Strength and chloride ion distribution brought by aggregate of basalt fiber reinforced coral aggregate concrete

Abstract

Low strength of concrete and chloride attack introduced by coral aggregate limit the application of coral aggregate concrete (CAC) on the island far from the mainland. This investigation explores the effects of different amounts of basalt fiber (BF) on the Cl− distribution brought by coral aggregates, splitting tensile strength, and compressive strength in BF-reinforced CAC (BFRCAC). The CAC samples were fabricated incorporating four volume fractions of BF (0.05, 0.1, 0.15, and 0.2 vol%) and without BF which used as the contrast group. The theoretical total pore volume of BFRCAC was calculated on the basis of thermogravimetric (TG) and the hydration products of BFRCAC was analyzed by X-ray powder diffraction (XRD). Furthermore, the surface topography and role of BF in CAC was analyzed using scanning electron microscopy (SEM). The results indicated the compressive strength and splitting tensile strength of CAC were enhanced by incorporating BF, and the addition of 1.5 vol% or 2.0 vol% BF has a better impact. The inclusion of 0.05% BF accelerates the exudation of chloride ions from the coral aggregate. In contrast, a dosage of BF above 0.05% can suppress the exudation of chloride ions. The results of XRD and TG demonstrated the Cl− in CAC from coral aggregate combined in the shape of Friedel’s salt. SEM can observe the BF tightly bonded to the CAC and the microcracks were controlled by BF, which is contribute to reduce the exudation of chloride ions in the aggregate.