Investigation of mechanical strength and permeability characteristics of pervious concrete mixed with coral aggregate and seawater

The availability of the conventional raw materials required to produce pervious concrete on sea islands remote from the mainland is lacking, which could be alleviated by utilizing marine resources. This study aimed to develop seawater coral aggregate pervious concrete (SCAPC) by utilizing coral waste and seawater and assess the potential application of this method to sea islands. The SCAPC specimens were designed with different coral aggregate sizes (2.36-4.75 mm, 4.75-9.5 mm) and aggregate/binder ratios (2, 2.5, 3), and the addition of 10 % of sea sand. The physical properties (hardened density and porosity), mechanical strengths (compressive and splitting tensile strengths), water permeability, and sulfate attack resistance were investigated. The failure sur-face under mechanical loading and the microtopography between matrix and coral aggregate of SCAPC samples were also characterized. The results showed that the compressive strength and water permeability coefficient of the resulting SCAPCs at 28 days with a porosity ranging from 16.9 % to 33.5 % could reach 6.2-18.5 MPa and 12.9-26.5 mm/s, respectively. This not only satisfied the ACI 522R-recommended values for pervious concrete applicable to pedestrian road areas, but the samples demonstrated excellent permeability. The SCAPC specimens manufactured with aggregate/binder ratios of 2.5 incorporating 10 % sea sand were found to achieve the required balance between compressive strength (11.8-12.5 MPa) and water permeability coefficient (19.6-20.9 mm/s). The failure patterns of the SCAPC samples presented a markedly different complete fracture of coral aggregate point from that of traditional aggregate pervious concrete, ascribing this variation to the characterized fragility of coral aggregate and intensified interfacial adhesion.