Effect of mix component on the mechanical properties of coral concrete under axial compression

Typical influences of mix component on the properties of coral concrete (CC) were analyzed in this paper. Different types of fine aggregates (sea sand and river sand), mixing water (seawater and fresh water) and cementitious materials (cement and fly ash) were considered. An experimental system was developed involving uniaxial compression tests and the use of digital image correlation (DIC) method to investigate the deformation distribution and crack propagation of CC. The variations in failure pattern, strength and deformation of CC were studied. Test results indicated that the failure of CC adopting sea sand and seawater was brittle compared to CC using fresh water and river sand. It was found that axial stress-strain curve (SSC) of ordinary concrete (OC) was different from that of CC. The curvature and the descending slope of SSC obviously changed with the variation of mix components. The seawater improved the strength and elastic modulus of CC compared to fresh water, however, the effect of sea sand was negative. It was verified that prismatic compressive strength of CC with fly ash (FA) developed slowly in early stage, while it increased quickly in late stage. After using different types of aggregates, mixing water and cementitious materials, obvious changes were found in the crack propagation and the axial deformation distribution. However, typical influence of mix component on horizontal displacement distribution was negligible. The cracking of CC was seldom observed before the peak stress when compared to OC, and the seawater and sea sand accelerated the CC crack growth after the peak point. Finally, a numerical stressstrain expression of CC considering the influences of mix component was suggested, which could be used in the theoretical analysis and practical design. (C) 2019 Elsevier Ltd. All rights reserved.