Development of high quality pervious concrete specifications for Maryland conditions.
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2013-02-01
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Edition:Final report.
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Abstract:One of the main objectives of this research was to develop preliminary specifications for high quality
pervious concrete suitable for use in Maryland State Highway Administration (SHA) projects. The study
utilized aggregates that are used in SHA projects and the durability studies that were conducted assumed
Maryland weather conditions. Investigations were conducted to enhance the structural and durability
characteristics of pervious concrete through the use of different admixtures. The admixtures included
cellulose fibers, a delayed set modifier and a viscosity modifier. Pervious concrete specimens were tested for
density, void content, compressive strength, split tensile strength, permeability, freeze-thaw durability, and
abrasion resistance. Three different types of freeze-thaw durability tests were conducted to mimic potential
field conditions including the possibility of clogged pavement. The freeze-thaw durability tests included:
fully saturated tests, 50% saturated tests, and 0% saturated dry hard freeze tests.
The study found that of the different admixtures tested, cellulose fibers had the largest impact in
improving durability. Including cellulose fibers in the pervious concrete mix resulted in significant increases
in resistance in all three freeze-thaw durability tests. It also resulted in significant increases in abrasion
resistance. By bridging the gap between the coarse aggregates, the cellulose fibers bound the pervious
concrete mixture with an interwoven matrix of fibers. This also improved the tensile strength of the pervious
concrete. The delayed set modifier resulted in a more fluid mix and in large gains in compressive strength at
seven and fourteen days. This admixture may inhibit some of the cement from setting around aggregates and
may result in some cement settling to the bottom and forming a less pervious layer. The viscosity modifying
admixture created a more workable and easier to mold mix. Its effect on strength and durability were
minimal.
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