251 / 2022-06-23 14:23:33

The Rheological Characteristics and mechanism of the Limestone Calcined Clay Cement

Pending

This report can be divided into two parts, firstly, the rheological properties of pastes made from ordinary Portland cement blended with different amounts of calcined clay and limestone were reported in order to understand the combined and independent effects of limestone and calcined clay on the rheological properties of limestone calcined clay cement (LC3). The results showed that calcined clay leads to increased static and dynamic yield stress, initial thixotropic index, plastic viscosity and cohesion, while limestone has an opposite effect (Table 1). It is believed that these results will aid in understanding the viscoelasticity of this blended cement.

Secondly, the thixotropy of LC3 was deeply investigated by using focused beam reflectance measurement, zeta potential, ¹H nuclear magnetic resonance relaxometry and micro X-ray computed tomography to track the colloidal interaction and hydration extent within LC3. Results showed that flocculation due to the negative surface charge (Fig. 1) and water affinity of calcined clay introduced by its physiochemical features appears to be the dominating factor. This leads to a reduction of the water available to contribute to the fluidity of paste and, in turn, governing the development of thixotropy over time (Fig.2 and Table 2). In addition, the dilution effect due to high clinker substitution diminishes thixotropy growth with time.