I tested my compressive strength samples at 3, 7, 28, 56,91, 182, and 360 days for standard concrete and recycled aggregates concrete. Up to 56 days, standard concrete samples behave better than recycled, but at later ages, especially 182 and 360 days, recycled aggregate concrete is better in strength increment.
I think the strength of the concrete depends on inter-facial transition zone in the concrete. In recycled aggregate the matrix around the aggregates remain weak in the initial days and that depends on how much layer of cement matrix of the old concrete is left over the recycled aggregate.As the time span increases the gel starts reacting with unhydrated cement of previous layer and this may result in increase in strength.
Thank you, Dr. Om Prakash Chhangani sir for a nice technical discussion
Because the segregation potential decreases along with days due to the removal of moisture. This makes the bond between old concrete and RAs stronger, thus resulting the increased strength.
Because the adhesion of cement with aggregates gradually increases and they gradually form a rigid body, and this increases the flexural and compressive strength of concrete, but until when?
How long ?
I do agree with Dr. Om Prakash Chhangani. Secondary hydration may takes place after 56days. But Percentage increase in strength is significant or marginally which were not mentioned by Prof. Mohammad.
What do you mean by recycled aggregate concrete? Please explain more.
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