Effect of Supplementary Cementitious Material Content and Binder Dispersion on Packing Density and Compressive Strength of Sustainable Cement Paste

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Title: Effect of Supplementary Cementitious Material Content and Binder Dispersion on Packing Density and Compressive Strength of Sustainable Cement Paste

Author(s): Iman Mehdipour and Kamal H. Khayat

Publication: Materials Journal

Volume: 113

Issue: 3

Appears on pages(s): 361-372

Keywords: cement paste; dispersion state; packing density; supplementary cementitious materials; sustainability

Date: 5/1/2016

Abstract:
The reduction of cement content and incorporation of high volume of supplementary cementitious materials (SCMs) are key factors for the design of environmentally friendly concrete (Eco-Crete). The effectiveness of incorporating an SCM to enhance rheological and mechanical properties and durability of concrete depends on the type and content of SCM, as well as the degree of dispersion of the binder resulting from the use of high-range water reducer (HRWR). An experimental investigation was undertaken to evaluate the effect of binary and ternary cementitious materials on the packing density of the binder and compressive strength at 7 and 56 days of cement paste. The influence of the dispersion state of the binder on packing density was evaluated using the wet packing density approach to determine the optimum water demand (OWD) needed to achieve maximum wet density. The effectiveness of incorporating a high volume of SCM to enhance packing density is shown to increase with an increase of HRWR dosage, resulting from a greater degree of dispersion of the binder. The incorporation of sufficient dosage of HRWR led to lower OWD needed to achieve maximum density and higher packing density. The coupled effect of these changes results in higher compressive strength. Compared to the packing density of 0.58 for binder with 100% cement, the use of SCMs in a well-dispersed system is shown to secure packing density of 0.60 to 0.73. The ternary binders containing 40 or 50% slag and 5 or 10% silica fume, by volume of total binder, can ensure lower OWD, greater packing density, lower CO2 emission, and higher compressive strength. Such binder systems can be adopted for use in sustainable cement-based materials.