Preparation of geopolymer concrete using Egyptian kaolin clay and the study of its environmental effects and economic cost

Abstract

Concrete is the basic building material in the world, and cement is the main material used in the production of concrete. However, there is an urgent need to reduce the consumption of cement, where cement production leads to 5–8% of global emissions of carbon dioxide. Geopolymer concrete is an innovative building material produced by alkaline activation of pozzolanic materials such as fly ash, granulated blast furnace slag, and kaolin clay. Geopolymers are widely used in the production of geopolymer concrete due to their ability to reduce carbon dioxide emissions and reduce high energy consumption. During the present study, the environmental impact of two strength grades (30 MPa and 40 MPa) of metakaolin geopolymer concrete (GPC) was evaluated to study its applicability in the construction sector. The kaolin clay extracted from the Aswan quarries was activated by a mixture of sodium hydroxide and sodium silicate solution. To introduce geopolymer concrete in the Egyptian industry sector, its environmental performance, together with its technical performance, should be competitive to the cement concrete used mainly for the time being. The cost of this new concrete system should also be evaluated. The environmental impact of GPC was evaluated and compared with cement concrete using life cycle assessment analysis and IMPACT 2002+ methodology. The cost of production was calculated for 1 m3 of geopolymer concrete and conventional cement concrete. Metakaolin geopolymer concrete achieved a high compressive strength of ~ 56 MPa, splitting tensile strength of 24 MPa, and modulus of elasticity of 8.5 MPa. The corrosion inhibition of metakaolin geopolymer concrete was ~ 80% better than that of conventional cement concrete. Geopolymer concrete achieved a reduction in global warming potential by 61% and improved the human health category by 9.4%. However, due to the heavy burdens of sodium silicate, the geopolymer concrete negatively affected the quality of the ecosystem by 68% and showed a slightly higher impact than cement concrete on the resource damage category for low strength grade of 30 MPa. The high cost of the basic ingredients of the geopolymer resulted in a high production cost of geopolymer concrete (~ 92 US$) that was three times that of cement concrete (~ 31 US$). Based on the environmental results, geopolymer concrete based on locally available metakaolin clay can be applied in the construction sector as a green alternative material for cement concrete.