Overview Building Features Grade JK-6 Grade 7-12

Reflective Concrete

Concrete MixturePortland cement concrete is a workhorse of construction materials. A lesser known sustainable benefit of concrete is its reflectivity.  

Surface color of a material affects how much of the sun's energy (heat) is absorbed. Darker colored surfaces absorb more heat. In the past, this quality was referred to as "albedo," but now, terms like "solar reflectance" or "solar reflectivity index" have become common. A material that has a higher solar reflectance absorbs less of the sun's energy. By virtue of its light color, concrete is naturally reflective.

Concrete SpecimentsWherever pavements and structures (especially those that are darker colored) are clustered closely together, as in large cities, the mass of building materials collects heat when warmed by the sun. This creates a microclimate with temperatures measurably higher than in less developed areas-the urban heat island effect. In turn, air conditioners must run longer and harder to keep people cool, which further adds to the high temperatures. This is bad for the environment because it wastes energy, which in turn increases carbon dioxide emissions. Effects of urban heat islands are reduced by selecting lighter colored paving and roofing materials, by situating buildings and parking lots to minimize their exposure to the sun, or by establishing trees and other foliage that provide shade for parking areas.

Reflective ConcreteConcrete is a mixture of cement, water, fine aggregate (sand), and coarse aggregate (rock or stone). Cement and water form the paste that binds the ingredients into a hardened mass. Most concrete is formulated with gray portland cement. This results in a light gray colored surface, which is an advantage over darker colored paving materials in terms of solar reflectivity. White cement is chemically similar to gray cement, but contains a lesser quantity of the metal oxides (iron & manganese) that impart portland cement with its characteristic gray color. Concrete made with white cement is significantly lighter in color than gray cement concrete, and therefore, more reflective.

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