Rapid and reliable condition assessment of reinforced concrete structures in high seismicity regions is a priority task in estimating their seismic safety. Non-destructive testing (NDT) methods may contribute to the condition assessment practice by providing fast and reliable strength estimation while causing minimal or no damage to the structure. Drilling resistance is an NDT method that has been used for mechanical characterization of natural stone and wood by measuring the force response for constant penetration rate and rotational speed. This paper focuses on the relationship between drilling resistance and compressive strength of concrete, including when it is combined with other NDT methods. Concrete cube samples produced using 6 different concrete mixtures were tested. Correlation equations were then obtained using statistical analysis. The results reveal that it may be possible to reliably estimate the compressive strength of concrete using drilling resistance method.

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There is an urgent need for rapid and reliable condition assessment of existing reinforced concrete (RC) buildings as a basis for structural safety evaluation, especially in developing countries in seismic regions such as Turkey. Traditionally, RC structures are evaluated by taking core samples from a limited number of structural elements for concrete strength and performing spot checks for the steel reinforcement by removing the concrete cover. In-situ concrete strength is determined through compression testing of core samples. Through spot checks, conformance of the existing reinforcement with the structural drawings is evaluated and a reinforcement realization factor is calculated for use in the analyses. Even though these conventional methods are relatively more accurate and reliable for condition assessment of existing RC structures, they are destructive, involved, time taking, slow and expensive. Non-destructive testing (NDT) methods are proposed as a solution to this problem. Using NDT methods in conjunction with a relatively small number of core tests potentially allows for more rapid yet still reliable condition assessment of existing structures. In this paper, a critical evaluation of rapid and reliable condition assessment methods is made through investigations on an 18-story residential RC building as a case study. Investigation results show that using NDT helps achieve time and cost savings while allowing for reliable condition assessment of existing buildings, and promises further savings through continued research and development in this area.