A Proposed New Mix Proportioning Method for Fly Ash-Based Geopolymer Concrete

Global warming on planet Earth results from the high emission of greenhouse gases, especially CO2. The Portland cement industry releases high amounts of CO2 and is responsible for about 5-8% of total emissions. Efforts have been made to look for alternative cementless binders to mitigate the impact on the environment. Geopolymers are one of the highlighted alternatives and can be obtained from the reaction of any aluminosilicate material with an alkaline solution. Aluminosilicate materials are found in byproduct materials such as fly ash. Geopolymer concrete is a promising environmentally friendly option. However, previous conventional mix proportioning methods for fly ash-based Geopolymer concrete have been limited. Most of these methods focused on a single weight ratio of SiO2/Na2O, which was 2. However, the sodium silicate solution is produced industrially with various concentrations depending on the weight ratio of SiO2/Na2O. Adding sodium hydroxide to the sodium silicate solution increases the alkalinity of the resulting activation liquid. This work proposes a new mix proportioning procedure named the "Ratio of the Resulting Sodium Silicate Method for Geopolymer Binder." The method has been successfully verified to achieve the desired compressive strength on the 7th and 28th days. We also tested different control specimens from previous studies using this new proposal to study the effect of different parameters on compressive strength predictions.