{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/105270"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/105270","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Flexibility index threshold optimization for various asphalt mixes and geographic locations","abstract":"Made available in DSpace on 2019-08-23T20:48:27Z (GMT). No. of bitstreams: 2 MOHAMEDALI-THESIS-2019.pdf: 954913 bytes, checksum: b30d9d58637a8d4d0463520f164d9e0f (MD5) LICENSE.txt: 4215 bytes, checksum: 2cc1d3148776785b166c87de9a7ec48b (MD5) Previous issue date: 2019-04-26","abstract_html":"Made available in DSpace on 2019-08-23T20:48:27Z (GMT). No. of bitstreams: 2 MOHAMEDALI-THESIS-2019.pdf: 954913 bytes, checksum: b30d9d58637a8d4d0463520f164d9e0f (MD5) LICENSE.txt: 4215 bytes, checksum: 2cc1d3148776785b166c87de9a7ec48b (MD5) Previous issue date: 2019-04-26","abstract_has_math":false,"creators":["Mohamed Ali, Uthman"],"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, Hassan"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-08-23T20:48:27Z","date_published":"2019-08-23T20:48:27Z","updated_at":"2026-07-22T22:24:44Z","subjects":["Illinois Flexibility Index test (I-FIT), asphalt concrete, cracking, asphalt binder grade"],"languages":["en"],"rights":["Copyright 2019 Uthman Mohamed Ali"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/105270","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, Hassan"]},{"key":"dc:creator","label":"Author","values":["Mohamed Ali, Uthman"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2019-08-23T20:48:27Z","2021-08-24T09:15:28Z","2019-04-26","2019-05"]},{"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":["Illinois Flexibility Index test (I-FIT), asphalt concrete, cracking, asphalt binder grade"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2019 Uthman Mohamed Ali"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/105270"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Made available in DSpace on 2019-08-23T20:48:27Z (GMT). No. of bitstreams: 2 MOHAMEDALI-THESIS-2019.pdf: 954913 bytes, checksum: b30d9d58637a8d4d0463520f164d9e0f (MD5) LICENSE.txt: 4215 bytes, checksum: 2cc1d3148776785b166c87de9a7ec48b (MD5) Previous issue date: 2019-04-26","Majority of the highways and paved roads in the United States use asphalt concrete (AC) as a surface layer. However, the performance of this material is adversely affected by cracking. Several tests were developed to predict AC susceptibility to cracking. The Illinois Flexibility Index Test (I-FIT) is a simple, rapid, repeatable, and cost-effective test used to assess the cracking potential of AC. The test is performed at 25°C and 50mm/min loading rate. The main resultant parameter of the test is flexibility index (FI). A high FI generally implies better resistance to cracking. Asphalt concrete’s binder impacts FI results. Soft binders, such as PG 58-28, yield relatively higher FI values compared to similar AC containing stiffer binder (e.g. PG 70-22). Illinois Department of Transportation (IDOT) established a single FI threshold of eight for all unaged AC mixes. In addition, IDOT proposes an FI threshold of four for long-term aged specimens. Several AC mixes met the unaged threshold but failed the criterion for long-term aging condition and vice versa. The goal of this thesis is to minimize impact of binder grade on FI results. To isolate the impact of binder grade on FI values, for both unaged and long-term aged specimens, ensure testing of AC with various binders at equivalent stiffness (equi-stiffness), the same secant modulus. The secant modulus is defined herein as the ratio of 50% of the peak load to its corresponding displacement. Two approaches, using various test temperatures or loading rates, were investigated. Five laboratory-designed AC mixes containing various binder grades (PG 52-40, PG 58-34, PG 64-22, PG 70-22, and PG 76-22) were tested. The AC mixes have the same aggregate type and gradation, as well as binder content to isolate the effect of binder grade on I-FIT results. The AC mix with PG 64-22 was selected as the control mix. When testing was performed at the same secant modulus for the five AC mixes, by varying loading rate, the resultant FIs were more consistent than when temperature varied. In addition, the variation in FI values increased with aging AC specimens for three days at 95°C using a forced-draft oven. In addition to identifying an FI threshold that corresponds to a geographic location (based on binder grade used), the proposed approach would better correlate unaged and aged FI values for the same AC mix.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01","The student, Uthman Mohamed Ali, accepted the attached license on 2019-04-25 at 18:45.","The student, Uthman Mohamed Ali, submitted this Thesis for approval on 2019-04-25 at 18:56.","This Thesis was approved for publication on 2019-04-26 at 10:22.","DSpace SAF Submission Ingestion Package generated from Vireo submission #13932 on 2019-08-22 at 16:24:00","Embargo set by: Seth Robbins for item 112392 Lift date: 2021-08-23T20:48:32Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 112392 on 2021-08-24T09:15:28Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Flexibility index threshold optimization for various asphalt mixes and geographic locations"]}]}],"canonical_facts":{"dc:contributor":["Al-Qadi, Imad L.","Ozer, Hassan"],"dc:creator":["Mohamed Ali, Uthman"],"dc:date":["2019-08-23T20:48:27Z","2021-08-24T09:15:28Z","2019-04-26","2019-05"],"dc:description":["Made available in DSpace on 2019-08-23T20:48:27Z (GMT). No. of bitstreams: 2 MOHAMEDALI-THESIS-2019.pdf: 954913 bytes, checksum: b30d9d58637a8d4d0463520f164d9e0f (MD5) LICENSE.txt: 4215 bytes, checksum: 2cc1d3148776785b166c87de9a7ec48b (MD5) Previous issue date: 2019-04-26","Majority of the highways and paved roads in the United States use asphalt concrete (AC) as a surface layer. However, the performance of this material is adversely affected by cracking. Several tests were developed to predict AC susceptibility to cracking. The Illinois Flexibility Index Test (I-FIT) is a simple, rapid, repeatable, and cost-effective test used to assess the cracking potential of AC. The test is performed at 25°C and 50mm/min loading rate. The main resultant parameter of the test is flexibility index (FI). A high FI generally implies better resistance to cracking. Asphalt concrete’s binder impacts FI results. Soft binders, such as PG 58-28, yield relatively higher FI values compared to similar AC containing stiffer binder (e.g. PG 70-22). Illinois Department of Transportation (IDOT) established a single FI threshold of eight for all unaged AC mixes. In addition, IDOT proposes an FI threshold of four for long-term aged specimens. Several AC mixes met the unaged threshold but failed the criterion for long-term aging condition and vice versa. The goal of this thesis is to minimize impact of binder grade on FI results. To isolate the impact of binder grade on FI values, for both unaged and long-term aged specimens, ensure testing of AC with various binders at equivalent stiffness (equi-stiffness), the same secant modulus. The secant modulus is defined herein as the ratio of 50% of the peak load to its corresponding displacement. Two approaches, using various test temperatures or loading rates, were investigated. Five laboratory-designed AC mixes containing various binder grades (PG 52-40, PG 58-34, PG 64-22, PG 70-22, and PG 76-22) were tested. The AC mixes have the same aggregate type and gradation, as well as binder content to isolate the effect of binder grade on I-FIT results. The AC mix with PG 64-22 was selected as the control mix. When testing was performed at the same secant modulus for the five AC mixes, by varying loading rate, the resultant FIs were more consistent than when temperature varied. In addition, the variation in FI values increased with aging AC specimens for three days at 95°C using a forced-draft oven. In addition to identifying an FI threshold that corresponds to a geographic location (based on binder grade used), the proposed approach would better correlate unaged and aged FI values for the same AC mix.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01","The student, Uthman Mohamed Ali, accepted the attached license on 2019-04-25 at 18:45.","The student, Uthman Mohamed Ali, submitted this Thesis for approval on 2019-04-25 at 18:56.","This Thesis was approved for publication on 2019-04-26 at 10:22.","DSpace SAF Submission Ingestion Package generated from Vireo submission #13932 on 2019-08-22 at 16:24:00","Embargo set by: Seth Robbins for item 112392 Lift date: 2021-08-23T20:48:32Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 112392 on 2021-08-24T09:15:28Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/105270"],"dc:language":["en"],"dc:rights":["Copyright 2019 Uthman Mohamed Ali"],"dc:subject":["Illinois Flexibility Index test (I-FIT), asphalt concrete, cracking, asphalt binder grade"],"dc:title":["Flexibility index threshold optimization for various asphalt mixes and geographic locations"],"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":"2026-07-22T22:24:44Z"}