Core strength of concrete using newly developed in situ compressive testing machine

Core tests are commonly used for the verification of the in situ compressive strength of concrete. Laboratory core testing (LCT) takes up to 5 d. A newly developed in situ compressive testing (ICT) machine, which reduces the time required for core testing from 4–5 d to 30 min by testing cores on site, was developed. Comparative studies were carried out between the proposed ICT and LCT on 54 core samples of 24 mm diameter and 36 samples each of 42 mm and 67 mm diameter with various height to diameter (H/D) ratios. Student's t-tests between the core strength results obtained by LCT and ICT indicated no significant difference between the two methods. The core strength was found to increase with a decrease in H/D ratio for a given core diameter, and the core strength increased with an increase in diameter for a given H/D ratio. The standard deviation of the results was found to increase with a decrease in core diameter. The same trends were observed in both LCT and ICT results, indicating that the proposed ICT machine can be used for testing concrete strength.