The Effect of the Utilization of Sustainable Materials on Some Mechanical Properties of Geopolymer Mortar

Geopolymer concrete has been developed as a means of reducing carbon dioxide (CO₂) emissions due to concrete manufacturing, which account for around 5–10% of the total global CO₂ emissions. Additionally, this innovative material aims to utilize industrial waste as a sustainable resource. This study concentrates on developing a geopolymer mortar composition comprising 70% fly ash and 30% metakaolin. The mixture also includes 14 molars of sodium hydroxide, sodium silicate, saturated surface dry sand, water at a volume of 10% of the mix, and 1.5% superplasticizer. The solution-to-solid materials ratio was established at 0.55 while the ratio between sodium silicate and sodium hydroxide was established at 2.5:1. The geopolymer mortar was enhanced by rice husk fibers at varying volume percentages of 1%, 1.5%, and 2%. Additionally, waste paper, in the form of paper ash, was introduced as filler at a volume percentage of 5%. Following the demolding process, the specimens were cured in the controlled environment of an oven, with the temperature set at 60 °C for a period of 24 hr. Subsequently, the cured samples were stored for 7 and 28 days and then were tested. When different amounts of rice husk fibers were mixed in with a fixed amount of 5% paper ash, the flexural resistance of the geopolymer mortar increased significantly. After 7 days of curing, it was seen that the flexural strength experienced an increase of 4%, 13%, and 25%, and a further increase of 11%, 18%, and 31% after 28 days of curing. The results of the impact test showed a notable enhancement in impact resistance and energy absorption when incorporating paper ash and rice husk fibers. Specifically, the initial crack results exhibited a 50% rise, while the specimen failure after 28 days of curing showed a 66% improvement.