The application of drillability properties in measuring the strength of hardened concrete

Abstract

The aim of this study is to establish a reliable equation to estimate the strength of in situ concrete from the results of a new non-destructive testing method that depends on measurements of the drilling penetration speed. Some previous studies used the same technique to determine the strength of other construction materials, such as rocks or marble. However, none of the previous studies attempted to use the drilling penetration speed method to estimate the strength of in situ concrete. In this study, a new drilling machine was designed, and all the factors that can affect the drilling speed were considered. In addition, the rebound hammer and ultrasonic pulse velocity tests were used to estimate the concrete strength for comparison with the new technique. Ten different concrete batches were prepared with different mix proportions; each batch consisted of twelve cubes with dimensions of 150x150x150 mm. Another thirty cubes for each mortar and cement paste with dimensions of 100x100x100 mm were cast for the calibration of the drill bit sharpness. Equations that were derived from the correlations between the drilling penetration speed and concrete strength using a 10 mm drill bit have high correlation coefficients; thus, these equations can be used to estimate the strength of concrete with high accuracy. The findings of this study show that the drilling test method can be used to estimate concrete strength in situ more accurately than the conventional non-destructive tests and without causing major structural damage to the concrete member being tested.