Effect of curing methods on the strength of high performance concrete

In recent years, the use of high strength concrete has become increasingly popular. It is technically and economically feasible to produce ready-mixed high-performance concrete, with strength over 68.9 Mpa, using conventional methods and materials. However, many State Engineers have observed that curing methods and conditions in the field affect the compressive strength and cracking behavior of HPC structures. Therefore, it is necessary to understand the behavior of HPC under various curing conditions. The results presented in this paper are part of an overall study for the New Jersey Department of Transportation (NJDOT) to develop and implement mix design and technical specifications for HPC transportation structures, such as pavements and bridges. An array of mixes is tested and the best mix. is selected based on strength and shrinkage test results. After selecting two mixes from each group, long-term durability was assessed by performing other tests such as the rapid chloride permeability, creep, and freeze-thaw behavior. In this paper, the effect of using four different curing methods on high-performance concrete, is investigated. The curing conditions consisted of 1) Moist curing; 2) Air-dry curing; 3) Burlap; and 4) Curing compound. The presence of pozzolanic material such as silica fume and fly ash and its effect on curing conditions and long-term behavior is also performed. The concrete compressive strength ranged between 48 and 82.7 Mpa. Results show that moist cured cylinders performed best in comparison with other types of curing methods. Moreover, a minimum of 14 days is required for curing to allow HPC to attain its full strength. Final results will be in the form of a technical specification for the use of HPC in the State of New Jersey.