Strength (Compressive) of Concrete Made by Recyclable Concrete Aggregates after Six Hour Fire by Nondestructive Testing

Quality of concrete is mainly measured by evaluating its strength. Destructive testing of concrete specimens is used for the purpose. An alternative to it is the non-destructive testing. This research work presents non-destructive testing of concrete cylinders made by using partial replacement of natural coarse aggregates with old concrete as coarse aggregates and exposed to 6-hour fire at 1000ºC. Rebound hammer is used in this work to evaluate concrete strength. 240 concrete cylinders are cast using 1:2:4 mix and 0.54 water cement ratio. After 28-days curing half of the cylinders are exposed to fire in purpose made oven. Remaining 50% aggregates are used as control specimen to compare the results. After rebound hammer testing, all the cylinders are tested for compressive strength using universal testing machine. Comparison of the results shows the reliability of non-destructive testing and effectiveness of the rebound hammer technique as the difference between NDT and UTM results is maximum up to 4.7%.