Title: Analysis of Concrete Strength Versus Water-Cement Ratio Relationship

Author(s): Sandor Popovics

Publication: Materials Journal

Volume: 87

Issue: 5

Appears on pages(s): 517-529

Keywords: air entrainment; cement content; compressive strength; concretes; mathematical models; mix proportioning; strength; water cement ratio; Materials Research

DOI: 10.14359/1944

Date: 9/1/1990

Abstract:
The Abrams rule implies that the quality of the cement paste solely controls the strengths of comparable concretes; the paste quantity does not matter. Analysis of a variety of experimental data shows that this is not absolutely true. For instance, if two comparable concretes have the same water-cement ratio, the strength of the concrete with higher cement content is lower. This observation is reflected by presenting new formulas (mathematic models). These were developed from formulas where the strength is a function of the water-cement ratio only (basic models), through the addition of, or augmentation by, a suitable term representing the concrete composition. The Abrams formula is one used in this paper as a basic model, but two linear models were also examined. Augmenting terms are: cement content, or water content, or paste content, or measure of consistency, or squared terms, or combinations of these. Experimental data from four different sources are used to check the reliability of the new models. The comparison shows that the augmented formulas are supported better by experimental data than are the unaugmented models. Formulas are also presented that take into consideration the effect of air content on the concrete strength. The use of the new formulas is shown to be as simple as that of any of the basic formulas, yet they provide an improved tool predicting concrete strength and concrete proportioning.