Shear stress limit, rheological properties and compressive strength of cement-based grout modified with polymers

Abstract

Grouting is a comprehensive technology used in the construction projects due to the rapid development of sub-surface urban infrastructures, the main reasons for grouting soils are strengthened the cohesion-less soils and increasing the shear stress (pure shear) of the grouted soils. Providing high flowability with high viscosity for the cement-based grout in the liquid stage (slurry) and high compressive strength of the cement-based grout in the hardened stage are significant challenges. In this study, the impact of two types of water reducer [polycarboxylate (PCE)] polymer on the rheological properties with the ultimate shear strength and compressive strength of cement-based grout with water-cement ratios (w/c) of 0.6 and 1.0 at two different temperatures 25 °C and 50 °C were studied. XRD and TGA were used to analysis the cement, polymers, and cement modified with polymers. The behavior of cement-based grout in the liquid phase (slurry) and hardened phase modified with different percentages of polymer up to 0.16% (by dry weight of cement) were investigated. The compressive strength of cement-based grout modified with polymer was tested from the young age up to 28 days of curing. Vipulanandan rheological model was used to predict the shear stress-shear strain behavior of cement-based grout slurry and compared to the Herschel–Bulkley (HB) model. The rheological and the compressive strength are increased with increasing the of PCE content. The polymer modification increased the yield stress, apparent viscosity and plastic viscosity of the cement grout by 19–136%, 32–319% and 58–367%, respectively based on the types of polymer, polymer content, w/c, and temperature. The compressive strength of the cement-based grout increased by 94–786% based on the types of polymer, polymer content, w/c and curing time. Increasing the temperature of cement-based grout slurry to 50 °C increased the maximum shear stresses by 110% and 107%, respectively. Effects of polymer content, w/c, curing time and the temperature of the plastic and hardened properties of cement-grout were modeled using a multiple nonlinear regression analysis.