An Experimental Investigation of the Effects of Fly Ash and Nano Titanium Dioxide (n-TiO2) Usage as Viscosity Modifying Agents(VMAs) in Cement-Based Grouts on Rheological Parameters.

Abstract

The effects of n-TiO2 additions at different amounts by mass (0.0%, 0.3%, 0.6%, 0.9%, 1.2% and 1.5%) on rheological properties (plastic viscosity and yield stress) of cement-based grouts incorporated with fly ash as mineral additive at different constitutes (0%-for control purpose, 5%, 10%, 15%, 20%, 25% and 30%) were investigated by analysis of experiments in this study. To prepare all samples, w/b ratio was defined as 1.0. To prevent sedimentation of TiO2 nanoparticles in free water and to supply uniform distribution of TiO2 nanoparticles in water with help of removing of these nanoparticles from each other, Ultrasonication method was applied by using a Horn type Ultrasonic Homogenizer in this experimental study. All experimental viscosity values of the cement-based grout samples were also obtained by using Coaxial Rotating Cylinder Rheometer test machine. Modified Bingham analytical model was used to investigate on this study for reference grout samples because of it shows dilatant (shear-thickening) flow behavior. Test results show that plastic viscosity values of the grout samples obtained by addition of FA remarkably decrease with rising amount of n-TiO2. Yield stress of fresh grout mixtures increases with respect to increase amount of FA content in all grout mixtures with different proportions of n-TiO2. the usage of FA as a mineral additive in cement-based grouts has improved the yield stress value of the samples. Since n-TiO2 has such a low specific surface area, the water requirement of the grout matrix tends to increase. Therefore, this situation causes increasing of cohesion. The developed ANNs model has been able to predict the plastic viscosity and yield stress of cement-based grouts containing TiO2 nanoparticle doped fly ash with very low error rates and high accuracy