Rheological and mechanical properties of mortars prepared with natural and manufactured sands

The conventional assessment methods for fine aggregate used in Portland cement concrete are mostly based on round natural sand performance in spite of the increasing use of angular manufactured sands. Two natural and two manufactured sands were selected and tested at different water-cement ratios and fine aggregate-to-cement ratios for the same standard gradation to identify shape-related differences on the mechanical performance of mortars. Three tests were used in this study: flowability, stiffness and strength. Results showed that adequate flow and compressive strength were attained when the volume of paste exceeded the volume of voids in the loosely packed aggregate, i.e., just above the maximum void ratio em, of the fine aggregate. Given the dependence of em,x on particle shape, mixture predesign can be facilitated by taking aggregate shape into consideration. (C) 2008 Elsevier Ltd. All rights reserved.