Advancements in pervious concrete technology

Abstract

Pervious concrete has been used for many years in the southern United States but only recently have stormwater mandates implemented by the United States (U.S.) Environmental Protection Agency (EPA) created interest for more wide-spread installations, especially in freeze-thaw climates. Validation of the freeze-thaw durability of pervious concrete under the most extreme conditions created an opportunity to explore many additional aspects of pervious concrete and to improve durability through additional mixture characterization and new construction practices. While the material components are similar to conventional concrete, the idiosyncratic behavior of pervious concrete requires revaluating material effects and relationships. Many different factors influence the performance of conventional concrete and many different factors also affect pervious concrete, although limited data exist to support observed and expected responses. The most crucial factors include the specific effect on freeze-thaw durability caused by the coarse aggregate type. Since the volume of paste in a pervious concrete system is much less than traditional concrete and exposure conditions much more severe, aggregate durability criteria must be determined for this specific application. The more extreme exposure conditions also require investigating the effect of air entrainment on the concrete mortar. Air entrainment improves freeze-thaw durability in conventional concrete, but to date has yet to be evaluated in pervious concrete. In addition to mixture properties, construction practices must be modified to suit pervious concrete. While the workability of conventional concrete can be simply checked using a standard slump cone, no method currently exists to determine the workability of pervious concrete. However, workability of pervious concrete influences the ease of placement and density, which also controls the yield and ultimate durability. Determining pervious concrete workability will allow more consistency between placements and help quantify the effect various mixture components have on the fresh mixture behavior. Due to it’s very low water-to-cement ratio (~0.30) curing of pervious concrete is particularly important. Pervious concrete is currently cured under plastic instead of using a conventional curing compound. No research has previously been performed to evaluate the effect various common curing methods have on strength and durability. By