Waste glass as a precursor in alkali-activated materials: Mechanical, durability, and microstructural properties

The long-term characteristics and durability of alkali-activated mortars based on waste glass are crucial to better understand their performance in aggressive environments. In this regard, the performance of waste glass as a building material and its characteristics such as mechanical (compressive, flexural, and tensile strengths), durability (chloride migration coefficient, sulfate resistance, and drying shrinkage), and microstructural properties [x-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) with energy dispersive x-ray analysis (SEM/EDX)] were evaluated. For this purpose, the specimens with different amounts of silica modulus and Na2O content were prepared. The specimens were cured at 95 degrees C for 20 h and then kept at a relative humidity of 50% at room temperature until testing. The specimen with 10% Na2O and a silica modulus of 1.5 demonstrated the highest compressive, flexural, and tensile strengths. The specimens illustrated a lower chloride migration coefficient and lower expansion than the Portland cement one. By increasing both silica modulus and Na2O contents, the drying shrinkage of the specimens increased due to the presence of more free water. The microstructural results indicated that amorphous gels such as sodium aluminum silicate hydrate (N-A-S-H) and sodium (calcium) silicate aluminum hydrate [N-(C)-A-S-H] were formed. The results of this study signify the utilization possibility of waste glass as an eco-friendly material with desirable characteristics.