Degree Type

Dissertation

Date of Award

2008

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

First Advisor

Vernon R. Schaefer

Second Advisor

Kejin Wang

Third Advisor

Christopher Williams

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 studying the important issues, consistency and durability can be improved and baseline values established for future research. This dissertation includes a selection of papers encompassing a variety of important aspects in pervious concrete research, all to improve pervious concrete durability. The papers include 1) The effect of aggregate type on the freeze-thaw durability of pervious concrete, 2) A novel approach to characterize entrained air content in pervious concrete, 3) Effect of curing regime on pervious concrete abrasion resistance, and 4) Evaluation of pervious concrete workability using gyratory compaction. The results show that freeze-thaw durability of pervious concrete is controlled by the aggregate absorption and specific gravity. Air entrainment can be quantified in pervious concrete and also used to improve workability and freeze-thaw durability. Workability can be characterized by two components, initial workability and resistance to additional compaction. Workability can be determined using a low-pressure gyratory testing apparatus and results show that increased binder amount influences properties more than increased water content. Lastly, for samples cured in the field using different methods, samples cured under plastic had the highest flexural strength and abrasion resistance. Curing compounds also improved strength and abrasion resistance over no curing method. From the results, highest priority recommendations for future research include development of standardized testing methods and standardized mixture proportioning methods. Strength and durability will be most significantly affected by improving the paste to aggregate bond strength, which will more effectively utilize the coarse aggregate strength. The basic properties established herein along with future research will allow pervious concrete to be utilized not only for parking areas but also successfully on high traffic volume roadways for improved safety and functionality.

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

John Tristan Kevern

Language

en

Date Available

June 1, 2013

Proquest ID

AAI3307059

OCLC Number

237770927

ISBN

9780549543077

File Format

application/pdf

File Size

117 pages

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