Performance evaluation of metakaolin geopolymer modified by different solid wastes

This paper investigated performance of metakaolin geopolymer (MGP) modified by fly ash, steel slag, and brake pad waste with the aim of reuse of industry solid wastes. The mechanical properties of MGP were measured at different mass contents of solid waste materials and curing conditions. The chemical resistance and immobilization ability for heavy metals were tested for pure and modified MGPs. The functional group composition, surface morphology, and amorphous microstructures of were characterized to evaluate the interaction between solid waste and MGP matrix in the geopolymerization process. The results showed that the addition of solid waste caused small fluctuations of compressive strength, but significant increase of bending strength as compared to pure MGP (except for the moist curing method). However, the modified MPGs showed the higher early-age strength. The modified MGPs presented relatively worse acid and alkali resistance compared to pure MGP, except the alkali resistance of MGP with 10% brake pad waste. The leaching test results showed that MGP had great immobilization ability to encapsulate heavy metals. The Fourier-Transform Infrared Spectroscopy (FTIR) test results indicated that after adding solid waste materials in MGP, the characteristic absorption peak of major function groups did not have significant changes. The Scanning Electron Microscope (SEM) images showed that the modified MGP had fewer cracks than the pure MGP. The X-ray Powder Diffraction (XRD) test results proved that all MGPs present amorphous microstructures. (C) 2019 Elsevier Ltd. All rights reserved.