Assessment of Thixotropy of Self-Consolidating Concrete and Concrete-Equivalent-Mortar—Effect of Binder Composition and Content

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Title: Assessment of Thixotropy of Self-Consolidating Concrete and Concrete-Equivalent-Mortar—Effect of Binder Composition and Content

Author(s): Joseph Assaad and Kamal H. Khayat

Publication: Materials Journal

Volume: 101

Issue: 5

Appears on pages(s): 400-408

Keywords: cement; concrete; friction; mortar; thixotropy

Date: 9/1/2004

Abstract:
A comprehensive research program was undertaken to determine the influence of thixotropy on the development of formwork pressure of self-consolidating concrete (SCC). Ten concrete and concrete-equivalent-mortar (CEM) mixtures were evaluated using different types of binder, including a Type 10 and Type 30 CSA cements and three other blended cements containing various combinations of supplementary cementitious materials (SCM). The binder content varied from 400 to 550 kg/m³. The paper aims at presenting test protocols to quantify the degree of thixotropy and attempts to correlate such response determined for SCC and CEM mixtures. The influence of binder type and content on the degree of thixotropy and pseudoplasticity are also investigated. For a given binder content, the degree of thixotropy is shown to be significantly affected by the type of binder; mixtures made with Type 30 cement exhibit a greater degree of thixotropy compared to those prepared with binary or ternary cement. On the other hand, SCC and CEM mixtures made with a quaternary cement containing 50% SCM or those with Type 10 cement without any SCM exhibit lower degree of thixotropy. For a given binder type, the increase in binder content is shown to increase thixotropy in the case of CEM mixtures. This is related to the increased degree of restructuring resulting from higher binder content. Conversely, in the case of SCC, the degree of thixotropy increases with the decrease in the binder content. This is attributed to the relative increase in coarse aggregate volume that can lead to a greater level of internal friction. Such phenomena seem to overshadow the restructuring process resulting from the use of higher binder content in the case of SCC.