Fast track concrete technology has been used over the past two decades for overnight highway repairs. Originally, fast track was concerned only with rapid strength gain and workability but little concern was paid to cost and durability of the concrete.
The purpose of this research study is to develop a current improved very early strength (VES) concrete mix, which was accepted by NJDOT in 1996. More than 50 concrete mixes were evaluated for strength, shrinkage, and curing rate (maturity), eventually leading to the development of an optimized VES concrete mix with improved performance characteristics.
The study has developed the new four mix designs, which can achieve the compressive strength in a range of 2,200-2,300 psi and the flexural strength (modulus of rupture) in a range of 350-365 psi at six and half hours with an improved shrinkage behavior. The study has found that an initial temperature of 27°C (81F) to 29°C (85F) is the influence factor to achieve a required strength in six and half hours. The test results also show that the required flexural and compressive strengths can be obtained with a maturity of 175 °C-hours. Using the non-destructive maturity test, this value can be used as an indicator to predict the real-time strength of concrete. Moreover, the maturity test can reduce a certain cost of breaking cylinder and can decrease the amount of debris, which can save natural resources and protect the environment.
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