Testing Rheological Properties of Alkali-Activated Cement Using Non-Traditional Test Methods

Department of Civil and Environmental Engineering, Brunel University, London, United Kingdom

^* Corresponding author: gediminas.kastiukas@brunel.ac.uk

Abstract

In this paper, the rheological parameters of alkaline activated cement (AAC) paste tailored for continuous extrusion using the non-traditional test method of the direct shear box test are presented. Characteristic changes of the material’s rheological behaviour are estimated in response to variations in the water-to-solid ratio and addition of a cellulosic rheology aid. The results indicate that the increase of the water-to-solid ratio from 0.18 to 0.19 does not impact the internal angle of friction (φ) but does, however, reduce the shear yield strength, or cohesion (c), by 85%. For mixes containing cellulosic rheology aid, the internal angle of friction shows no significant change also. However, the shear yield strength for the mix with a water-to-solid ratio of 0.18 is 51% higher. The shear yield strength increases by a further 28% for the mix with a water-to-solid ratio of 0.19. These results indicate that the cellulosic rheology aid does not necessarily increase the "flow-like" characteristics of the mix which provides it plasticity and the ability to move through the extruder. It does however significantly improve its ‘green strength’, even at an increased water-to-solid ratio of 0.19, which would ultimately assist with lowering the binder density.