Strength assessment of steel fibre reinforced recycled aggregate concrete by means of correlation between ultrasonic and point load tests

This paper aimed at assessing the in-situ strength of steel fibre reinforced concrete containing recycled coarse aggregate (RCA) using the correlation between ultrasonic and point load tests. The mechanical properties of recycled aggregate concrete can be improved by adding fibres in concrete mixes. On the other hand, the importance of strength estimation of existing concrete at the building site has led to use non-destructive and partially testing methods. So, in this research, the compressive strength of wet and dry cured mixes made with RCA and steel fibre (SF) at 1.5% by volume was evaluated by mean of point load test (PLT) and ultrasonic method. As per the experimental outputs, the standard deviation (SD) values increased up to 20% by increasing the substitution amount of natural aggregate with RCA from 50% to 100%. In addition, the point load index (PLI) of wet cured concrete mixes was obtained averagely about 14.3% more than that of dry cured concrete mixes. Furthermore, the strength estimation of conventional concrete or fibre reinforced recycled aggregate concrete at different ages was carried out using a two-variable equation between ultrasonic pulse velocity (UPV) and PLI values.