Recycling of pre-treated medical waste fly ash in mortar mixtures

This paper presents the results of an experimental investigation on the treatment of medical waste fly ash (MWFA) from heavy metals and the possibility of recycling it in mortar mixtures. Samples of MWFA were collected and treated to remove heavy metals. Mixtures of mortar were prepared using MWFA as a partial replacement for cement with different percentages ranging from 0 to 20% of the cement weight. Silica nanoparticles were added to the mortar mix to promote early strength development. Different characteristics of the MWFA-mortar were evaluated including microstructure, properties and compositions, workability, compressive and flexural strengths, and finally its ability to stabilize the heavy metal. The results showed that the ashes of MWFA have significant concentrations of heavy metals. Chemical pre-treatment using ethylene diaminetetra acetic acid disodium (EDTA) as a chelating agent was able to reduce the concentration of heavy metals to be below the allowable limits. The fresh and hardened properties of MWFA-mortar results showed that the workability of MWFA-mortar was not significantly affected by MWFA additions, and the compressive strength and the flexural strength values were acceptable up to 20% replacement. The leaching test results proved that the leachability of the heavy metals was reduced below the limits set by EPA.