Strength and durability of metakaolin-based geopolymer concrete

Abstract

Portland cement is the most popular material used in construction. It is characterized by exceptional thermal, mechanical and durability properties. It also has high availability around the world. However, an alarming amount of pollution and energy consumption is generated during its production. With the increase in the demand for cement and concrete construction, and the constant growth of the cement industry, these problems became much more significant and worrying. As stated by Li et al. (2020), the country that produces and consumes the highest amount of cement, the People’s Republic of China, found out that the highest emitter of hazardous air pollutants is its cement manufacturing industry, and since 1980, has been growing 10% year on year on average [1]. Therefore, cementitious materials having good mechanical properties, eco-friendly, and can withstand moderate to elevated temperatures have been the focus of scientists lately. Geopolymer is one of the new inorganic binders that has become the focus of scientists in the past decades. Geopolymer concrete can be produced using either a Potassium or Sodium based alkali activator (solution), sand (fine aggregates), and most importantly Metakaolin (binder). Throughout the years, the mechanical properties of geopolymer concrete have been studied, and it was mentioned by Singh et al. (2015) that very high compressive and tensile strengths have been attained, which indicates that it is a contestant that can replace Ordinary Portland cement [2]. The compressive and tensile strengths of geopolymer concrete samples have also been tested after exposure to ambient temperature by Zhang et al. (2014), and exhibited better results than the specimens made with ordinary Portland cement [3]. However, very few testing have been done on geopolymer concrete specimens after exposure to high temperature, especially geopolymer concrete made using Lebanese metakaolin. In addition to that, very few research concerning the effect of porosity on geopolymer concrete have been conducted. The aim of this study is firstly to create Lebanese metakaolin based geopolymer mixes, each having dissimilar porosities. The porosity in each mix can be altered by adding different amounts of a certain admixture. Then, each batch of specimens will be mechanically tested before and after exposure to high temperatures. This will allow us to study how both porosity and temperature affect the mechanical performance of GPC made with Lebanese and French metakaolin. In addition to that, the durability of geopolymer concrete will be tested in this research, by placing it in different environments replicating real life situations, such as saline water, acidic solutions and heat.