Assessment of Rutting Behavior of Warm-Mix Asphalt (WMA) with Chemical WMA Additives towards Laboratory and Field Investigation

Mannan

Transportation Research Record: Journal of the Transportation R

2019

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Asphalt binder acts as a lubricant between two aggregates during mixing and compaction. The frictional behavior of asphalt binder as a lubricant in an asphalt-aggregate system plays an important role in mixing and compaction (workability) of warm-mix asphalt (WMA). This study evaluates the frictional behavior of foamed WMA through tribological characterization using a ball-on-three-plates apparatus assembled inside a dynamic shear rheometer (DSR). The tribological test was conducted on six foamed asphalts with varying foaming water contents (FWCs) and on a controlled unfoamed asphalt binder at four different temperatures: 25°C, 60°C, 100°C, and 135°C. These binders were also characterized for rheological and chemical properties. Test results show that the foaming process alters the frictional resistance of the foamed asphalts; specifically, the foaming process reduces the coefficient of friction in elastohydrodynamic and hydrodynamic lubrication regimes. Reduced frictional resistance helps in the formation of a better coating during mixing and improves the sliding ability between aggregates during compaction at reduced temperature.

Section: Resultssupporting

confidence: 92%

Tribological Evaluation for an In-Depth Understanding of Improved Workability of Foamed Asphalt

Mannan

Transportation Research Record: Journal of the Transportation R

2019

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“…A linear variable displacement transducer measures the rut depth at 11 points along the wheel passing direction with 0.01 mm precision. There are several different methodologies to analyze HWT testing data to evaluate rutting and stripping (23)(24)(25)(26)(27).…”

Section: Laboratory Testing For Mechanistic Evaluationmentioning

confidence: 99%

Evaluation of Full-Depth Reclamation and Cold Central-Plant Recycling Mixtures for Laboratory Compaction, Mechanistic Response, and Performance Properties

Transportation Research Record: Journal of the Transportation R

Hasan

et al. 2022

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Cold recycled mixtures (CRM) are gaining wider acceptability in the United States for rehabilitating existing pavement or new construction while reducing construction costs, environmental impacts, and construction time. However, the technology is still in development owing to inconsistency in design and limited research on mechanistic and engineering properties. To this end, this study evaluates full-depth reclamation (FDR) and cold central-plant recycling (CCPR) materials for evaluating (i) laboratory compaction protocols, (ii) mechanistic properties, and (iii) engineering performances. Two compaction methods—the Superpave gyratory compaction and the modified proctor—were developed for designing test specimens with adequate design properties. The mechanistic properties resilient modulus ( MR) and dynamic modulus (| E*|) were evaluated. Laboratory performance testing such as Texas overlay tester, semi-circular bending, and a modified Hamburg wheel tracking (HWT) were performed. This study also proposed a new parameter, loading limit ( Nmax), based on the modified HWT test configuration. The study found that the FDR exhibits less temperature dependency compared with the CCPR while subjecting to loading. Based on damage properties such as critical fracture energy, J-integral, crack propagation index, and Nmax, the CCPR exhibits more flexibility and damage resistance than FDR.

“…Again, the stripping inflection point (SIP)-the intersection of the creep phase slope and the stripping phase slope-is used as a stripping potential indicator (30). The identification of SIP may introduce bias in the analysis (31,32).…”

Section: Permanent Deformation Modelingmentioning

confidence: 99%

Effects of Asphalt Foaming on Damage Characteristics of Foamed Warm Mix Asphalt

Hasan

Transportation Research Record: Journal of the Transportation R

2021

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In the asphalt foaming process, the foaming water content (FWC) controls the formation and characteristics of water bubbles. These water bubbles are expected to be expelled from the foamed warm mix asphalt (WMA) during mixing and compaction. However, foaming water may not be completely expelled, rather some of the microbubbles may be trapped in the foamed WMA even after compaction. These microbubbles, or undissipated water, can diffuse over time and cause damage to the foamed WMA. To this end, this study has determined the effects of foaming on the fatigue, moisture damage, and permanent deformation characteristics of foamed WMA. Foamed asphalt and mixtures were designed with varying FWCs and they were tested using linear amplitude sweep, multiple stress creep recovery, four-point flexural beam, and Hamburg wheel tracking tests. Primarily, asphalt foaming dynamics were assessed with a laser-based non-contact method. A simplified viscoelastic continuum damage concept and a three-phase permanent deformation model were used for damage evaluation. The study reveals that foaming softens the binder, which results in slightly higher rutting and moisture susceptibility, though an equivalent or slightly improved fatigue characteristic compared with the regular hot mix asphalt.