Using Historical Cylinder Strength Data for Structural Evaluation

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Title: Using Historical Cylinder Strength Data for Structural Evaluation

Author(s): F. Michael Bartlett

Publication: Special Publication

Volume: 284

Issue:

Appears on pages(s): 1-12

Keywords: concrete cylinder tests, equivalent specified concrete strength, specified concrete compressive strength, strength evaluation, structural concrete

Date: 3/1/2012

Abstract:
Section 20.2 of ACI 318-08 gives provisions for determining required dimensions and material properties for the strength evaluation of an existing concrete structure. Subsection 20.2.3 states “If required, concrete strength shall be based on results of cylinder tests from the original construction or tests of cores removed from the part of the structure where the strength is in question. For strength evaluation of an existing structure, cylinder or core test data shall be used to estimate an equivalent fc’.” The commentary cites two methods presented in ACI 214.4R for determining an equivalent-to-specified fc’ using cores from an existing structure. There are no criteria provided or references cited, however, suggesting how to compute an equivalent fc’ based on cylinder strength data. The paper first identifies necessary conditions for using original cylinder test data to determine a concrete compressive strength for structural evaluation. To investigate strength compliance during initial construction, methods to compute an equivalent-to-specified fc’ value are presented that are based on inverting the conventional acceptance criteria given in ACI 318-08 Section 5.6.3.3. To evaluate an older structure, a method to determine an equivalent-to-specified strength based on the lower-bound fractile of the concrete strength represented by fc’ is presented.