Study of the rheological behavior of fresh cement emulsified asphalt paste

Cement emulsified asphalt (CA) paste is a suspension with organic and inorganic components, whose rheological behavior is more complicated than that of plain cement paste. The placement quality of CA mortar cushion layer of ballastless track is strongly influenced by its rheological behavior. In this paper, the shear conditions of construction of CA mortar in practical engineering were characterized, and effect of important parameters on its rheological behavior (specially focus on shear rate in practical engineering) was investigated, including solid volume fraction (Vs), mass ratio of asphalt to cement (A/C), and superplasticizer (SP) type and dosage. Pastes were proportioned with A/C of 0.3, 0.5, 0.7 and 0.9, various Vs of 30%, 40%, 50% and 60%, and SPs of polycarboxylate (PCA) and polynaphthalenesulfonate (PNS). Rheological curves were measured at 25 °C, using a rotating coaxial cylinder viscometer. Results indicate that most of the CA pastes are shear thinning flow in the shear rate range of practical engineering. The shear thinning behavior is slacked down with the decreasing of Vs, increasing of A/C and concentration of SPs. Severe shear thinning behavior maybe not good for the placement quality of CA mortar cushion layer.