Title: Concrete Quality Control: 28 Days-24 Hours-15 Minutes
Author(s): Paul A. Howdyshell
Publication: Symposium Paper
Appears on pages(s): 183-200
Keywords: accelerated tests; cement content; chemical tests; compres-sive
strength; fresh concretes; quality control; water-cement ratio;
This study evaluates the field worthiness and accuracy of a chemical technique (Kelly/Vail) for determining water and cement contents of fresh concrete. The results are compared directly to mixture proportions of cement and water and to cement contents obtained by a nuclear cement content gauge method. The study also evaluates the accuracy of estimating 28 day compressive strengths by both accelera-ted curing technique and the Kelly/Vail technique. The study proved the Kelly/Vail system to be field worthy, rapid (less than 15 min.) and simple enough to be operated by technicians or inspectors. Kelly/ Vail water and cement contents when used in conjunction with an air content test can estimate the strength potential of fresh concrete. The Kelly/Vail strength estimates are not as accurate as the accelera-ted curing estimates of 28 day compressive strengths, but the Kelly Vail tests are sufficiently accurate to be meaningful and they are significantly more timely - 15 min. versus 24 hours than accelerated strength tests.