The fundamental reason for testing concrete is to ensure that customers get what they pay for. The most common tests for fresh concrete are slump, air content, unit weight, and compressive strength tests. The slump test measures consistency of the concrete. This is its relative ability to flow. The location of the slump test depends on the specifications of the owner. Some owners want the test taken at the point of discharge, while others specify the point of placement. The air content test measures the total air content in a sample of fresh concrete. It does not tell you which air is entrapped and which is entrained, and it does not tell you what the final in-place air content is. There are three widely used field tests for measuring air content in fresh concrete: the pressure meter, volumetric, and Chace Indicator tests. The unit weight test is an indicator of yield. Yield is the actual volume produced based on actual batch quantities of cement, water, and aggregates. The compressive strength test is most often used for acceptance testing. It tests the strength of the concrete as delivered. This result isn't always the same as the strength of the concrete in-place.