Internal Curing with Lightweight Aggregate: The Common Sense Contribution to Sustainable Concrete Pavements

Internal Curing (IC) has been used in concrete for more than 100 years in which the main usage of lightweight aggregate (LWA) was to decrease the density of the concrete. However, over the last decade, the research community has observed additional benefits of IC. This paper summarizes the main benefits obtained when using IC in normalweight concrete, with the final purpose of enhancing its durability by means of reducing shrinkage cracking and fluid transport properties while maintaining strength. At the same time it improves the aggregate-paste interface and the cement hydration, making more efficient use of the cement. More durable concrete infrastructures are expected, yielding more sustainable solutions. Lightweight aggregates are typically used for providing IC in concrete. Even though lightweight aggregates require energy to manufacture, when evaluated from a lifecycle perspective the overall economical and environmental impact of a pavement or structure is almost always lowered. The recent Auburn University and Purdue University research indicating reduced micro cracking and shrinkage, and increased ‘reserve capacity’ for temperature effects during construction will also be covered, with examples of how this research is being tested in real world concrete pavements and structures. Real projects will then be presented that show how internal curing improves concrete pavement performance.