Multi-scale mechanical performance and Weibull statistical damage constitutive simulation on alkali activated mortar

The purpose of this study is to systematically explore the effect of fly ash (FA) replacement rate on the macro mechanical properties, microstructure and damage constitutive relationship of slag-fly ash based alkali activated mortar (S-FA-AA mortar) The results showed that mortar workability is significantly improved with increasing FA replacement rate, with a maximum expansion of 31%. However, the mechanical properties showed the opposite rule. The compressive and flexural strengths decreased significantly with increasing FA replacement rate. When FA was fully replaced, the strength decreased by more than 80%, but its later strength growth rate was significant. Microscopic SEM analysis showed that increasing the FA replacement rate led to more products transforming into N-A-S-H gel with a loose structure. Based on the test results, the Weibull distribution constitutive model of S-FA-AA mortar was established. The key parameters of the model were discussed and compared with the existing models. The model can provide a reference for the engineering application of alkali activated materials.