Utilization of municipal solid waste incinerator fly ash as a partial cement replacement

Abstract

The research was conducted to investigate the physical properties, chemical and mineralogical compositions of municipal solid waste incineration (MSWI) fly ash collected from mass-bum incinerator in Phuket, Thailand. MSWI fly ash was used to replace cement for making fly ash-cement mortars. Mechanical properties of MSWI fly ash mortar under investigation included water requirement, setting time, and compressive strength. The development of hydration and pozzolanic reactions of fly ash-cement pastes was also conducted using X-ray diffraction (XRD) analysis. Solidified fly ash products were evaluated for their environmental safety by performing the leachate extraction procedure described in the Notification of Ministry of Industry No. 6 (1997). The experimental results indicated that MSWI fly ash could not be classified as a pozzolanic material according to ASTM C618 requirements. MSWI fly ash mortars showed slightly lower compressive strengths and longer setting times as well as required more water to obtain normal consistency than the control. MSWI fly ash can be used to directly replace Portland cement up to 15 percent by weight with a 1 : 2.75 ratio of binder to sand and a water to binder ratio of 0.485. The 28-day unconfined compressive strength of this optimum mortar mix possessed satisfactory strength of about 90% of the control. Finally, the amounts of all heavy metals in leachates of both MSWI fly ash and solidified MSWI fly ash products met the regulatory limits.