Incorporation of glass powder and metakaolin as cement partial replacement to improve concrete mechanical properties and increase service life

Abstract

The search for the application of alternative materials, that can partially replace cement and increase the service life of concrete structures, is necessary from the environmental and technological point of view. In this context, the partial substitution of cement in concretes by pozzolanic additions can be performed as ternary mixtures, such as the combined incorporation of glass powder and metakaolin, enabling the reduction of cement consumption and the minimisation of the CO2 emissions and the natural resources consumption. Therefore, this research evaluated the incorporation of glass powder and metakaolin in an isolated and combined way, as partial substitutes for cement in concretes. The compressive strength and the chloride penetration resistance were evaluated by means of electrical resistivity, chloride permeability, steady-state chloride migration test and chloride diffusion test, obtaining the diffusivity and chloride contaminated depth by the colorimetric method. The alkali–silica reactivity test was also conducted, because of the alkali content of the waste glass being higher than the standard requirements. It was concluded that the combined use of ground glass powder and metakaolin in concrete allowed the replacement of up to 20% of the cement, promoting microstructural improvements and increasing properties related to durability and compressive strength already available at 28 days. Furthermore, it increased the estimated service life up to five times, working as an alternative for the reduction of cement use and concrete properties' improvement.