Early Age Shrinkage and Cracking of Nevada Concrete Bridge Decks
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The shrinkage and cracking perfonnance of concrete bridge decks at very early age must be minimized in order to provide durnble concrete. The main objective of this research project is to develop shrinkage-compensated concrete for Nevada and recommend measures, which might be used to engineer concrete possessing excellent shrinkage behavior as well as precautions that should be taken during construction to minimize ambient effects. To accomplish this objective, a series of concrete mix designs incorporating the usage of commercially available shrinkage reducing admixtures (SRA) and shrinkage compensating cement or additive (SCC/SCA) were developed and evaluated for their suitability to be used in Nevada bridge decks. In this research program, a total of 27 mix designs were prepared using the SRA, the SCC/SCA, fly ash, and various combinations of these admixtures. Laboratory testing based on several standard and recommended procedures was performed to evaluate the performance of each trial batch. The test program consisted of compressive strength, drying shrinkage, modulus of rupture, chloride ion penetration, cracking tendency, temperature evolution or heat of hydration, and the hardened air-void system. Results of the experimental program reveal that both the SRA and the SCC/SCA have a significant impact on the early age shrinkage and cracking behavior and performance of concrete, therefore its durability. In order to extract full benefits from these admixtures, NDOT should adopt a shrinkage performance based concrete.
Report No. CCEER 01-1