scholarly journals Evaluation of the Performance of a Warm Mix Asphalt (WMA) Considering Aged and Unaged Specimens

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1241
Author(s):  
Giuseppe Piccone ◽  
Giuseppe Loprencipe ◽  
Arminda Almeida ◽  
Nicola Fiore
Keyword(s):  
Fatigue Behavior ◽  
Permanent Deformation ◽  
Road Construction ◽  
Warm Mix Asphalt ◽  
Environmental Aspects ◽  
Bituminous Mixtures ◽  
Water Sensitivity ◽  
Short And Long Term ◽  
High Level

In the last decades, all technology production sectors reached a high level of development, without neglecting the attention to environmental aspects and safeguarding energy resources. Moreover, in the sector of pavement industry, some alternatives of bituminous mixtures were proposed to reduce the greenhouse gas emissions. One of these is the warm mix asphalt (WMA), a mixture produced and compacted at lower temperatures compared to traditional hot mix asphalt (HMA) (about 40 °C less), to allow a reduction of emissions into the atmosphere and the costs. Other operative benefits concern the health of workers during the whole road construction process, the reduction of distances to which the mixture can be transported, and therefore also the positioning of the plants. However, it is not all benefits, since reduced production temperatures can bring short- and long-term water sensitivity issues, which could threaten the pavement performance. This paper evaluated the performance (water sensitivity, stiffness, fatigue, and permanent deformation) of a WMA produced using a warm mix fabrication bitumen and compared it with an HMA tested in parallel. In general, except for the resistance to permanent deformation, the WMA presented performances comparable to HMA. Regarding the fatigue behavior of asphalt mixtures, the WMA was less affected by ageing conditions, despite it showing lower performance than HMA.

scholarly journals Performance Assessment of Reclaimed Asphalt Pavement (RAP) in Road Surface Mixtures

Recycling ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 32
Author(s):  
Vítor Antunes ◽  
José Neves ◽  
Ana Cristina Freire
Keyword(s):  
Current Knowledge ◽  
Asphalt Pavement ◽  
Permanent Deformation ◽  
Reclaimed Asphalt Pavement ◽  
Reclaimed Asphalt ◽  
Bituminous Mixtures ◽  
Road Pavement ◽  
Water Sensitivity ◽  
Short And Long Term

Considerable amounts of Reclaimed Asphalt Pavement (RAP) are produced every year, as the road network requires maintenance to ensure the safety and comfort of its users. RAP is a 100% recyclable material and a useful fit to be re-introduced into another cycle without downgrading its functionality. Despite the current knowledge about the benefits associated with RAP use, it is not yet largely applied in several countries. This paper aims to validate, on the basis of both short- and long-term mechanical behaviours, the application of a bituminous mixture with a high RAP incorporation rate (75%) in road pavement wearing courses. A crude tall oil rejuvenator was used. Both short- and long-term oven ageing procedures were employed to simulate the ageing that occurs during mixture production and in-service life, respectively. The tests for validating the RAP mixture as an alternative solution comprised stiffness, resistance to fatigue, permanent deformation, and determination of the water sensitivity. Furthermore, the RAP bitumen mobilisation degree was evaluated and a mixing protocol was established. In comparison with virgin bituminous mixtures, it was found that, in general, the high RAP mixtures presented similar or better behaviour. The ageing process had a hardening effect namely in terms of stiffness and resistance to permanent deformation, without significant effects on the resistance to fatigue and water damage.

scholarly journals The Influence of Reclaimed Asphalt Pavement on the Mechanical Performance of Bituminous Mixtures. An Analysis at the Mortar Scale

2020 ◽  
Vol 12 (20) ◽  
pp. 8343
Author(s):  
Ana E. Hidalgo ◽  
Fernando Moreno-Navarro ◽  
Raúl Tauste ◽  
M. Carmen Rubio-Gámez
Keyword(s):  
Mechanical Performance ◽  
Asphalt Pavement ◽  
Mechanical Analysis ◽  
Elastic Response ◽  
Reclaimed Asphalt Pavement ◽  
Reclaimed Asphalt ◽  
Bituminous Mixtures ◽  
Water Sensitivity ◽  
Term Performance

The main characteristics of bituminous mixtures manufactured with a considerable amount of reclaimed asphalt pavement (RAP), compared to conventional mixtures, are a reduction in workability, an increase in stiffness, and a loss of ductility, due to the presence of the aged bitumen contained in the RAP particles. To minimize these impacts, softer binders or rejuvenators are commonly used in the design of these mixtures in order to restore part of the ductility lost and to reduce the stiffness. In spite of previous investigations demonstrating that the mortar plays an essential role in the workability, long-term performance, and durability of bituminous mixtures (where cracking, cohesion, and adhesion problems all start at this scale), not many studies have assessed the impacts caused by the presence of RAP. In response to this, the present paper analyzes the workability, fatigue performance, and water sensitivity of bituminous mortars containing different amounts of RAP (from 0% to 100%) and rejuvenators. Mortar specimens were compacted using a gyratory compactor and studied via dynamic mechanical analysis under three point bending configuration. The results demonstrated that the presence of RAP reduces the workability and ductility of asphalt mortars. However, it also causes an increase in their stiffness, which induces a more elastic response and causes an increase in their resistance to fatigue, which could compensate for the loss of ductility. This aspect, together with the low water sensitivity shown, when using Portland cement as an active filler, would make it possible to produce asphalt materials with high RAP contents with a similar long-term mechanical performance as traditional ones. In addition, the use of rejuvenators was demonstrated to effectively correct the negative workability and ductility impacts caused by using RAP, without affecting the fatigue resistance and material adhesion/cohesion.

scholarly journals Learner-Centered Inquiry in Undergraduate Biology: Positive Relationships with Long-Term Student Achievement

2010 ◽  
Vol 9 (4) ◽  
pp. 462-472 ◽  
Author(s):  
Terry L. Derting ◽  
Diane Ebert-May
Keyword(s):  
Learning Experience ◽  
Collaborative Work ◽  
Introductory Courses ◽  
Traditional Lecture ◽  
Undergraduate Biology ◽  
Learner Centered ◽  
Short And Long Term ◽  
High Level ◽  
Biology Curriculum

We determined short- and long-term correlates of a revised introductory biology curriculum on understanding of biology as a process of inquiry and learning of content. In the original curriculum students completed two traditional lecture-based introductory courses. In the revised curriculum students completed two new learner-centered, inquiry-based courses. The new courses differed significantly from those of the original curriculum through emphases on critical thinking, collaborative work, and/or inquiry-based activities. Assessments were administered to compare student understanding of the process of biological science and content knowledge in the two curricula. More seniors who completed the revised curriculum had high-level profiles on the Views About Science Survey for Biology compared with seniors who completed the original curriculum. Also as seniors, students who completed the revised curriculum scored higher on the standardized Biology Field Test. Our results showed that an intense inquiry-based learner-centered learning experience early in the biology curriculum was associated with long-term improvements in learning. We propose that students learned to learn science in the new courses which, in turn, influenced their learning in subsequent courses. Studies that determine causal effects of learner-centered inquiry-based approaches, rather than correlative relationships, are needed to test our proposed explanation.

scholarly journals Effect of Oxidative Aging on the Engineering Properties of DGAMs

2018 ◽  
Vol 7 (4) ◽  
pp. 50
Author(s):  
Al-Hadidy A.I. ◽  
Abdullah M. Rashed
Keyword(s):  
Service Life ◽  
Flexural Strength ◽  
Permanent Deformation ◽  
Engineering Properties ◽  
Base Layer ◽  
Short Term ◽  
Asphalt Cement ◽  
Oxidative Aging ◽  
Short And Long Term

Short and long term aging were conducted on the dense graded asphalt mixtures (DGAMs) containing 40-50 penetration grade asphalt cement binders. The short term oven aging (STOA) was conducted on loose mixtures at temperature of 135 °C for four hours and at temperature of 154 °C for two hours, whereas, the long term oven aging (LTOA) was conducted at temperature of 85 °C and at two periods of time between four and eight days. Marshall properties, tensile and compressive strength at 25 and 60°C, flexural strength at 0 and -10°C, cohesion at 60°C, tensile strength ratio, and index of retained strength were carried out on unaged and aged DGAM. A mechanistic-empirical design approach using BISAR program was adopted for estimating the improvement in service life of the pavement or reduction in thickness of DGAM and base layer for the same service life due to the aging of DGAM. The results showed that the STOA and LTOA: (1) increases resistance of DGAM against permanent deformation, stripping, and flexural strength; (2) increases traffic benefit ratio between 10 and 20%; (3) reduces the thickness of the surface layer between 8 and 14%; and (4) the base thickness reduces between 35% and 57%.

scholarly journals Evaluation of Warm Rubberized Stone Mastic Asphalt Mixtures through the Marshall and Gyratory Compactors

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 265
Author(s):  
Juan Gallego ◽  
Ana María Rodríguez-Alloza ◽  
Leticia Saiz-Rodríguez
Keyword(s):  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Mechanical Behaviour ◽  
Permanent Deformation ◽  
Warm Mix Asphalt ◽  
Asphalt Mixtures ◽  
Reflective Cracking ◽  
Mastic Asphalt ◽  
Water Sensitivity ◽  
Stone Mastic Asphalt

Stone mastic asphalt (SMA) mixtures exhibit excellent behaviour; they are highly resistant to reflective cracking and permanent deformation, as well as providing the wearing surface with an optimal texture. However, the production and compaction temperatures are similar to conventional mixtures, which means that there is a significant consumption of energy, as well as greenhouse gas emissions. Warm mix asphalt (WMA) technology, which has been developed over the last few years, might allow lower temperatures without compromising the mechanical behaviour of the mixtures. Also, over the last few decades, rubberized asphalt has proved to be effective in improving the performance and being environmentally suitable, but it requires higher production temperatures than conventional mixtures. In this study, several tests were performed to evaluate the effect of a chemical WMA additive on the compactability and water sensitivity of rubberized SMA mixtures with both the Marshall and the gyratory compactor. The investigation has shown that the gyratory compactor is more suitable for studying compactability and the water sensitivity of rubberized SMA with WMA additives.

Factors that Affect the Fatigue Life of Rubber: A Literature Survey

2004 ◽  
Vol 77 (3) ◽  
pp. 391-412 ◽  
Author(s):  
W. V. Mars ◽  
A. Fatemi
Keyword(s):  
Fatigue Life ◽  
Volume Fraction ◽  
Mechanical Load ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Loading Waveform ◽  
Constitutive Response ◽  
Short And Long Term

Abstract Many factors are known to influence the mechanical fatigue life of rubber components. Four major categories of factors are reviewed here: the effects of mechanical loading history, environmental effects, effects of rubber formulation, and effects due to dissipative aspects of the constitutive response of rubber. For each category, primary factors are described, and existing literature is presented and reviewed. Rubber's fatigue behavior is extremely sensitive to both the maximum and minimum cyclic load limits. Other aspects of the mechanical load history are also discussed, including the effects of static loaded periods (“annealing”), load sequence, multiaxiality, frequency, and loading waveform. Environmental factors can affect both the short and long term fatigue behavior of rubber. The effects of temperature, oxygen, ozone, and static electrical charges are reviewed. A great range of behavior is available by proper manipulation of formulation and processing variables. Effects of elastomer type, filler type and volume fraction, antidegradants, curatives, and vulcanization are discussed. The role of dissipative constitutive behavior in the improvement of fatigue properties of rubber is also reviewed. Four distinct dissipative mechanisms are identified, and their effects on fatigue behavior are described.

Rheological and chemical characteristics of warm mix asphalt binders at intermediate and low performance temperatures

2013 ◽  
Vol 40 (9) ◽  
pp. 861-868 ◽  
Author(s):  
Feipeng Xiao ◽  
V.S. Punith ◽  
Serji N. Amirkhanian ◽  
Bradley J. Putman
Keyword(s):  
Rheological Properties ◽  
Warm Mix Asphalt ◽  
Environmental Benefits ◽  
Asphalt Binders ◽  
Testing Procedures ◽  
Binder Type ◽  
Creep Stiffness ◽  
Short And Long Term ◽  
Low Performance

Warm asphalt has been gaining increasing popularity in recent years around the world due to many reasons including the energy reductions and environmental benefits. In the present study, the objective was to conduct a laboratory investigation of rheological properties of eight binders with four non-foaming warm mix asphalt (WMA) additives at intermediate and low performance temperatures in terms of Superpave low temperature test criteria. The conventional testing procedures such as dynamic shear rheometer (DSR), bending beam rheometer (BBR) test as well as specific Fourier transform infrared spectroscopy (FTIR) were performed to determine the influences of non-foaming additives on asphalt binders after a long-term aging procedure. The test results indicated that the binder type and source play key roles in determining the G*sin δ values of WMA binders with the non-foaming WMA additive. All eight binders containing Sasobit generally have higher creep stiffness values compared to the binders with other WMA additives. The FTIR tests illustrated that the absorbance of the C-O stretch and C-H bend regions of the WMA binders after a short and long-term aging procedure can be considered similar. Moreover, the WMA binders generally exhibit better performance properties than control binders at intermediate and low temperatures after a long-term aging procedure. Furthermore, FTIR analysis results indicate that the binder type and source play important roles in determining the rheological properties of WMA binders.

AGM-Derived Endothelial Cells and Notch Ligands Provide Embryonic Hematopoietic Stem Cell-Supportive Niches In Vitro

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1167-1167
Author(s):  
Brandon K Hadland ◽  
Barbara Varnum-Finney ◽  
Randall T Moon ◽  
Jason M Butler ◽  
Shahin Rafii ◽  
...  
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Hematopoietic Cells ◽  
Hematopoietic Stem ◽  
Small Molecule Inhibition ◽  
Short And Long Term ◽  
High Level ◽  
Notch Ligands

Abstract Greater knowledge of embryonic niche signals regulating the establishment, maintenance, and expansion of hematopoietic stem cells (HSC) during development will be essential in deriving therapeutically useful HSC from pluripotent stem cells (PSC). To this end, we have used the murine embryo model to dissect components of embryonic hematopoietic microenvironments which are sufficient to support nascent HSC and their precursors in vitro. We demonstrate that Akt pathway-activated endothelial cells (ECs) derived from the AGM (aorta-gonad-mesonephros) region, a critical site of HSC emergence during development, can substantially increase short and long-term multilineage engraftment potential from isolated embryonic day 11 (E11) VE-Cadherin+/CD45+ AGM-derived hematopoietic cells by co-culture in vitro. Furthermore, preliminary experiments show that co-culture with AGM-ECs also promotes high level, multilineage engraftment capacity from VE-cadherin+/c-kit+ precursors isolated from younger embryos (E9-E10). These results suggest that endothelial cells from an embryonic HSC-producing niche provide signals sufficient to promote maturation of HSC from embryonic precursors and subsequently support early HSC expansion in vitro. Further dissection of required signals for embryonic HSC expansion identified a unique combination of Notch activation by immobilized Notch ligands, cytokines, and small molecule inhibition of the TGF-β pathway, which is sufficient to inhibit differentiation and enhance self-renewal of embryonic, definitive-stage hematopoietic precursors in vitro. Notably, these conditions significantly increased short and long-term, multilineage repopulating HSC from E11 VE-Cadherin+/CD45+, but not E9-10 VE-Cadherin+/c-kit+ AGM-derived hematopoietic cells, indicating AGM-ECs provide additional, yet to be identified, signals for HSC maturation from developmental precursors. These findings have important implications for dissecting critical niche signals for HSC formation and expansion that will be essential for addressing the elusive goal of deriving HSC from pluripotent precursors. Disclosures: Rafii: Angiocrine Bioscience: Founder Other.

Corrected transposition of the great arteries and dextrocardia: a case of prenatal diagnosis of these rare anomalies and literature review

2018 ◽  
Author(s):  
I.V. Komarova
Keyword(s):  
Prenatal Diagnosis ◽  
Literature Review ◽  
Septal Defect ◽  
Prenatal Counseling ◽  
Prenatal Consultation ◽  
Short And Long Term ◽  
Long Term Prognosis ◽  
High Level ◽  
Corrected Transposition

The case of prenatal ultrasound diagnosis of combination corrected transposition of the great arteries (cTGA) with dextrocardia at 21 weeks of gestation is presented. The high-level ventricular septal defect and stenosis of pulmonary artery were associated cardiac pathologies. Another anomalies of the fetus were not detected. The fetus karyotype was normal, defined by classical cytogenetic analysis. The prenatal consultation assessed the prognosis for life and health as unfavorable. According to patient’s decision the pregnancy was terminated. Literature review of antenatal diagnostics of cTGA and combined cTGA with dextrocardia and the matters of short- and long-term prognosis for the fetus were presented in the paper. The issues of the difficulty of detecting cTGA in a fetus and prenatal counseling is discussed, especially in the presence of an abnormality of the intrathoracic location of the heart.

Sign in / Sign up

Export Citation Format

Share Document