The environmentally responsible disposal of slag originating from refuse-derived fuel produced via plasma gasification in MOC composites

Abstract

This paper presents a new approach in the research into new construction materials with a low CO₂ footprint, using magnesium oxychloride cement (MOC) as a matrix and plasma gasification slag from refuse-derived fuel (SRDF) combustion as a filler. As a first step of the experiment, SRDF was analyzed to determine its chemical and phase composition, particle size, microstructural and hygric properties, and heavy metals (HMs) content. After that, a series of experiments were conducted in which various types of MOC-based composites were synthesized and analyzed. Reference MOC sample was prepared with silica sand as a filler and in the samples containing SRDF, silica sand was replaced by SRDF in the amount of 50, 100, and 150 wt%. The prepared samples' microstructure, chemical and phase composition, mechanical properties, structural parameters, and water resistance were analyzed. For these purposes, XRD, XRF, OM, SEM, EDS, AAS, ICP-OES, and standardized tests for micro- and macrostructural, mechanical, and hygric parameters were used. The obtained results showed the positive influence of the addition of SRDF on the water resistance of the MOC-based composites manifested in reduced water uptake and absorption and an increase in the softening coefficient after immersion in water. Therefore, using SRDF as the sole filler, especially in significant quantities, positively impacted water resistance, effectively addressing the principal deficiency inherent in MOC-based materials. Moreover, the hazardous HMs present in SRDF were effectively immobilized within the structure of the synthesized composites. The replacement of sand with SRDF thus demonstrated the potential to realize both environmental and economic benefits in the domain of construction material production.