Mechanical properties of alkali-activated slag concrete mixed by seawater and sea sand

Abstract

The utilization of slag as an alternative to Portland cement in producing alkali-activated slag concrete (ASC) contributes to environmental protection. Replacement of freshwater and river sand by seawater and sea sand in concrete production is meaningful to island construction. Thus, the intention of this paper is to analyze the mechanical properties of ASC mixed by seawater and sea sand. Four types of ASC are prepared by considering the effects of seawater, sea sand and combination of the two constituents, respectively. Based on the SEM (scanning electron microscope) and XRD (X-ray diffraction) analysis, the seawater and sea sand are found to have some effect on the morphology and hydration products of the ASC. Therefore, the strengths of the four ASC are close to each other. The ASC with seawater or sea sand has slightly higher drying shrinkage but better resistance to chloride ion permeability. Moreover, bond performance of FRP (fiber-reinforced polymer) and steel bars to ASC is studied using pull-out tests. The short-term bond strength, interfacial shear rigidity and shear fracture energy of steel bars with ASC are apparently higher than those of FRP bars with ASC. But the ratios of the residual frictional stress to the bond strength are larger for the FRP bars. The bond strength and residual frictional stress in the ASC with sea water or sea sand are slightly higher and the largest shear fracture energy is observed in the ASC with the combination of sea water and sea sand.