Production of geopolymer on a laboratory scale

Abstract

The study of Geopolymer in current international research is booming, particularly since the year 2010. Historically, the use of alkali-activated materials in the field of civil engineering dates back to the 1950s in the former USSR, where Professor Glukhovsky developed a slag and alkali waste-based alternative cement to mitigate the Portland cement shortage that affected the country. Those buildings are still in place after nearly 50 years and have not encountered any significant durability problems. In 2013, the world’s first public building with structural ‘‘Geopolymer concrete” was built in Australia: the University of Queensland’s Global Change Institute (GCI). And, in November 2014, the first airport made with more than 30,000 cubic meters of a low carbon, cement-free Geopolymer concrete (Wagners’ Earth Friendly Concrete (EFC)) opened. The example of real constructions made with alkali-activated materials shows the interest and the viability of this Portland cementfree binder. This project deals with the synthesis of a Geopolymer material. It aims to find and test an optimum mix of Geopolymer concrete binder. This material is considered as an eco-friendly alternative that has lower carbon dioxide (CO2) emission than regular Portland cement. A simple synthesis method was adopted by mixing Metakaolin (MK) calcined at 700 °C with normalized sand and an alkali silicate solution of the desired Na2O/ SiO2 ratio. The experimental work applied in the Material Lab at the University of Balamand consisted of testing the mechanical properties of the several Geopolymer samples (4*4*4 cm) done in order to find the most adequate one. Variations in the water to binder ratio (W/B) and Na2O/ SiO2 ratios were done. These samples were tested for compressive strength at 3, 7 and 28 days. The results demonstrated that samples having a W/B of 1.8 and Na2O/ SiO2 of 1.5 presented the highest compressive strength (that even exceeded the one of the regular Portland cement mix).