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Concrete In Practice Series
Inspection and Testing of Ready Mixed Concrete
Concrete is a manufactured product. Specific control tests and evaluations are required during the manufacturing process to produce predictable high-quality concrete. The customer may want to verify that concrete meets specifications. Some of the important properties of concrete that are measured by basic quality control tests are strength, temperature, slump, air content, and unit weight. In general concrete is tested at a frequency of 1 in 150 cubic yards.
Each test helps to determine the quality of concrete and it should be performed in accordance with American Society for Testing and Materials (ASTM) standards. A certified ACI Concrete Field Testing Technician – Grade I, must make the tests.
When there are no formal job specifications, such as with a homeowner or small contractor, it is important for the concrete producer to agree to furnish concrete in accordance with ASTM C 94 or at least certain critical sections of ASTM C 94. This reference should also be included on the delivery ticket.
ASTM C 94 includes a number of things that should be a part of any agreement between the producer and a purchaser. Some of them are:
- Define the basis of purchase, cubic yards, and how it is measured.
- Define acceptable material specifications and acceptable industry practice and tolerances.
- Define strength testing procedures and acceptance criteria.
- Set laboratory personnel qualifications. The testing laboratory must comply with ASTM C 1077, which is required in ASTM C 94.