Preliminary investigation of geopolymer binder from waste materials

Abstract

Concrete produced from ordinary Portland cement (OPC), is a building material with wide applications, due to various factors, including strength and durability characteristics. Nevertheless, OPC concrete has a significant environmental impact due to resource consumption and energy intensive production of the cement as a result also of the high temperatures during manufacture. The main factors that affect the geopolymerisation process include the type and characteristics of the raw materials, the alkaline activators and the curing conditions. The optimum alkaline solution used and activator, to raw material mass ratio depend on the type and characteristics of the raw materials being used. Furthermore, the curing conditions adopted depends on the characteristics of the raw materials and activators. Industrial by-products and waste rich in SiO2 and Al2O3 can be utilized as raw material for geopolymer concrete. In this research, three different waste materials were considered: Polish coal burning fly ash (FA), Lithuanian biomass bottom ash (BMBA), AlF3 production waste (PW). Paste was produced to determine the influence of the Al2O3/Na2O ratio on the geopolymer paste properties. The material properties were determined for the curing conditions set with respect to X-Ray diffraction characterisation (XRD), Helium Pycnometry (HP) and Mercury Intrusion Porosimetry (MIP) and compressive strength. This research shows that, the three waste materials analysed, all have great potential for use as a geopolymer concrete, to varying degrees. It was further determined that the mix ratios and the curing environment are critical for the performance of the material in cast in situ and precast concrete applications.