Performance of normal-weight and lightweight 3D printed cementitious composites with recycled glass: Sorption and microstructural perspective

The development of sustainable mixtures has been a widely researched topic in the last decade, as the cement and concrete industries are among the most polluting sectors. Recycled materials can eliminate the need for extraction of natural materials through re-utilization of waste, reducing the environmental impact. To date, few studies have analyzed the effects of incorporating recycled glass aggregates on the water transport properties and microstructure of 3D printable mixtures. This study assesses the feasibility of incorporating recycled glass as a replacement for natural aggregate in 3D printable mixtures. For this purpose, three normal-weight and three lightweight mixtures containing 0, 50, and 100 vol.% of recycled glass aggregate as basalt aggregate replacement were evaluated in cast and printed samples. Expanded thermoplastic microspheres (ETM) were included to create the lightweight mixture composition. This experimental work evaluated the effects of incorporating recycled glass, ETM, and the impact of the printing process on the microstructure, sorption, and capillary water porosity (CWP). The printing process has proven to be an influential factor affecting the shape, size, and quantity of porosity. In addition, the printing process was demonstrated to be more influential on porosity formation than the inclusion of recycled glass or ETM. Incorporating recycled glass results in a slight decrease in the P Hg porosity, more spherical pores, and lower anisotropic tendency. Furthermore, adding ETM has a filling effect, leading to a more compact microstructure. • Incorporating recycled glass creates a micro-filling effect that slightly reduces the porosity (P Hg ). • ETM inclusion can lead to more compact microstructures acting as fillers. • The printing process could be the most influential factor in porosity formation. • The greatest variations in CWP and sorptivity are caused by either the printing process or the inclusion of ETM.