Synthesis and environmental impact assessment of sustainable geopolymer bricks incorporating vitrified tiles sludge powder.

Utilization of the by-products of the industries in the synthesis of the building materials is of research interest. The objective of the current study is to investigate the use of vitrified tiles sludge powder which is rich in oxides of silica and aluminium as one of the precursors along with fly ash in the synthesis of sustainable geopolymer bricks. The experimental work was carried out to optimize the amount of sludge powder and fly ash as precursors. Ten mix proportions were formulated by varying the molarity of NaOH (3, 6, 9 and 12 M), ratio of NaOH: Na2SiO3 (2 and 2.5) and vitrified tiles sludge powder to fly ash in the range of 10-50%. The specimens cast with the formulated mix proportions were analyzed for compressive strength, water absorption and bulk density, which are the crucial parameters pertaining to the study of bricks. Life cycle analysis was also carried out to assess and compare the environmental impact in terms of mid-point and endpoint categories. It was found that the brick containing vitrified tiles sludge to fly ash in the ratio of 50:50, cast with 6 M NaOH and 1:2 of NaOH to Na2SiO3 performed better in terms of strength (23 MPa) at 28 days and water absorption (less than 6%). The strength attainment may be attributed to the densification of matrix with the formation of hydration products such as C-A-S-H and N-A-S-H. It was also observed that geopolymer bricks showed zero impact towards climate change when compared to the cement brick contributing to about 100% towards climate change. In terms of mid-point categories, the optimum mix has shown minimal disturbance when compared to the cement bricks and other synthesized bricks. Hence the resulting green geopolymer brick can be used as construction material possessing significant physical and mechanical properties while also environmentally competent.