Impact of humidity and vegetable oil addition on mechanical properties and porosity of geopolymers

In this study, the effects of humidity and vegetable oil addition (3.6 wt% of the total mix) on the mechanical and microstructural properties of metakaolin-slag-based geopolymer materials were studied. Oil addition resulted in a significantly modified porous microstructure, dramatically reducing the specific inner surface as well as the gel and capillary porosity of the materials. Most importantly, this modification mitigated negative effects on material properties induced by desiccation. Results were used to adopt the fib Model Code from 2010 to obtain predictive values for mechanical properties for geopolymer materials which are essential for the design of composite structures with normal concrete. The promising results from this study may contribute to solving other well-known weaknesses of geopolymers, such as high drying shrinkage and other diffusion-related (durability) issues. These new findings highlight the potential of geopolymer-vegetable oil composites as a future high-tech and low-carbon construction material.