The Correlation between the Water/Cementitious Material Ratio and HPC Compressive Strength

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Title: The Correlation between the Water/Cementitious Material Ratio and HPC Compressive Strength

Author(s): S.F. Freyne, W. Micah Hale, and B.W. Russell

Publication: Special Publication

Volume: 228

Issue:

Appears on pages(s): 165-172

Keywords: coefficient of determination; compressive strength; high-performance concrete (HPC); linear regression model; water/cement ratio (w/c); water/cementitious material ratio (w/cm)

Date: 6/1/2005

Abstract:
The water/cementitious material ratio (w/cm) remains an essential, descriptive statistic for today’s increasingly complex HPC mixtures. The water/cement ratio (w/c) is also useful. A sample of 125 high performance concrete (HPC) mixtures of various materials and proportions was fitted with linear regression models relating compressive strength at ages of 1, 28 and 56 days to the w/cm and/or w/c. It was observed that strength generally increased as the w/cm or w/c was lowered. But linear regression models using a single independent variable, either the w/cm or w/c, failed to return a coefficient of determination, R2, more than 0.535. It was learned that the w/c provides a stronger indication of strength at 1 day. By 28 and 56 days, because of pozzolanic activity, the w/cm becomes a better indication of strength. Multiple linear regression models using both the w/cm and w/c capture more of the variability in the data.