National Concrete Pavement Technology Center

Project description

Shrinkage significantly impacts concrete infrastructure, leading to durability issues like cracking in pavements and structures. A 2022 National Concrete Consortium survey ranked bridge deck cracking as a top research need. NCHRP Synthesis 500: Control of Concrete Cracking in Bridges highlighted the necessity for specifications to manage shrinkage cracks and research on shrinkage-reducing admixtures, cementitious materials, and internal curing to mitigate cracking in concrete mixes. Research in concrete shrinkage is crucial for advancing the understanding, improving the performance of concrete structures, mitigating damage and cracking, optimizing construction practices, and ensuring long-term durability. It also enables the development of more accurate predictive models, informed design guidelines, and effective mitigation strategies, leading to safer and more sustainable concrete. The first step is quantifying shrinkage effectively. Existing test methods have limitations and may not apply to new cements such as AASHTO Type 1L or supplementary cementitious materials such as calcined clay or “green”/special concrete mixtures. Understanding shrinkage impact in these materials is crucial. The second step is developing guidelines to mitigate shrinkage’s effects on materials and construction to reduce cracking. Characterizing all shrinkage mechanisms and practical ways to minimize them is essential. Current specifications do not account for field-specific variations in materials, construction practices, and restraint conditions, potentially leading to cracking issues without effective management techniques. The two objectives of this research are: (1) Test method(s): Develop recommendations for new or (enhance existing) test methods to characterize and measure shrinkage (all types) of concrete that may include new materials or combinations. The recommended outcome should address field verification and the limitations of the existing test methods such as time dependent behavior, duration of testing, environmental factors, sample size, restraint conditions, repeatability and practicality. (2) Guidance manual: Develop design recommendations for pavements and bridge decks given its critical effect due to their restraint behavior, as well as pre-and post-construction guidelines/strategies to reduce the impact of shrinkage to a pre-established minimum shrinkage threshold based on infrastructure restraint conditions to minimize cracking.