Title: Proportioning Workable Concrete Mixtures with Specific Gravity of Cement-Water Paste

Author(s): Robert W. Cannon

Publication: Materials Journal

Volume: 102

Issue: 5

Appears on pages(s): 338-346

Keywords: aggregate; air entrainment; cement; consolidation; fly ash; mixture proportion; pozzolan; slump

DOI: 10.14359/14713

Date: 9/1/2005

Abstract:
Strengths of all materials are proportional to their respective unit weights and specific gravities relative to age and maturity. The principal material controlling the strength and maturity of concrete is the cement-water paste. Therefore, its specific gravity (SPG) is the major strength factor in the proportioning of concrete mixtures at any specific age and curing regime. The SPG of the cement-water paste is a function of the weight relationship of Abram’s Law of water-cement ratio (w/c) divided by the volumetric relationship of w/c. The SPG is actually the key to economic mixture proportioning for both workability and strength with air entrainment, chemical admixtures, and fly ash or other pozzolans. The economics of mixture proportioning of concrete is as much or more about workability of the mixture than it is about material costs. This paper is based on a very broad range of test data accumulated by the author over the last 40 years for mixtures varying in maximum aggregate sizes up to 6 in. and placement conditions varying from roller-compacted concrete to vibration placement by bucket, pump, and self-consolidating concrete. It also discusses the basic ways of changing the consistency of concrete to obtain optimum workability for a given slump, aggregate size, and method of placement and presents proportioning graphs and demonstrates their use in economic proportioning of the right mixture for the right placement.