Correlating Rheology of Self-Consolidating Concrete to Corresponding Concrete-Equivalent Mortar

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Title: Correlating Rheology of Self-Consolidating Concrete to Corresponding Concrete-Equivalent Mortar

Author(s): Tahir Kemal Erdem, Kamal H. Khayat, and Ammar Yahia

Publication: Materials Journal

Volume: 106

Issue: 2

Appears on pages(s): 154-160

Keywords: concrete-equivalent mortar; plastic viscosity; rheology; self-consolidating concrete; thixotropy; yield stress.

Date: 3/1/2009

Abstract:
The investigation reported in this paper seeks to develop a methodology to evaluate the rheological parameters and thixotropy of self-consolidating concrete (SCC) using those of concrete-equivalent mortar (CEM). The mixture proportioning of CEMs are derived from their corresponding concrete mixtures by eliminating the coarse aggregate fraction and replacing it by a certain mass of sand of the same surface area. SCC mixtures with water-cementitious material ratios (w/cm) of 0.35, 0.38, and 0.42 and coarse aggregate-total aggregate volume ratios (CA/A) of 0.44 to 0.53 were investigated. The mixtures with a w/cm of 0.38 and 0.42 incorporated low and moderate dosages, respectively, of a viscosity-modifying admixture to enhance stability. For each SCC, the dosage of high-range water-reducer (HRWR) was varied to cover a wide range of slump flow consistencies ranging between 570 and 730 mm (22.4 and 28.7 in.). All SCC mixtures were proportioned with 450 kg/m3 (758.5 lb/yd3) of ternary silica fumeground granulated blast-furnace slag cement. A simple method is also proposed to determine the HRWR demand of SCC from that of the corresponding CEM. Test results showed that a good correlation can be established between the yield stress, plastic viscosity, and thixotropy of SCC and their corresponding CEM mixtures. Both thixotropy and plastic viscosity of SCC mixtures and their corresponding CEM mixtures are shown to vary primarily with variations in the w/cm and relative volume of coarse aggregate.