Fractionated reclaimed asphalt pavement as a coarse aggregate replacement in a ternary blended concrete pavement

Brand, Alexander

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Description

Title

Fractionated reclaimed asphalt pavement as a coarse aggregate replacement in a ternary blended concrete pavement

Author(s)

Brand, Alexander

Issue Date

2012-05-22T00:29:40Z

Director of Research (if dissertation) or Advisor (if thesis)

Roesler, Jeffery R.

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• fractionated reclaimed asphalt pavement
• fractionated reclaimed asphalt pavement (FRAP)
• reclaimed asphalt pavement
• reclaimed asphalt pavement (RAP)
• concrete
• ternary concrete
• slag
• fly ash
• pavements
• durability
• fracture
• shrinkage
• recycling pavements
• green concrete
• sustainability

Abstract

Due to increasing quantities of fractionated reclaimed asphalt pavement (FRAP) generated from rehabilitation projects, the Illinois State Toll Highway Authority (Tollway) initiated a study to determine the application of the coarse fraction of FRAP in concrete. The concrete mix proportions contained 0, 20, 35, and 50% FRAP replacement levels by weight of the coarse aggregate. Two other by-product materials, ground granulated blast furnace slag and fly ash, were utilized as partial replacements for cement. A cementitious content of 630 lb/yd3 was used, which consisted of 65% Type I Portland cement, 25% Grade 100 slag, and 10% Class C fly ash. Past research efforts have primarily studied the effects of RAP on the hardened properties in concrete, but there have been limited studies on the comprehensive effect on the fresh, hardened, and durability properties of a single source of FRAP in concrete at various replacement levels. In this study, as the FRAP content increased, it was found that the workability increased (even with lower water reducing admixture dosages), the unit weight decreased, and the air content remained relatively unaffected although somewhat more variable. A hardened air void analysis revealed acceptable parameters for freeze/thaw durability, but the hardened air content was found to be higher than measured volumetric fresh concrete air content. The concrete was workable for good pavement constructability at all levels of FRAP replacement tested. The compressive, split tensile, and flexural strengths all decreased with increasing coarse FRAP contents. The compressive strength decreased up to 39% with a FRAP content of 50%. Similarly, with 50% FRAP, the split tensile strength decreased as much as 52% and the flexural strength decreased approximately 33%. At 35% FRAP replacement, the Illinois Department of Transportation (IDOT) compressive strength requirement of 3500 psi at 14 days could still be met, while at 50% FRAP, the FRAP concrete mixture was 0.3% below this strength requirement. Based on the third-point (four point) flexural strength results, it is expected that up to 50% FRAP would meet the IDOT center-point (three point) flexural strength requirement of 650 psi at 14 days. Similar to the strength properties, both the static and dynamic elastic moduli decreased with increasing FRAP content. The elastic modulus was reduced by 30% at 50% FRAP while the dynamic modulus decreased by 46% (at 4C) with 50% FRAP replacement. At 21C, the dynamic modulus was about 15% higher than the static elastic modulus for the control (0% FRAP) concrete, but at 50% FRAP, the static elastic modulus was 11% higher than the dynamic modulus. From the dynamic modulus tests, the phase angle only increased approximately 1 degree with the addition of 50% coarse FRAP to concrete. Changes in temperature and frequency did not significantly affect the concrete dynamic modulus at all testing ages and FRAP contents. The concrete fracture properties with single edge notched beam specimens revealed that the critical stress intensity factor was generally reduced with the addition of FRAP. Despite the reduction in tensile strength and peak load at specimen failure with increasing quantities of FRAP replacement, both the total fracture energy and initial fracture energy were relatively unchanged. This fracture behavior suggests the load capacity of concrete slabs with FRAP will not be reduced at the same rate as the concrete tensile strength reduction. In this study, the concrete free drying shrinkage was found to be unaffected by the coarse FRAP replacement levels and total cementitious content utilized. At the 0% and 50% FRAP contents, specimens under restrained ring shrinkage (AASHTO T334) did not crack after 90 days. The 50% FRAP ring experienced lower restrained shrinkage strains and higher stress relaxation at later ages relative to the control concrete, indicating potential positive tensile creep benefits of concrete containing FRAP. A rapid chloride penetration test was also conducted, and it was found that the FRAP content did not affect the chloride penetrability after an age of 56 days. The freeze/thaw durability was found to be suitable, with all mixes having a durability factor greater than 85 after 300 freeze/thaw cycles, although higher FRAP contents did reduce the durability factor relative to the control. A test for alkali-silica reactivity (ASTM C1260) evaluated the virgin coarse aggregate, the virgin fine aggregate, the fine FRAP particles (passing the #4 sieve), and the FRAP coarse aggregate with the binder extracted. The test revealed that the virgin fine aggregate was mildly reactive while the other aggregates were negligibly reactive. According to the IDOT specifications, the addition of supplementary cementitious materials or the use of a low-alkali cement would likely mitigate the expansion due to alkali-silica reaction in the fine aggregate. Another FRAP source was also evaluated to determine the effects of a “dirty” unwashed FRAP, which contained a higher amount of fine particles (passing the #4 sieve) compared to the washed “clean” FRAP used in the main part of the study. The dirty FRAP was either washed or dry sieved to remove the fine particles or unprocessed before concrete batching. The removal of the fine particles did not improve the compressive and split tensile strengths of the concrete relative to unprocessed dirty FRAP concrete, but all dirty FRAP mixes, processed and unprocessed, up to 50% coarse FRAP met the IDOT strength requirements at 14 days. Based on the results from this study, the replacement of virgin aggregate with 50% coarse FRAP in concrete will still produce acceptable paving concrete in terms of fresh, strength, durability, shrinkage, and fracture properties. Although the main mix design and FRAP source used for this study met the IDOT strength requirements at coarse FRAP contents up to 35%, a secondary “dirty” FRAP source as well as mixes tested by an independent laboratory were found to meet the IDOT strength requirements up to 50% FRAP.

Graduation Semester

2012-05

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Copyright 2012 Alexander Sebastian Brand

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