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Significance and Use
4.1 This test method provides standardized procedures for obtaining cored specimens to determine the compressive strength and splitting tensile strength of shotcrete during pre-construction, during construction, and from older shotcrete structures.
4.2 Generally, test specimens are obtained in situ when doubt exists about the in-place shotcrete quality due either to low strength test results during construction or signs of distress in the structure. Other uses of this method are to provide specimens for acceptance testing, construction control and to assess the condition, quality and uniformity of the shotcrete in accordance with Practice C823 (see Note 1).
4.3 Specimens obtained by this method are used to verify the thickness of shotcrete and aid in the visual assessment of the shotcrete quality, workmanship, defects, shotcrete-to-substrate bond and the condition of any reinforcement used in the shotcrete4.
4.4 Shotcrete strength is affected by the location of the shotcrete in a structure. Vertical, sub-horizontal and overhead elements of the shotcrete structure may show variability. Core strength is affected by core orientation relative to direction of shotcrete application. These factors shall be considered in planning the locations for obtaining shotcrete samples and in interpreting strength test results.
4.5 Shotcrete is applied in single or multiple layers, as plain shotcrete, reinforced shotcrete, or fiber-reinforced shotcrete. Core samples containing wire-mesh and reinforcing bars shall not be used for compressive strength testing.
4.6 The strength of shotcrete is affected by moisture content, the specified moisture conditioning procedure for cores is intended to provide test specimens with reproducible moisture contents that minimize within-laboratory and between-laboratory variations.
4.7 Sample acquisition may require a combination of core-drilling, sawing, and grinding that may have the potential to adversely affect the sample condition if care is not taken during sampling and testing.
4.8 A sampling plan shall be established that indicates the number of samples and their locations (see Note 1). The acceptance criteria for shotcrete core strengths shall be established by the specifier of tests (see Note 2).
1.2 The values stated in either inch-pound units or SI units shall be regarded separately as standard. SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.3 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
ACI Standards506.4R Guide for the Evaluation of Shotcrete
C39/C39M Test Method for Compressive Strength of Cylindrical Concrete Specimens
C42/C42M Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
C125 Terminology Relating to Concrete and Concrete Aggregates
C174/C174M Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete Cores
C496/C496M Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens
C617 Practice for Capping Cylindrical Concrete Specimens
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
C823 Practice for Examination and Sampling of Hardened Concrete in Constructions
C1140 Practice for Preparing and Testing Specimens from Shotcrete Test Panels
C1231/C1231M Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Concrete Cylinders
ICS Number Code 91.100.30 (Concrete and concrete products)