MOC Cement-Based Composites with Silica Filler and Wood Chips Ash Admixture

As Portland cement and cement-based materials are the most widespread materials in construction industry, there is a concern to develop and search cement alternative materials with similar or better functional properties and a lower negative environmental impact. Magnesium oxychloride cement (MOC) is considered as low-energy and low-carbon binder possessing some advantageous properties superior to Portland cement. Therefore, lightweight MOC-based composites were designed and tested in the presented study. As filler, silica sand was used in composition of control composite mix. Later, it was partially replaced with wood chips ash coming from bioenergy production from biomass. The chemical composition and morphology of wood chips ash were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analyses. For the hardened composites, bulk density, specific density, and total open porosity were measured. Among mechanical parameters, flexural and mechanical strengths were tested. The thermal performance of composites was studied using a transient hot disk method and the assessed parameters were thermal conductivity and volumetric heat capacity. The use of fly ash led to the great decrease in porosity compared to the control materials with silica sand as only filler. The mechanical strength of all developed materials was high. Both the compressive strength and flexural strength decreased the dosage of wood chips ash in composite mix. However, the decrease in mechanical resistance was lower than the send replacement ratio. It clearly proved assumption of filler function of fly ash, whereas its assumed reactivity with MOC cement components was not proven. The heat transport was partially mitigated by wood chips use, similarly as heat storage. Based on the obtained data, the developed composites were considered as alternative low-carbon materials possessing interesting functional properties for construction practice. Moreover, the reuse of by-product from biomass bioenergy treatment can be considered as an environmentally friendly solution for production of sustainable advanced building materials.