Core testing is the most direct method to determine the compressive strength of concrete in a structure. Generally, cores may be obtained to assess whether concrete in a new structure complies with strength-based acceptance criteria or to evaluate the structural capacity of an existing structure based on the in-place concrete strength. In either case, the process of obtaining core specimens and interpreting strength test results is often confounded by various factors affecting in-place concrete strength or measured strength of test specimens. The scatter in strength test data, which is unavoidable given the inherent randomness of in-place concrete strengths and the uncertainty attributable to preparation and testing of the specimens, may further complicate compliance and evaluation decisions. This guide summarizes practices for obtaining cores and interpreting core compressive strength test results. Factors that affect in-place concrete strength are reviewed so sampling locations that are consistent with objectives of the investigation can be selected. Strength correction factors are presented for converting the measured strength of non-standard core-test specimens to the strength of equivalent specimens with standard diameters, length-to-diameter ratios, and moisture conditioning. This guide provides direction for checking strength compliance of concrete in a structure under construction and methods for determining equivalent specified strength to assess capacity of an existing structure. The materials, processes, quality control measures, and inspections described in this document should be tested, monitored, or performed as applicable only by individuals holding the appropriate ACI Certifications or equivalent. Keywords: compressive strength; core; hardened concrete; sampling; test.<\/p>\n
| PDF Pages<\/th>\n | PDF Title<\/th>\n<\/tr>\n | ||||||
|---|---|---|---|---|---|---|---|
| 3<\/td>\n | CONTENTS <\/td>\n<\/tr>\n | ||||||
| 4<\/td>\n | CHAPTER 1\u2014 INTRODUCTION 1.1\u2014 Introduction 1.2\u2014Background 1.3\u2014Scope <\/td>\n<\/tr>\n | ||||||
| 5<\/td>\n | CHAPTER 2\u2014 NOTATION AND DEFINITIONS 2.1\u2014 Notation 2.2\u2014Definitions CHAPTER 3\u2014 VARIATION OF IN-PLACE CONCRETE STRENGTH IN STRUCTURES <\/td>\n<\/tr>\n | ||||||
| 6<\/td>\n | 3.1\u2014Bleeding 3.2\u2014Consolidation 3.3\u2014Curing 3.4\u2014Microcracking <\/td>\n<\/tr>\n | ||||||
| 7<\/td>\n | 3.5\u2014Overall variability of in-place strengths CHAPTER 4\u2014 PLANNING THE TESTING PROGRAM 4.1\u2014Investigating concrete in a new structure using strength-based acceptance criteria 4.2\u2014Evaluating existing structure capacity using in- place strengths <\/td>\n<\/tr>\n | ||||||
| 8<\/td>\n | CHAPTER 5\u2014 OBTAINING TEST SPECIMENS <\/td>\n<\/tr>\n | ||||||
| 9<\/td>\n | CHAPTER 6\u2014 CORE TESTING CHAPTER 7\u2014 ANALYZING STRENGTH TEST DATA 7.1\u2014ASTM C42\/C42M precision statements <\/td>\n<\/tr>\n | ||||||
| 10<\/td>\n | 7.2\u2014Review of core strength correction factors 7.2.1 Length-to-diameter ratio 7.2.2 Diameter <\/td>\n<\/tr>\n | ||||||
| 11<\/td>\n | 7.2.3 Moisture condition 7.2.4 Presence of reinforcement bars or other inclusions 7.2.5 Coring location 7.3\u2014Statistical analysis techniques <\/td>\n<\/tr>\n | ||||||
| 12<\/td>\n | CHAPTER 8\u2014 INVESTIGATION OF LOW- STRENGTH TEST RESULTS IN NEW CONSTRUCTION USING ACI 318 CHAPTER 9\u2014 DETERMINING AN EQUIVALENT VALUE FOR EVALUATING STRUCTURAL CAPACITY OF AN EXISTING STRUCTURE 9.1\u2014Conversion of core strengths to equivalent in-place strengths 9.2\u2014Uncertainty of estimated in-place strengths <\/td>\n<\/tr>\n | ||||||
| 13<\/td>\n | 9.3\u2014Percentage of in-place strengths less than 9.4\u2014Methods to estimate the equivalent specified strength <\/td>\n<\/tr>\n | ||||||
| 14<\/td>\n | 9.4.1 Tolerance Factor Method (Hindo and Bergstrom 1988) 9.4.2 Alternate Method <\/td>\n<\/tr>\n | ||||||
| 15<\/td>\n | CHAPTER 10\u2014 REFERENCES 10.1\u2014 Referenced standards and reports 10.2\u2014Cited references <\/td>\n<\/tr>\n | ||||||
| 17<\/td>\n | APPENDIX\u2014 EXAMPLE CALCULATIONS A.1\u2014 Outlier identification in accordance with ASTM E178 criteria A.2\u2014Student\u2019s t test for significance of difference between observed average values (for example, Larsen and Marx [2006]) <\/td>\n<\/tr>\n | ||||||
| 18<\/td>\n | A.3\u2014Equivalent specified strength by tolerance factor approach ( Hindo and Bergstrom 1985) <\/td>\n<\/tr>\n | ||||||
| 19<\/td>\n | A.4\u2014Equivalent specified strength by alternate approach ( Bartlett and MacGregor 1995) <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" 214.4R-10 Guide for Obtaining Cores and Interpreting Compressive Strength Results<\/b><\/p>\n |