Using Ultrasonic Pulse Velocity (UPV) to Predict Properties 1 and Performance of Pervious Concrete

摘要

Pervious concrete is a type of porous portland cement concrete with interconnected voids. This material has been increasingly used to reduce the amount of stormwater runoff from paved areas. It has also been shown to improve the water quality near low volume and low speed pavements as well as in parking lots. Due to the low compressive strength of pervious concrete associated with the high void content, it currently is not used in highway structures except perhaps as an overlay for conventional concrete pavement. The large, open pore structure of this material resulting from the use of gap-graded coarse aggregates and little or no fine aggregate allows water to pass through its structure, thereby helping to reduce the deleterious effects of storm-water runoff. The pore structure features such as pore volume and sizes, specific surface areas, and interconnectivity dictate the properties of porous materials. Since pervious concrete is a relatively new type of material, standard methods for testing its performance characteristics are currently being developed. As with many other construction materials, control of density is important. If pervious concrete is too dense, with less than approximately 15 % voids, the voids will not be interconnected and the pavement will not drain. On the other hand, if the void percentage is too high, the pervious concrete will lack the strength and durability to support traffic. As a result, it is important to assess in place density. At present, this is generally accomplished by removing cores, which of course damages the pavement. Therefore, for this research, it was desired to relate void ratio, density, and hydraulic conductivity to Ultrasonic Pulse Velocity (UPV). For this purpose, a total of 42 pervious concrete cylinders removed from different field installations in the United States were collected and studied. Density, void ratio, hydraulic conductivity (falling head method) of pervious specimens were evaluated. UPV tests were conducted on all specimens and the results were compared to develop the use of UPV to estimate the properties and performance of pervious concrete. Results indicate that the UPV through pervious concrete may be related to density and void ratio values.