(3) The Effect of Ageing on the Fatigue and Healing Properties of Bituminous Mortars. Proefschrift. ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op woensdag 14 december 2011 om 10:00 uur door Wim VAN DEN BERGH Industrieel Ingenieur Bouwkunde, Hogeschool Antwerpen Geboren te Bornem, België.
(4) Dit proefschrift is goedgekeurd door de promotor: Prof. dr. ir. A.A.A. Molenaar Copromotor: Ir. Ing. M.F.C. van de Ven Samenstelling promotiecommissie: Rector Magnificus Prof. dr. ir. A.A.A. Molenaar Ir. Ing. M.F.C. van de Ven Prof. dr. ir. G. Thenoux Prof. dr. M. Othman Hamzah Prof. ir. A.Q.C. van der Horst Dr. H. Soenen Ir. A.C.A. De Jonghe. voorzitter Technische Universiteit Delft, promotor Technische Universiteit Delft, copromotor Pontificia Universidad Católica de Chile Universiti Sains Malaysia Technische Universiteit Delft Nynas Competence Centre Antwerp, adviseur KOAC-NPC Belgium, adviseur. Prof. dr. ir. K. van Breugel. Technische Universiteit Delft, reservelid. Published and distributed by: Wim Van den bergh E-mail: email@example.com Section of Road and Railway Engineering Faculty of Civil Engineering and Geosciences Delft University of Technology P.O. Box 5048 2600 GA Delft The Netherlands ISBN 978-90-8570-784-4 Printing: Wöhrmann Print Service, Zutphen, The Netherlands © 2011 Wim Van den bergh All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the author..
(5) To our two beautiful daughters Hanne and Fien.
(7) Acknowledgements It must have been in October 2003, after seven years of work as a researcher at the Hogeschool Antwerpen, that my former head of section Luk Allonsius and my project leader Tony De Jonghe approached me for a sincerely –almost fatherly- talk to start with doctoral research project. Anno Domini 2011, I can show my three dear women, family, friends, colleagues, mentors and the rest of the world the result of what I have been doing during these last 7 (seven) years, called ‘het doctoraat /the Ph.D.’. With this report I will finally demonstrate in a scientifically way that the healing, which has crossed many times our path, is in this case indeed not some kind of alternative therapy but a certain property of that black material on the road, called asphalt. This research work was definitely not a one-man-show and some words for appreciation are appropriate. I am grateful to the Artesis University Colleges of Antwerp and the Delft University of Technology for their financial and infrastructural support. Special thanks to my current and former heads of the building section: Amaryllis Audenaert and Luk Allonsius, finally we can start our day without asking about the status of the project. The collaboration with many former master students was appreciated and I mention especially Kim, Ann, Paul and Sarah. To my colleagues of the Building and Construction Section and of the department of Applied Engineering are thanked especially Rita, Ariane, Rozemarijn, Lut, Sabine, Steven, Guido, Letty, Dirk. I appreciated the effort of many people who contributed less or more to this work: the foreign coffee-grower whose intense labour was appreciated several times each day; Dirk Anthierens (former head of Artesis department), Ann Vanelstraete, Stefan Vansteenkiste and Joëlle De Visscher of Belgian Road Research Centre. Special acknowledgement is appropriate for the team of the Flemish Road Agency and especially Pieter De Winne, René Reynaert and Ronny Williams. Thank you Pieter Veulemans for the technical support and for the supply of aggregates and reclaimed asphalt. I express my gratitude to all members of the laboratory staff of Road and Railway Engineering section in the Faculty of Civil Engineering and Geo-sciences at the Delft University of Technology, in particular Abdol Miradi, Marco Poot and Jan Moraal, who are thanked for their technical assistance, interesting talks and advice. Also the secretaries Jacqueline and Sonja are thanked for their support. A special word is reserved for Wim Verwaal (Faculty of Geo-Engineering, Department of Geotechnology) for conducting the interesting CT-scans. Milliyon and Jian, I will keep nice memories of you both, thank you for the support and kindly cooperation. I wish them, and all other PhD-students all the best for their own research. To Rien Huurman, I would like to express my appreciation for his advice and hospitality.. i.
(8) I thank the NYNAS Competence Centre team Tine Tanghe, Hilde Soenen, Marianne and Serge for their important support on the FTIR and the binder supply. A special word of thanks is appropriate for Dirk Lacaeyse, the quality supervisor of Belgian asphalt mixtures (Copro vzw). Thanks for the supportive talks and information! We keep on going. Some parts of the research in this work were conducted within the RILEM ATB-TG5 group “Recycling of bituminous materials”. This collaboration was an important support during my work the last years. I thank all active members for their contributions, with a special thank to Laurent Porot, Thomas Gabet and Chantal de La Roche. I appreciate the efforts of Dieter, Matthias, Katrien and Lut for their linguistic advices. Acknowledgement is dedicated to my former and current colleagues of the Road Engineering Research Section: thank you all for your appreciation and encouraging words. Frank, Bart, Matti, Jan, Jan, Karolien and Dieter, without your technical and comradely support the research work in the lab would certainly have been less attractive; Dieter and Jan, especially a ‘dankjewel’ for your supporting efforts during the last weeks. To Jan Verheyen: Jan, we have been working a long time together in the lab on the recycling of roofing, now our ways parts, I thank you a lot for the nice co-operation and interesting views. And to Cedric, thank you my friend for the support and the nice talks; for both of us it was a race against time with many sacrifices. Let us have soon a nice research project with a lot of jazz. To my promoters and mentors, André A.A. Molenaar, Tony C.A. De Jonghe and Martin F.C. van de Ven, I would like to dedicate a special acknowledgement for their long time of substantial support, advice and hospitality at the TU Delft. Thank you sincerely. Thank you all. I will keep good memories on the people with whom I have worked. To my closest friends, Lies, Marjan, Marleen, Christophe and Sam: I appreciated you keeping up my spirit by your encouraging words and nice messages. Een dikke dankjewel aan mijn drie ouders, schoonouders, broer en zus, Liesbet, tante Lisette en grootouders voor het vele geduld en inleving met mijn gezin. Als laatste zou ik mijn waardering willen uiten voor mijn partner An en onze twee lieve dochters Hanne en Fien. Ik weet dat ik er niet altijd voor jullie was, dikwijls verzonken in gedachten; daarom ben ik jullie zeer dankbaar voor de onvoorwaardelijke ondersteuning en begrip tijdens de voorbije 7 jaar. Dit was ons teamwerk. Heel veel dank. Wim Van den bergh December 2011 If you cannot in the long run tell everyone what you have been doing, Your doing has been worthless. Attributed to Erwin Schrödinger (1887-1961) ii.
(9) Table of Contents Acknowledgments. i. Table of Contents. iii. Summary. ix. Samenvatting. xi. Abbreviations. xv. 1. Introduction. 1. 1.1 The Belgian Road Network 1.2 Research description 1.2.1 Problem background 1.2.2 Research objectives 1.3 Outline of the dissertation 1.4 References. 1 5 5 7 8 8. Recycling of Asphalt Pavement in Flanders. 11. 2.1 Introduction 2.2 Flemish specifications for recycling 2.2.1 Policy for accepting reclaimed asphalt (RA) 2.2.2 Maximum amount of RA in hot asphalt mixtures 2.3 A brief survey of RA characteristics in Flanders 2.4 Production facilities of hot mixtures using RA 2.5 Reproducibility round robin for RA-binders in Flanders 2.6 Conclusions 2.7 References. 11 14 15 18 19 23 24 28 29. Literature Review. 31. 3.1 Ageing of the bituminous binder in the asphalt mixture 3.1.1 The constitution of bituminous binders 3.1.2 Binder hardening 3.1.3 Effects of ageing on the chemical structure 3.1.4 Binder ageing tests 3.1.5 Ageing of bituminous binders in asphalt mixtures 3.1.6 Influence of aggregates on ageing 3.1.7 Accelerated asphalt ageing in the laboratory 3.1.8 Ageing indicators for bituminous binders. 31 31 36 38 41 45 47 48 51. 2. 3. iii.
(10) 4. 3.1.9 Effect of film thickness on binder ageing 3.2 Fatigue and healing: definitions and test methods 3.2.1 Introduction 3.2.2 Fatigue mechanisms and definitions for bituminous mixtures 3.2.3 Healing of bituminous mixtures: definitions and test methods 188.8.131.52 Introduction 184.108.40.206 Healing mechanism 220.127.116.11 Healing storage tests 18.104.22.168 Dynamic bending fatigue test on asphalt mixtures 22.214.171.124 Healing via energy dissipation 126.96.36.199 Quantification of healing by using DMA 188.8.131.52 Other research concerning the healing mechanism and quantification 184.108.40.206 Surface energy 220.127.116.11 Healing shift factors in pavement design 3.2.4 Fatigue and healing tests on bituminous binders and mastics with DSR 3.3 The influence of using RA on the performance of the asphalt mixture 3.4 Main conclusions of Literature Review 3.5 References. 52 53 53. 76 79 81. Research Methodology. 95. 55 59 59 60 62 63 66 67 71 71 73 75. 4.1 Problem description 95 4.2 Research methodology 98 4.2.1 Research topic 1: Artificially Aged Asphalt Mixture 99 18.104.22.168 Research approach 100 22.214.171.124 Experimental research method 101 126.96.36.199 Practical restrictions and adjustments 104 4.2.2 Research topic 2: the effect of ageing on the fatigue and healing properties of bitumen and bituminous mortar 105 188.8.131.52 Justification of mortar as test material 105 184.108.40.206 Research approach and test methods 107 4.3 References 109. 5. Infrared Spectroscopy 5.1 Theoretical Principles of Infrared Spectroscopy (IR) 5.2 The Attenuated Total Reflectance Spectrometer 5.2.1 ATR/FTIR Spectrometer Thermo Scientific Nicolet iS10 5.2.2 ATR/FTIR Spectrometer Perkin Elmer. iv. 111 112 117 122 123.
(11) 5.3 Specific functional groups for bituminous binders regarding ageing 5.4 Infrared Spectrum Semi-Quantitative analysis 5.4.1 Settings for limits of the areas and peaks 5.4.2 Method 1: area calculation method 5.4.3 Method 2: settings as defined by the Rilem ATB-TG5 project group 5.4.4 Method 3: modified areas of method 1 (Artesis) 5.4.5 Method 4: modified areas of method 2 5.4.6 Method 5: peak calculation 5.5 Repeatability tests with ATR-FTIR 5.5.1 Statistical functions 5.5.2 Experimental program 5.5.3 Results and analysis 220.127.116.11 Repeatability of single and successive ATR/FTIR test: cold and hot sampling 18.104.22.168 Repeatability of ATR/FTIR for virgin and aged binders 5.6 Conclusions and recommendations 5.7 References. 6. Rheological Test Methods, Materials and Ageing Procedures 6.1 Bitumen Rheology Tests 6.1.1 Penetration and softening point 6.1.2 Penetration Index 6.1.3 Dynamic shear rheology 22.214.171.124 Dynamic shear rheometer principles for oscillation 126.96.36.199 Modelling of bitumen: master curves of G* and delta 188.8.131.52 Bitumen healing and fatigue test 6.1.4 Penetration EN1426 versus Dynamic Shear Rheometer 6.2 Dynamic Shear Rheometers 6.2.1 Dynamic Shear Rheometer MCR300: conditions and sample preparations 6.2.2 Dynamic Shear Rheometer AR2000 184.108.40.206 Settings AR2000 for the mortar fatigue and healing testing 220.127.116.11 Data processing and output interpretation 18.104.22.168 Software settings in function of the exact number of loading cycles 22.214.171.124 Preliminary tests: stress and strain control for DSR loading. 124 127 128 129 132 133 134 134 135 135 136 138 138 144 148 151. 153 153 153 154 155 155 158 160 160 162 162 164 164 166 169 171 v.
(12) 6.3 Artificial ageing of binders 6.3.1 Selection of the reference binders B0601, B0701 and B0801 6.3.2 Selection of short term ageing tests 6.3.3 Selection of long term ageing test 6.4 Development of an ageing procedure for the artificial ageing of asphalt mixtures in the laboratory 6.4.1 Objective and scope 6.4.2 Ageing characterization 126.96.36.199 Rheological ageing indicators for the evaluation of binder ageing 188.8.131.52 Chemical ageing indicators 6.4.3 Materials and mixture composition for AAAM 184.108.40.206 Materials and mixture composition for AAAM1 to AAAM7 220.127.116.11 Materials and mixture composition for AAAM8 to AAAM9 6.4.4 Production of AAAM and production facilities 18.104.22.168 Mixing process procedure 22.214.171.124 Ageing facilities RERS (Antwerp) 126.96.36.199 Ageing apparatus 2 (TU Delft) 6.4.5 Overview of the ageing procedures and sampling 188.8.131.52 Sampling of AAAM1 to AAAM7 184.108.40.206 Participation in RILEM ATB-TG5 Round Robin 220.127.116.11 Binder Test Methods Round Robin 6.5 Mortar Composition and sample preparation 6.5.1 Research approach mortar production 6.5.2 Mortar definition and composition 6.5.3 Mortar fabrication 18.104.22.168 Virgin (unaged) mortar 22.214.171.124 Aged mortar 126.96.36.199 RA- mortar 188.8.131.52 Sampling 184.108.40.206 Production of the mortar specimens for AR2000 6.6 References. 7. vi. 177 177 179 180 182 182 184 184 185 186 188 189 190 190 191 193 194 194 195 198 198 198 199 205 205 206 206 206 206 210. Development of Artificially Aged Asphalt Mixture. 213. 7.1 Binder Ageing 7.1.1 Rheological results 220.127.116.11 Ageing of Binder B0601 18.104.22.168 Ageing of Binder B0701 22.214.171.124 Ageing of Binder B0801 126.96.36.199 Comparison of ageing tests on binder B0601, B0701 and B0801. 215 215 215 219 219 222.
(13) 8. 188.8.131.52 Correlation of B0801 binder ageing within RILEM project 7.1.2 Chemical characterization 184.108.40.206 Binder B0601 series 220.127.116.11 Binder B0801 series 18.104.22.168 Correlation B0801 ageing with RILEM TG5 22.214.171.124 Comparison laboratory aged binders and correlation with RA-binder 7.1.3 Correlating rheological and chemical data 7.1.4 Conclusions laboratory binder ageing 7.2 Laboratory Asphalt Ageing: AAAM- Artificially aged asphalt mixture 7.2.1 Experimental program 7.2.2 Results of binder ageing in AAAM1 to 5 126.96.36.199 Rheological binder properties 188.8.131.52 Results of infrared measurements 7.2.3 Results of AAAM7 7.2.4 Contamination of filler or solvent 7.2.5 SARA analyses 7.2.6 Results of AAAM8 and AAAM9 part Artesis/Delft 184.108.40.206 Rheological evaluation of recovered binder 220.127.116.11 FTIR evaluation for Rilem binders 7.2.7 RCAT ageing of mortar 7.2.8 Saal and Labout check 7.3 Rheological and infrared binder ageing charts 7.4 Conclusions and recommendations binder ageing in the Laboratory: virgin binder, mortar and asphalt mixtures 7.4.1 Rheological approach 7.4.2 Infrared measurements 7.4.3 Final recommendations for the laboratory ageing of bituminous binder, mortar and asphalt mixtures 7.5 References. 266 267. Fatigue and Healing of Bituminous Mortars. 269. 224 225 225 228 230 231 234 235 237 237 239 239 242 244 246 248 248 249 254 259 259 260 263 263 264. 8.1 Introduction 269 8.2 Selection of the fatigue and healing procedure and definition 270 8.2.1 Constant torque shear fatigue test 270 8.2.2 Discontinuous oscillation test with constant shear torque AR2000 (Healing test) 276 8.2.2 Healing factor 277 8.3 Experimental test scheme for mortar 277 8.4 Results 277 8.4.1 Results of torque sweeps – determination of LVER 277 8.4.2 Master Curves of mortar MO05, MO06 and MO07 279 vii.
(14) 8.4.3 Results for Nf,G*xC in function of sample stress and initial strain 8.4.4 Results for Nf,DER in function of dissipated energy 8.4.5 Fatigue and healing tests versus chemical composition 8.5 CT-scans 8.6 Conclusions and Recommendations 8.7 References. 9. 281 288 292 293 298 299. Conclusions and Recommendations. 301. 9.1 The Development of Artificially Aged Asphalt Mixture 9.1.1 Main conclusions 9.1.2 Final recommendations for FTIR measurements concerning the evaluation of binder ageing 9.1.3 Final recommendations for the ageing of binders and bituminous mortars in the laboratory 9.1.4 Final recommendations for the ageing of asphalt mixtures in the laboratory 9.2 Fatigue and healing tests on bituminous mortars 9.2.1 Main conclusions 9.2.2 Final recommendations for fatigue and healing tests on bituminous mortars 9.3 Discussion note concerning the hypotheses and achievements of this work 9.4 References. 301 303. Addenda (on CD). 304 305 306 307 307 308 309 312. 313. A.1.0 List of Standards A.5.1 Description of specific groups which occur within the region 600 cm-1 to 1800 cm-1 A.5.2 List of data of FTIR-measurements A.6.1 Aggregate Grading and Mixture Design A.7.1 Test settings for frequency sweeps B0801 series A.7.2 List of data of FTIR measurements A.7.3 Reference to submitted part for the SoA Report ATB-TG5 A.7.4 Summary binders A.8.1 Settings and results of mortar fatigue and healing tests. Curriculum Vitae. 315. Propositions - Stellingen. 319. viii.
(15) The Effect of Ageing on the Fatigue and Healing Properties of Bituminous Mortars Summary. As from the manufacture of the asphalt mixture, the bituminous binder is affected by an ageing process. During its service life, this process is observed by a change in its mechanical properties, such as an increasing stiffness modulus, and changing chemical composition. Ageing is believed to be an important factor in the durability of asphalt mixtures and their mechanical performance. After service life, the asphalt can be recycled and used as reclaimed asphalt aggregate (RA) in hot asphalt mixes. The aged binder of this RA, as well as the inert aggregates, is taken into account in the mixture design. Questions arise whether this binder will affect the fatigue and the healing properties of the new asphalt mixture containing RA. In Flanders up to 50 % of the binder content of asphalt mixture for base layers is allowed to be originating from RA. The aim of this study was to investigate the effect of RA-binder on the fatigue and healing properties of asphalt mixtures –c.q. bituminous mortars for base layers. In order to achieve this, two research objectives were defined: i) the development of a laboratory aged asphalt mixture and ii) the evaluation of RA on the fatigue and healing property of mortars. The first research objective aimed to a procedure, which allows us to be provided by a reproducible and homogenous RA of which the components are known and also available for other tests, e.g. tests on the mastic or in round robin experiments. RA from the road can hardly fulfil this requirement. In this research, a procedure was defined and tested to age an asphalt mixture in the laboratory. In order to understand the ageing process in the laboratory, asphalt mixtures were aged and the binder was extracted and recovered. Accordingly the binder was aged by the Rotating Cylinder Ageing Test Device (RCAT). The rheological and chemical properties were determined from the binders at different ageing times and compared to extracted binders from RA. The chemical properties, in particular the increase of the C=O and S=O bonds were evaluated by Fourier Transform Infrared measurements (FTIR). For this, various methods were used since a standard is not available. The increase of these bonds as well as the G* and Softening Point R&B resulting from the rheological measurement were taken as ageing indicators. The evolution of other bonds during ageing were observed and evaluated. Different mixtures and binder grades were used in this study and the rheological and chemical indicators were compared to the respective properties of genuine RA samples. By means of this study of the recovered binders and a comparative survey on Flemish RA, two methods are recommended in this work. For asphalt mixtures for base layers a short term ageing period of 3 hours at 130 °C succeeded by a long term ageing period of 168 hours at 90 °C is recommended for an adequate ageing of the binder in the asphalt mixture. A standard air ventilated oven can be used. A second procedure consists of 4 hours at 135 °C succeeded by 168 hours ix.
(16) at 85 °C. This procedure was developed and evaluated within a RILEM round robin test. The ageing of the mixtures showed that the chemical ageing indices for C=O and S=O increased significantly during 140 hours without reaching a clear level. The rheological parameters G* and softening point R&B increased during short term and long term without reaching a maximum level after 140 hours. After a long term ageing period of 168 hours a sufficient ageing level is being reached for all ageing indicators. Considering the pure binder aged by means of the RCAT, the combination of both rheological and chemical results indicates a progressive ageing process even after 140 hours. Taking into account the results of the RAsurvey, where repeatedly hard binders were found, it is recommended to condition the binders for a longer time than the time given in the Standard (144 hours). It should be mentioned that the laboratory ageing of the asphalt mixtures is only established by these rheological and chemical ageing indicators of the binder. The mixture shows no partly uncovered aggregates, which is not the case for in-situ RA. It is recommended for a next project to select a proper treatment for this aged mixture in order that also the coating is comparable to RA. The influence of RA on the fatigue and healing properties was determined by continuous and discontinuous oscillation tests on mortars. The mortar design is composed by bitumen, filler and fine sand aggregates (< 0.5 mm). Virgin and aged mortars were tested by using the Dynamic Shear Rheometer (DSR). The recommended long term ageing for the binders defined in topic one was used to age mortars by means of RCAT during 168 hours. Due to the relative larger sizes of the aggregates compared to mastic, cylindrical mortar specimens were manufactured instead of specimens for the standard plate-plate configuration. For one mortar, an aged binder recovered from RA was used as binder. A preliminary experimental program was conducted in order to study the controlling and data acquisition of the DSR. These tests revealed that at high torque levels a controlled strain test is not feasible since during the first cycles the strain is larger than required and the number of loading cycles is different to the setting in the software. Also the DSR oblige a minimal adjusting time, which does not allow a discontinuous test such as one cycle loading succeeded by a rest period. For that reason, a discontinuous loading scheme of 30 cycles loading and 90 cycles of rest was defined. Stress controlled fatigue tests with and without rest periods were conducted in oscillation shear mode at 15 °C and 10 Hz. Considering an equal stress in the sample, the fatigue properties of laboratory-aged mortars improved when the mortars are aged. The RA-mortar shows similar fatigue properties as the laboratory-aged mortar. The introduction of rest periods increases the fatigue life of the samples significantly. Healing factors between 1.8 and 4.5 are obtained, depending on the stress and the mortar type. The healing factor of the RAmortar is less than for the laboratory-aged mortar, respectively 1.8 and 4.0 although the chemical (C=O and S=O) and rheological properties of the binders are similar. Key-words: Ageing, Asphalt, Binder, Bitumen, Dissipated Energy, DSR, Fatigue, FTIR, Healing, Mortar x.
(17) De Invloed van Veroudering op het Vermoeiingsgedrag en het Zelfherstellend Vermogen van Bitumineuze Mortels. Samenvatting. Reeds vanaf de productie van een asfaltmengsel is het bindmiddel ervan onderhevig aan een verouderingsproces. Dit proces wordt gedurende de levensduur waargenomen door een verhoogde stijfheidmodulus en een gewijzigde chemische samenstelling. Aan deze veroudering wordt een belangrijke rol toegeschreven in de duurzaamheid en de mechanische prestaties van het mengsel. Wanneer het asfalt wordt gerecycleerd als asfaltaggregaat (AG) voor toepassing in een nieuw asfaltmengsel, dan wordt dit verouderd bindmiddel net zoals de inerte aggregaten in rekening gebracht bij het mengselontwerp. In Vlaanderen mag tot 50% van het bindmiddelmengsel afkomstig zijn uit asfaltaggregaat voor een toepassing in een asfaltmengsel voor een onderlaag. De laatste jaren worden er vragen gesteld betreffende het vermoeiingsgedrag en het zelfherstellend vermogen van het samengestelde asfaltmengsel van nieuwe en oude materialen. In dit doctoraatsonderzoek wordt de invloed van het gebruik van het verouderd bindmiddel op het vermoeiingsgedrag en zelfherstellend vermogen van asfaltmengsels voor onderlagen onderzocht. Hiervoor werden twee onderzoekstopics gedefinieerd: i) uitwerken en toetsen van een procedure om asfalt te verouderen in het laboratorium tot asfaltaggregaat, en ii) de evaluatie van asfaltaggregaat op het vermoeiings- en healingsgedrag van bitumineuze mortels. Het eerste deel omvat het verouderingsprotocol om asfaltmengsels te verouderen in het laboratorium. Zo’n procedure laat ons toe te beschikken over een homogeen en reproduceerbaar verouderd materiaal waarvan de basiscomponenten gekend zijn. Dit materiaal kan dan verder gebruikt worden voor andere tests, bijvoorbeeld mastiektests en rondzendonderzoeken. In-situ AG kan hieraan meestal niet aan voldoen. Om het verouderingsgedrag van deze verouderde asfaltmengsels vast te leggen, werd het bindmiddel op regelmatige tijdstippen teruggewonnen en beproefd. Daarnaast werd het originele bindmiddel verouderd door middel van het Rotating Cylinder Ageing Test Device (RCAT) en eveneens op regelmatige tijdstippen beproefd en vergeleken met de bindmiddeleigenschappen van de eerder vernoemde bitumenmonsters. Aan de hand van Fourier Transform InfraRed metingen (FTIR) werd de toename van C=O en S=O bindingen als verouderingsindicator en de evolutie van andere bindingen in functie van de veroudering geëvalueerd. Hiervoor werden verschillende methoden gehanteerd, daar er geen standaardprocedure is om kwantitatief en kwalitatief deze bindingen te meten. Voor de rheologische verouderingsparameter werd de toename van G* en het verwekingspunt R&B geselecteerd. De rheologische en chemische indices werden vergeleken met de respectieve eigenschappen van bitumina uit in-situ AG-monsters. Door middel van de resultaten uit dit experimenteel programma en een vergelijkende studie xi.
(18) van AG in Vlaanderen, wordt in dit werk een verouderingsmethode aanbevolen. Voor een toepassing in onderlagen wordt aanbevolen om asfaltmengsels te verouderen in een geventileerde oven in twee stappen: een korte termijnveroudering gedurende 3 uur bij 130 °C gevolgd door een lange termijnveroudering bij 90°C gedurende 168 uur. Gelijkwaardige resultaten werden gevonden voor korte termijn veroudering bij 135 °C gedurende 4 uur gevolgd door een lange termijn veroudering bij 85 °C gedurende minstens 168 uur. Deze procedure werd verder uitgewerkt en geëvalueerd binnen een Round Robin van de RILEM TG5-werkgroep en kan aldus ook gebruikt worden om een asfaltmengsel te verouderen. Tijdens het verouderen verhoogden de chemische indices voor C=O en S=O significant zonder een duidelijk maximum te bereiken na 140 uur. De rheologische parameters G* en verwekingspunt verhoogden tijdens korte termijn- en lange termijnveroudering, maar eveneens zonder een maximum te bereiken, zelfs na 140 uur. Bij een verouderingstijd van 168 uur wordt een voldoende verouderingsniveau bereikt. De combinatie van rheologische en chemische resultaten duiden op een continue veroudering van het bindmiddel na 140 uur. Gezien de resultaten uit het vergelijkend onderzoek van AG in Vlaanderen, waarbij telkens harde bindmiddelen werden teruggevonden, wordt aanbevolen om de bindmiddelen aan een langere conditionering te onderwerpen dan aangegeven in de norm. Het moet vermeld worden dat de evaluatie van het verouderen van de mengsels gebaseerd is op louter rheologische en chemische verouderingsindicatoren van het bindmiddel. Het verouderd mengsel bestaat uit volledig omhulde aggregaten, wat niet het geval is voor in-situ AG. In een volgend onderzoek dient de verdere behandeling van het mengsel onderzocht te worden opdat ook de omhulling vergelijkbaar is met dat van AG. Het effect van AG op het vermoeiings- en zelfherstellend vermogen werd in dit werk uitgevoerd op de bitumineuze mortel door middel van continue en discontinue oscillatietesten. Mortel wordt in dit werk samengesteld uit bitumen, vulstof en fijn zandaggregaat met een diameter kleiner dan 0.5 mm. Virgin- en verouderde mortels werden beproefd door gebruik te maken van de Dynamic Shear Rheometer (DSR). De RCAT- veroudering met de aanbevolen verouderingstijd van 168 uur uit topic 1 werd geselecteerd om de bitumineuze mortel te verouderen. Gezien de grootte van de aggregaten in de mortel ten opzichte van mastiek, werden cilindrische proefstukken gebruikt in plaats van de standaard plaat-plaatconfiguratie. Voor één mortel werd bitumen, teruggewonnen uit AG, gebruikt (AG-mortel). Eerst werd een experimenteel vooronderzoek uitgevoerd om de besturing en de gegevenscaptatie van de DSR vast te stellen. Uit deze testen bleek dat bij hoge torsieniveaus een oscillatie met een gecontroleerde rek niet uitvoerbaar was, omdat tijdens de eerste cycli de initiële rekgrootte hoger was dan gevraagd en het aantal cycli in de software niet overeenkwam met de uitgevoerde cycli. De hardware van de DSR vereist bovendien een minimale aanstuurtijd waardoor een discontinue test met één cyclus belasting gevolgd door een rustperiode eveneens niet uitvoerbaar is. Daarom werd beslist om een discontinue test te definiëren als een belastingsduur van 30 cycli telkens gevolgd door een rustperiode van 90 cycli.. xii.
(19) Er werden continue en discontinue krachtgestuurde vermoeiingsproeven uitgevoerd bij 15 °C en 10 Hz met de DSR op cilindrische proefstukken. Bij een gelijke spanningconditie, vertonen de mortelproefstukken die verouderd werden in het laboratorium, een betere vermoeiingskarakteristiek ten opzichte van de niet-verouderde mortels. De vermoeiingskarakteristieken voor de AG-mortel en de laboratorium verouderde mortel zijn gelijkwaardig. Het toepassen van rustperiodes tijdens de vermoeiingsproef leidt tot een verlenging van de vermoeiingslevensduur. Er werden healing factoren verkregen tussen 1.8 en 4.5, afhankelijk van de toegepaste spanning en het morteltype. De healing factor voor de AG-mortel is significant lager dan voor de laboratorium verouderde mortel, respectievelijk 1.8 en 4.0, ondanks dat de chemische (C=O en S=O) en rheologische eigenschappen van de bindmiddelen gelijkwaardig zijn. Key-words: veroudering, asfalt, bindmiddel, bitumen, gedissipeerde energie, DSR, vermoeiing, FTIR, zelfherstellend vermogen, healing, mortel.. xiii.
(21) Abbreviations AC-14 Artesis AI AAAM AM AI AR B BRRC CiTG COPRO. Dense asphalt concrete with 0/14 mm gradation Artesis Hogeschool Antwerpen - University Colleges of Antwerp Ageing Index Artificially Aged Asphalt Mixture Asphalt Mixture Ageing Index Ageing Rate Binder Belgian Road Research Centre Faculty of Civil Engineering and Geosciences Impartial organisation for the COntrol of PROducts in the building environment DE Dissipated Energy DER Dissipated Energy Ratio DSR Dynamic Shear Rheometer EME Enrobé à Module Elevé; Asphalt Concrete with high stiffness FAM Fine Aggregate and binder Matrix materials HPI Healing Potential Index ICO Index Carbonyl ISO Index Sulfoxides ITS Indirect Tensile Strength ITS-R Indirect Tensile Strength Ratio FLI Fatigue Life Increase FRA Flemish Road Agency – Agentschap Wegen en Verkeer van de Vlaamse Gemeenschap FTIR Fourier Transform InfraRed LOT Lifetime Optimisation Tool LTA Long Term Ageing MO Mortar RA Reclaimed Asphalt (Dutch: Asfaltaggregaat - AG) RCAT Rotating Cylinder Ageing Test RCAT163ST Rotating Cylinder Ageing Test- short term ageing conditioning RCAT90LT Rotating Cylinder Ageing Test- long term ageing conditioning RCAT90LTE Rotating Cylinder Ageing Test- extended long term ageing RDEC Ratio Dissipated Energy Change RERS Road Engineering Research Section (Artesis) RILEM International Union of Laboratories and Experts in Construction Materials, Systems and Structures ATB-TG5 RILEM Technical Committee ATB- Advanced Testing of Bituminous Materials -Task Group 5 (TG5) RTFOT Rotating Thin Film Oven Test SB250v2.2 Standard specifications for Road Construction and Maintenance in Flanders (Standaardbestek voor de Wegenbouw versie 2.2) STA Short Term Ageing xv.
(22) TRA13 TU Delft PAV PV. xvi. Guiding Practice for the application and evaluation of reclaimed asphalt in bituminous mixtures version 3.0 Delft University of Technology Pressure Ageing Vessel Test Plateau Value.
(23) 1. I NTRODUCTION. 1.1. T HE B ELGIAN R OAD N ETWORK The Belgian authorities and industry invest continuously in road infrastructure, development and maintenance because of the corridor function for road traffic between the Netherlands, Germany and France, the growth of the international port of Antwerp and the specific situation for Brussels being the capital of Europe. As shown in Figure 1-1, Belgium has one of the most dense road networks in Western Europe. Density of Primary Road Network 90. 70 60 50 40 30 20. 0. EU27 FLA BRU WAL. 10. A B BG CZ CY DK D EST FIN F GB GR H IRL I LV LT L M NL PL P RO SK SLO E S. Density [km road / 1000km²]. 80. Figure 1-1: Density of Primary Road Network in Europe (data source: FOD2010a). Asphalt is a frequently used material for road pavement. In Belgium, most of the primary, secondary and local roads are made of flexible asphalt pavements. The major reasons for this extensive use are to be found in the acquired knowledge and experience of the road agencies and its advantages in terms of durability, lower costs compared to concrete pavements and the possibility to allow traffic shortly after construction. Since 1989 the jurisdiction of road construction, maintenance and development is allocated to three regions: Flanders, the Brussels-Capital region and Wallonia. 1.
(24) CHAPTER 1. Each region has its own administration which declares specifications for road construction, design and materials. For Flanders, the Flemish Road Agency (FRA) compiled the standard specifications for the construction of public roads in Standaardbestek 250 version 2.2 (SB250v2.2). This standard is not only used for all public works by the Flemish Government but also by most local authorities. In Table 1-1 a summary is given of the length of primary, secondary and local roads in Belgium for the years 2000 and 2009. The figures of primary roads take into account the parking places, access and exits of motorways. In 2009, the FRA governs both the primary and secondary roads (7,085 km of pavement) while the Flemish local authorities control 54,020 km of road. Table 1-1: Summary of the length of the primary, secondary and local paved roads in Belgium and its regions (data source: (1) FOD2010b; (2) FOD2010c). Road Primary roads Secondary roads Category [km] [km] Year 2000(1) 2009(2) 2000(1) 2009(2) Flanders 849 883 6035 6202 Brussels 12 11 320 320 Wallonia 866 869 7544 7587 Belgium 1727 1763 13899 14109. Local roads Total [km] [km] 2000(1) 2009(2) 2000(1) 2009(2) 51501 54020 58385 61105 1553 1540 1885 1871 46700 48929 55110 57385 99754 104489 115380 120361. The FRA also advices about road design for its own roads and for local authorities by means of standard structures for all road types from high to low traffic category via a website (FRA 2010) and a directive concerning road material choice (FRA 2006). An example for a road in the highest category (in Dutch: Bouwklasse 1), is illustrated in Table 1-2. Table 1-2: Recommendation for the structure of a primary road in Flanders (FRA2010b). Road Category Top layer. Base layer Base. Structure in Concrete 23 cm reinforced concrete 5 cm asphalt. Structure in Asphalt Pavement. Structure in Asphalt Pavement. 4 cm SMA. 4 cm SMA. 15 cm AC-14 or AC-20 25 cm lean concrete. 14 cm EME. The structure should be able to endure heavy traffic -expected to be between 64 million and 128 million standard axle loads of 100 kN- during 20 years. In this case, two types of asphalt concrete for base layers are recommended: dense 2.
(25) Introduction. asphalt concrete AC-14 (or AC-20) and an EME (asphalt concrete with high stiffness modulus). This latter is rather new and only applied since 2009. The AC-14 (or AC-20) asphalt mixture is also used for roads with lower traffic. One can assume that in Flanders most of the base layers are of this type. For roads with lower traffic volumes, dense asphalt mixtures are also used for top layers. From the directives it can be concluded that for primary roads both cement concrete and asphalt pavements are recommended. However, in practice mostly asphalt concrete is used, also for secondary and local roads. With this recommendation and the fact that in the past most roads were constructed as flexible pavements, it is clear that asphalt pavement technology is important for Flanders. For Wallonia and the Brussels-capital region similar aspects in recommendations and practice concerning the use of asphalt pavements can be concluded. In Figure 1-2 the total production of asphalt is given for Belgium.. asphalt production [kton]. Production of asphalt in Belgium 6000 5000 4000. surface course base course. 3000 2000 1000 0 2002 2003 2004 2005 2006 2007 2008 2009. Year Figure 1-2: Annual production of asphalt in Belgium (Data source: EAPA). The extensive use of asphalt for new construction and small or larger maintenance works implies that a large quantity of asphalt has been used in Flemish pavements. Since the ‘90s major road rehabilitation works were started. This rehabilitation includes full depth reconstruction of the asphalt layers, in particular of asphalt roads constructed in the mid 70’s. Consequently a lot of old asphalt is available for recycling. Recycling of asphalt pavement in hot mixtures is indispensable in durable resource management. Recycling of materials is at present not a new topic in pavement engineering in Belgium. Before WWII bricks and cobblestones were frequently reused as pavement. After the war the economic welfare in our regions allowed us to use 3.
(26) CHAPTER 1. only new or energy expensive materials. Since bitumen is an oil derivative and therefore dependent on oil price and availability, the oil crisis of 1973 for the first time evoked a serious concern in the world of asphalt pavement. At a too high oil price asphalt becomes economically unattractive. The economic value of old crushed asphalt with its aggregates and aged binder grew. After the crisis the value of old asphalt decreased again to the former level. In the late ‘80s several governments introduced sustainable development criterions in their building projects. Recycling of materials again became a hot topic. For Flanders and its neighbouring country the Netherlands there are clear technical and environmental rules and criteria when using these secondary materials. When old milled or crushed asphalt pavement is brought back into the cycle as a secondary material, it is called regeneration asphalt, reclaimed asphalt pavement (RAP) or reclaimed asphalt (RA in accordance with EN13108-8 Bituminous Mixtures – Material Specifications– Part 8: Reclaimed Asphalt).. Figure 1-3: Black and white aggregates both required in durable asphalt production. Reclaimed asphalt is used extensively in Flanders –and the Netherlands– since the 1980s. Hot reuse of RA permits to replace a significant part of the expensive virgin bitumen by aged bitumen in RA. One thing is clear: the production process is becoming much more complicated when using RA. A composite material is added instead of separately added components. Nevertheless, the use of RA as a basic component in hot mix asphalt has become common practice because for society and the environment, the use of RA means less use of primary components (stone, sand, filler and bitumen) and a reduction in transportation and production of primary raw materials. For an asphalt plant, the production of asphalt mixtures with RA is in most cases economic competitive compared to mixtures with only virgin components (Van den bergh et al 2009). The use of RA is in most cases an advantage, since RA has a very low economical cost compared to virgin materials. The investment in. 4.
(27) Introduction. parallel drums was not an issue compared to the prospect of scaling up the use of RA. RA is generated when (part of) the pavement is milled or broken up. Recycling RA can be a good example of a closed cycle within resource management: before the material was asphalt concrete and the milled material is re-used again in asphalt concrete at the highest possible recycling level. For many years recycling with low amounts of RA was common practice and quite simple, because it is mostly done with cold addition of the RA in the pug mill of a batch plant mixer (allowed up to 20 %) or by hot recycling using a parallel drum (allowed up to 50 %). Since traffic is becoming more intense, it is a technological challenge for the present to design asphalt mixtures that are meeting the higher mechanical and durable quality requirements while using higher amounts of RA (50 % and more).. 1.2. R ESEARCH DESCRIPTION 1.2.1.. Problem background. Does the use of RA affect the quality of asphalt mixtures?. Asphalt mixtures contain stones, sand, filler and binder. Because the bituminous binder is a visco-elastic material, the asphalt mixture will show visco-elastic behaviour at most of the loading conditions. For design purposes, the mechanical behaviour (stiffness and fatigue) of pavement materials in general and asphalt concrete in particular can be simulated by different models. These models were mostly verified by experimental testing of asphalt mixtures using new materials. Inevitable the question arises whether re-use of RA in hot mix will influence the quality of the end product: asphalt concrete with and without RA will have to fulfil the same functional requirements in the new CEmarking system and standards. There is only limited information available in Belgium on the influence of addition of RA on the properties of the asphalt mixture. In Flanders RA is used in most asphalt mixtures for base layers, without a scientific validation of the influence of RA on the durability of the mixtures in situ. RA contains aged bitumen and has not always a homogeneous composition. Furthermore impurities can be part of it. It is then very difficult to predict the material properties after production and compaction. The same holds for the quality control of mixtures with RA. In 2010, a new Flemish directive for the specification of asphalt mixtures (Standaardbestek 2010 v2.2) is published in accordance with the European Standards (EN13108-series). The fundamental material characteristics must be 5.
(28) CHAPTER 1. evaluated in order to have the asphalt mixtures accepted for public works. These material characteristics involve resistance to fatigue, permanent deformation as well as the stiffness modulus. The healing factor. The asphalt mixture resistance to fatigue is an important design parameter in the structural design of asphalt pavements. In this structural design a factor is used to take into account the healing that occurs during rest periods and the lateral wandering of the traffic; both will result in a longer structural design life for the mixture in situ compared to the fatigue life determined with a continuous sinusoidal test in the laboratory. Healing of a bituminous material is the mechanism of self-reparation of the chemical structure in a way that micro fatigue damage is repaired. The chemical structure in this context can be bitumen (or its components), mastic or mortar. The healing capacity might be reduced when using RA with a higher viscosity of the mastic or the incompatibility of the two different binders. Healing is very important: a higher healing factor will result in a thinner asphalt layer thickness for the same structural service life or a longer service life at the same asphalt thickness. In Belgium a healing factor of 7.1 is used in the structural design of the standard structures. This value was determined by means of fatigue testing with and without rest periods carried out on asphalt mixtures in the ’80 of the last century. In these mixtures no RA was applied. In the Netherlands a healing factor of 4 is used. However research by Huurman et al (2003) indicated that the shift factor of 4 used in the Netherlands might be reduced in case of mixtures with RA because of the relatively higher viscosity of the bituminous binder in the RA. Because of the economic consequences of thicker asphalt layers with RA compared to new asphalt mixtures, the advantages of RA could become questionable. Although a specified standard test to measure healing is not available, it can be measured. Healing factors are mostly determined with a dynamic bending test. These tests however take a long time and are expensive. No clear coherence in test methods and interpretation of results is observed. One trajectory is promising being the method of surface-energy combined with rheological tests as proposed by Little, Lytton and co-workers of the Texas A&M University (Little and Basin 2008). For fundamental research this method based on surface energy measurements can be helpful. However, for the asphalt manufacturer in Europe who wants to determine the healing factor of his mixtures linked to CE marking, this procedure seems too extensive. There is a need for a simple procedure to determine the healing potential of a binder, mastic or mortar in an adequate but fast way.. 6.
(29) Introduction. When investigating asphalt mixtures with RA a particular problem occurs because each RA has a different quality, composition and unknown ageing history. This problem could be solved by using a standard RA of which the components and ageing history are known. Hitherto, there is no standard ageing procedure accepted to manufacture RA in the laboratory. Also, the aged binder in this RA should have a similar ageing history as a typical binder from real RA. If such ageing procedures are available it will be possible to manufacture binder, mastic and mortar containing aged components. 1.2.2.. Research objectives. The objective of this study is to investigate the effect of RA on the fatigue and healing property of asphalt mixtures for base layers (AC-14). The study focuses on the effect of ageing on the healing and fatigue properties of binders and mortars. Two main objectives are defined: i) development and evaluation of an asphalt ageing procedure in order to manufacture reproducible aged asphalt mixtures and mortars in the laboratory; ii) evaluation of the fatigue and healing characteristic of aged binder and mortar. In the first topic a standard procedure for ageing of asphalt mixtures in the laboratory is defined and validated experimentally. The main objective is to provide a protocol for the production of a standard and reproducible RA. This RA will, in that case, have a known composition and components which are available for other tests; for instance binder and mortar can be separately aged in the laboratory for respective binder and mortar research. The development of this ageing procedure is started within this work and has later been integrated in the research project of RILEM TC-ATB-TG5 - “Recycling of bituminous materials”. In the second research topic a fatigue and healing test procedure is selected from literature review which will provide fatigue and healing characteristics of the binder and bituminous mortar in their virgin and aged state. The research will contribute to the scientific answer on the question whether the use of RA will affect the life span of the mixture. The determination of the healing factor is necessary for the economically and durable justification of recycling RA in asphalt mixtures.. 7.
(30) CHAPTER 1. 1.3. O UTLINE OF THE DISSERTATION In order to answer the main research question in this work in a scientific way – does the use of RA affect the healing and fatigue property of asphalt mixturesa number of other issues should be investigated. This dissertation consists of 9 chapters, each dealing with an important issue. The first chapter presents a global introduction of the Belgian Road network and the importance of asphalt mixtures. The research description with the outline and the research objectives are given. In chapter two the state of the art of the use of RA in Flanders is reported. In this chapter a survey is summarized which shows the different properties of RA in Flanders. These properties are used as target values for the laboratory aged binders and mixtures, mentioned in chapter seven. Chapter three presents a literature review regarding ageing and healing of bituminous binders and mixtures. From this review the test procedures are selected or used as a basis for further development in chapter seven and eight. The research methodology of the two research topics is explained in chapter four. In chapter five the infrared test method is discussed since this method is extensively used further in this work for the chemical characterisation of ageing of binders. Although this technique is frequently used for bitumen characterisation, no standard is available for data interpretation. In this work a recommendation is proposed, based on a comparative study of five qualitative methods for data interpretation. Rheological test methods, ageing procedures, mixture design and sample manufacture procedures are elucidated in chapter six. In chapter seven the development and recommendations for the laboratory aged asphalt mixtures and the binder ageing are described. Chapter eight discusses the results of the fatigue and healing tests with virgin and aged bituminous mortars. The last chapter contains the conclusions and recommendations.. 1.4. R EFERENCES EAPA, European Asphalt Pavement Organisation (2003-2009). Asphalt in figures, years 2002-2008, Brussels. FOD, Federale Overheidsdienst Mobiliteit en Vervoer, FOD Algemene Directie Statistiek (België en gewesten) & Eurostat (2010). Brussel. Source:http://www4.vlaanderen.be/dar/svr/cijfers/Exceltabellen/mobiliteit/ infrastructuur/MOBIWEGE001.xls, website accessed in 2010. 8.
(31) Introduction. FOD, Federale Overheidsdienst Mobiliteit en Vervoer & FOD Economie, Algemene Directie Statistiek en Economische Informatie Brussel. Source: website http://statbel.fgov.be/nl/binaries/roadkm2000_tcm325-33658.xls, accessed in 2010. FOD, Federale Overheidsdienst Mobiliteit en Vervoer, Brussel (2010). Source: http://www.mobilit.fgov.be/data/mobil/broroutn.pdf, website accessed in 2010. FRA - Flemish Road Agency (2006). Wegstructuren, versie 2, Administratie Wegen en Verkeer, Ministerie van de Vlaamse Gemeenschap, Brussel. FRA - Flemish Road Agency (2010). Dienstorder Keuze van asfaltmengsels en bindmiddelen, Administratie Wegen en Verkeer, Ministerie van de Vlaamse Gemeenschap, Brussels. FRA - Flemish Road Agency (2010). Administratie Wegen en Verkeer, Ministerie van de Vlaamse Gemeenschap, Brussel. Source: http://wegen.vlaanderen.be/documenten /bouwklasse/, website accessed in 2010. Huurman, M., Hopman, P. (2003). The influence of RAP on healing and fatigue in StAC, report (in Dutch), NPC, Utrecht, The Netherlands. Little, D.N., Bhasin, A. (2008). Exploring Mechanism of Healing in Asphalt Mixtures and Quantifying its Impact, Self Healing Materials, ed. Sybrand van der Zwaag, Springer Netherlands, 2008, Volume 100, pp.205-218. SB250v2.2 (2010). Standaardbestek voor de Wegenbouw versie 2.2, Administratie Wegen en Verkeer, Ministerie van de Vlaamse Gemeenschap, Brussels. Van den bergh, W. et al (2009). Aged-bitumen bound base: state of the art, Final report, Artesis University Antwerp, Road Engineering Research Section, Antwerp.. 9.
(32) CHAPTER 1. 10.
(33) 2. R ECYCLING OF A SPHALT PAVEMENT IN F LANDERS. 2.1. I NTRODUCTION Reclaimed asphalt, why are we using it?. In this chapter, the state of the art of the use of reclaimed asphalt (RA) in Flanders is described. In the first subchapters, a view is given of the advantages of using RA and their economical-political and environmental impact in the asphalt production sector. Further on, the technical restrictions and requirements are described. RA may not be used without considering quality rules and its reflection on the performance of the new mixture. Bituminous road pavements show after a while some kind of deterioration due to traffic and climate. For safety reasons or to slow down the damage progress, road administrators rehabilitate the pavement surface layer. When too much damage occurs, the whole structure, top- and base layers, is renewed. Reclaimed asphalt is the term used for removed and reprocessed asphalt pavement. The RA is generated when an old asphalt pavement is removed by milling layer by layer or digging up the whole construction. Since RA was once a bituminous mixture, RA will contain aggregates and aged bituminous binder. The main objective of asphalt recycling is to re-use this valuable material preferably in its own production cycle. In this way the use of natural resources is decreased. Also, this type of recycling allows using the reclaimed binder and aggregates in new asphalt mixtures as in their original function: the aged binder will participate as a binder and the aggregates are part of the grading. During the last 30 years much research was done, and still is, on the re-use of old asphalt pavements. The main reasons for using this reclaimed asphalt appear to be: •. Economic benefits: RA has an economic value because it can replace new aggregates and binders in the new mixture. This value should take into 11.
(34) CHAPTER 2. •. account all costs as if it was new aggregate: stockpiling, handling, testing, milling and transport. RA has a negative economic value (which still increases) when it is dumped. More and more RA is used in concrete mixtures as an aggregate in Flanders. This concrete is manufactured in situ by a temporary concrete plant, which is easier to realize than a temporary asphalt plant. At this moment, this application is only used for larger works. Environment: Re-use is a factor within sustainable development. For some customers and authorities construction works must hold a recycling part. Each use of RA conserves primary natural resources: - aggregates: stone, sand and filler; bituminous binders; - less transport and production actions lead to a reduction of fuel needs and emissions; - recycling RA as new hot mix asphalt contributes to a reduction of Greenhouse Gas Emissions by means of total energy savings and environmental emissions (Levis et al 2011).. Precautions and opportunities. Because RA is not a new and production-controlled material, some precautions are needed. However, these restrictions have not obstructed a worldwide growing use of this recycling material. Although asphalt recycling requires more knowledge, quality and production facilities, practice and experience have made it possible to control the use of RA in new hot mixtures without a decrease in quality. Asphalt is an excellent material for pavements when it is used in a proper way. The asphalt mixture must not only be of a good quality and show a good performance; one must also be able to apply it correctly. Quality is the most strict criterion and concern: asphalt pavements with RA must meet the criteria of new asphalt. Busschots and De Backer (1998) concluded that the use of RA does, in general, not affect the quality of new mixtures. Exceptions are, however, possible. 37 test sections were investigated. Four of them showed damage after 4 years but three of those are a cold RA application. When RA is added, several points have to be addressed. Because of the addition of RA, different binders, fillers and sands will be mixed together. This will have consequences on the viscosity of both the mastic and asphalt mixture. In case of huge contents of RA, these variable parameters have to be studied first, predicted and controlled. Therefore, it is necessary to investigate the influence of the added RA or its components on the performance of the asphalt mixture. RA has a certain degree of variance in composition. For instance, the milling process can contribute to inhomogeneity of the RA by 12.
(35) Recycling of Asphalt Pavement in Flanders. changing the grading. This leads to a more complex design and production process. Not each batch of RA can be fully mastered. The best choice for using high amounts of RA is the use of the same type of RA and to produce the same type of asphalt mixture. The variance in composition and binder characteristics can be decreased when each type of RA is separately milled and stored. This is not always possible so RA batches coming from smaller milling sites are first homogenized before recycling. In that case different types of aggregates and binders are mixed together giving more chance to incompatibility and quality decrease in the new mixture. For example, different types of filler are used in asphalt production; all with different origin, composition and thus performance. The principle of hot mix recycling is the reactivation of the binder and the reuse of the aggregates. Preheating of RA in a parallel drum and/or contact with hot new aggregates ensures that the old binder becomes liquid. It is important that this process is very well controlled: ageing of the binder must be limited and the end characteristics of the mixed binder must be obtained within feasible limits. This can be done by adding a softer binder or a binder with a rejuvenator in order to compensate the low penetration of the old binder. For the mixture composition it is important that new granulates are added so a new composition is designed. For the regeneration of RA, a new overall composition is aimed at, meaning new aggregates are added, and a new binder is needed. This new binder has three functions: cover the new granulates, compensate the oxidation grade of the RA-binder and homogenize with the RA-binder in the total mastic. Certain “softer” properties can be obtained by adding a rejuvenator or softer bitumen. The question is if these binders are compatible and if it is useful to approach the original properties. In principle, one can reuse 100 % RA when a rejuvenator is added and the grading of the RA is suitable; however this latter is most of the time not fulfilled since the RA has been manipulated. Moreover, some technical problems occur at high percentages of recycling. For example for a typical Flemish asphalt plant equipped with a parallel drum, it is technically impossible to add small ‘missing’ fractions to the RA in order to obtain the aimed composition: the primary drum needs a minimum quantity of aggregates running through in order to prevent overheating the aggregates and the filter for the combustion fumes. For safety reasons and to anticipate on extreme ageing of the binder during preheating the RA, the maximum temperature of the parallel drum is 140 °C. This temperature is too low for an optimal mixing and further handling such as laying and compaction. When bitumen from RA is reused and mixed with new bitumen, it is important to estimate the binder characteristics of the mix of old and new bitumen. 13.
(36) CHAPTER 2. Because of ageing, RA contains harder bitumen. Mostly harder bitumen increases the stiffness, thus the bearing capacity, and the resistance to rutting. However, this harder bitumen could have disadvantages in the lower temperature zone (cracking) and during mixing and compaction (higher viscosity). Since the first test sites date from the 1980’s, it is very probable that the current RA already contains a certain percentage of RA. Can this RA be brought back in the recycling procedure? This question will dominate the research subjects the next decennia.. 2.2. F LEMISH SPECIFICATIONS FOR RECYCLING In Flanders, the Flemish Government (OVAM 2008) has declared reclaimed asphalt as a secondary material. In order to be able to re-use RA it has to fulfil certain requirements which are: •. the concentration of polluting elements which are a danger for health, soil and water contamination should be limited. This involves metals, organics, volatile organo-halogens and polyaromatic hydrocarbons (PAC). The concentration of PACs is limited to such a quantity that tar containing asphalt is not allowed for RA hot recycling: The concentration limit for benzo(a)pyrene is limited to 8.5 mg/kg; • the mixture with the candidate secondary material may not lixiviate heavy metals (arsenic, copper and zinc) in a watery environment. The lixiviation limit for zinc is 2.8 mg/kg; • the mixture which contains recycled materials must have a strength which is at least equal to that of primary materials; • the recycled material may not contain asbestos. Laethem and Vrancken (1998) studied 9 different types of Flemish asphalt mixtures on their chemical composition. They concluded that asphalt with tar may not be used in hot mixed asphalt in Flanders. They contain too much PAC’s. RA without tar fulfils the requirements for recycled materials to be used in soils and materials in contact with the soil. These conclusions are confirmed by De Jonghe et al (2003). When the asphalt has no tar tracks, RA can be declared as an aggregate for use in hot mix asphalt within a strict regulation. Both contractors and the government agencies intend to use a RA percentage as high as possible but without a decrease in quality and performance of the mixture. This percentage can be determined in several ways: by mixture design programs, experimental verification and performance tests, practice, etc. In order to ensure good quality mixtures, the Flemish Road Agency and COPRO a certifying body- have defined a frame with guidelines how to take into account the RA components. These guidelines are described in TRA13 and 14.
(37) Recycling of Asphalt Pavement in Flanders. SB250v2.2. In general, the maximum percentage of RA added to new asphalt mixtures is related to its quality, the quantity of macro contaminations in RA (presence of wood, concrete is limited), its homogeneity, binder properties and to the way of addition of RA into the mixer (cold or warm). 2.2.1.. Policy for accepting reclaimed asphalt (RA). In a first step, before milling, the old asphalt layer is visually inspected on homogeneity and then analyzed via tests on cores. The composition, stone type, thickness, possible impurities (for instance tar) and binder characteristics (content, penetration, type of bitumen) are determined. RA with asbestos fibres is not allowed for recycling. In a second step, the RA is accepted at the asphalt production plant. If the RA has an identification sheet (from the first step), this information is adopted by the asphalt plant administration. Otherwise, according to SB250v2.2 and TRA13, each RA-freight must be inspected conform to requirements stipulated in Table 2-1. Table 2-1: Acceptation requirements for RA. Parameter Visual control (organoleptic) Tar verification, preliminary done by a PAK-marker Presence of foreign matter (EN12697-42 + fraction below 8 mm) Size of aggregate (EN933-1) Penetration of recovered binder (EN12697-3 + EN1426). Frequency Continuous Continuous Internal procedure Internal procedure Internal procedure. If the results of this preliminary study are within the environmental requirements and the penetration of the binder is larger than 10 dmm, then it is allowed to use this RA in hot mixtures for Public Works. When the RA is accepted by the production plant, for recycling in a hot asphalt mixture, the tests in Table 2-2 are obliged before further processing can take place. Table 2-2: Inspection and testing procedure before processing the RA. Parameter Presence of foreign matter (EN12697-42 + fraction below 8mm) Size of aggregate (EN933-1) Type of asphalt. Frequency No foreign matter indication: intern testing procedure plant; foreign matter: 1 test per 500 ton (and minimum 1 test per batch) Internal procedure 1 declaration per batch 15.
(38) CHAPTER 2. The specifications for macro-contamination of the RA are given in Table 2-3. Table 2-3: Requirements for macro-contamination in RA. Component Bituminous materials. Material Requirements Milled reclaimed asphalt > 95 % (*) Very small amount of cold asphalt and bitumen Materials from pavement and Natural coarse material < 5 % (**) base without traces of bitumen (density > 2100 kg/m³) Concrete, concrete mortar, masonry, terracotta Metal Other materials Plaster, rubber, plastic, glass.. <1% Organic material (*) The 95 %-value is obliged for asphalt mixtures for Public Works. For other works, this value may decrease to 70 %. (**) The 5 %-value is obliged for asphalt mixtures for Public Works. For other works, natural coarse grained material may increase to 30 %.. In most cases, small quantities or different types of RA are mixed before testing in order to obtain a homogenous RA. The specifications for a homogenous RA are given in Table 2-4 (ref. FRA2011) and the classification of different types of reclaimed asphalt is shown in Table 2-5 (ref. COPRO 2009). Table 2-4: Requirements for homogeneous RA in Flanders. Parameter Coarse < 10mm Coarse < 6.3 mm Sand <2mm passing Fines < 0.063mm passing Binder content (residual) Penetration. 16. Type H Tolerance for each individual test 10 % 3% 1% 10 dmm. Type HE Tolerance for each individual test 15 % 15 % 10 % 2.5 % 0.8 % 10 dmm.
(39) Recycling of Asphalt Pavement in Flanders Table 2-5: Classes for RA. Class HE NHEL NHEH H NH BD. Specifications Homogenous RA conforming EN13108-8 Non-Homogenous RA, conforming EN13108-8; not allowed for Public Works starting from 1/03/2012 Non-Homogenous RA conforming EN13108-8; not allowed for Public Works starting from 1/03/2012 Homogenous RA not conforming EN13108-8 Non -Homogenous RA not conforming EN13108-8 Granulates from bituminous roofing (not conforming EN13108-8). Note: as from 2012, the selected type of RA, as mentioned in Table 2-5, depends on the type mixture in which the RA is used. For example, for Public Works only RA type HE is permitted in base layer mixtures for primary roads, these mixtures are conforming to EN13108-1 with stiffness and fatigue requirements. From that, a stockpile reference is chosen: this is the global RA identification. The characteristics of this RA will fulfil the requirements as mentioned above. Each RA-reference is stockpiled separately. In Table 2-6 the specifications of RA for the final stockpile are given. Each RA is defined by its maximum size of asphalt aggregate U (Smallest sieve with 100 % passing), smallest sieve size of the aggregates in RA (d) and the largest sieve size of the aggregates in RA (D), for example “40 RA 0/14 mm”. Table 2-6: Required specifications for RA. Test and method Visual control (organoleptic) Binder content (EN12697-1) Binder penetration (EN12697-3 + EN1426) Binder type (penetration, hard, modified, Trinidad, other) Aggregate grading (EN12697-2) Aggregate identification ( Intern testing procedure plant and 13043) Size of aggregates (EN933-1) Moisture (EN1097-5). RA must be stored similar to other aggregates and no other RA material may be added. After these tests, the RA may not be changed by any process and is from this point considered as RA-granulate. 17.
(40) CHAPTER 2. 2.2.2.. Maximum amount of RA in hot asphalt mixtures. For mixtures of base layers conforming EN13108-1 and with specific stiffness and fatigue requirements, no maximum limit for the binder part from RA is given. However for EME a maximum of 20 % of RA-binder on the total binder mixture may be substituted by RA-binder. Only RA type HE is allowed and the RA must be preheated. The maximum amount of RA in standard hot asphalt mixtures conforming SB250v2.2 (without stiffness and fatigue requirements) is expressed as a function of the maximum quantity of binder coming from the RA in the final mixture. In base layers a maximum of 50 % of bitumen from homogeneous RA (HO) or 20 % of bitumen from non-homogenous RA (NH) is allowed in the final mixture. When different RA-categories are used, formula (2-1) is taken: ሾΨሺ ሻʹǡͷሺΨ ሻሿ. (2-1). ൏ͷͲΨ Ǥ. An outline of the maximum allowed quantities is given in Table 2-7. Table 2-7: Maximal use of RA in Flemish asphalt mixtures according to SB250v2.2. Maximum quantity of RA-bitumen in the composed binder for hot recycling in Flanders Asphalt type Addition of RA-binder; with or without pre-heating (parallel drum) Pre-heating via parallel drum (“hot addition >110 °C”) No maximum level except for EME: max. 20 % binder (%HO) + 2,5x(%NH) < 50 %. Cold addition. Base layer mixtures Not permitted EN13108-1 with stiffness and fatigue requirement Base layer < 20 % AC-(20;14;10;6,3) Top layers No RA permitted since 2011 Note: as from 1/03/2012 the use of RA type NH is not allowed for Public Works. An important additional requirement for using RA is that the composed bitumen with RA in the final mixture has to fulfil the same requirements as for mixtures with only virgin bitumen in the mixture. Example: when a binder 35/50 is mentioned in the contract, then the combined binder of old and new. 18.
(41) Recycling of Asphalt Pavement in Flanders. should have a penetration between 35 and 50 according to the log penetration rule: ݈݃ሺ݊݁௫ ሻ ൌ ܽȀͳͲͲǤ ݈݃ሺ݊݁ଵ ሻ ܾȀͳͲͲǤ ݈݃ሺ݊݁ଶ ሻ. (2-2). where penmix is the penetration of the binder in the mixture, pen1 and a respectively the penetration of the old binder and its percentage; pen2 and b respectively the penetration of the new binder and its percentage in the binder mixture. In Table 2-8 an example is given for this log-pen rule in case of a binder of which the penetration specification must be at least 50 dmm (for example AB-3A with a binder type 50/70). When the RA-binder has a penetration of 15 dmm, 40 % RA addition is only possible when a very soft binder is used, for example a 100-150 grade. Table 2-8: Results of the log-pen rule for some examples of RA-binder and new binder. Required penetration in asphalt mixture [dmm] 35. 50. Measured penetration of RA-binder [dmm] 15 20 30 15 20 30. % RA-binder in total binder mixture 20 % 30 % 40 % 50 % Required penetration of new binder [dmm] 43 50 62 82 40 44 51 61 36 37 39 41 68 84 111 167 63 74 92 125 57 62 70 83. The log-pen rule also implies that the penetration test for the RA-binder must be performed accurately in order to select the proper virgin binder grade. Considering composition and performance, RA-containing mixtures have to fulfil the same criteria as for non-RA containing mixtures. In that case RA containing mixtures can agree with the requirements stated in tender documents and CE-marking.. 2.3. A BRIEF SURVEY OF RA CHARACTERISTICS IN F LANDERS In Flanders, no official RA characterization database is available. Some information can be obtained at the FRA and certifying bodies like COPRO. On the basis of individual registrations an overview was made for 2002 by De Jonghe et al (2003) for 29 different RA-samples. The origin of these RAsamples can be of all types of asphalt mixtures for top and base layers. Based 19.
(42) CHAPTER 2. on the data of the individual technical notes of manufactured asphalt mixtures (source: FRA), the RA-fractions were analyzed on composition and binder characteristics. In Figure 2-1, the grading of these 29 samples of different (homogenized) RA-stockpiles is given.. Sieve Rest [%]. RA-Grading 2002 (n=29) 0 10 20 30 40 50 60 70 80 90 100 0.01. 0.1. 1 sieve [mm]. 10. 100. Figure 2-1: RA-grading 2002: mean grading and 29 individual specimens. It is shown that the gradings of the RA-stockpiles are very different. However, some of these stockpiles are continuously supplied with a RA with almost the same grading and binder characteristics resulting in a RA-stockpile with an almost constant grading. In order to survey the change in composition of RA and its binder characteristics in time, all registrated RA analyses of COPRO for the years 2002 to 2009 are taken for analysis. The properties of the binders recovered from the RA samples are summarized in Table 2-9. Table 2-9: RA-binder characteristics 2002-2009. 20. year. n. 2002 2005 2006 2007 2008 2009. 29 55 90 59 105 108. Binder penetration Mean s Median [dmm] 27.1 5.4 25 24.4 6.5 23 18.6 5.6 18 18.8 3.9 18 19.7 6.1 18 20.3 5.9 19. % binder Median Mean s (m/m % on aggregates) 6.1 6.2 0.9 5.8 5.9 0.8 n.a. 5.4 5.6 0.9 5.7 5.9 1.0 5.8 5.8 0.7.
(43) Recycling of Asphalt Pavement in Flanders. Figure 2-2 shows the mean grading of RA – samples from 2002 to 2009. The figure demonstrates that the mean grading is almost constant over the years. This is because the asphalt mixture compositions in Flanders have hardly changed during the survey period.. RA Grading 2002-2005-2007-2008-2009 0. upper level 2009 upper level 2002 mean grading 2002 mean grading 2005 mean grading 2007 mean grading 2008 mean grading 2009 lower level 2002 lower level 2009. 10 20. sieve rest [%]. 30 40 50 60 70 80 90 100 0.01. 0.1. 1 Sieve [mm]. 10. 100. Figure 2-2: Mean grading of RA samples in 2002, 2005, 2007, 2008 and 2009. The penetration value of the RA-bitumen is showing a clear trend. The mean value decreased from 27.1 to 20.3 dmm (median from 25 to 19 dmm). Possible causes for this decrease are the use of harder bitumen (to reduce rutting) and delayed maintenance. It should be noted that these results are only valid for RA of asphalt plants working under certificate. Moreover, the mean value is calculated as the mean of single RA batches without taking into account the quantity of the RA batch. There are no detailed data about recycling available for Belgium. General figures about production and recycling are collected by EAPA. In Figure 2-3, the total asphalt production in Belgium since 2002 is given together with total RA-recycling rates (data source: EAPA).. 21.
(44) CHAPTER 2. Total asphalt production and recycling in Belgium 5000. 50. 4000. 40. 3000. 30. 2000. 20. 1000. 10. 0. total asphalt production. [% ]. ktonnes. source: EAPA2002Ͳ2009. RA used in production % mix containing RA % RA in asphalt production. 0 2002 2003 2004 2005 2006 2007 2008 2009 Year Figure 2-3: Production and recycling figures for asphalt in Belgium. In 2009, the total production of hot mix asphalt mixtures in Belgium was estimated at 4,700,000 tons of which 44 % contained RA (EAPA2009). Yearly about 1,300,000 tons RA is released for recycling. 57 % of this RA is used for hot mix recycling (741,000 ton). Based on these figures it is concluded that only 16 % of the mixtures contains RA; this is rather low. 52 % of the total asphalt production was used for top layer mixtures and 48 % for base layers. Up to 2010, in dense asphalt concrete up to 50 % recycling was allowed. As from 2011, no recycling will be allowed in surface layers. For base layers (dense asphalt concrete according to EN13108-1), all mixtures are allowed to contain RA up to 50 %. For Public Works, asphalt mixtures and RA must be certified. The certifying body is COPRO. In 2009, a total of 3,218,627 ton hot mix asphalt was certified for road construction (68 % of the total asphalt production). Approximately 54 % of all certified asphalt mixtures contained RA, with a mean recycling rate of 41 %. This implies that 715,000 ton RA was used in 1,750,691 ton certified asphalt (Source: COPRO (2010)). This is a very high recycling rate. Most certified RA was used in Flemish mixtures for public works. Asphalt mixtures for base layers have a high recycling rate: 92 % of the mixtures contain RA. The estimated 284,501 ton certified asphalt mixtures containing RA for top layers in 2009 is rather low. For these asphalt mixtures it is allowed to use RA up to 50 % in Flanders but in Walonnia the use of RA for top layers is forbidden. Moreover, this low recycling rate can also be explained by economical and quality reasons for instance typical small works done during the last years. In the new standards for Public Roads in Flanders (2011), the use 22.