Either possibility compromises the strength of the shaft.
If temperature measurements during early curing show a relative temperature reduction in a section of the shaft, it could indicate a reduction in cement content due to a cross-section reduction or poor quality concrete. Likins notes that the scientific basis for ASTM D7949 is that concrete emits heat during the curing stage. Because this test is performed sooner than any other nondestructive test - typically within 12-14 hours of casting - the construction process can be accelerated. The test described in D7949 can be used to find major defects anywhere in a cross section of concrete. “Lack of quality concrete either inside or outside the reinforcing cage can lead potentially to foundation failures, particularly when a defect is located relatively near the top of the shaft and when lateral forces are present.”
“Evaluating the full cross-section of drilled shafts is important,” says Likins, senior partner, Pile Dynamics Inc. Now, a routinely used temperature assessment method has been developed as a new ASTM standard.Īccording to ASTM member Garland Likins, ASTM D7949, Test Methods for Thermal Integrity Profiling of Concrete Deep Foundations, was developed to ensure that the correct procedures would be used. Temperature can be a key indicator of the integrity of concrete deep foundations.