Many roads and bridges across the United States were constructed over fifty years ago. With increases in traffic and vehicle weight loads, repairs and replacements are necessary, as sound infrastructure impacts daily quality of life and studies have shown that improved infrastructure is a global competitive advantage for any country. Latex Modified Concrete (LMC) plays an integral role in preserving bridge decks to prolong service life and reducing infrastructure maintenance and repairs.
What is LMC?
LMC is a latex or polymer modified concrete designed to meet latex specifications and concrete performance requirements of the Federal Highway Administration (FHWA). It has been recognized for longevity, superior performance, and overall economic advantage when used for bridge deck overlay repair.[i]
The use of latex as a performance-enhancing additive in modified concrete systems for bridge deck overlays is a proven technology. With a combination of excellent compressive, flexural, and bond strength and chloride permeability resistance an LMC overlay is one of the best choices for many bridges and roadway repair projects.
The Drawback
One drawback, as with many concrete systems for infrastructure repairs, is pouring season limitations in the spring and fall due to cooler temperatures. Similar to other concrete systems, freshly placed LMC must also be protected from cold temperatures. Curing blankets are recommended to help maintain heat when the temperature drops below minimally accepted levels to ensure full and proper curing of the concrete.
In isolated cases, there is concern that these curing blankets, although useful for temperature maintenance, can hinder air drying and latex particle coalescence, resulting in less than desirable performance properties such as chloride ion permeation resistance.
However, a study conducted by Trinseo has demonstrated that LMC can cure under longer wet cure conditions and lower temperatures, while still exhibiting required compression strength, thus reinforcing its efficacy under these conditions.
The Study
This study set out to determine the impact of using curing blankets by simulating extended wet cure conditions to evaluate the effects of low temperatures on compression strength development and chloride permeation resistance.
For both compression strength development and chloride ion penetration resistance, results were excellent under all cure conditions. These results are good news for concrete professionals looking to effectively repair concrete bridge decks and overlays quickly and cost-efficiently, while navigating state regulations for minimum temperature and cure time for LMC projects.
Future studies should evaluate whether LMC will cure properly under even lower ambient temperatures, to facilitate understanding of performance under different environmental conditions to better define pouring season limitations and preferred curing conditions.
For more information on this study, my colleague Chuck Fifelski, Technical Service & Development Specialist for Latex Binders, recently published an article about it in ASPIRE Magazine.
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[i] “Modifier A™ / NA Binder for Concrete Modification.” Latex Concrete Modifier For Construction - Meets FHWA Requirements, Trinseo, www.trinseo.com/Products/Latex-Binders/Products/Modifier-A.