Mechanical property, volume stability and microstructure of lightweight engineered cementitious composites (LECC) containing high-volume diatomite

Abstract

Due to the requirement of sustainable development, the number of coal-fired power plants has gradually decreased, resulting in insufficient supply of traditional supplementary cementitious materials (SCMs). In this study, diatomite is proposed to replace fly ash in the lightweight engineered cementitious composites (LECC), and mechanical properties, shrinkage deformation and microstructure of diatomite-modified LECC (D-LECC) are investigated. The results show that the incorporation of diatomite reduces compressive strength, tensile strength and tensile strain capacity of LECC because of reduction of hydration degree and increase of porosity. Meanwhile, incorporating extra water (EW) into diatomite further increases the amount of hydration products and compactness of D-LECC, so the D-LECC with EW has higher compressive strength, tensile strength and less tensile strain capacity in comparison without EW. Besides, compared to reference specimen, autogenous shrinkage of D-LECC increases due to the reduction of mixing water. As the EW is absorbed in diatomite, the autogenous shrinkage of D-LECC reduces because of the internal curing effect of EW. The 14-d autogenous shrinkage of F50E is 1151 μm/m, which reduces by 68.3 % of the autogenous shrinkage of F50. In the microstructure, incorporating diatomite decreases hydration degree and increases the porosity of sample. Meanwhile, incorporating EW into diatomite improves hydration degree and refines pore structure of D-LECC sample. Therefore, it is found that diatomite absorbing EW has a great potential to be incorporated into the LECC for solving the shortage reserves of traditional SCM.