Investigation on fundamental properties of microfine cement and cement-slag grouts

To ensure excellent rheological behavior, penetrability and mechanical property of microfine cement (MC) grout in the field work, it is essential to obtain and control its property by laboratory tests. In this study, rheological and mechanical properties of six different MC grouts (three portland-based and three slag-blended) and two ordinary Portland cements (ASTM I and III) are measured. MC suspension was prepared at five W/C ratios (1.0, 1.2, 1.5, 2.0 and 3.0) without or with superplasticizer (SP). The properties investigated in this study were: particle size distribution, rheological properties (apparent viscosity, yield stress and plastic viscosity), fresh states (mini-slump, bleed capacity and final setting time) and mechanical properties (early strength development, compressive strength, flexural strength, elasticity modulus, shrinkage/expansion and sand-consolidation strength). The results showed that rheological behaviors and mechanical properties of MC grouts were affected obviously by the W/C ratio, cement fineness, cement type and the addition of SP, etc. All MC suspensions behaved as the Bingham fluids and were stable for W/C = 1.0, 1.2 and 1.5. The detrimental effect of finer grain size on viscosity can be negated by using SP. To ensure less leaching, sufficient fluidity and enough penetrability in sand voids or micro cracks, the W/C ratio was recommended as 1.0-2.0. The SP dosages should not be excessive to avoid instability, oversaturation or long-setting.