The thixotropic behavior of fresh cement asphalt emulsion paste

• A new model is proposed to quantitatively evaluate the thixotropic behavior of CA paste.
• Constant shear rate test is employed in the thixotropy model.
• The de-flocculation and structure rebuilding processes of CA paste are studied.
• The thixotropic behavior of CA paste is clearly different from cement paste.

The workability of grouting cement asphalt emulsion (CA) mortar is governed by the intrinsic thixotropic behavior of CA paste, but limited information is reported about the thixotropic behavior of CA paste. A new thixotropy method of constant shear rate test is proposed to study the thixotropic behavior of CA paste with different asphalt emulsion to cement ratios (AE/C). In the model, the initial structure parameter and the structure rebuilding rate are used to quantitatively describe the structure rebuilding process, the characteristic time of de-flocculation is used to evaluate the de-flocculation process, and the equilibrium shear stress is used to study the irreversible change of CA paste in the thixotropy test. Results show that CA pastes have significantly different thixotropic behavior compared to cement paste. The initial structure parameter and structure rebuilding rate of CA pastes are much smaller than cement paste, and the structure rebuilding rate decreases significantly with AE/C. The characteristic time of de-flocculation of cement paste changes little at different resting time, however, it increases significantly at the first 5 min resting time and then keep stable for CA pastes. The equilibrium shear stress of cement paste does not change in 20 min, but it increases with time for CA pastes due to the demulsification of asphalt emulsion.