TT1825 Mix design and field evaluation of foamed bitumen stabilised pavements December 2014 www.arrb.com.au Advancing safety and efficiency in transport through knowledge

Need for cost-effective pavement rehabilitation treatments

Commonly use about 3% bitumen Increasing use of foamed bitumen to stabilise unbound granular bases of rural highways Commonly use about 3% bitumen and 1.5% quicklime

National procedures for design of FBS treatments mix design distress modes improved Austroads thickness design procedures project commenced in July 2012 two progress reports published completion June 2016

Collaboration is maximising research outcomes research being guided by a Working Group comprising road agencies and industry extensive collaborative of road agencies, industry and ARRB laboratory testing by two experienced labs, Downer and TMR road agencies and industries are contributing through the construction of under-designed pavts

Foamed bitumen (FB) mix design Existing mix design process in need of improvement

Requirements for untreated material requirements for grading and plasticity of the untreated material, generally accepted not the focus of research

Amount of bitumen and lime determined from indirect tensile modulus testing

Department of Transport and Main Roads (TMR) Queensland modulus requirements Austroads building on TMR experience over the last 15 years TMR lab mixes are compacted into 150 mm diameter moulds and 10 kg Marshall hammer

TMR mix requirements initial modulus 3 hours after lab compaction used as a indicator of early-life rut resistance also undertake wheel tracking

TMR mix requirements bitumen and lime content adjusted to satisfy requirements for cured dry and wet modulus

Issues being addressed in the research project Need to harmonise test methods throughout Australia various compaction methods in use (e.g. gyratory, standard Marshall, large Marshall) recently agreed that the interim Austroads method would be large Marshall based on TMR experience various mixing and compacting moisture contents being used 70% standard Proctor OMC untreated material 85% modified Proctor OMC untreated material some labs using quicklime other hydrated lime

Effect of mixing moisture

Research will lead to Austroads test method and mix design procedure

Issues being addressed in the research project The most challenging issue is validation of usefulness of lab moduli in materials characterisation/mix design. Need to link lab moduli to field performance usefulness of initial moduli in evaluating early-life rut resistance usefulness in cured dry and wet moduli in predicting long term field performance

Purpose The purpose of this project is: to improve and harmonise national mix design procedures for bituminous stabilised materials to identify distress modes of bituminous stabilised pavements from the trial sites. to improve the Austroads thickness procedures.

Field performance to address the project objectives data on the field performance of FBS pavement is required to obtain performance data during the research project (4 years), a number of under-designed pavements have been constructed and are being monitored to date we have five trials Kwinana Freeway Perth (2010) Port Wakefield Road South Australia (2011) Kewdale Road, Welshpool Perth (2011) Calder Freeway, Woodend Victoria (early 2013) Newell Highway Bellata, NSW (late 2013)

Summary of trials Site Surface FBS thickness (mm) Nominal bitumen content (%) Nominal lime content (%) Kwinana Freeway OGA on DGA 150 mm 3.5% 0.8% hydrated lime Port Wakefield road seal 150 mm and 200 mm 3% 1% hydrated lime Kewdale road DGA 100 mm and 150 mm 0.8% quicklime Calder Freeway 1.5% quicklime Newell Highway 175 mm

Kwinana Freeway after FBS placement before asphalt and GRS placed, 2010

Port Wakefield Road 2011

Calder Freeway Victoria under construction March 2013

Newell Highway 2013

Sites tested during construction and monitored for performance

Proposed trial on Western Highway Victoria Heavily trafficked road about 1-2 million ESA per year 200 mm depth FBS, anticipate fatigue after 2-3 years Two binder contents 2.7% and 3.5%

Findings to date

Ravelling of Calder Freeway when pavement was opened to traffic the day of construction ravelling next day may have been affected by adding additional material late in construction to adjust level to match adjacent lane

Cracking has been observed at commencement of trial doubts whether fatigue cracking was a distress mode for FBS to date observed cracking at 2 of the 3 trial sites with seal surfaces Port Wakefield Road, 18 months Calder Freeway, 18 months

Only one instance of rutting, when an old asphalt patch was inadvertently stabilised

Foamed bitumen and lime stabilisation produces high modulus in situ With high temp in summer construction enabled rapid water loss, FBS cores can be taken 7 days after construction

Modulus varies with markedly depth/density in situ modulus can decrease significantly with depth due to lower densities

Back-calculated moduli being monitored to predict time to fatigue damage

Issues being addressed to improve thickness design FBS design modulus currently values of 2000 – 3000 MPa are commonly used need improve process to determine the flexural design modulus from the lab IDT moduli

Data being obtained to improve determination of design modulus relationship between moduli of lab specimens and moduli of early-life field cores relationship to correct the lab moduli to the field densities relationship to adjust IDT modulus to a flexural modulus

Issues being addressed to improve thickness design currently fatigue relationship used is that for asphalt with a reduced volume of binder given material contains 1-2% lime and the bitumen distribution is different from asphalt this relationships needs to be validated

Summary research is being undertaken to improve Austroads procedures for foamed bitumen stabilisaton: mix design thickness strong collaboration and involvement of road agencies and industry will maximise research outcomes progress report published in 2014 project is due for completion in June 2016