Rebound hammer test to predict in-situ strength of concrete using recycled concrete aggregates, brick chips and stone chips

This paper aims to investigate the performance of normal strength concrete with the use of rebound hammer, with particular emphasis on the influence of coarse aggregate. Existing codes provide guidelines for concrete using stone chips (SC). However, concrete using clay brick chips (CBC) and recycled concrete aggregates (RCA) behaves differently. Hence, the development of reliable estimation methods of compressive strength from rebound hammer is imperative for investigating the in-situ concrete quality of such concretes. Aggregate properties, mortar content and water cement ratio are used to explain the variation of compressive strength and rebound number for each type of concrete. The study suggests empirical expressions by correlating rebound number to actual compressive strength. Because of uncertainties involved and heterogeneous characteristics of concrete, a threefold cross-validation of the experimental data which includes a bi-objective approach was carried out in selecting the reliable correlation form for each concrete type. The correlations are also compared to results of previous studies as a means of validation. The study suggests a linear correlation for SC concrete whereas exponential and power based correlation for CBC and RCA concretes respectively. (C) 2020 Elsevier Ltd. All rights reserved.