Prediction of Reflection Cracking Resistance of Reinforced Asphalts - Dr Binh Vuong (ARRB/Swinburne Uni) pot

Prediction of Reflection Cracking Resistance of Reinforced Asphalts Dr Binh Vuong (ARRB/Swinburne Uni) Dr Zahid Hoque (RTA NSW) Dr Xavier Choi (CSRIO) www.arrb.com.au Building on 50 years of road research 1. Background 2. Constructability and field performance 3. New pavement design models for reinforced asphalt 4. New material assessment methods for pavement design 5. Evaluation of reinforced asphalt products for a road application in NSW Contents in this presentation… www.arrb.com.au Building on 50 years of road research 1. Background NEED MORE COST-EFFECTIVE SOLUTION FOR • reflective cracking in asphalt overlays on existing cracked concrete and flexible pavements that can significantly shorten fatigue life of asphalt overlays www.arrb.com.au Building on 50 years of road research Use of asphalt reinforcing materials (ARM) Theoretically, ARMs • have very high tensile stiffness and strength • can be selected according to their capacity to deal with the dominating failure mode • can offer a more cost- effective solution to retard deflection cracking than using traditional materials (asphalt, concrete, unbound) Asphalt overlay Reinforced grid Existing cracked concrete or asphalt layer Granular subbase Reflective cracking retardation www.arrb.com.au Building on 50 years of road research Commercial ARMs • Examples of ARMs used in Europe and USA Glass fibre grid Bonded grid Carbon fibre woven Stitched or warp knitted Steel mesh Polyester grid www.arrb.com.au Building on 50 years of road research 2. Constructability and predictability of ARMs MAJOR ISSUES NEED TO BE ADDRESSED www.arrb.com.au Building on 50 years of road research Overseas experience • Trialled in Europe and USA (>30 years) – Manufacturers’ claims: proper installation & good performance – Road authorities’ claims: construction problems/ material defects & poor field performance • Pavement design models – Not sufficient field data (construction standards and field performance) for empirical pavement design procedures – Detailed analytical (finite element) procedures are too complex and do not consider construction issues (not accepted for routine practical use) www.arrb.com.au Building on 50 years of road research Australian experience • Slow usage of ARMs to date due to issues of availability, constructability and predictability • Trialled in Australia (< 10 years) – construction problems related to bonding between pavement layers and bulging of reinforcement products • Austroads mechanistic pavement design procedure – does not consider reflection cracking in pavements in the overlay thickness design – does not enable quantification of the effects of reinforcing materials Reinforcing materials used in Appin Road truck bay, Sydney (RTA) www.arrb.com.au Building on 50 years of road research 2. New pavement design procedures NEED • similar framework as used in current Austroads pavement design procedures • taking into account construction issues www.arrb.com.au Building on 50 years of road research Pavement modelling approach considered • Reinforcing material (ARM) and the surrounding asphalt (used to hold the reinforcing material) are combined into a thin reinforced asphalt layer (RAL) • RAL is used as interlayer in asphalt overlays to retard the rate of propagation of reflective cracking Asphalt overlay Existing cracked concrete or asphalt layer Granular subbase Reinforced asphalt product (asphalt slurry + reinforcing material) Extend cracks in asphalt overlay [...]... For further information … Contact Dr Binh Vuong Principal Scientist ARRB Group Ltd, Vermont South, Victoria, Australia Email: binh. vuong@ arrb.com.au Tel: +61 (3) 9881 1571 Associate Professor Swinburne University of Technology, Hawthorne, Victoria, Australia Email: bvuong@swin.edu.au Tel: +61 (3) 9624 8220 Mobile: +61 (4) 2091 9985 www.arrb.com.au Building on 50 years of road research ... 300 200 100 0 -1 00 0 10 20 30 40 50 60 All RALs produced different tensile strains to the unreinforced case Depth from surface (mm) www.arrb.com.au Building on 50 years of road research Mode II failure at extended cracking condition • Comparison of shear strains due to shear loading Strains induced by shear displacement at one side of crack 2000 Wire mesh - extended crack Glass grid - extended crack... years of road research FE analysis at extended crack condition Tensile strain results for Mode I www.arrb.com.au Building on 50 years of road research Mode I failure at initial cracking condition • Comparison of tensile strains due to crack opening All cases (unreinforced and RALs) produced similar maximum tension strains at bottom of the correction asphalt layer Strains induced by thermal contraction of. .. shear displacement at one side of crack 2000 Wire mesh - Initial crack Carbon fibre - Initial crack Glass grid - Initial crack 1800 Soft subgrade 1600 Strain (micro strain) 1400 Composite asphalt + reinforced mesh layer 1200 Initial crack tip 1000 800 600 400 200 Crack in concrete base 0 0 50 100 150 200 250 Depth from surface (mm) www.arrb.com.au 300 350 400 All cases (unreinforced and RALs) produced... strains at bottom of the correction asphalt layer Building on 50 years of road research Mode I failure at extended cracking condition • Comparison of tensile strains due to crack opening Strains induced by thermal contraction of concrete base 700 Crack tip Composite asphalt + carbon fibre mesh layer 600 Unreinforced Top asphalt Strain (micro strain) 500 Glass grid Wire mesh Carbon fibre 400 Unreinforced Wire... using average stress-strain relationships uniaxial tension Reinforcing material m a In-plane tensile strain in xm direction xm xm a m xm (3) Em In-plane tensile strain in m direction m a a Em m xm (4) Em In-plane shear strains in xm-m direction xm m www.arrb.com.au 1 E xm (5) Gxm m Building on 50 years of road research Calculated stresses and strains using 3D FE analysis • • Typical reinforced asphalt... Young’s modulus of asphalt www.arrb.com.au Building on 50 years of road research Laboratory methods for measuring RAL properties • • Applied to real reinforced asphalt samples (with defects such as bulging, lack of bonding, tear and wear, etc) Proposed laboratory tests for in-plan tensile and shear properties – ASTM D3039 and ASTM D3518 (Test Methods for In-plan Tensile and Shear Properties of Polymer Matrix... GlassGrid Carbon Fibre plane shearing mode Steel mesh www.arrb.com.au GlassGrid Carbon Fibre Building on 50 years of road research Calculated RAL orthotropic elastic properties Reinforcing material Young’s modulus (MPa) Em Exm En Poisson’s Ratio m-xm xm-n Shear modulus (MPa) n-m G m-xm G xm-n T mxm Steel mesh 7000 7900 EAC AC AC AC Fibreglass grid 5312 5312 EAC AC AC AC Carbon fibre 10400 7990 EAC AC... contraction of concrete base 200 Tip of existing crack in concrete base Composite asphalt + carbon fibre Strain (micro strain) 150 Top asphalt Bottom asphalt 100 Unreinforced Wire mesh Glass grid Carbon fibre 50 0 -5 0 0 20 40 60 80 100 120 Depth from surface (mm) www.arrb.com.au Building on 50 years of road research Mode II failure at initial cracking condition • Comparison of shear strains due to shear loading... local stress and strain measurement methods to produce more consistent results – better interpretation methods of the test results 35 30 Tensile force per metre (kN) • 25 20 RA-GF-YY RA-GF-45o 15 10 5 0 0.000 0.005 0.010 0.015 0.020 0.025 0.030 Strain www.arrb.com.au Building on 50 years of road research Measured bonding and shear interlock properties • preliminary test results – able to show different . Prediction of Reflection Cracking Resistance of Reinforced Asphalts Dr Binh Vuong (ARRB/Swinburne Uni) Dr Zahid Hoque (RTA NSW) Dr Xavier Choi. (Deformation dependent)  AC  AC  AC E AC 79007000Steel mesh T m- xm G xm-n G m-xm  n-m  xm-n  m-xm E n E xm E m Shear modulus (MPa) Poisson’s RatioYoung’s