Laboratory Evaluation of Warm-Mix Asphalt Open-Graded Friction Courses

Abstract

This study aimed at evaluating the laboratory performance and physical characteristics of warm-mix asphalt (WMA) open-graded friction course (OGFC) mixes prepared with three warm-mix additives (two chemical additives and an organic additive). To achieve this objective, four mixes were prepared including a control mix (CM) prepared with a PG 76-22 binder and two sources of aggregate (i.e., # 78 limestone and # 67 sandstone). Air voids and coefficient of permeability ( k) were used to evaluate the functionality of the OGFC mixes. In relation to constructability, the compaction energy index was used to compare the required compaction effort during construction. Furthermore, the Cantabro test, Hamburg wheel-tracking test, Texas overlay test, Modified Lottman, and boil tests were conducted to evaluate durability, permanent deformation, cracking, and moisture-damage resistances of the evaluated mixes. Results indicated that the use of WMA technologies enhanced OGFC durability and performance. Among the evaluated mixes, the organic additive-OGFC met all Louisiana Department of Transportation and Development and NCHRP 01-55 requirements, as it notably enhanced OGFC durability, cracking, and moisture-damage resistance. Furthermore, the use of WMA notably reduced the required compaction effort and mixing temperature needed during production and construction as compared with the CM.

Effects of Air Void Content, Crumb Rubber, and Pozzolanic Fillers on OGFC Laboratory Performance

“…In the experimental program, a state-approved job mix formula for an OGFC mix was used to fabricate the CM ( 1 ). This mix is typically produced using two aggregate types (#78 limestone and #67 sandstone) and a PG 76-22 SBS-modified asphalt binder at a rate of 6.5% by weight of the mix.…”

“…To control binder draindown, cellulose fibers were added to the mixture at a specified dose of 0.2% by weight of the mix. Fibers and ASA were added to the mixture using the procedures described elsewhere ( 1 ). The CM was first modified by decreasing the NMAS from 12.5 to 9.5 mm mix.…”

“…These tests were conducted according to the test methods described in Table 2. Abohamer et al described in details the procedure for each test ( 1 ).…”

“…To facilitate water drainage during rain events, open-graded friction course (OGFC) is often favored given its superior drainage capability because of its high air void (AV) content (i.e., typically between 18 and 24%) ( 1 ). With OGFC, hydroplaning is less likely as there is no water film caused by water buildup.…”

Investigating the Seepage Characteristics of an Open-Graded Friction Course Using Finite Element Modeling

“…In Louisiana, the AV content of the OGFC is required to be in the range of 18%–24% ( 7 , 12 , 13 ). The high AV content of the OGFC promotes its functionality by allowing the water to drain horizontally through the interconnected voids, therefore preventing hydroplaning, splash, and spray ( 14 , 7 ).…”