Recycling of aluminosilicate solid wastes in a novel glass calcined clay cement (GC³)

Abstract

The limited availability of high-quality kaolin clay restricts the large-scale operation of limestone calcined clay cement (LC³) in concrete production, especially in these resource-scare coastal areas like Hong Kong and Singapore. In this study, locally abundant wastes of glass and marine clay were valorized to develop a novel glass calcined clay cement (GC³) as a promising alternative to LC³. The hydration behavior, mechanical strength, and durability of GC³ were investigated in terms of hydration heat, compressive strength, autogenous and drying shrinkages, chloride resistance, microstructure, and phase assemblages. The findings indicate that thermal–mechanical treatment can activate the pozzolanic reactivity of marine clay. The synergistic utilization of waste glass powder and calcined marine clay in GC³ system makes a limited contribution on early strength gain compared to the control LC³ system due to their limited early reactivities. Notably, the GC³ system exhibits excellent long-term strength, volume stability and chloride resistance due to the refined pore structure and the enhanced paste matrix with desirable hardness. These benefits can be attributed to the synergistic effects between alkali-rich waste glass powder and alumina-rich calcined marine clay, thereby contributing to the continuous formation of calcium aluminate silicate hydrate (C–A–S–H) phases. This study provides new insights for the development of novel low-carbon cement with a significantly reduced carbon footprint, thereby promoting its practical application.