Prediction of cement suspension groutability based on sand hydraulic conductivity

Abstract

The experimental investigation reported herein aims toward the development of groutability prediction models based on the hydraulic conductivity of sand and other parameters affecting the groutability of cement suspensions. For the purposes of the present study, suspensions of three different cement types, each at four different gradations, having water to cement (W/C) ratios of 1, 2 and 3, by weight, were injected into dry and dense sand columns with a height of 36.5 cm. The tested cements cover the range from ordinary to microfine materials having nominal maximum grain sizes of 100, 40, 20 and 10 μm. Six uniform, clean sands with different grain sizes were used alone or mixed in various proportions to obtain 48 additional sands, with different gradations, for grouting. Suspension groutability is improved by increasing cement fineness and suspension W/C ratio or by decreasing apparent viscosity and is controlled by the hydraulic conductivity and the gradation of the sand. The groutability and filtration limits defined in the present study, are based on sand hydraulic conductivity and suspension apparent viscosity and depend on cement fineness and sand gradation. The best model developed by performing Binary Logistic Regression analyses of the injection test results is regarded as an efficient tool for the prediction of groutability of cement suspensions in sands with different gradations, as it exhibits a coefficient of multiple determination equal to 0.914 and estimates successfully the outcome of the injection tests available from this study and collected from other studies at a rate equal to 89% and 70.5%, respectively. © 2020