Effects of fineness on viscoelasticity of microfine cement-based grouts with fly ash, silica fume and superplasticiser

In geotechnical engineering, microfine cement-based grouts (MCGs) are used to ensure correct grouting of microcracks, medium-fine sands and so on. To determine the viscoelastic behaviour of MCG comprehensively and enhance its injectability, the viscosity variation characteristics of MCG suspensions need to be known. In this research, the new test method of ‘static viscosity’ was adopted and the synergistic effects of microfine cement (MC) fineness, water/solids (w/s) ratio and contents of microfine fly ash (MFA), silica fume (SF) and superplasticiser (SP) on the static viscosity of MCGs were studied comprehensively. The maximum MCG grain size was in the range 20–35 μm, the w/s ratio was varied from 0·8 to 3·0 and the contents of MFA, SF and SP were varied from 0 to 50%, 5 to 15% and 0 to 3·0%, respectively. The viscoelastic behaviours of the MCGs were determined by analysing the viscosity, hydration temperature, spreading ability and flowability of suspensions under different conditions. MCGs composed of blends of MC + MFA, MC + SF and MC + MFA + SF, with low initial viscosity and desirable viscoelastic properties, are discussed and recommended. The optimised viscoelastic behaviour, desirable spreading ability and flowability of MCGs can ensure their injectability, grouting effects and substitution for chemical solution in grouting applications, especially for small voids and microcracks.