Energy and emissions analysis of fly ash based geopolymers

Abstract

Alkali activated aluminosilicates (geopolymers) have been of particular research interest in recent times as an alternative to ordinary Portland cement (OPC). The primary drivers for this interest are that geopolymers can take advantage of industrial by-products as raw materials and also can greatly reduce green house gases (GHG), in particular carbon dioxide (CO2) emissions. Analysis has been undertaken to calculate the embodied energy and related GHG emissions of the input materials often used to make geopolymers. Findings show the geopolymer pastes typically have a range of emissions between 100-800kg.CO2/t depending on the mixture used. This gives a more accurate procedure compared to existing predictions of 80-85% reduction in CO2 compared to ordinary Portland cement. This paper will provide a method for calculating the embodied energy and GHG emissions of fly ash based sodium hydroxide activated geopolymer. It gives emissions curves for various mix designs, helping the selection of appropriate mixtures for desired energy and emissions profiles. Additionally it makes clear the process for future studies and development to predict the potential emissions reduction possible by using geopolymer cements in place of ordinary Portland cement.