Document Type : Original Article
Department of Environmental Engineering, University of Tehran, Tehran, Iran
Today, concrete is the most widely used building material. Cement production releases about 7% of carbon dioxide gas into the atmosphere and increases greenhouse gases, so it seems necessary to use an alternative to Portland cement. In recent years, geopolymers (mineral polymers) have been proposed as a new environmentally friendly cement. Metakaolin, bentonite, zeolite, iron blast furnace slag and fly ash can be mentioned as aluminosilicate sources. In the field of geopolymer concrete construction, few articles have been working on the composition and effect of replacing aluminosilicate sources. In this experimental study, the effect of replacing slag aluminosilicate sources, class F fly ash and bentonite with proportions of 5-45% with metakaolin on the mechanical properties and durability of geopolymer concrete based on metakaolin was investigated. After making the samples, compressive, bending, tensile and carbonation tests were performed on the geopolymer concrete samples to obtain the optimal strength and carbonation depth of the samples. Also, to determine the validity of the tests, machine learning estimation analysis was performed on the samples. The findings showed that bentonite leads to a decrease in strength, while fly ash and slag lead to an increase in strength. The predicted R2 values showed the highest matching of the correlation matrix (more than 93%) for the pressure samples. In addition, the results of the tests showed that the metakaolin-based geopolymer concrete sample replaced with fly ash (35%) had a lower penetration depth (carbonation) and higher mechanical properties than other samples.