Field and simulated rutting behavior of hot mix and warm mix asphalt overlays

AbstractDespite significant economic and environmental benefits, performance of warm mix asphalt (WMA) containing reclaimed asphalt pavement (RAP) remains a matter of concern. Among the current WMA technologies, the plant foaming technique (called “foamed WMA” in this study) has gained the most attention, since it eliminates the need for chemical additives. In the present study, the laboratory performance, namely rutting and moisture-induced damage potential of foamed WMA containing RAP were evaluated and compared with those of similar hot mix asphalt (HMA) containing identical amount of RAP. Dynamic modulus, Hamburg wheel tracking (HWT) and flow number tests were performed to assess the rutting resistance of the mixes. Also, stripping inflection point from HWT tests and tensile strength ratio after AASHTO T 283 and moisture induced sensitivity test (MIST) conditioning were used to evaluate the moisture-induced damage of asphalt mixes. It was found that MIST conditioning effectively simulates the moisture-induced damage and can capture the propensity of asphalt mixes to moisture damage more distinctly compared to AASHTO T 283 method due to application of cyclic loadings. The foamed WMA was found to exhibit higher rutting and moisture-induced damage potential due to lower mixing and compaction temperatures compared to HMA. However, the increase in RAP content was found to reduce rutting and moisture-induced damage potential for WMA. Therefore, the lower stiffness of foamed WMA may be compensated with the addition of stiffer binder from RAP.

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

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198121997823 ◽

2021 ◽

pp. 036119812199782

Author(s):

Biswajit K. Bairgi ◽

Md Amanul Hasan ◽

Rafiqul A. Tarefder

Keyword(s):

Permanent Deformation ◽

Warm Mix Asphalt ◽

Creep Recovery ◽

Deformation Model ◽

Contact Method ◽

Moisture Susceptibility ◽

Viscoelastic Continuum Damage ◽

Foamed Asphalt ◽

Flexural Beam ◽

Wheel Tracking

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.

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The dark-ventral-patch of male red deer, a sexual signal that conveys the degree of involvement in rutting behavior

BMC Zoology ◽

10.1186/s40850-021-00083-9 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Eva de la Peña ◽

Javier Pérez-González ◽

José Martín ◽

Giovanni Vedel ◽

Juan Carranza

Keyword(s):

Sexual Behaviors ◽

Red Deer ◽

Decisive Role ◽

Female Mate Choice ◽

Doñana National Park ◽

Sexual Signal ◽

Mating Competition ◽

Dark Patch ◽

Rutting Behavior

Abstract Background In polygynous mammals, signalling may play a decisive role in mating behavior, mediating the intensity of male fights and female mate choice. During the rutting season, male red deer may show a visible dark patch in their ventral fur. Recently, this patch has been suggested to act as a flexible sexual signal, due to its relationships with other variables such as age, body size, antler development, volatile compounds, or the competitive environment. The analysis of fur pigmentation at the ventral patch suggests that this might also visually indicate the male intrinsic predisposition to take part in mating competition. Results To assess the possible role of this trait as a communicative signal related to mate competition, we used red deer behavioral observations during the rut in Doñana National Park (Spain) to examine the link between the degree of expression of the dark ventral patch and the rutting activity (assessed from both intra-and-inter-sexual behaviors). Consistent with our predictions, we found in a field study that males with large dark patches showed a higher frequency of rutting behaviors (mainly roaring and flehmen), more interactions with females, and attained larger harem sizes. Conclusions The dark ventral patch was a better predictor of male behavior than antler tines or territory holding, thus standing as a short-term indicator of male willingness to invest in mating competition.

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