Pozzolanic characteristics of pulverized incinerator bottom ash slag

Abstract

The latent hydraulic characteristics of slag derived from pulverized municipal solid waste incinerator bottom ash (MSWIBA) slag were investigated. The results indicate that the MSWIBA slag blended cement (SBC) pastes with a 10% and 20% cement replacement by slags generated from the bottom ash developed a 90-day compressive strength that was similar to that of ordinary Portland cement. From the pore size distribution, as shown by Mercury Intrusion Porosimetry results, it was found that, with increasing curing ages, the gel pores increased and the total porosity and number of capillary pores decreased – a result that shows that hydrates had filled the pores. X-ray diffraction analysis indicated that the hydrates in the slag blended cement pastes were mainly Ca(OH) 2, calcium silicate hydrate (C–S–H) gels and C–A–H salts, like those found in ordinary Portland cement paste. This indicates that the slag reacted with Ca(OH) 2 to form C–S–H and C–A–H. The reaction also led to the later development of strength in MSWIBA slag blended cement pastes. It can be concluded from the study results that municipal solid waste incinerator bottom ash can be processed by melting to recover reactive pozzolanic slag, which may then be used in SBC to partially replace cement.