Sulfate resistance of sustainable geopolymer mortars

Abstract

Nowadays, besides the important properties such as strength, durability and costs for construction materials, criterion such as environmental and sustainability have gained importance. For this reason, projects related to the production of cementless concrete especially in the academic field are being carried out. These well-meaning works take place in the media and create an expectation. In the concept of cementless concrete, Portland cement is generally replaced by geopolymers. Geopolymer represents one of the most effective environmental friendly alternatives to the conventional Portland cement binders. Reducing the need for cement, thus saving energy, bringing this waste by-product to the market, will help to reduce industrial and air pollution. In this study, the mechanical properties of geopolymer samples produced by using different amounts of fly ash and metakaolin were investigated with sodium and magnesium sulfate effects. 7 and 28 days compressive and flexural strength and ultrasonic pulse velocity results were investigated for 4 series samples with together unit weight, water absorption and porosity results. The highest yielding series sample was exposed to 10% magnesium and sodium sulfate solutions for up to 56 days. Geopolymer mortars were placed in an oven at 105 o C for 24 hours to improve absorption of sulfate ions before being exposed to the solutions. The results of weight change, ultrasonic pulse velocity, compressive and flexural strength after 14, 28 and 56 days immersion in each sulfate solution were compared.