Fracture properties and response surface methodology model of alkali-slag concrete under freeze–thaw cycles

Qixuan Li, Liangcai Cai, Yawei Fu, Haifu Wang, Yong Zou
  • Construction and Building Materials, September 2015, Elsevier
  • DOI: 10.1016/j.conbuildmat.2015.06.037

What is it about?

In this paper, response surface methodology and Design Expert software are used to study alkali-slag concrete(ASC) fracture toughness; the influence on fracture toughness from high to low is slag content, age and sol ratio, the interaction of slag content and age is the most significant; initiation fracture toughness is about 50%~70% of unstable fracture toughness, crack initiation should be the warning indicator of ASC structure; fracture toughness decreases with freeze-thaw times increasing, its declining rate and degree increase with sol ratio and slag content; increase of sol ratio reduces internal density and hinders depolymerization. Cementitious material content reduces ASC toughness.

Why is it important?

1.Response surface methodology is used to study ASC’s fracture toughness 2.The influence on fracture toughness from high to low is slag content, age and sol ratio, the interaction of slag content and age is the most significant. 3.Initiation fracture toughness is about 50%~70% of unstable fracture toughness, crack initiation should be the warning indicator of ASC structure. 4.Fracture toughness decreases with freeze-thaw times increasing, its declining rate and degree increase with sol ratio and slag content. 5.Increase of sol ratio reduces internal density and hinders depolymerization. Cementitious material content reduces ASC toughness.

Perspectives

Dr Qixuan Li (Author)
University of Auckland

Alkali-slag concrete(ASC) is prepared with Na2SiO3 and NaOH composite activator. Fracture properties of ASC under freeze-thaw condition are studied using response surface methodology(RSM), Design Expert software and Box-Benhnken design(BBD). The RSM model of fracture toughness is built, thus the influence law of sol ratio, slag content, age on fracture toughness and the relationship between initiation fracture toughness and unstable fracture toughness is established. The influence law of freeze-thaw, sol ratio and slag content under freeze-thaw on unstable fracture toughness is built. Then the impact mechanism of the two factors on unstable fracture toughness is analyzed. Results show that the RSM model fits well and can be used to analyze and predict ASC fracture toughness. The rank of three factors’ significance for unstable fracture toughness is slag content>age>sol ratio, and the most significant interaction is between slag content and age. Initiation fracture toughness is about 50%~70% of unstable fracture toughness, crack initiation should be the warning indicator of ASC structure. Fracture toughness decreases with the increasing of freeze-thaw times, its declining rate and degree increase with sol ratio and slag content. With sol ratio increasing, more intense is the alkali slag reaction, reducing internal density and hindering depolymerization. With more cementitious material content, effective water-cement ratio is relatively decreased, subsequent hydration is limited, some slag powder doesn’t participate in the reaction, reducing ASC toughness.

The following have contributed to this page: Dr Qixuan Li