Influence of heterogeneity on size effect models and fracture characteristics of plain concrete

Abstract

Material heterogeneity strongly influences the fracture process zone in concrete, which is responsible for the exhibition of size effect in the nominal strength. The fundamental aspect in deriving the size effect law lies with the non-negligible process zone, which strongly correlates with the material heterogeneity size. Therefore, it is essential to establish the correlation between the size effect parameters and the heterogeneity size to predict fracture behaviour. In this work, detailed experimental investigations have been performed under the centre point loading of beams to evaluate the influence of heterogeneity on the fracture performance of plain concrete members through the DIC and AE techniques. A new definition of fully developed FPZ under monotonic loading has been proposed to occur between 95%–75% of the post-peak load. The effects of aggregate size on the fracture characteristics of concrete have been observed with reference to the work of fracture method (WFM), size effect law (SEL), and boundary effect method (BEM) and found in agreement with the existing literature. The existing size effect models, such as the size effect law and boundary effect model, have been modified by establishing the correlations between the model material parameters, namely, D0 and a∞ and the material heterogeneity. Finally, regression-based equations have been developed to establish the correlation between Lch, predicted through WFM, the effective lengths of fracture process zone, Cf of SEL, and Lch and a∞ of BEM. The applicability of the developed equations has been verified with the available experimental data from the literature.