Abstract
Introduction
The construction of offshore wind turbine foundations in the South China Sea faces exorbitant material transportation costs. While locally sourced coral aggregate concrete (CAC) offers an effective in-situ solution, the high water absorption of coral aggregates negatively impacts mechanical properties and durability. This study aims to develop a high-performance steel slag–silica fume composite coral concrete (SSCAC) to overcome these limitations.
Methods
A systematic investigation was conducted using an L9(3³) orthogonal experimental design. The effects of water-to-binder ratio (w/b: 0.25, 0.30, 0.35), silica fume content (2%, 5%, 8%), and steel slag content (2%, 5%, 8%) on workability (slump), mechanical properties (compressive and splitting tensile strength), and rapid chloride permeability were evaluated. Microstructural evolution was characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Results
Range analysis identified w/b as the dominant factor governing compressive strength, while silica fume content critically controlled workability and impermeability. The optimal mix proportion (S4: 5% silica fume, w/b 0.25, 5% steel slag) achieved a synergistic balance, exhibiting a high splitting tensile strength of 3.20 MPa and low chloride permeability (1842.3 C) without compromising construction applicability. SEM observations confirmed that SSCAC-4 possessed the smallest pore size and the tightest paste–aggregate interfacial bonding among all groups.
Discussion
The performance enhancement is attributed to a synergistic mechanism of "physical filling + chemical chloride binding + interfacial optimization." Silica fume underwent secondary hydration to form low Ca/Si ratio C–S–H gels, effectively refining pores and eliminating visible defects in the interfacial transition zone (ITZ). This research provides a theoretical basis and engineering guidance for the resource utilization of solid wastes and the durable, in-situ application of CAC in severe marine environments.