Mechanical properties of coral concrete subjected to uniaxial dynamic compression

Abstract

The uniaxial compressive behavior of coral aggregate concrete was experimentally investigated under quasi-static to dynamic loading rates. Quasi-static compression tests of coral concrete at different curing ages were performed at a constant strain rate of 10−5 s−1 using an electro-hydraulic servo-controlled test machine. Dynamic impact loading tests were conducted at stain rates from 101.48 s−1 to 102.16 s−1 utilizing a 100-mm-diameter split Hopkinson pressure bar (SHPB) system. The strain rate effects on the mechanical properties of coral concrete were assessed in terms of the uniaxial compressive strength, energy dissipation, fractal dimension and failure pattern. The coral concrete exhibits high-early strength and the post-peak stress-strain curves behave in a more brittle manner than conventional concrete. A more remarkable rate-dependence in the compressive strength of coral concrete than other cement-based composites was observed as the dynamic increase factor (DIF) increased from 1.73 to 2.56 with the strain rate increasing from 30.12 s−1 to 143.32 s−1. Different from the failure pattern of conventional concrete, the fracture plane of coral concrete directly penetrated through the coral shingles rather than cracking in the interface between the cement mortar and the coarse aggregate under both quasi-static and dynamic loadings, ascribing to the low strength of coral aggregates and the high intensity of bonding interface. The ratio of the absorbed energy to incident energy is between 0.3–0.5 and tends to decrease with an increase in strain rate. A higher loading rate may lead to more energy absorption consumed by generating more fracture planes and smaller fragments, which is in consistent with a higher value of fractal dimension. The fractal dimension in the range of 2.027–2.302 for coral concrete was also found to be proportional to the logarithm of the loading strain rate.