Compressive strength tests are used for concrete acceptance based on criteria defined in ACI 318 and ACI 301. Test results not meeting these criteria are referred to as low strengths. This presentation covers the “low strengths” topic in detail and provides answers to questions such as: what is considered a strength test and what is not, what the minimum frequency of testing is, what the acceptance criteria for strength tests are, and how to investigate strength tests not meeting the acceptance requirements. In addition, steps needed by a concrete supplier, in case acceptance criteria are not met, will also be discussed. To better understand discussed concepts, the presentation will use statistical concepts and numerical examples. A list of reading resources will be provided for those interested to study the topic in more detail.
Table of Contents
1. Define what a strength test is and is not
2. Explain proper methods of sampling, fabrication, handling and curing strength test specimens
3. Define acceptance criteria for strength tests
4. Describe how to interpret strength tests not meeting acceptance requirements and how to investigate non-compliant concrete
5. Explain how to address low strength concrete issues in production
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