A feasibility study of municipal solid waste leachate utilisation in concrete

Abstract

Water was replaced with raw municipal solid waste leachate in a concrete mix. Compared with the control specimen (prepared with freshwater), the hardened concrete specimen made with 100% leachate and cured in freshwater for 28 days showed reductions of 20% in ultrasonic pulse velocity and 45% in unconfined compressive strength. Scanning electron microscopy revealed that an increase in leachate content increased the microscopic pores and cracks within concrete owing to organic matter in the leachate. Heavy metals are contaminants in leachate and can leak from leachate-produced concrete. The toxicity characteristic leaching procedure revealed that the heavy metal leakage of the 100% leachate specimen was lower than the maximum permissible range. Furthermore, the use of leachate in fresh cement paste induced a 56 min delay in initial setting compared with the control specimen. Slump measurements performed 0, 30 and 60 min after concrete fabrication indicated that leachate addition could double the concrete slump as compared with the control specimen. This research provides basic information for the use of raw leachate in concrete mixes. Fresh and hardened concrete properties decreased with an increase in the percentage of leachate in the mix design. Replacement of tap water with 10% leachate satisfied the US standard for ready-mixed concrete. Further investigations are recommended to approve the use of leachate as a part of concrete mixing water.