Experimental study on rheological properties of cement mortars

Using a Viskomat XL mortar rheometer, parameters related to the rheological properties of machine-sprayed mortar were studied, and the effects of cement, fly ash (FA), and additives such as hydroxypropylmethylcellulose (HPMC) and starch ether (SE) on the rheological properties of cement mortar were studied. The results show that τc, Δτ, g, and h can be used to characterize the rheological properties of machine-sprayed mortar, where τc and Δτ reflect the sagging resistance properties, thixotropy, and plasticity of the mortar in the previous stage during the process of mortar changing from plastic structure to plastic fluid. Together, g and h determine the flowability of mortar in the later stage, and h is positively correlated with the stability and water retention of the mortar. Cement, FA, and HPMC have different effects on the rheological properties of cement mortar. SE changes the fluid properties of mortar from Bingham plastic fluid to the thixotropic fluid.