Volume 5, Issue 2 (February 2008)
Pervious Concrete Mixture Proportions for Improved Freeze-Thaw Durability
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.