Determination of fracture parameters of coral aggregate concrete after immersion in seawater

Abstract

This paper is mainly concerned with the determination of fracture parameters of coral aggregate concrete (CAC) under different curing ages and conditions by virtue of three-pointbending tests. Four groups of CAC are tested. The first ones were cured for 56 days under standard environment and the second ones were immersed in seawater for 28 days after 28-day curing under standard environment. The third ones were cured for 118 days under standard environment and the fourth ones were immersed in seawater for 90 days after 28-day curing under standard environment. The initial crack length-to-beam depth ratios are set from 0.1 to 0.7 in each group. Results show that the failure modes of all the specimens are coral aggregate fracture without interfacial debonding between the aggregate and surrounding mortar. The maximum fracture load increases with the curing age. Besides, the beams cured by immersion in seawater have higher maximum facture loads compared to those cured under standard environment. Moreover, an analytical approach is proposed to determine the fracture parameters of CAC. The size-independent tensile strength and fracture toughness are obtained based on the boundary effect model by virtue of the experimentally determined maximum fracture loads. The analytically predicted maximum fracture loads are given related to the local fracture energy at the crack-tip region. The local fracture energy distribution and size-independent fracture energy can be obtained by the comparison between the analytical and experimental maximum fracture loads. It is found that the tensile strength increases with the curing age and becomes larger if the specimens were immersed in seawater for curing. But both the fracture toughness and fracture energy seem insensitive to the curing ages and conditions.