On drying shrinkage of geopolymer and how to mitigate it with vegetable oil

This study investigates the drying shrinkage behaviour of metakaolin-slag-based geopolymer across six distinct relative humidity levels: 33 %, 57 %, 65 %, 75 %, 88 %, and 99 %. Additionally, it explores the potential of vegetable oil as a drying shrinkage-reducing agent. To gain a comprehensive understanding, two drying regimes, stationary and cyclic drying and wetting, were employed. The highest shrinkage was recorded at ∼65 % RH. The incorporation of oil into geopolymer resulted in a noteworthy reduction of gel and small capillary pores, consequently reducing the material’s diffusion rates. This leads to substantially lower drying shrinkage and therefore minimizing the risk of cracking. Newly developed geopolymer-oil composites possess favourable characteristics for practical applications as highly durable and low-CO2 construction materials.