Document Type

Report

Publication Date

11-22-2016

Abstract

Concerns persist regarding pervious concrete durability in cold climates related to freeze-thaw and exposure to salt. This study was conducted as an extension to previous work regarding pervious concrete in Vermont, to further investigate freeze-thaw durability with salt exposure in a laboratory environment representative of field conditions. Pervious concrete specimen variations included the addition of sand, replacement of cement with slag, replacement of cement with slag with silica fume, curing time, and saltguard treatment. The addition of 5% sand improved freeze-thaw durability, while the addition of 10% sand led to decreased workability, density, and durability. Both the slag and slag with silica fume cement replacements improved the freeze-thaw durability in comparison to the cement only base mix. Curing time (7 to 56 days) did not influence freeze-thaw durability of pervious concrete with slag or slag with silica fume replacement. The application of liquid saltguard treatment for freeze-thaw resistance was found to be best performed using a dipping procedure over spraying the surface of the pervious concrete. Considering the results of the current work as well as previous work regarding pervious concrete conducted at the University of Vermont and Norwich University, the following general conclusions are drawn which may assist in future pervious concrete mix designs and treatments. In general, the presence of sand replacing a small portion of coarse aggregate (up to about 10%) seems to improve freeze-thaw durability of pervious concrete. Adding sand to a mix design without making adjustments to water-tocement ratio and other ingredients will most likely be not beneficial, as adding sand makes the cement ratio lower, resulting in decreased workability, and lower densities. Replacing up to 20% of Portland cement with slag or slag with silica fume also appears to have benefits in improving freeze thaw durability of pervious concrete. Use of slag or slag with silica fume seem to yield better durability than using fly ash as cement replacement. It is likely that incorporating both sand replacement and cementitious alternatives (slag and slag with silica fume) may represent a more durable pervious concrete mix. If precast pervious concrete slabs were to be used, longer curing times and coating the slabs with saltguard may prove to be beneficial; however, any environmental concerns associated with the latter need to be investigated in future studies.

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