Effect of mix proportions on rheology and permeability of cement grouts containing viscosity modifying admixture

This paper reports the effect of mix composition of grout on the fluidity, rheological behaviour and hydro-mechanical behaviour (permeability and compressibility). Factorial design was used in this investigation to assess the combined effects of the four mix composition parameters on fluidity, rheological properties, permeability and compressibility: water/binder ratio (W/B), percentage of limestone filler as replacement of cement (LF), dosage of viscosity modifying admixture (VMA), and dosage of superplasticiser (SP). To evaluate both the rheology of the cement grout and its hydro-mechanical behaviour, mini-slump test, Lombardi plate test, and forced bleeding test, coaxial rotating cylinder viscometer were used. A two-level fractional factorial model was used to model the effect of key variables on the fluidity, the cohesion, permeability and compressibility. The predicted models are valid for mixtures made with W/B ranged from 0.35 to 0.42, LF from 12% to 45% as replacement of cement, VMA (percentage of binder) from 0.02 to 0.7%, and SP from 0.3 to 1.2%. The effects of W/B, LF, VMA and SP were analysed using polynomial regression which can identify the primary factors and their interactions on the measured properties. Prediction models were developed for mini-slump, plate cohesion meter, permeability and compressibility as function of W/B, LF, VMA, and SP. The factorial statistical approach used highlighted the effect of W/B, the dosages of SP and VMA on the various rheological properties, permeability and compressibility.