Laboratory freeze-thaw durability of pervious concrete with respect to curing time and addition of sand, slag, silica fume, and saltguard.

PDFTech Report730Concrete pavementsFreeze thaw durabilityWinter maintenanceConcrete curingAdmixturesPorous concretePorous pavementsVermontVermont. Agency of Transportation. Materials and Research SectionSevi, AdamWalsh, DylanAnderson, Ian A.Schmeckpeper, Edwin R.Dewoolkar, Mandar M.University of VermontVermont. Agency of Transportation. Materials and Research SectionUS Transportation CollectionConcerns persist regarding pervious concrete durability in cold climates related to freeze-thawand exposure to salt. This study was conducted as an extension to previous work regarding perviousconcrete in Vermont, to further investigate freeze-thaw durability with salt exposure in a laboratoryenvironment representative of field conditions. Pervious concrete specimen variations included theaddition 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 todecreased workability, density, and durability. Both the slag and slag with silica fume cementreplacements improved the freeze-thaw durability in comparison to the cement only base mix. Curingtime (7 to 56 days) did not influence freeze-thaw durability of pervious concrete with slag or slag withsilica fume replacement. The application of liquid saltguard treatment for freeze-thaw resistance wasfound 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 concreteconducted at the University of Vermont and Norwich University, the following general conclusions aredrawn which may assist in future pervious concrete mix designs and treatments. In general, the presenceof sand replacing a small portion of coarse aggregate (up to about 10%) seems to improve freeze-thawdurability of pervious concrete. Adding sand to a mix design without making adjustments to water-tocementratio and other ingredients will most likely be not beneficial, as adding sand makes the cementratio lower, resulting in decreased workability, and lower densities. Replacing up to 20% of Portlandcement with slag or slag with silica fume also appears to have benefits in improving freeze-thaw durabilityof pervious concrete. Use of slag or slag with silica fume seem to yield better durability than using flyash as cement replacement. It is likely that incorporating both sand replacement and cementitiousalternatives (slag and slag with silica fume) may represent a more durable pervious concrete mix. Ifprecast pervious concrete slabs were to be used, longer curing times and coating the slabs with saltguardmay prove to be beneficial; however, any environmental concerns associated with the latter need to beinvestigated in future studies