Investigation of the effect of zinc metal slag on the mechanical and micro structural properties of fly ash based geopolymer mortars

Slag waste generated during the purification of zinc metal causes various problems such as environmental pollution and storage. For effective management, these wastes need to be evaluated in different areas. In this study, the effect of slag from zinc production facilities on the mechanical and microstructural properties of mortar samples by adding 10%, 20%, 30%, 40% and 50% by weight instead of fly ash in geopolymers was investigated. Mortar mixtures were subjected to various tests such as workability, flexural strength, compressive strength, water absorption and void ratio. NaOH and Na2SiO3 were used as activators. Mortar mixtures containing NaOH with a liquid/binder ratio of 0.40 and mortar mixtures containing Na2SiO3 were subjected to thermal curing at 90°C for 24 hours. Flexural and compressive strength tests were carried out on 7 and 28 day old samples. 28-day-old samples were subjected to high temperature tests at 400°C, 600°C and 800°C. Phase analysis and microstructure analyzes were carried out on selected samples to evaluate the effect of slag wastes on geopolymer mortars. As a result of the tests, the flexural strength of sodium hydroxide mortars produced with slag varied between 3.0 MPa and 5.8 MPa after 28 days, and the compressive strength varied between 28.2 MPa and 45 MPa, and the flexural strength of sodium silicate mortars varied between 1.7 MPa and 4.9 MPa. It was determined that the compressive strength varied between 4.9 MPa and 14 MPa. High temperature tests (400, 600, 800 °C) revealed that mortar mixtures containing up to 30% slag achieved higher flexural and compressive strengths than mortar without slag. As the amount of slag in the mortar increased, water absorption and void rates also increased. These results show that slag waste can improve the physical and mechanical properties of geopolymers up to 30% usage.