Development of Blended Cements and Geopolymers Using Municipal Solid Waste Incineration Ash in the United Arab Emirates

Due to the population growth and economic activities, the per capita municipal solid waste (MSW) generation) in the UAE has significantly increased and reached 1.8 kg/day. The decision to implement the waste-to-energy plant would substantially reduce the large amount of MSW while generating energy. However, the incineration residue, known as municipal solid waste incineration ash (MSWI ash), remains a pressing environmental issue, as it is toxic and hazardous. The characteristics of MSWI ash vary from place to place, attributed to the difference in the waste streams, incineration technology, and recycling behavior. In the UAE, MSWI ash is currently disposed of in landfills or dumpsites, which adds to its adverse environmental impact. As such, it is necessary to develop novel and sustainable waste management techniques that can beneficially recycle this waste. Of these techniques, the blending of MSWI ash in cement or geopolymers has been promising in other places worldwide. Yet, its use in the UAE has not been investigated. Accordingly, this research aims to study the feasibility of the utilization of locally available MSWI ash in the production of MSWI ash blended cement and MSWI ash geopolymer composites. Different percentages of MSWI ash, namely 0, 5, 10, 15, and 20%, will be blended with ordinary Portland cement (OPC) to produce the MSWI ash blended cement. The MSWI ash geopolymer will be prepared either exclusively or in combination with a calcium-carrying waste, such as ladle slag, depending on its chemical composition. Different mix design parameters will be varied, including sodium hydroxide (SH) molarity, sodium silicate-to-sodium hydroxide (SS/SH) ratio, and alkaline activator solution-to-binder ratio (AAS/B), among others. The physical properties, chemical properties, and engineering performance of the MSWI ash blended cement and MSWI ash geopolymer will be assessed and compared with control specimens. The heavy metals leaching potential of the MSWI ash blended cement and MSWI ash geopolymer will also be examined to assess the heavy metal immobilization efficiency of the binder matrices. The optimum mix of the MSWI ash blended cement and MSWI ash geopolymer will be further evaluated by substituting the mining sand with the locally abundant desert dune sand at percentages of 0 and 100%. The environmental footprint and economic feasibility of the MSWI ash blended cement and MSWI ash geopolymer will be subsequently evaluated. Eventually, multi-criteria performance analysis will be employed to attain the optimum MSWI ash blended cement and MSWI ash geopolymer mixes that balance the engineering properties, environmental footprint, and economic cost.

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