ACI 214R-11: راهنمای ارزیابی نتایج آزمایش مقاومت بتن

This guide provides an introduction to the evaluation of concrete strength test results. Procedures described are applicable to the compressive strength test results required by ACI 301, ACI 318, and similar specifications and codes. Statistical concepts described are applicable for the analysis of other common concrete test results, including flexural strength, slump, air content, density, modulus of elasticity, and other tests used for evaluating concrete and ingredient materials. This guide assumes that the concrete test results conform to a normal distribution. Most construction projects in the United States and Canada require routine sampling of concrete and fabrication of standard molded cylinders. These cylinders are usually cast from a concrete sample taken from the discharge of a truck or a batch of concrete. They are molded and cured following the standard procedures of ASTM C31/C31M and tested as required by ASTM C39/C39M. If the concrete is so prepared, cured, and tested, the results are the compressive strength of the concrete cured under controlled conditions, not the in-place strength of the concrete within the structure. It is expected that, given the uniformity of the curing conditions, these cylinders would have essentially the same strength, thereby indicating concrete with consistent properties. It is these cylinders that are used for acceptance purposes. Statistical procedures provide valuable tools for evaluating the results of concrete strength tests. Information derived from such procedures is valuable in defining design criteria, specifications, and other parameters needed for structural evaluation and repair. This guide discusses variations that occur in concrete strength and presents statistical procedures useful in interpreting these variations with respect to specified testing and criteria.