Influence of maximum aggregate weight ratio on tensile strength and fracture toughness of concrete

Abstract

This study examines the influence of the weight percentage of large aggregates with maximum size dmax on the tensile strength and fracture toughness of concrete using a simple fracture mechanics model. The concrete mixes were grouped according to the content by weight of large aggregates with dmax of 15%, 30%, 45%, 60% and 100% relative to the total coarse aggregates. For each group, three-point bending (3-p-b) specimens with different crack/depth ratios (0.1, 0.2, 0.3 and 0.4) were used to extract the tensile strength and fracture toughness of the concrete mixes and link them to the aggregate compositions and weight percentage of large aggregates. A boundary effect model (BEM) was used for the fracture analysis, which considers the heterogeneous aggregate structures in concrete by using a discrete number. The fictitious crack growth Δafic at the peak load Pmax is linked to the discrete number β and the maximum aggregate size dmax. The results indicate that the fracture toughness and tensile strength from the BEM exhibited the highest value for the group of 45% large aggregates with dmax. At the same time, a similar trend was observed in the change in β with varying percentage of aggregates with dmax. The fact that the average value of β from different groups led to reasonable predictions about tensile strength, fracture toughness and thus the peak load for the 3-p-b beams reveals that the influence of the amount of large aggregates with dmax on β could be ignored.