Rationale

ASTM C94 Paragraph 17.6 allows for testing of slump and air content on a preliminary sample before concrete is discharged for placement. These test permit adjustments to the load. Acceptance and rejection of concrete is based on testing an acceptance sample obtained in accordance with ASTM C172/C172M. C94 previously required a check test if slump and air content failed the requirements on the acceptance sample. In the current version of ASTM C94/94M, the check test is required if tests performed on the preliminary sample fail.(note that check test is defined in ASTM C125) This revision defines the preliminary sample and its purpose. If Slump, Slump flow, or air content is higher than permitted range, these are measured on a sample obtained in accordance with ASTM C172-the acceptance sample. If these are lower, adjustments to the load are permitted and subsequent tests are made on the acceptance sample. It clarifies that a check test is required if the acceptance sample does not comply with the requirements of the order before decisions are made regarding rejecting the load. Rejection of a load should not be based on tests performed on the preliminary sample.