Currently, tons of high quality commercial glass are down-cycled or landfilled due to contaminants that prevent close-loop recycling. Yet, this glass is potentially a valuable resource for casting robust and aesthetically unique building components. Exploring the potential of this idea, different types of non-recyclable silicate glasses are kiln-cast into $$30\times 30\times 240$$ 30 × 30 × 240  mm beams, at relatively low temperatures (820–1120$$\,^{\circ }\hbox {C}$$ ∘ C ). The defects occurring in the glass specimens due to cullet contamination and the high viscosity of the glass melt, are documented and correlated to the casting parameters. Then, the kiln-cast specimens and industrially manufactured reference beams are tested in four-point bending, obtaining a flexural strength range of 9–72 MPa. The results are analysed according to the role of the chemical composition, level of contamination and followed casting parameters, in determining the flexural strength, the Young’s modulus and the prevailing strength-limiting flaw. Chemical compositions of favourable performance are highlighted, so as critical flaws responsible for a dramatic decrease in strength, up to 75%. The defects situated in the glass bulk, however, are tolerated by the glass network and have minor impact on flexural strength and Young’s modulus. The prerequisites for good quality recycled cast glass building components are identified and an outline for future research is provided.

In order to study the mechanical properties and micro-mechanism of industrial waste fly ash-reinforced cement calcareous sand (FCS), the triaxial unconsolidated undrained (UU) test and scanning electron microscope tests (SEM) were carried out on it. The results of UU test show that the peak stress and energy dissipation of the FCS sample first increase and then decrease with the increase in fly ash content. Fly ash enhances the cement calcareous sand by increasing both the cohesion and internal friction angle, and adding 10% content of fly ash gives the largest values. The SEM test results shows that the hydration products of cement and fly ash filled the pores and cracks on the surface of the calcareous sand, which increased the compactness and structure of the FCS samples. The porosity of cement calcareous sand can be reduced from 27.6% to 12.8% by adding 10% fly ash. A brittleness evaluation index based on energy dissipation is proposed to quantitatively characterize the brittleness of FCS samples. The results show that when the content of fly ash is 5%, the brittleness of FCS samples is the lowest. This study shows that the mechanical properties of cement calcareous sand can be effectively enhanced by adding the appropriate amount of fly ash.

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