Cracks weaken concrete and permit water and harmful chemical ingress into structures. Shrinkage also decreases the load-carrying capacity of bridges. This study investigates shrinkage cracking prevention of infrastructure concretes used in New Jersey. The 15 initial evaluation mixtures were first tested to evaluate their shrinkage behavior. Based on the results of the tests, control mixtures were selected for modification with shrinkage control admixtures and additives. The admixtures and additives were a shrinkage-reducing admixture, a shrinkage-compensating admixture, fibers, an internal curing agent, and two coatings. The modified mixtures were then tested for the effects of the admixtures and additives on shrinkage, mechanical properties, and durability.NJDOT Research
The cracking potential of control mixtures ranged from moderate-low to high. Initial evaluation mixture autogenous shrinkage increases with the increasing volume of fine aggregate and decrease of coarse aggregates. On the other hand, increasing the portland cement and total binder while decreasing the amount of fine and coarse aggregates tends to increase the drying shrinkage. Different types of admixtures and additives had varied effects on shrinkage. To mitigate cracking in concrete by using admixtures and additives, the standard restrained ring test ASTM C1581 can be adopted for evaluating the concrete’s performance after modification. It is recommended that specifications for concrete shrinkage cracking be met by three specimens from the same batch.
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