Influence of calcium content on structure and strength of MSWI bottom ash-based geopolymer

Abstract

This study explored the strength limitations of municipal solid waste incineration (MSWI) bottom ash-based geopolymer, which can limit its use in building materials. The calcium content in MSWI bottom ash was increased by the addition of varying amounts of granulated blast furnace slag (GBFS) and calcium-containing chemicals. The results showed that the low calcium content of MSWI bottom ash in geopolymer was the main cause of insufficient polymerisation. Both GBFS and calcium-containing chemicals improved geopolymer microstructure and enhanced the degree of polymerisation, which clearly improved the compressive strength. However, further increases in geopolymer compressive strength were not significant when the GBFS content was greater than 40%, and the compressive strength decreased sharply when hydrated Ca(OH)2 content was greater than 5%.