Effects of high-calcium sepiolite on the rheological behaviour and mechanical strength of cement pastes and mortars

Abstract

This paper presents an experimental study on the rheological behaviour and mechanical strength of cement pastes and mortars prepared with high-calcium sepiolite (HCSP). HCSP was used to replace 0.0%, 2.5%, 5.0%, 7.5%, 10.0%, and 15.0% of cement. The rheological behaviour of fresh specimens was investigated along with the yield stress and plastic viscosity, which were approximated using the Bingham plastic model. Tests were also conducted to investigate the compressive strength, flexural strength, and drying shrinkage of hardened specimens. The results showed that the addition of HCSP has an adverse effect on the rheological behaviour of fresh specimens. The compressive strength and flexural strength are highest for specimens with an HCSP content of 7.5% but this is somewhat negated by the high drying shrinkage values. In contrast, the drying shrinkage values are lowest for specimens with the highest HCSP content (15.0%). It can be concluded that HCSP is a potential cement replacement material, but it is necessary to improve the workability of the fresh specimens and reduce drying shrinkage of the hardened specimens before this mineral can be used in the production of structural concrete.