Performance of waste glass powder as a pozzolanic material in blended cement mortar

In this study, the pozzolanic activity of finely ground waste glass powder (WGP) used as a partial cement replacement in mortars was investigated, and the WGP particle size, WGP content, and curing age were selected for analysis. Tests to determine the fluidity, compressive strength, scanning electron microscopy (SEM), energy dispersive X–ray spectroscopy (EDS), X–ray diffraction (XRD), Thermo–gravimetry analysis (TGA), Differential thermal gravity (DTG) and Fourier transform infrared spectroscopy (FTIR) were performed on a blended mortar. The results showed that when the WGP particle size was 20–44 μm and the WGP content was 20%, the fluidity of the slurry was higher than that of the control group, and the slurry exhibits good cohesion and water retention performance. When the WGP particle size ranges were 74–150 μm and 44–74 μm, the compressive strength of the blended mortar was smaller than that of the control group for all curing days regardless of the WGP content. When the WGP particle size was 20–44 μm, the compressive strength was lower than that of the control group at 7 d of curing, whereas it was 3.5% and 9.6% higher than that of the control group at 28 d and 90 d curing, respectively, with a WGP content 20%. When the WGP particle size was 15–20 μm, the compressive strength did not significantly increase compared with when the WGP particle size was 20–44 μm for the same WGP content, but slightly decreased. SEM and EDS showed that when the WGP particle size was 20–44 µm and the WGP content was 20%, the hydration products in the microstructure of the cement slurry were abundant, whereas pore cracks were few. This was additionally confirmed by XRD and TGA–DTG results, thereby verifying the formation of the lowest content of calcium hydroxide (CH) and the highest content of calcium silicate gel in the blended mortar. Variations in the Si–O and Al–O bond intensities shown in the FTIR spectrum supported this conclusion. Furthermore, the TGA–DTG results showed that the increase in calcium silicate gel content from 28 d to 90 d was higher than that from 7 d to 28 d, and that the activity of the WGP was more significant in the later curing period.