Design method for the mix proportion of geopolymer concrete based on the paste thickness of coated aggregate

Abstract

Geopolymer is an environmental-friendly cementitious material, but few systematic designed methods for the mix proportion of geopolymer concrete have been developed due to the multitudinous factors. In this paper, a method for the mix proportion of the geopolymer concrete was proposed based on the paste thickness of coated aggregate and the close packing theory. In this method, the water-to-metakaolin ratio was selected based on the minimum water requirement method. Aggregate gradation was designed according to the close packing theory and the amount of metakaolin was determined by the paste thickness of coated aggregate. In addition, geopolymer concretes with the paste thickness of 10 μm, 20 μm and 30 μm were prepared by the alkali activated-metakaolin at ambient temperature, while the effect of the paste thickness on the compressive strength, sulphate attack and electrical resistivity of geopolymer were examined. Results showed that geopolymer concrete had a well fluidity and the strength degree of C30∼C50 can be achieved. Moreover, the relation among alkali content, modulus and compressive strength of geopolymer mortar was proposed.