Geopolymers are inorganic materials that result from the alkali activation of aluminosilicates. The aluminosilicates source materials can either occur naturally (e.g. kaolin, metakaolin, rice husk ash, volcanic rock powders) or produced by industrial processes (e.g. fly-ash, blast furnace slag). While the potential application of geopolymers as construction materials (e.g. concrete manufacturing and soil stabilization) has been studied in the past, their widespread use has been limited. This is mainly because the technology is still relatively new and research in this field is still emerging. However, the use of geopolymers in lieu of conventional binders (e.g. cement and lime) has substantial environmental advantages particularly in terms of the energy expended for their production and greenhouse gas emissions. The current trend to enhance sustainability practices in the construction industry has recently driven research in this area. This paper aims to offer a comprehensive overview of past studies on geopolymers synthesised from various precursors, the factors affecting geopolymerisation process, their microstructural characteristics as well as mechanical, chemical, thermal and environmental properties of geopolymers. Further, recent developments associated with the use of geopolymers as construction materials in civil engineering applications have also been discussed. Research findings show that geopolymers can achieve comparable or superior performance to conventional binders and/or concrete in terms of shear strength and durability but with a reduced environmental footprint.

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This is a repository copy of Development and evaluation of a novel geopolymer based on basalt rock waste and ground granulated blast furnace slag.

Basalt rock waste is a major industrial waste generated as a result of quarrying of rocks and artificial sand manufacturing for construction projects and its disposal can lead to several landfill hazards. However, it shows potential to be used as a source material for the manufacturing of geopolymers. This paper presents the triaxial stress-strain characteristics of a novel geopolymer developed from basalt rock waste considering partial replacement with ground granulated blast furnace slag (GGBFS) up to 30%. A detailed mix-design investigation revealed the optimum molarity (M) of the sodium hydroxide solution to be 8M whereas the optimum ratio (R) of sodium silicate to sodium hydroxide solution as 0.75. The axial stressstrain relationships were developed after a series of triaxial laboratory tests for low confining pressures (0 to 800 kPa) and Hoek cell tests for high confining pressures (1 to 5 MPa). A constitutive model predicting the complete stress-strain behaviour has been proposed. The geopolymer stress-strain behaviour shows some degree of similarity to Portland cement binder, however, differences such as increase in stiffness and reduction in ductility were observed. The scanning electron microscopy (SEM) images also suggested a dense geopolymer gel formation resulting in a homogeneous and compact microstructure. This study demonstrates that the innovative material proposed herein produced from industrial wastes has suitable characteristics to be used as an alternative and sustainable construction material.