{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/99532"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/99532","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Balancing asphalt mixes containing recycled materials for optimum field performance","abstract":"Asphalt concrete (AC) is the most common material used for the construction of pavements in the U.S. and many other countries in the world. With the increasing use of recycled materials like reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS), the cracking resistance of asphalt pavements might be jeopardized. Therefore, such AC mixtures should be carefully investigated to ensure that performance is not compromised in the pursuit of an economical and sustainable solution. This study investigates 17 mixes including five leveling binders (LB) and 12 surface mixes, which have been used by the Illinois Department of Transportation (IDOT) in different rehabilitation projects across the State of Illinois, between 2013 and 2015. These AC mixes contain asphalt binder replacement (ABR) from 15 to 60%, acquired from RAP and RAS, whereas these mixes also contain steel slag and crushed concrete. In order to evaluate these AC mixes, a thorough laboratory testing, including indirect tensile creep compliance and strength, Hamburg wheel tracking test, and the Illinois flexibility index test (I-FIT) was conducted to evaluate thermal cracking susceptibility, rutting, and cracking resistance, on plant-mixed lab-compacted (PMLC) mixes and three sets of field cores. The extensive exploratory data analysis on creep compliance showed that softer binder and higher asphalt content result in more compliant mixes, while recycled materials tend to decrease the compliance of AC mixes. Likewise, softer binder and recycled materials tend to counterbalance each other’s impact. Similarly, the LB has relatively higher creep compliance as expected due to its design which is intended to retard reflective cracking. The IDT strength at -10°C is very similar across all AC mixes irrespective of the amount of recycled materials. Results also show that IDT creep compliance and strength might not distinguish the effect of field aging. The Pavement Mechanistic-Empirical Design Guide (MEPDG) uses the empirically developed model for the prediction of creep compliance as an input for Level 3 analysis, which uses mix and binder properties. However, the impact of recycled materials was not captured in the MEPDG nor in the modified models. This research proposes a new model to predict creep compliance that captures the effect of recycled materials. The I-FIT results show that PMLC mixes have relatively lower flexibility index (FI) as compared to first field cores due to the difference in aging and compaction conditions. FI decreases with the increase in aging and recycled materials, while the strength and secant modulus increase. All AC mixes offered excellent rutting resistance, because they contain high ABR, and the resistance increased with aging as expected. The balanced mix design approach was utilized, based on rut depth and FI, which showed the convergence of AC mixes to stiffer zone with field aging. Similarly, secant modulus was added to the existing balance mix design as a stiffness indicator to control soft mixes. Furthermore, the field results confirm an excellent rutting performance in all sections. In addition, an exponential increase in transverse cracking was observed, which correlates with FI values obtained on the corresponding mixes. Thus, it is believed that I-FIT is a very simple, promising, and distinguishable test for evaluating the cracking resistance of AC mixes, which could be used as a performance evaluation tool along with rutting results to obtain balanced mix designs.","abstract_html":"Asphalt concrete (AC) is the most common material used for the construction of pavements in the U.S. and many other countries in the world. With the increasing use of recycled materials like reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS), the cracking resistance of asphalt pavements might be jeopardized. Therefore, such AC mixtures should be carefully investigated to ensure that performance is not compromised in the pursuit of an economical and sustainable solution. This study investigates 17 mixes including five leveling binders (LB) and 12 surface mixes, which have been used by the Illinois Department of Transportation (IDOT) in different rehabilitation projects across the State of Illinois, between 2013 and 2015. These AC mixes contain asphalt binder replacement (ABR) from 15 to 60%, acquired from RAP and RAS, whereas these mixes also contain steel slag and crushed concrete. In order to evaluate these AC mixes, a thorough laboratory testing, including indirect tensile creep compliance and strength, Hamburg wheel tracking test, and the Illinois flexibility index test (I-FIT) was conducted to evaluate thermal cracking susceptibility, rutting, and cracking resistance, on plant-mixed lab-compacted (PMLC) mixes and three sets of field cores. The extensive exploratory data analysis on creep compliance showed that softer binder and higher asphalt content result in more compliant mixes, while recycled materials tend to decrease the compliance of AC mixes. Likewise, softer binder and recycled materials tend to counterbalance each other’s impact. Similarly, the LB has relatively higher creep compliance as expected due to its design which is intended to retard reflective cracking. The IDT strength at -10°C is very similar across all AC mixes irrespective of the amount of recycled materials. Results also show that IDT creep compliance and strength might not distinguish the effect of field aging. The Pavement Mechanistic-Empirical Design Guide (MEPDG) uses the empirically developed model for the prediction of creep compliance as an input for Level 3 analysis, which uses mix and binder properties. However, the impact of recycled materials was not captured in the MEPDG nor in the modified models. This research proposes a new model to predict creep compliance that captures the effect of recycled materials. The I-FIT results show that PMLC mixes have relatively lower flexibility index (FI) as compared to first field cores due to the difference in aging and compaction conditions. FI decreases with the increase in aging and recycled materials, while the strength and secant modulus increase. All AC mixes offered excellent rutting resistance, because they contain high ABR, and the resistance increased with aging as expected. The balanced mix design approach was utilized, based on rut depth and FI, which showed the convergence of AC mixes to stiffer zone with field aging. Similarly, secant modulus was added to the existing balance mix design as a stiffness indicator to control soft mixes. Furthermore, the field results confirm an excellent rutting performance in all sections. In addition, an exponential increase in transverse cracking was observed, which correlates with FI values obtained on the corresponding mixes. Thus, it is believed that I-FIT is a very simple, promising, and distinguishable test for evaluating the cracking resistance of AC mixes, which could be used as a performance evaluation tool along with rutting results to obtain balanced mix designs.","abstract_has_math":false,"creators":["Safi, Fazal Rehman"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Civil Engineering","degree_department":null,"school":null,"contributors":["Al-Qadi, Imad L.","Ozer, Hasan"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-03-13T17:35:56Z","date_published":"2018-03-13T17:35:56Z","updated_at":"2026-07-22T22:24:37Z","subjects":["Asphalt binder replacement (ABR)","Reclaimed asphalt pavement (RAP)","Recycled asphalt shingle (RAS)","Mechanistic-Empirical Design Guide (MEPDG)","Thermal cracking","Creep compliance modeling","Balance mix design","Total recycled asphalt (TRA) mixes","Field cores","Transverse cracking","Field performance","Illinois flexibility index test (I-FIT)","Secant modulus"],"languages":["en"],"rights":["Copyright 2017 Fazal Safi"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/99532","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Al-Qadi, Imad L.","Ozer, Hasan"]},{"key":"dc:creator","label":"Author","values":["Safi, Fazal Rehman"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-03-13T17:35:56Z","2020-03-14T09:15:25Z","2017-12-13","2017-12"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Civil Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Asphalt binder replacement (ABR)","Reclaimed asphalt pavement (RAP)","Recycled asphalt shingle (RAS)","Mechanistic-Empirical Design Guide (MEPDG)","Thermal cracking","Creep compliance modeling","Balance mix design","Total recycled asphalt (TRA) mixes","Field cores","Transverse cracking","Field performance","Illinois flexibility index test (I-FIT)","Secant modulus"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2017 Fazal Safi"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/99532"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Asphalt concrete (AC) is the most common material used for the construction of pavements in the U.S. and many other countries in the world. With the increasing use of recycled materials like reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS), the cracking resistance of asphalt pavements might be jeopardized. Therefore, such AC mixtures should be carefully investigated to ensure that performance is not compromised in the pursuit of an economical and sustainable solution. This study investigates 17 mixes including five leveling binders (LB) and 12 surface mixes, which have been used by the Illinois Department of Transportation (IDOT) in different rehabilitation projects across the State of Illinois, between 2013 and 2015. These AC mixes contain asphalt binder replacement (ABR) from 15 to 60%, acquired from RAP and RAS, whereas these mixes also contain steel slag and crushed concrete. In order to evaluate these AC mixes, a thorough laboratory testing, including indirect tensile creep compliance and strength, Hamburg wheel tracking test, and the Illinois flexibility index test (I-FIT) was conducted to evaluate thermal cracking susceptibility, rutting, and cracking resistance, on plant-mixed lab-compacted (PMLC) mixes and three sets of field cores. The extensive exploratory data analysis on creep compliance showed that softer binder and higher asphalt content result in more compliant mixes, while recycled materials tend to decrease the compliance of AC mixes. Likewise, softer binder and recycled materials tend to counterbalance each other’s impact. Similarly, the LB has relatively higher creep compliance as expected due to its design which is intended to retard reflective cracking. The IDT strength at -10°C is very similar across all AC mixes irrespective of the amount of recycled materials. Results also show that IDT creep compliance and strength might not distinguish the effect of field aging. The Pavement Mechanistic-Empirical Design Guide (MEPDG) uses the empirically developed model for the prediction of creep compliance as an input for Level 3 analysis, which uses mix and binder properties. However, the impact of recycled materials was not captured in the MEPDG nor in the modified models. This research proposes a new model to predict creep compliance that captures the effect of recycled materials. The I-FIT results show that PMLC mixes have relatively lower flexibility index (FI) as compared to first field cores due to the difference in aging and compaction conditions. FI decreases with the increase in aging and recycled materials, while the strength and secant modulus increase. All AC mixes offered excellent rutting resistance, because they contain high ABR, and the resistance increased with aging as expected. The balanced mix design approach was utilized, based on rut depth and FI, which showed the convergence of AC mixes to stiffer zone with field aging. Similarly, secant modulus was added to the existing balance mix design as a stiffness indicator to control soft mixes. Furthermore, the field results confirm an excellent rutting performance in all sections. In addition, an exponential increase in transverse cracking was observed, which correlates with FI values obtained on the corresponding mixes. Thus, it is believed that I-FIT is a very simple, promising, and distinguishable test for evaluating the cracking resistance of AC mixes, which could be used as a performance evaluation tool along with rutting results to obtain balanced mix designs.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-12-01","The student, Fazal Safi, accepted the attached license on 2017-12-12 at 15:09.","The student, Fazal Safi, submitted this Thesis for approval on 2017-12-12 at 15:27.","This Thesis was approved for publication on 2017-12-13 at 09:21.","DSpace SAF Submission Ingestion Package generated from Vireo submission #11957 on 2018-03-13 at 10:38:19","Made available in DSpace on 2018-03-13T17:35:56Z (GMT). No. of bitstreams: 2 SAFI-THESIS-2017.pdf: 4573829 bytes, checksum: 7b102b9421fbc1ae764d0e8094b499bf (MD5) LICENSE.txt: 4207 bytes, checksum: 351d80adafa14a6f2773467a8a046a49 (MD5) Previous issue date: 2017-12-13","Embargo set by: Seth Robbins for item 105501 Lift date: 2020-03-13T17:36:05Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 105501 on 2020-03-14T09:15:25Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Balancing asphalt mixes containing recycled materials for optimum field performance"]}]}],"canonical_facts":{"dc:contributor":["Al-Qadi, Imad L.","Ozer, Hasan"],"dc:creator":["Safi, Fazal Rehman"],"dc:date":["2018-03-13T17:35:56Z","2020-03-14T09:15:25Z","2017-12-13","2017-12"],"dc:description":["Asphalt concrete (AC) is the most common material used for the construction of pavements in the U.S. and many other countries in the world. With the increasing use of recycled materials like reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS), the cracking resistance of asphalt pavements might be jeopardized. Therefore, such AC mixtures should be carefully investigated to ensure that performance is not compromised in the pursuit of an economical and sustainable solution. This study investigates 17 mixes including five leveling binders (LB) and 12 surface mixes, which have been used by the Illinois Department of Transportation (IDOT) in different rehabilitation projects across the State of Illinois, between 2013 and 2015. These AC mixes contain asphalt binder replacement (ABR) from 15 to 60%, acquired from RAP and RAS, whereas these mixes also contain steel slag and crushed concrete. In order to evaluate these AC mixes, a thorough laboratory testing, including indirect tensile creep compliance and strength, Hamburg wheel tracking test, and the Illinois flexibility index test (I-FIT) was conducted to evaluate thermal cracking susceptibility, rutting, and cracking resistance, on plant-mixed lab-compacted (PMLC) mixes and three sets of field cores. The extensive exploratory data analysis on creep compliance showed that softer binder and higher asphalt content result in more compliant mixes, while recycled materials tend to decrease the compliance of AC mixes. Likewise, softer binder and recycled materials tend to counterbalance each other’s impact. Similarly, the LB has relatively higher creep compliance as expected due to its design which is intended to retard reflective cracking. The IDT strength at -10°C is very similar across all AC mixes irrespective of the amount of recycled materials. Results also show that IDT creep compliance and strength might not distinguish the effect of field aging. The Pavement Mechanistic-Empirical Design Guide (MEPDG) uses the empirically developed model for the prediction of creep compliance as an input for Level 3 analysis, which uses mix and binder properties. However, the impact of recycled materials was not captured in the MEPDG nor in the modified models. This research proposes a new model to predict creep compliance that captures the effect of recycled materials. The I-FIT results show that PMLC mixes have relatively lower flexibility index (FI) as compared to first field cores due to the difference in aging and compaction conditions. FI decreases with the increase in aging and recycled materials, while the strength and secant modulus increase. All AC mixes offered excellent rutting resistance, because they contain high ABR, and the resistance increased with aging as expected. The balanced mix design approach was utilized, based on rut depth and FI, which showed the convergence of AC mixes to stiffer zone with field aging. Similarly, secant modulus was added to the existing balance mix design as a stiffness indicator to control soft mixes. Furthermore, the field results confirm an excellent rutting performance in all sections. In addition, an exponential increase in transverse cracking was observed, which correlates with FI values obtained on the corresponding mixes. Thus, it is believed that I-FIT is a very simple, promising, and distinguishable test for evaluating the cracking resistance of AC mixes, which could be used as a performance evaluation tool along with rutting results to obtain balanced mix designs.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-12-01","The student, Fazal Safi, accepted the attached license on 2017-12-12 at 15:09.","The student, Fazal Safi, submitted this Thesis for approval on 2017-12-12 at 15:27.","This Thesis was approved for publication on 2017-12-13 at 09:21.","DSpace SAF Submission Ingestion Package generated from Vireo submission #11957 on 2018-03-13 at 10:38:19","Made available in DSpace on 2018-03-13T17:35:56Z (GMT). No. of bitstreams: 2 SAFI-THESIS-2017.pdf: 4573829 bytes, checksum: 7b102b9421fbc1ae764d0e8094b499bf (MD5) LICENSE.txt: 4207 bytes, checksum: 351d80adafa14a6f2773467a8a046a49 (MD5) Previous issue date: 2017-12-13","Embargo set by: Seth Robbins for item 105501 Lift date: 2020-03-13T17:36:05Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 105501 on 2020-03-14T09:15:25Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/99532"],"dc:language":["en"],"dc:rights":["Copyright 2017 Fazal Safi"],"dc:subject":["Asphalt binder replacement (ABR)","Reclaimed asphalt pavement (RAP)","Recycled asphalt shingle (RAS)","Mechanistic-Empirical Design Guide (MEPDG)","Thermal cracking","Creep compliance modeling","Balance mix design","Total recycled asphalt (TRA) mixes","Field cores","Transverse cracking","Field performance","Illinois flexibility index test (I-FIT)","Secant modulus"],"dc:title":["Balancing asphalt mixes containing recycled materials for optimum field performance"],"dc:type":["text"],"thesis:degree_discipline":["Civil Engineering"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:37Z"}