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Title:Impact of recycled asphalt shingles on asphalt concrete characteristics
Author(s):Kanaan, Ahmad
Advisor(s):Al-Qadi, Imad L.
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Recycled materials
asphalt Binder replacement (ABR)
recycled asphalt shingles (RAS)
reclaimed asphalt pavements (RAP)
Abstract:The use of recycled materials in asphalt mixtures such as reclaimed asphalt pavements (RAP) and more recently recycled asphalt shingles (RAS) have become widely accepted in the United States as a replacement for virgin asphalt binder or virgin aggregates. However, the economics and the challenges of using them were not viable until recently. The use of RAP and RAS thus represents one of the most convenient ways of reducing production costs even while improving the sustainability of pavement systems by replacing part of the virgin materials in Hot-Mix Asphalt (HMA). This study examined the effect of high asphalt binder replacement for a low N-design asphalt mixture, including RAP and RAS on the different asphalt mixture performance indicators such as permanent deformation, fracture, fatigue potentials, and stiffness. In addition, fine asphalt mixture (FAM) samples were prepared using fine aggregates (FM-20) and different RAS percentages mixed with either PG46-34 or PG64-22 asphalt binder. The main objective of this part of the study was to develop time efficient protocols to evaluate the influence of recycled materials on asphalt mixture performance. An experimental program for the regular mixes included complex modulus, fracture, overlay reflective cracking resistance, wheel track permanent deformations, and push-pull fatigue tests. The asphalt binder replacement levels in the mix using combinations of RAS and RAP were in the range of 43% to 64%. For the FMA, in addition to the control mix with PG64-22 (0.0% RAS), mixes with 7.1% RAS content, and RAS contents at 2.5% and 7.1% were used with PG46-34. The testing program for the FAM specimens included complex shear modulus, shear strength and fatigue. For the asphaltic mixtures, RAS reduced rutting potential. However, fracture tests at low temperature did not reveal any significant difference between the specimens prepared with varying percentages of asphalt binder replacement. The fatigue potential of mixtures increased with increasing RAS content and asphalt binder replacement. The specimens prepared with 2.5% RAS and PG46-34 showed the best fatigue performance. The impact of asphalt binder bumping was noticeable when the asphalt binder type was changed from PG 58-28 to PG 46-34 at the highest asphalt binder replacement level; fatigue life and fracture energy were improved. The results showed that complex modulus test results can provide crucial information about the mix viscoelastic properties such as relaxation potential and long-term stiffness that can be used, along with fracture tests, to evaluate mix brittleness at relatively high asphalt binder replacement levels. Results obtained from FAM testing shown to be comparable to the asphalt mixture results. A good correlation was observed between both asphalt mixture complex modulus and the FMA complex shear modulus obtained using the DSR. The results from the FAM specimens were shown to be consistent and sensitive to varying RAS percentages. Results obtained from the DSR testing showed that the mixes prepared with PG64-22 have higher stiffness, tensile strength, and complex modulus compared with the mixes prepared with PG46-34 asphalt binder. In addition, as RAS content increases, complex modulus and shear strength increase. As to the fatigue life, it decreases as RAS content increased when conducted in the strain-control (low cycle) setting. However, as expected, stress-control fatigue tests showed an improvement in the fatigue life when higher RAS content was used. Results obtained from the statistical analysis showed that most of the complex modulus results for the various mixes were significantly different from each other, except the mix with 0.0% RAS and 2.5% RAS using PG46-34, and the mix with 7.1% RAS using PG46-34 and the mix with 0.0% RAS using PG64-22 at some frequencies only. In general, statistical analysis and test observations, showed that the repeatability of proposed FAM specimen preparation methods and tests is satisfactory and the FAM testing can be useful in identifying critical parameters for high ABR mixes that can be used to select the type and amount of rejuvenators, RAS source variability, and identifying the proper binder grade.
Issue Date:2013-08-22
Rights Information:Copyright 2013 Ahmad Kanaan
Date Available in IDEALS:2013-08-22
Date Deposited:2013-08

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