Effects of calcined dolomite on marine engineered geopolymer composites (EGC): Formation of denser matrix structures

Abstract

Enhancing matrix densification represents an effective strategy for improving the corrosion resistance of structural materials in marine environments. This study introduces calcined dolomite (CD) into engineered geopolymer composites (EGC) to achieve a denser matrix structure suitable for marine applications. A multi-scale investigation comprehensively analyzed the influence of CD incorporation on the mechanical performance, microstructure characteristics, and reaction mechanisms of the developed CD-EGC. Results showed that CD incorporation slightly enhanced compressive strength and tensile strain capacity while the average crack width remained stable. For matrix properties, CD induced the formation of brucite and hydrotalcite-like phases, which contributed to matrix densification and refinement of the pore structure. BSE analysis revealed that the CD grains were surrounded by dark rims, where hydrotalcite-like phase and C-(K-)A-S-H gel were highly cross-linked. The CD incorporation also increased the matrix Ca/Si ratio, promoting the formation of high-density C-(K-)A-S-H gel and consequently elevating the high-density/low-density gel ratio. However, at a CD content of 20 %, excessive brucite generation compromised matrix densification simultaneously. The findings of this study provided useful insights for designing and developing EGC with a denser matrix structure for marine infrastructures.

Keywords

• Engineered geopolymer composites (EGC)
• Strain-hardening geopolymer composites (SHGC)
• Calcined dolomite
• Microstructure
• Marine construction