Influence of Cement on Rheology and Stability of Rosin Emulsified Anionic Bitumen Emulsion.

Ordinary portland cement (OPC) has been extensively used in cold recycling asphalt and cold-mix asphalt as an additive in order to improve the early age performances of these mixtures. The main purpose of its application is that cement hydration benefits the strength development by consuming water and by accelerating the bitumen emulsion breaking. The aim of this study is to investigate the influence of cement on the rheology and stability of rosin-emulsified anionic bitumen emulsions. With this purpose, an anionic bitumen emulsion blended with various amounts of cement and limestone filler was studied by means of a Brookfield viscometer. Optical microscopy was used to investigate the breaking process of the bitumen emulsion and the morphology of bitumen droplets in the presence of cement and filler. In addition, the stability of anionic bitumen emulsions was studied in dependence of the pH and the calcium ion concentration. The results indicate that, unlike limestone filler, which has no significant influence on anionic bitumen emulsion, cement reacts with rosin emulsifiers and causes flocculation and partial coalescence of bitumen emulsions. This gelation of cement-bitumen emulsion blends appears to be caused by the interaction between cement grains and emulsifiers. While a decrease of the pH would lower the solubility of the emulsifiers, this is not a concern since cement dissolution increases the pH. [ABSTRACT FROM AUTHOR]