Our Communities want better road surfaces and external environmental agencies are requiring then on major projects as part of consenting conditions. NZTA has about 7,000,000 m2 of Open Graded Porous Asphalt (OGPA). Its quiet and smooth with good skid resistance. Our RONs programme will double the amount of OGPA. About 6.4% of the network, but 50% of > 20000 AADT. Around $20/m2- $30/m2 to replace? The average life for OGPA is 7.2 years. Maintenance Budgets are Static and look to remain so.
Are we Agile enough to cope? Herrington, P.R., Reilly, S., Cook S. 2005. Porous Asphalt Durability Test. Transfund New Zealand Research Report 265. The most common form of distress of aged open graded porous asphalt (OGPA) is loss of chip from the surface (fretting and ravelling) caused by embrittlement through reaction with atmospheric oxygen. Resistance to chip loss (the durability of the mix) depends not only on the oxidation resistance of the binder but also on binder film thickness, aggregate grading and percentage of air voids.
OECD WORKING GROUP ON LONG LIFE PAVEMENT SURFACING The OECD long-life pavement surfacing project was conducted in three distinct phases: Phase 1 (2001-2003): Economic viability of long life wearing courses and identification of candidate materials for long life surfacing; Phase 2 (2005-2007): Laboratory elaboration and accelerated load testing of suitable candidate materials. Phase 3 (2009-2013): Field tests of the selected materials.
OECD Phase 1 – Innovation in life Surfaces Phase 1 concluded that long-life pavement surfacing costing around three times that of traditional wearing courses per square metre would find a market for a range of high-traffic roads, depending on: an expected life of 30 years, discount rates of 6% or less, an annual average daily traffic (AADT) of 80,000 or more with at least 15% of heavy trucks. two innovative materials had potential: Epoxy Asphalt and High Performance Cementitious Materials (HPCM).
What is Epoxy Bitumen? Innovative material developed by Shell in 1960’s for Airfields but mainly been used on difficult Bridge decks. Commercially available (at least 4 Suppliers Active In Market – Chemco, Colas, ICOPAL, and a Chinese Supplier) Mixture of specially formulated epoxy resins and ~80-100 bitumen Two part material Cures to hard rubbery-plastic consistency
Chemco Two Part Acid Epoxy Part A (used at 14.6% by weight) consists of an epoxy resin formed from epichlorhydrin and bisphenol-A. Part B type V (85.4%) consists of a fatty acid curing agent in approximately 70 penetration grade bitumen. The product is free from solvents. Source: Turner-Fairbank Highway Research Center, USA
OECD Main findings regarding Epoxy Asphalt Stiffer (higher modulus) at service temperatures, with greater load spreading ability. More resistant to rutting. More resistant to low temperature crack initiation. More resistant to surface abrasion from tyre action, even after oxidation. More resistant to fatigue cracking (although the benefits are less marked at higher strain levels). Less susceptible to water induced damage. More resistant to oxidative degradation at ambient temperatures.
OECD Phase 3 Field Trials The aims of the field tests were to: Confirm the performance of the two materials under real traffic and environmental conditions. Develop construction methods. Improve cost estimates. Optimise material mixes. Thanks to the GFC sites using Epoxy asphalt: Two 60 m OGPA sections in Christchurch, built 2007 Three 210 m OGPA sections in Christchurch, built 2012. The United Kingdom: a 110 m SMA section near Truro (in Cornwall) built 2012. Increase contractor experience levels.
Beam Fatigue Mix Initial flexural modulus at 25°C (MPa) (± sd) Cycles to failure at 25°C and 900 µ ε (± sd) Control 800 ± 15031,900 ± 9700 25% EMOGPA 685 ± 4840,300 ± 3100 100% EMOGPA 576 ± 6430,500 ± 7700
IDT Fatigue After 171 Days Oxidation MixCycles to failure at 100 ± 20µ ε (± 95% confidence limits) Control 8700 ± 5500 25% EMOGPA 12,600 ± 12,200 50% EMOGPA 10,300 ± 12,300 100% EMOGPA >223,000
Fail Fast, Fail Early Trial at CAPTIF 198,000 wheel passes over 3 weeks 8.2 tonne axle load 45 km/hr Average of 12.1ºC Tyre set at 1.5º angle after 175,000 passes Epoxy section undamaged Surface damage to control
Field Trial 1 - State Highway 1 CHCH Three 60m sections laid – December 2007 Standard TNZ P/11 – PA 14 OGPA (20% Void) 20% Void Epoxy OGPA 30% Void Epoxy OGPA Site ~ 16,000 vpd heading north – with 6% Heavy Commercial Vehicles Existing OGPA laid in 1992 being replaced due to fretting Site checked for structural soundness with FWD
TRIAL 2 2012 - CSM Materials 3 x 100 Tonne (210m) trial sections Laid on Structural AC 100% EMOGPA Prevented pick up and marks of 1 st Trial 1. Lay down Trial invaluable practice 50% EMOGPA Made a bit hot, left dull marks, now ok. 25% EMOGPA Made and Laid like normal OGPA.
CSM 2 EMOGPA Manufacture Manufactured at the Fulton Hogan asphalt plant in Miners Road Christchurch Continuous drum plant with a mixing box. Aggregate is heated to the desired temperature in a rotating drum before entering a “mixing box” into which bitumen is feed at the desired rate. Mixing is achieved by an augur in the box. The box is not separately heated.
CSM 2 EMOGPA Manufacture Part A (the less viscous component) was heated to 85°C in a small tank, Part B was decanted from the 200L drums in which it was supplied into a bitumen distributor truck Part B maintained at 125°C Part A was pumped into the main bitumen line (through which Part B travelled) about 2 m from the mixing box, so that minimal blending would have occurred before entering the box.
EPOXY OGPA – TRIAL 2 Economics 25% EMOGPA 40 Year Analysis, 6% Discount rate Extremely good Contract Rate for OGPA Long Term $6/m2 extra for Epoxy Bitumen 8 Year Life OGPA, 40 Year Life Epoxy PWOC OPGA 2.4 times Epoxy 11 year Epoxy has same PWOC as OGPA EI of 4.7, 14 year life for EI of 1
Where is it at! NO BUDMT and VAC approved Use on new and existing RONS where possible Innovation bedded down in Draft Specification Available (P/11E) 1st Contract Tendered and sensible rates received Agility being tested with negotiated rates
The REAL CONCLUSION We were agile enough to implement a innovative solution to the emerging issue of low noise surfaces and fixed budgets Potential reduction of OGPA surfacing maintenance budget to 1/6 of current level. Or more good low noise surfaces for the same money