Core testing is the most direct method to determine the in-place compressive strength of concrete in a structure. Generally@ cores are obtained to: a) Assess whether suspect concrete in a new structure complies with strength-based acceptance criteria; or b) Determine in-place concrete strengths in an existing structure for the evaluation of structural capacity. In new construction@ cylinder strengtin rests that fail to meet strength-based acceptance criteria may be investigated using the provisions given in ACI 318. This guide presents procedures for obtaining and testing the cores and interpreting the results in accordance with ACI 318 criteria. If strength records are unavailable@ the in-place strength of concrete in an existing structure can be evaluated using cores. This process is simplified when the in-place strength data are converted into an equivalent value of the specified compressive strength f c that can be directly substituted into conventional strength equations with customary strength reduction factors. This guide presents procedures for carrying out this conversion in a manner that is consistent with the assumptions used to derive strength reduction factors for structural design. The analysis of core test data can be difficult@ leading to uncertain interpretations and conclusions. Strength interpretations should always be made by@ or with the assistance of@ an investigator experienced in concrete technology. The factors that contribute to the scatter of core strength test results include: a) Systematic variation of in-place strength along a member or throughout the structure; b) Random variation of concrete strength@ both within one batch and among batches; c) Low test results attributable to flawed test specimens or improper test procedures; d) Effects of the size@ aspect ratio@ and moisture condition of the test specimen on the measured strengths; and e) Additional uncertainty attributable to the testing that is present even for tests carried out in strict accordance with standardized testing procedures. This guide summarizes past and current research findings concerning some of these factors and provides guidance for the interpretation of core strength test results. The presentation of these topics follows the logical sequence of tasks in a core-testing program. Chapter 2 reviews factors that affect the in-place concrete strength so that sampling locations consistent with the objectives of the investigation can be identified. Chapters 3@4@ and 5 present guidelines for planning the test program@ obtaining the cores@ and conducting the tests. Chapter 6 discusses the causes and magnitudes of the scatter usually observed in core test strengths and provides statistical methods for data analysis. Chapter 7 summarizes criteria given in ACI 318 for investigating low-strength tests in new construction. Chapter 8 presents methods for determining an equivalent f c for use in evaluating the capacity of an existing structure. Various example calculations appear in the Appendix.?
ACI 214.4R-2003 history
2010ACI 214.4R-2010 Guide for Obtaining Cores and Interpreting Compressive Strength Results
2003ACI 214.4R-2003 Guide for Obtaining Cores and Interpreting Compressive Strength Results