Assessment of concrete compressive strength using the Lok test

This paper reports the results of a comprehensive investigation to assess the accuracy and predictability of the Lok test for estimation of the in situ compressive strength of concrete made with: (i) three water-to-cement ratios, (ii) two cement contents, and (iii) two types of local carbonate aggregates from eastern Saudi Arabia. The compressive strength of both cast and cored cylindrical specimens was statistically correlated with the Lok force. Based on a regression analysis of the generated data, the influence of the above mixture design variables on the compressive strength-Lok force correlation was assessed. The results of the statistical analyses compared well with those reported in the international literature. Among the linear, bi-linear, quadratic and cubic models used, the results indicated that the linear relationship between the compressive strength and the Lok force was very significant and totally independent of all the mixture design variables. Hence, the Lok test can be used in estimating the in situ compressive strength with a high degree of reliability.