Demulsification process of asphalt emulsion in fresh cement-asphalt emulsion paste

Abstract

The demulsification process of asphalt emulsion in fresh cement asphalt emulsion (CA) paste was investigated by measuring the viscosity and the particle size distribution of CA paste. The morphology evolution of asphalt droplets was also observed by optical microscope. Superplasticizer was used to adjust different demulsifying speed of asphalt emulsion in CA paste. Results indicate that the viscosity development of CA paste can reflect the demulsification process of asphalt emulsion in CA paste. The demulsification process of asphalt emulsion in CA paste has two main stages under the continual induction effect of cement hydration. Asphalt droplets in CA paste are firstly coalesced to big droplets, and then recover their adhesive force. In the first stage, the viscosity of CA paste increases little with the changing particle size distribution. However, the viscosity of CA paste increases sharply in the second stage.

Rheology of fresh cement asphalt emulsion pastes

“…This SP dosage was chosen because SP has little effect on the viscosity in CA paste when SP/C is above 0.4% [7]. Furthermore, superplasticizer can retard the demulsification process of asphalt emulsion in CA paste [11].…”

“…Besides, the same volume of spherical particles has the lowest viscosity compared to cubes or plates. In the suspension of CA pastes, cement grains are coarse particles with grain shape which size ranges from 1 to 100 lm, and asphalt droplets are fine spherical particles with the size between 0.1 and 20 lm [11]. Therefore, the / m value increases sharply when AE/C rises from 0 to 0.2 in consideration of the filling effect.…”

“…The results indicate that the shear thinning behavior of CA paste is slacked down with the decreasing of particle volume fraction, increasing of AE/C and concentration of superplasticizer. For asphalt emulsion is unstable when mixed with cement, the growth of the rheological properties of CA paste is gained much concerning [9][10][11]. The results showed that the growth of the rheological properties was related with the content and type of asphalt emulsion used in the CA paste.…”

“…CA paste with more asphalt emulsion content and anionic asphalt emulsion had the smaller growth rate of the rheological properties [9,10]. The growth of the rheological properties can be due to cement hydration and demulsification of asphalt emulsion [10,11]. Superplasticizer can retard the demulsification process of asphalt emulsion in CA paste, which prolong the low viscosity retention time of CA paste [11].…”

“…The growth of the rheological properties can be due to cement hydration and demulsification of asphalt emulsion [10,11]. Superplasticizer can retard the demulsification process of asphalt emulsion in CA paste, which prolong the low viscosity retention time of CA paste [11]. Asphalt emulsion was proved to have retarding effect on cement hydration.…”