Improved Surface Drainage of Pavements Final Report (1998) / Chapter Skim
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Chapter 4 Experimental Studies
Chapter 4 Experimental Studies
Pages 69-116
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From page 69... ...
In the field, full-scale skid testing measurements were needed to extend the hydroplaning model to porous pavement surfaces and to verify the effect of Portland cement concrete grooving on hydroplane g speed. These data were obtained by conducting filll-scale skid test measurements on porous asphalt surfaces installed at the Penn State Pavement Durability Research Facility.
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From page 70... ...
The porous asphalt concrete and Portland cement concrete were placed In the channel, providing the test surfaces for measuring Mami'ng's n. Artificial rainfall was generated with a series of nozzles placed above the test surface, as shown In figure 17.
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From page 71... ...
Figure 15. Cross-section of pavement used in laboratory rainfall simulator.
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From page 72... ...
Figure 16. Overall view of test channel used with laboratory rainfall simulator.
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From page 73... ...
~ : ~.,~ ~ ~ ~ ~ ~:::::: :~: ~i: :~: :::::::::: ::::::::::::::::::::::::::::::::::::::::::::::::::: ::: ~:~::~: ~:~::~:::~:::::: If: Figure 17. Laboratory rainfall simulator.
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From page 74... ...
The flow introduced at the top of the channel was commensurate with the rainfalls rate on the channel, adjusted for non-turbulent conditions in the first 0.5 m of flow. A small adjustment in the introduced flow rate, as calculated on the basis of the rainfall rate, was necessary because the turbulence caused by pelting raindrops impede flow.
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From page 75... ...
A number of trial mixtures were prepared to obtain a range In air void content and MTD. The composition of the resulting three porous asphalt mixtures placed in the laboratory is shown in table 8, and the gradations are presented in figure 19.
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From page 76... ...
Cross-section of flow for porous asphalt sections In laboratory 76 .
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From page 77... ...
Gradations of laboratory and field porous asphalt mr~tures.
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From page 78... ...
This mixture was placed by hand, resulting in a very high a~-void content, as illustrated In table 8. Mixtures B and C were placed with a vibratory compactor; the gradations and max~m~,rn aggregate size were selected to account for the increased compaction and to give a range in air voids and MTD.
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From page 79... ...
Figure 20. Photograph of vibratory compactor.
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From page 80... ...
0.9 32.1 23.0 19.5 1.8 33.7 -- 20.2 2.7 34.6 23.7 23.4 3.7 29.0 22.9 19.8 4.6 32.5 22.9 21.8 5.5 32.5 22.5 20.0 6.4 7.3 Avg. 33.1 33.0 32.6 25.5 23.4 20.7 -20.8 Maxi Theoretical 2.460 2.467 2.504 Specific Gravity Outdoor Test Facilities Full-scale field skid testing was needed to verify the hydroplaning potential of the open graded asphalt concrete and grooved Portland cement concrete surfaces.
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From page 81... ...
Unfortunately, after considerable planning, it became logistically impossible to place the test sections at the Wallops Flight Facility. After careful consideration of the alternatives, a decision was made to install four porous asphalt sections at the Penn State Pavement Durability Research Facility.
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From page 82... ...
Schematic of test sections at the Penn State Pavement Durability Research Facility.
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From page 83... ...
. The mixtures were designed to yield a range of air void contents and maximum aggregate size.
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From page 84... ...
Applying water in the conventional manger with the standard ASTM E 274-90 ("Standard Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale Tire") skid Mailer would not give controlled or measurable water film thicknesses, and therefore, it was necessary to flood the test sections.
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From page 85... ...
Water film thickness measurements were obtained just prior to each skid test using a color-indicat~ng gauge as described later In this chapter. Sand patch and profile measurements were also acquired for each section, and cores were obtained for laboratory permeability testing.
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From page 86... ...
Figure 22. Introduction of water onto test section at the Penn State Pavement Durability Research Facility.
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From page 87... ...
Skid test in progress at the Penn State Pavement Durability Research Facility 87
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From page 88... ...
Unforhmately, the water fiLn thickness was not as controlled as at the Penn State site, and only one water film thickness was reliably obtained. A photograph of a test in progress is shown in figure 24, and a photograph of the Portland cement concrete surface is presented in figure 25.
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From page 89... ...
Figure 24. Test in progress at the Wallops Flight Facility.
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From page 90... ...
Figure 25. Grooved concrete surface at the Wallops Flight Facility.
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From page 91... ...
In order to relate the hydroplaning speed to the water fihn thickness and to validate the water film thickness model, the water film thicknesses had to be measured In the field and In the laboratory during rainfall. The point gauge and other devices available for making these measurements were judged unacceptable for field use because the measurements are slow and tedious to perform and cannot be obtained during rainfall.
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From page 92... ...
Measurement of water film thickness with point gauge on a porous asphalt surface In laboratory.
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From page 93... ...
Schematic of the color-indicatillg water film thickness gauge.
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From page 94... ...
The color-~ndicat~g gauge was used for all of the held testing conducted at the Penn State Pavement Durability Research Facility and the Wallops Flight Facility.
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From page 95... ...
Correlation of water film thickness measurements obtained with the color indicating gauge and point gauge.
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From page 96... ...
Mean texture depths were also obtained from sand patch testing (ASTM E 965) performed in the field and on laboratory 96
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From page 97... ...
Steps in determining texture depth using the profiling method (42~.
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From page 98... ...
The area of the resulting "patch" of glass beads is related to the MID. Measurement of Mann~ng's n Mann~ng's n for the Portland cement concrete surface and for the porous asphalt surface was calculated by measuring the water film thickness on these surfaces with varying rainfall rates arid surface slope.
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From page 99... ...
This procedure ensured that there was no leakage around the periphery of the samples and that the flow occurred In the vertical direction. S~x-~nch cores were obtained from the test track facility, and the lower layer of hot mix was trimmed from the cores, yielding a section that consisted of only the permeable asphalt mixture.
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From page 100... ...
Schematic of drainage lag permemneter. 100 Tank Quick opening valve 7
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From page 101... ...
A vacuum was applied to die samples until they ceased bubbling, using techniques similar to those used In measuring the maximum specific gravity for asphalt concrete, as specified ASTM D 3203-94, "Standard Test Method for Percent Air Voids In Compacted Dense and Open Bituminous Paving Mixtures." Once the samples were saturated, they were placed In the tank, the quick opening value was opened, and the water draining from the tank was collected in a container during the tune interval when the water level in the tank Intersected successive points on the hook gauge. This provided sufficient data to calculate the coefficient of permeability in accordance with the equation reported by Barker (43)
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From page 102... ...
Measured permeability values for the porous asphalt mixes from the field (mixtures 1 through 4) and the laboratory mixtures (mixtures A through C)
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From page 103... ...
Definition of base and surface flow in porous asphalt sections.
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From page 104... ...
Plot of total flow versus flow path to determine flow depth.
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From page 105... ...
To overcome this problem, texture measurements were made on the laboratory porous mixtures using the conventional sand patch procedure on a cast of the surface. Texture depths were also estimated from profile measurements made on the original surfaces as presented in table 1 1.
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From page 106... ...
Based on these facts, sand patch measurements on replicates of the surface are the recommended technique for making texture measurements even though it may not be convenient for field testing, particularly on highly trafficked pavements. Texture measurements made at the Penn State Pavement Durability Research Facility are found in table 12.
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From page 107... ...
(in) MixStation ~2 3 4 Average Station Section Average Average 1105 149.2 136.5 139.7 139.7 1411.55 75 139.7 139.7 146.1 136.5 1401.60 45 146.1 146.1 146.1 139.7 1441.55 15 152.4 158.8 158.8 158.8 157 145 1.27 1.5 2 105 88.9 95.3 88.9 88.9 90 3.66 75 95.3 95.3 88.9 88.9 92 3.66 101.6 101.6 101.6 88.9 98 3.12 15 88.9 88.9 82.6 82.6 85 91 4.11 3 105 133.4 133.4 133.4 136.5 134 1.73 75 136.5 139.7 133.4 139.7 137 1.65 45 146.1 146.1 139.7 139.7 142 1.55 15 146.1 127.0 139.7 146.1 139 138 1.60 1.6 4 105 165.1 165.1 158.8 168.3 164 1.14 75 177.8 165.1 171.5 177.8 173 1.04 177.8 165.1 177.8 177.8 174 1.02 15 171.5 158.8 165 166 169 1.12 1.1 Full-Scale Skid Testing Full-scale skid testing was done at the Penn State Pavement Durability Research Facility and at the Wallops Flight Facility.
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From page 108... ...
For each section, the skid resistance decreased as the water film thickness Increased. However, the skid resistance typically reached a minimum and then unexpectedly increased with increasing water film thickness.
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From page 109... ...
Skid resistance measurements at ache Penn State Pavement Durability Research Facility, mixture I
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From page 110... ...
Skid resistance measurements at the Penn State Pavement Durability Research Facility, mixture 2.
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From page 111... ...
Skid resistance measurements at the Penn State Pavement Durability Research Facility, mixture 3 .
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From page 112... ...
Skid resistance measurements at the Penn State Pavement Durability Research Facility, mixture 4.
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From page 113... ...
~ the opinion of the researchers, this is also the case with porous asphalt surfaces. In other words, We main contribution offered by porous asphalt pavement surfaces to the lowering of hydroplaning speed, even though it is a very significant contribution, is ache Increase In the mean texture depth that these surfaces offer.
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From page 114... ...
Pavement Water Film (skp~ ehd) Skid Number Average Brushed Concrete 12.5~' 60 14.8 14.8 12.5 75 9.6 9.6 12.5 90 6.1 6.1 12.5 82 7.1 7.1 12.5 100 4.6 4.6 Grooved Concrete 12.5 60 17.3 17.3 12.5 80 12.7 12.7 12.5 90 6.0 6.0 Brushed Concrete ASTM`2' 30 26.9 ASTM 30 31.5 ASTM 30 31.8 30.1 ASTM 60 18.6 ASTM 60 20.3 ASTM 60 24.2 23.2 ASTM 90 13.8 ASTM 90 15.3 ASTM 90 17.0 15.4 Grooved Concrete ASTM 30 30.9 ASTM 30 32.9 31.9 ASTM 60 22.4 ASTM 60 22.6 ASTM 60 46.2 30.4 ASTM 90 30.1 30.1 (')
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From page 115... ...
II A S Tag Standennj T est L B' Flood ed to ~ 2 m m 3 5 3 0 2 5 e 2 0 , 1 5 ._ 1 0 5 o n 3 0 6 0 7 5 82 90 1 00 S peed k m/h Ft ore 37. lest res ^ far pi ^ ccdlcretc sections at the TVillcqps Il1~1~ Facility 115
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From page 116... ...
MASTS Standard Test ~ Flooded to 12 mm 35 30 25 20 z ~ 15 ._ oh 10 5 a KEgg 1 ~ 1 9 30 1 60 80 Speed, km/in 90 Figure 38. Test results for grooved concrete sections at the Wallops Flight Facility 116 .
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