As the world becomes more urbanized, concerns over the urban heat island (UHI) are more pronounced. Increased urban temperatures have a negative affect on the natural and human environment by producing increased energy usage and smog formation. Pervious concrete pavement is one technology that may help mitigate increased urban temperatures. Temperature data from an instrumented site in Iowa and heat storage phenomena for various weather patterns are presented. The site contains both pervious concrete pavement with a solar reflectance index (SRI) of 14 and traditional concrete pavement with an SRI of 37. Leadership in Energy and Environmental Design (LEED) accepted a high SRI (>29) as one method to characterize a cool surface. Heat capacities of both systems were studied along with a sensitivity analysis of the inputs. The research supports the conclusion that even though pervious concrete may have a much lower SRI than traditional concrete made with similar materials, it can be considered a cool pavement option. In addition, daytime rainfalls combined with the internal high surface area result in significantly more removal of stored heat from the system, with a more rapid mitigation of UHI impacts and reduction in the potential for thermal shock from impervious surface runoff.

Pervious concrete is becoming more common as a storm-water management tool in freeze-thaw climates. One of the main concerns or obstacles preventing a more widespread application is the aspect of freeze-thaw durability, whether perceived or actual. This paper describes a series of tests designed to determine the specific role coarse aggregate has on the freeze-thaw durability of pervious concrete using the ASTM C666A procedure. 17 different coarse aggregate samples were obtained from locations across the United States and Canada. Pervious concrete mixtures were placed using a mixture proportion previously determined as freeze-thaw durable. The range of durable aggregate gradations clearly defined a gradation specification and suggestions are made for optimizing the gradation with a small portion of sand. Mixtures with excellent freeze-thaw performance contained either granite or highly durable river gravel. The impact of aggregate angularity on mixture proportions and ultimate yield is also discussed.

Recent stormwater management regulations from the Environmental Protection Agency (EPA) and greater emphasis on sustainable development has increased interest in pervious pavement as a method for reducing stormwater runoff and improving stormwater quality. Pervious concrete is one of several pervious pavement systems that can be used to reduce stormwater runoff and treat stormwater on site. Pervious concrete systems have been used and are being proposed for all parts of the United States, including northern climates where severe freezing and thawing can occur. The purpose of the research is to develop pervious concrete mixtures that have sufficient porosity for stormwater infiltration along with desirable porosity, strength, and freeze-thaw durability. In this research, concrete mixtures were developed with single-sized river gravel aggregate (4.75 mm) and constant binder contents, together with high range water reducer. River sand was used as a replacement for up to 7 % coarse aggregate. Two different types of polypropylene fibers (a shorter fibrillated variable-length and a longer fibrillated single-length) were incorporated at several addition rates from 0 to 0.1 % by volume of concrete. The engineering properties of the aggregate were evaluated along with the porosity, permeability, strength, and freeze-thaw durability of selected concrete mixtures. The results indicate that the use of sand and fibers provided beneficial effects on pervious concrete properties, including increased strength, maintained or improved permeability, and enhanced freeze-thaw resistance.

To achieve the permitted stormwater effluent limits required by the Clean Water Act, many best management practices (BMPs) are being utilized to reduce the overall stormwater volume and provide initial pretreatment and pollutant removal. One such BMP is use of portland cement pervious concrete (PCPC), which allows stormwater to pass through the pavement into an aggregate base below to infiltrate. Until now, the temperature response of the entire system (concrete, aggregate base, and natural soil) was not known. Since PCPC is an infiltration-based BMP, once a frost line forms under the base the infiltrating capacity is reduced or eliminated. PCPC also is recommended for use in warmer climates as a cooler pavement alternative to conventional concrete or asphalt. To quantify the temperature behavior of a pervious concrete system, a fully monitored parking lot—composed of half traditional concrete and half PCPC—was constructed at Iowa State University as part of the Iowa Pervious Concrete Stormwater Project. Sensors were installed through the profile of both pavements and into the underlying soil. The results show that insulation from the aggregate base underneath the pervious concrete substantially delays the formation of a frost layer and permeability is restored when meltwater is present. It was also observed that in direct sunlight, the pervious pavement became hotter than traditional concrete, whereas the daily low temperature of the two was similar, indicating less heat storage capacity in the pervious concrete.