Mechanical, durability properties, and environmental assessment of geopolymer mortars containing waste foundry sand

Today, with the expansion of industries and construction activities, attention to environmental issues such as sustainable development, recycling, reuse, etc. becomes important. The global demand for cement production has been increasing. One ton of cement releases about one ton of carbon dioxide into the atmosphere. Also, after freshwater, sand is considered the second natural resource that is consumed.Due to the limited sand resources and the concerns around the environmental issues of cement production, in this study, the use of waste foundry sand (WFS) as an alternative to aggregate in slag-based geopolymer mortars as an alternative to cement has been considered. WFS is a by-product of the foundry industry, which is produced in large quantities and buried in landfills, and slag is the by-product of iron and steel making process which is highly cementitious and high in calcium silicate hydrates (CSH).In this study, the mechanical, durability properties, and environmental assessment of geopolymer mortars using WFS were investigated. The results show that the compressive strength of geopolymer mortars containing treated WFS at the age of 91 days had an increase of 158% compared to cement-based mortars. The adhesion and flexural strength in geopolymer mortars containing treated WFS compared to untreated mortars increased by 145% and 18%, respectively. Toxicity characteristic leaching procedure (TCLP) results showed that the concentration of heavy metals in the leachate WFS, mortars containing treated and untreated WFS, and ground granulated blast-furnace (GGBF) slag was within the standard permitted limitations and WFS is not a hazardous waste.