STUDY ON RHEOLOGICAL PROPERTIES AND MECHANICAL PROPERTIES OF MODIFIED STICKY RICE MORTAR

In 2017, an earthquake struck the Jiuzhaigou Valley, causing the collapse of the Huohua("spark")Lake dam. The reinforcement materials for natural heritage sites must be ecological and environmentally friendly. The sticky rice mortar developed is made of amylopectin-agglomerated lime, gypsum, and silica powder, which achieved the purpose of strengthening the travertine dam. In this paper, additives, silica fume, and gypsum were added to traditional sticky rice mortar to improve its rheological properties and mechanical properties. The mass ratio of lime to gypsum in modified sticky rice mortar was changed(0, 0.11, 0.25, 0.43, 0.67). The rheological curves of modified sticky rice mortar were measured by conventional shear(0.01~100 s^-1) and cyclic shear(0.01~1300 s^-1). The rheological properties and thixotropy of modified sticky rice mortar were analyzed. In addition, the mechanical properties of modified sticky rice mortar stone body were studied, and the microstructure of the modified sticky rice mortar stone body was studied by SEM. The result shows that the maximum viscosity of mortar decreases by 84.7% ~91.3% while lime/gypsum mass ratios change from 0 to 0.67, and the corresponding shear rate increased gradually. Modified sticky rice mortar is a pseudoplastic fluid material with yield value. Compared with the Bingham model, the Herschel-Bulkley model can better describe the rheological properties of modified sticky rice mortar. Modified sticky rice mortar has thixotropy, and the addition of lime leads to the decrease of the thixotropy of mortar, which is similar to the effect of viscosity. The thixotropy is controlled by shear history and decreases with the increase of the number of shear cycles. The mechanical properties can be illustrated as follows. The compressive strength of modified sticky rice mortar stone can reach 9.78 MPa after 28 d. With the increase of lime/gypsum mass ratios, the elastic modulus of the modified sticky rice mortar stone decreases gradually, making the macroscopic fracture mode transition from brittle failure to ductile failure.