MEASURING THE STRENGTH OF CONCRETE USING THREE DIFFERENT DRILLING TEST PARAMETERS

The aim of this study is to establish a new non-destructive test method that has better accuracy than the ordinary non-destructive tests that are used to estimate the strength of in situ concrete using the measured parameters from a drilling test. Some previous studies obtained highly reliable equations using the drilling test to measure the strength of different homogenous construction materials, i.e., mortar and clay bricks. However, none of the previous studies attempted to construct a reliable formula to measure the strength of in situ concrete. The test performed in this work focused on measuring the drilling penetration rate using two different drill bit diameters (10 mm and 14 mm). Two other measurements from the drilling test were included. A number of single and multiple regression analyses of the measured parameters were carried out to determine the most reliable equation. In this study, a new drilling machine was designed to measure the drilling penetration rate, the exerted total pressure, and the drilling rotational speed using concrete cubes of size 150 x 150 x 150 mm by considering all of the factors that influence the measurements of the drilling test. Ten different concrete batches were prepared to cover a wide range of concrete strength values. The findings of this study show that the most accurate and reliable equation was the one derived from the correlations between the drilling penetration speed and concrete strength using a 10-mm drill bit; this equation had the highest coefficient of determination value of 0.94. Therefore, the drillability test method could offer a more reliable alternative to the other non-destructive methods used to estimate the strength of in situ concrete.