Adsorption behaviour between cement and asphalt emulsion in cement–asphalt mortar

The workable time of cement–asphalt mortar (CA mortar) is controlled by the early age interaction between cement and asphalt emulsion, which could be indicated by the adsorption of asphalt droplets in the emulsion on cement grains. The adsorption behaviour leads to an increase in particle size in the cement and asphalt emulsion (CAE) system. In the present study, a laser particle size analyser was employed to characterise the particle size variation, and the results indicated that the cement/asphalt emulsion ratio (C/AE) and types of asphalt emulsion had great influence on the particle size in the CAE system. Within the same period, the particle size increased more prominently with a larger C/AE, but when the C/AE exceeded 0·625, it had little influence on the particle size increase after 30 and 60 min. The particle size and its increasing magnitude during different periods in the cement–cationic asphalt emulsion system were both greater than those in the cement–anionic asphalt emulsion system. The viscosity test indicated that particle size increase led to the loss of flowability of the CAE system. A filtration method was used to investigate the adsorption behaviour of asphalt droplets to the cement grains and the adsorption ratio was correlated with the variation in particle size, indicating that the particle size increase in the CAE system was mainly attributed to this adsorption behaviour.