CONCRETE PAVEMENT PROGRESS 10 WWW.ACPA.ORG Emerging Technologies Innovation for the Future of the Concrete Pavement Industry By Sheryl S. Jackson Steve Jobs famously said, “Innovation distinguishes between a leader and a follower.” When examining concrete pavement through this lens, one can see how the industry is leading through innovations. In this final segment of a two-part series on innovations in the concrete pavement industry, ACPA examines how innovative concrete pavement engineers and researchers are creating solutions today that will become the basis for building resilient, sustainable, cost-effective, and long-lasting pavements in the future. Editor’s Note: To see part one, refer to Concrete Pavement Progress, Quarter 2, 2022: Innovative Approaches Address Today’s Challenges, p. 10. Self-Healing Concrete Pavement: Extending Pavement Life Concrete pavements are already well-known for their resilience and long lifespan. However, an emerging technology promises to improve upon these characteristics even more. The key? An enzyme that promotes the growth of calcium carbonate crystals to fill cracks as they develop. Although still in the research phase and a few years from testing in the field, lab results have demonstrated self-healing samples with millimeter-scale flaws heal within 24 hours. This is significantly faster than other methods, such as the use of bacteria, which requires a minimum of 28 days for strength recovery of microscale cracks.1 “The Carbonic Anhydrase (CA) enzyme can be added to the concrete mix to create a selfhealing material to apply to cracked concrete or mixed into fresh concrete to create a pavement that can heal itself over time,” says Jessica A. Rosewitz, P.E., Ph.D., Assistant Teaching Professor of Civil, Environmental and Architectural Engineering at Worcester Polytechnic Institute and co-author of the research article describing the process. “The CA enzyme uses CO2 and a calcium source to create calcium carbonate, our healing material. When a crack forms in enzymatic concrete, exposing the enzyme to CO2 in the air triggers the growth of a new matrix that fills the crack.” The process is also environmentally sound. “The enzyme absorbs CO2 to heal the pavement, which reduces greenhouse gases,” Rosewitz adds. Healing small cracks as they develop prevents them from growing into larger cracks or faults that affect the pavement’s strength, water tightness, and durability, which reduces maintenance requirements and extends the concrete pavement’s already long lifespan. Internal Curing: Minimizing Cracking In 2010, the early use of internal curing for concrete began on bridge decks in Indiana and New York. Unlike conventional curing, which supplies water from the concrete’s surface, internal curing provides curing water from the aggregates within the concrete. While external water can only penetrate to a limited depth, using expanded lightweight aggregate for internal curing disperses water throughout the depth of the concrete. “Internal curing has proven to reduce shrinkage cracks and fluid transport and increase hydration,” said Jason Weiss, Ph.D., Professor of Civil and Construction Engineering at Oregon State University. “In Indiana, the use of internal curing and high-performance mixture has tripled the life of the bridge.” Following Indiana and New York, states including Ohio, Iowa, Utah, and many others
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