Mechanical properties of an eco-friendly one-part alkali-activated binder: Influence of metakaolin and water content

Abstract

Alkali-activated binder (AAB) is a product with lower carbon footprint and has great potential to be an alternative to Portland cement in civil construction. In this study, one-part AAB has been synthesized by mixing alternative sodium silicate powder, obtained from rice husk ash (RHA) and metakaolin (MK). The main objective was to verify the effect of MK (two types were used with different reactivity characteristics) and water content on the mechanical properties of pastes and mortars produced with the one-part AAB. Some tests were conducted (e.g. setting times, flexural and compressive strengths, elastic modulus) and the results indicated that the MK type and the water content directly affect different properties. As expected, the decrease in water content decreased the workability of the mortars and improved the mechanical strength. A more reactive MK provided an increase in compressive strength higher than 60%. The results confirm the possibility of producing an alternative sodium silicate powder from RHA dissolution, that when mixed with MK, results in AAB with acceptable compressive strength. This paper reveals that with the correct materials and a good mix design, the properties of this eco-friendly AAB can be considerably improved.