Non-linear rheological behavior of superplasticized cementitious suspensions at high shear rates

Abstract

The growing demand for high-performance concrete in the construction industry requires understanding how its flow behavior is. For this reason, rheology has become an essential tool when designing this typology of materials, as it allows ensuring their stability after the manufacturing and pouring processes, as well as guaranteeing the requirements of strength and durability in the desired application. In particular, the study of the flow curve of cementitious suspensions at increasing shear rates is necessary to design processes like pumping, extrusion, or 3D printing. Therefore, here we investigate the rheological behavior of superplasticized cementitious suspensions at high shear rates. We tested 31 different mixes. Each of them was sheared from rest to high strain rates, 600 s−1, employing a suitable rheological protocol. The results indicate that the initial stretch of the shear stress-shear strain rate curves is close to a straight line, mostly (27) showing a mild shear-thinning. Later there is a transition to distinct shear-thickening at higher shear rates, happening in the interval between 250 s−1 and 420 s−1, which remains until the end of the test. We did not observe a significant reduction in the transition shear rate as a function of the amount of admixture. The intensity of the shear-thickening at high shear rates is very similar in all the suspensions.