTH OF CONCRETE

Effect of Maximum size of Aggregate on Strength:

At one time it was thought that the use of larger size aggregate leads to higher strength.
This was due to the fact that the larger the aggregate the lower is the total surface area and,
therefore, the lower is the requirement of water for the given workability. For this reason, a
lower water/cement ratio can be used which will result in higher strength.
WHAT ARE THE EFFECTS OF MAXIMUM SIZE OF AGGREGATE ON THE STRENGTH OF CONCRETE
However, later it was found that the use of larger size aggregate did not contribute to
higher strength as expected from the theoretical considerations due to the following reasons.
The larger maximum size aggregate gives lower surface area for developments of gel
bonds which is responsible for the lower strength of the concrete. Secondly bigger aggregate
size causes a more heterogeneity in the concrete which will prevent the uniform distribution
of load when stressed.
WHAT ARE THE EFFECTS OF MAXIMUM SIZE OF AGGREGATE ON THE STRENGTH OF CONCRETE
When large size aggregate is used, due to internal bleeding, the transition zone will
become much weaker due to the development of micro cracks which result in lower
compressive strength.

Generally, high strength concrete or rich concrete is adversely affected by the use of large
size aggregate. But in lean mixes or weaker concrete the influence of size of the aggregate
gets reduced. It is interesting to note that in lean mixes larger aggregate gives highest strength
while in rich mixes it is the smaller aggregate which yields higher strength. Fig.  1 shows
the influence of maximum size of aggregate on compressive strength of concrete. Fig. 2
depicts the influence of size of aggregate on compressive strength of concrete for different w/
c ratio.





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