Effect of Paraffin Oil Nanoemulsion as a Hydrophobic Modifier on Cement Paste Workability and Hydration

Abstract

How to realize hydrophobic modification of the capillary wall of cement-based materials is still a challenge. The hydrophobic modifier in the emulsion type is more promising than the original form due to the good compatibility with cement paste for integral hydrophobic modification of cementitious materials. Their influence on cement hydration and fresh-state behavior is less concerned. In this study, low-cost and nanoscale paraffin oil emulsion (POE) was first prepared as a new hydrophobic modifier. POE was then mixed with cement pastes to investigate its influence on hydrophobicity, cement hydration, compressive strength, and fresh-state behavior. Furthermore, the absorption of POE with cement paste was studied by zeta potential measurement and organic carbon analysis to clarify the associated micromechanisms. The results indicated that the incorporated POE could improve the integral hydrophobicity of hardened cement paste and decrease the capillary water absorption as well. Meanwhile, due to the hydrogen-bond interaction between the ─ OH group of POE and the ─ OH group of cement or hydration products, POE adsorbs onto the surface of cement and results in a reduction of water demand for standard consistency of cement pastes. In addition, a decrease in cement hydration degree, prolonged setting time, and increase in workability can be observed. These findings can provide important guidelines for the development of hydrophobic cementitious materials.