Model for predicting the unit weight of cement-treated soils

Abstract

In this paper, a rational method for estimating the unit weight of cement-treated clay is proposed, which takes into account the relationship between the various phases and changes in these phases during curing. The simplest unit weight estimate is the unreacted unit weight which may be used as a lower-bound estimate of the cured unit weight. More accurate estimates of the unit-weight are possible by considering the effects of hydration of the cement-water paste during curing period, using the “drained” and “undrained” estimates of the unit weights. The drained and undrained assumptions refer to the drainage conditions during curing. Both are consistently closer to the measured unit weights than the unreacted unit weight, with undrained assumption having a slightly better agreement. An empirical relationship is also proposed for estimating the effect of the change of volume arising from consolidation during curing. This may be significant if the treated soil layer lies deep in the ground, where the effective stress levels are high. Comparison with unit weight measurements from a soil mixing project indicate that the calculated unit weight agrees well with the range of unit weight measurements for soft clay. For the loose sand, the calculated unit weight is higher than the measured unit weight, possibly owing to the dilation of sand when sheared, ahead of the mixing shaft.