Title: Effect of Core Length-to-Diameter Ratio on Concrete Core Strengths

Author(s): F. Michael Bartlett and James G. MacGreggor

Publication: Materials Journal

Volume: 91

Issue: 4

Appears on pages(s): 339-348

Keywords: compressive strength; concrete cores; evaluation; high-strength concretes; tests; Materials Research

DOI: 10.14359/4042

Date: 7/1/1994

Abstract:
Data are analyzed to determine the effect of the specimen length-to-diameter ratio (l/d) on the magnitude and precision of the compressive strength of concrete cores. The data represent strength tests of 758 core specimens, all 4 in. in diameter, obtained from 10 different elements cast from ordinary portland cement concretes with strengths between 2000 and 14,000 psi. Strength correction factors are determined for converting the strength of a core with an l/d between 1 and 2 to the strength of an equivalent standard specimen with an l/d of 2. The data indicate that both the core moisture condition and the core strength significantly affect the strength correction factors. The proposed strength correction factors differ only slightly from those currently recommended in ASTM C 42-90. The single-operator coefficient of variation is found to be independent of the core length-to-diameter ratio. Typical values are 4 percent if the effect of spatial variation of the in situ strength is accounted for, or 5 percent otherwise.