Porosity of Permeable Friction Courses (PFC) Brandon Klenzendorf April 28, 2009 CE 397 – Statistics in Water Resources

 Layer of porous asphalt 1 to 2 inches thick over impervious roadway surface  Water enters pore space and provides benefits: ◦ Reduced splash/spray ◦ Improved traction ◦ Reduced hydroplaning ◦ Improved water quality  Pores become clogged with sediment over time resulting in a loss of porosity  Can we predict the extent of clogging over time? Conventional Asphalt PFC Overlay

 PFC cores are extracted from three roadways for the past three years: ◦ Loop 360 ◦ FM 1431 ◦ FM 620 ◦ March 2007 ◦ February 2008 ◦ February 2009 PFC layer

 33 total porosity measurements

 Kruskall-Wallis Test ◦ H 0 : all groups have identical distributions ◦ Reject H 0 if K ≥ K α (from tables)  Mann-Whitney Test (Rank Sum Test) ◦ H 0 : the means of two groups are identical ◦ Reject H 0 if T ≤ T α/2 (from tables)

 Kruskal-Wallis Test Grouped byK calc K 0.05 DecisionComment Do Not Reject H 0 All locations had the same porosity in Reject H 0 At least one location had a different porosity Reject H 0 At least one location had a different porosity Loop Reject H 0 At least one year had a different porosity FM Reject H 0 At least one year had a different porosity FM Reject H 0 At least one year had a different porosity

 Compare two years of Loop 360 porosity ◦ Mann-Whitney Test  Extend this analysis to the other roadways  Extend this analysis to individual years Grouped byStatisticCriticalDecisionComment ‘07 & ‘08T=167.0 Do Not Reject H and 2008 had the same porosity ‘08 & ’09T=2627.0Reject H and 2009 had different porosities ‘07 & ‘09T=2323.0Reject H and 2009 had different porosities

 Multiple variables can influence PFC porosity ◦ Life of pavement ◦ Traffic volume ◦ Precipitation ◦ Roadway geometry (slope, width, etc.) ◦ Nearby construction sites, etc.  Only consider first four variables

 Estimate annual average daily traffic (AADT)  Linear regression from 16 years of data

 LCRA Hydromet data for Loop 360 and FM 1431  Need to find precipitation data for FM 620

 Complete multiple variable trend analysis  Write final report  Extend this analysis to hydraulic conductivity data (data set not complete)  Determine correlation between porosity and hydraulic conductivity  How can these measurements be used to predict PFC benefits (water quality)?

Questions or Comments?

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 PFC Introduction  Porosity Data  Statistical Tests ◦ Kruskall-Wallis Test ◦ Mann-Whitney Test  Test Results  Trend Analysis  Future Work

 Compare porosity in travel lane to shoulder on Loop 360 ◦ Both Kruskal-Wallis test and Mann-Whitney test Grouped byStatisticCriticalDecisionComment Travel LaneK= Do Not Reject H 0 All years had the same porosity in the travel lane ShoulderT=76.0 Do Not Reject H 0 All years had the same porosity in the shoulder ComparisonT= Do Not Reject H 0 No difference between travel lane and shoulder

Remove impervious base material Vacuum sealed core Submerged specific weight device