Evaluation of reclaimed municipal solid waste incinerator sands in concrete

Abstract

U.S. municipal solid waste incinerator (MSWI) ash is generally disposed of in landfills, due to the absence of approved avenues to repurpose the material through recycling. This work investigates the utilization of MSWI bottom ash sands in concrete that have been reclaimed from a recycling plant in Central Pennsylvania. Physical and chemical properties of the reclaimed sands are examined for suitability as a partial replacement for fine aggregates in concrete. The performance of raw incinerator ash vs. Reclaimed sands in concrete are compared through microstructure SEM analysis, shrinkage, compression strength, and hydrogen gas production due to metallic aluminum present in incinerator ash. It is found that reclaimed sands satisfy most ASTM requirements to be used as a lightweight concrete aggregate. Despite this, it is currently not recommend to use reclaimed sands in concrete due to the formation of empty holes in the cement matrix microstructure due to hydrogen gas production. These holes cause cracks in the concrete which leads to reduced structural capacity of the material. It is also not recommended that raw ash be used in concrete due to significant amounts of drying shrinkage, leaching concerns, and the unclean nature of the ash.