Influence of Water–Cement Ratio on the Hydraulic Behavior of an Artificially Cemented Sand

Abstract

In general, the prescription of the amount of water used in soil–cement mixtures is done to define the optimal compaction conditions for bases and sub-bases, or to ensure the fluidity necessary for a good mixture by injection. A better knowledge about the hydraulic behaviour of the resulting mixtures may be useful in service conditions, when permeability is important or when the layers are exposed to wetting and drying cycles. The relationship between saturated hydraulic permeability, coefficient of water absorption by capillarity and water retention properties were investigated for an artificially cemented sand prepared with different and realistic cement dosages, and with different water–cement ratios for each dosage. The water–cement ratio was considered in the analysis because it affects porosity and pore size distribution of the cement paste, and consequently tortuosity. Low values of this ratio mimic compacted sand–cement mixtures and large values simulate grouted sands. The dosages adopted simulate those used in pavement layers and obtained in grouted bodies. The results of an extensive set of experimental tests, performed to determine the hydraulic properties mentioned, are interpreted in the paper considering the presence and structure of the hardened cement paste. The materials prepared with low water–cement ratio have higher permeability and different water retention properties from those prepared with high ratios. Nevertheless, the water used in the hydration of the cement also affects the porosity and tortuosity of the hardened paste and may increase porosity if grout is very fluid. This study contributes to increase the knowledge about the effects of design parameters cement dosage and water–cement ratio on the hydraulic behaviour of the mixtures, which may be relevant when evaluating water retention and percolation.