Effect of Municipal Solid Waste Incineration Ash on Microstructure and Hydration Mechanism of Geopolymer Composites

Abstract

The geopolymerization process is an appropriate way of disposing of municipal solid waste incineration fly ash (MSWIFA), and possesses the advantages of immobilizing the heavy metals and making full use of its pozzolanic properties in manufacturing green, cementitious materials. In this study, coal fly ash (FA) and metakaolin (MK) were used to prepare a geopolymer composite, with MK partially replaced by different proportions of MSWIFA through the alkali-activation method. The microstructure and hydration mechanism of the geopolymer composites containing MSWIFA were investigated through mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and Fourier transform-infrared spectroscopy (FT-IR) tests; and the immobilization effect of the geopolymer paste on heavy metal ions was explored through inductively coupled plasma-atomic emission spectrometry (ICP-AES). The MIP analysis showed that the addition of MFARR had an overall degrading effect on the pore structure of the matrix. When the content of MSWIFA reached the maximum of 35%, the porosity and average pore diameter increased by 25% and 16%, respectively, corresponding to the case without MSWIFA. However, the pore size distribution exhibited an improving trend when the MFARR was increased from 15% to 25%. The SEM images revealed that the integrity of the micromorphology of the geopolymer mortar became weaker after adding MSWIFA. When the MSWIFA content was increased to 35%, the microstructural compactness decreased and more pores and microcracks appeared in the matrix. The FT-IR pattern study suggested that all the geopolymer composites had a similar internal structure, consisting of O-H, C-O, Si-O-Si, and Si-O-Al. The main component of the geopolymer paste hydrated at 28 d remained dominated by calcium silica-aluminate (C-A-S-H), when the MSWIFA ranged from 0% to 35%. Finally, the ICP-AES results showed that the leaching concentrations of the geopolymer paste of J-40 at 28 d for Cd, Cr, Cu, Pb, and Zn met the requirements of Chinese standards.

High-Performance Construction Materials: Latest Advances and Prospects

“…The geopolymerization process is an appropriate way of disposing of municipal solid waste incineration fly ash (MSWIFA). In Wang et al's [5] study, coal fly ash (FA) and metakaolin (MK) were used to prepare a geopolymer composite, with MK being partially replaced by different proportions of MSWIFA through the alkali-activation method. Their results showed that when the content of MSWIFA reached the maximum of 35%, the porosity and average pore diameter increased by 25% and 16%, respectively, compared with that without MSWIFA.…”

Experimental Study on the Strength and Hydration Products of Cement Mortar with Hybrid Recycled Powders Based Industrial-Construction Residue Cement Stabilization of Crushed Aggregate

“…The academic literature has emphasized the significance of reducing dependence on Portland cement as a crucial sustainability challenge within the construction sector. Consequently, prior research has dedicated considerable effort to identifying alternative or supplementary cementitious materials that can partially or completely substitute cement in civil engineering applications [ 2 , 3 ]. As a result, extensive research has been conducted to assess the viability of various typical industrial by-products, such as fly ash, glass, marble, coal-bottom ash, and others as partial replacements for Portland cement [ 4 , 5 ].…”

Application of Industrial Waste Materials by Alkaline Activation for Use as Geopolymer Binders

“…There is also the possibility of alkaline activation of other raw materials considered to be waste from mining, processing, and other industries, i.e., the energy industry. Examples of alkaline-activated raw materials that the researchers have used in their research include volcanic tuff [30,31], mine waste [32], or plasma waste [33][34][35]. Hypo slime (waste cellulose material from the paper industry) has proven to be a great alternative to replacing cement.…”