scholarly journals Flexible Pavement Performance in relation to In Situ Mechanistic and Volumetric Properties Using LTPP Data

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Mohammad Jamal Khattak ◽  
Nagaraju Peddapati
Keyword(s):  
Hot Mix Asphalt ◽  
Compressive Strain ◽  
Strong Relationship ◽  
Ambient Air ◽  
Flexible Pavement ◽  
Pavement Performance ◽  
Volumetric Properties ◽  
Actual Performance ◽  
Air Voids

This research study focuses on the actual performance of the flexible pavements and its relationship with the in-situ mechanistic and volumetric properties. The data required for the study were obtained using the Long Term Pavement Performance database. Approximately, 116 flexible pavement sections throughout United States were analyzed and discussed. The results indicated that the temperature has a significant affect on the backcalculated modulus of the hot mix asphalt layer. However, no strong relationship was observed between the hot mix asphalt backcalculated modulus and in situ air voids. It was found that fatigue life was a function of tensile strain at the bottom of hot mix asphalt layer, peak surface deflection, hot mix asphalt air voids and maximum specific gravity, and ambient air temperature. Similar relationships between the rut life, mechanistic and volumetric properties were established for wet-freeze and wet-no-freeze climatic zones. The sensitivity analysis revealed that the rut performance in wet-no-freeze sections is mainly affected by higher base and roadbed compressive stresses and strains. On the other hand, the performances in wet-freeze sections are highly depended on roadbed compressive strain and modulus ratio of subbase to roadbed.

scholarly journals RELATING FLEXIBLE PAVEMENT ACCEPTANCE CRITERIA TO PERFORMANCE USING MEPDG SIMULATIONS AND PIECEWISE CUBIC SPLINE INTERPOLATION / LANKSČIŲJŲ DANGŲ ATRANKOS KRITERIJŲ SUSIEJIMAS NAUDOJANT MEPDG MODELIUS IR DALINĘ KUBINĘ SPLAININĘ INTERPOLIACIJĄ

2012 ◽  
Vol 18 (1) ◽  
pp. 125-132 ◽  
Author(s):  
Anshu Manik ◽  
Karim Chatti ◽  
Kasthurirangan Gopalakrishnan
Keyword(s):  
Spline Interpolation ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
Pavement Performance ◽  
Air Voids ◽  
Field Investigations ◽  
The Relationship

The performance of the highway system is inevitably linked to its quality of design and construction. To control the quality of construction, elaborate Quality Assurance (QA) programs have been developed by highway agencies based on statistical sampling and acceptance procedures to ensure that the work is in accordance with the plans and specifications. The QA procedure is intended to ensure that the constructed pavement would perform well during its design life. However, numerous field investigations and research studies over the years have identified a gap in our understanding of the relationship between the QA test results and pavement performance (fatigue cracking, rutting, etc.). This paper is intended to present the framework for developing an understanding of the relationship between QA tests and flexible pavement performance, which is essential for developing Performance Related Specifications (PRS). In the first part of the paper, the Michigan Department of Transportation's (MDOT) QA program and Long-Term Pavement Performance (LTPP) databases were used to empirically investigate any relationship between key QA variables and various pavement performance measures. In the second part of the paper, the Mechanistic-Empirical Pavement Design Guide (MEPDG) software was used together with an accurate and efficient interpolation technique to develop many simulations for the purpose of showing the effect of variability in QA parameters including plant air voids, in-situ density and asphalt content on flexible pavement performance. Santrauka Greitkelių sistemos darbas (funkcionavimas) yra neišvengiamai susijęs su jo projektavimo ir statybų kokybe. Greitkelių agentūros, remdamosi statistinėmis atrankos ir ėmimo procedūromis, parengė kokybės užtikrinimo (KU arba QA) programas, kad būtų kontroliuojama statybų kokybė ir užtikrinamas darbas pagal planus ir specifikacijas. KU (QA) procedūra siekiama užtikrinti, kad pagaminta danga gerai funkcionuotų projekte nurodytą laiką. Tačiau metams einant, atlikus daugybę natūrinių ir mokslinių tyrimų, buvo nustatytas didelis santykio tarp KU (QA) bandymų rezultatų ir dangos darbo (funkcionavimo) (plyšių atsiradimo dėl nuovargio, provėžų ir kt.) vertinimo skirtumas. Šiame darbe skatinama plėtoti supratimą apie ryšius tarp KU (QA) bandymų ir lanksčiųjų dangų funkcionavimo, kuris yra nepaprastai svarbus kuriant su darbu (funkcionavimu) susijusias specifikacijas (PRS). Pirmoje darbo dalyje buvo naudojamos Mičigano transporto departamento (MDOT) KU (QA) programos ir ilgalaikės dangos darbo (funkcionavimo) (LTPP) duomenų bazės, siekiant empiriškai ištirti bet kuriuos santykius tarp pagrindinių KU (QA) kintamųjų ir įvairių dangų darbo matavimų. Antroje darbo dalyje buvo naudojama mechanistinio ir empirinio dangų projektavimo vadovo (MEPDG) programinė įranga kartu su tikslia ir efektyvia interpoliacijos technika, siekiant sukurti modelius, kuriuose perteiktas KU (QA) parametrų kintamumo poveikis lanksčiųjų dangų funkcionavimui, įskaitant augalų oro ertmes, vietinį tankį ir asfalto sandarą.

scholarly journals Sensitivity of the Flow Number to Mix Factors of Hot-Mix Asphalt

2019 ◽  
Vol 4 (2) ◽  
pp. 34 ◽  
Author(s):  
Md Rashadul Islam ◽  
Sylvester A. Kalevela ◽  
Shelby K. Nesselhauf
Keyword(s):  
Hot Mix Asphalt ◽  
Permanent Deformation ◽  
Asphalt Mixture ◽  
Flexible Pavement ◽  
Binder Content ◽  
Flow Number ◽  
Air Voids ◽  
Different Types ◽  
Asphalt Content ◽  
Mineral Aggregates

In the design of pavement infrastructure, the flow number is used to determine the suitability of a hot-mix asphalt mixture (HMA) to resist permanent deformation when used in flexible pavement. This study investigates the sensitivity of the flow numbers to the mix factors of eleven categories of HMAs used in flexible pavements. A total of 105 specimens were studied for these eleven categories of HMAs. For each category of asphalt mixture, the variations in flow number for different contractors, binder types, effective binder contents, air voids, voids in mineral aggregates, voids filled with asphalt, and asphalt contents were assessed statistically. The results show that the flow numbers for different types of HMA used in Colorado vary from 47 to 2272. The same mix may have statistically different flow numbers, regardless of the contractor. The flow number increases with increasing effective binder content, air voids, voids in mineral aggregates, voids filled with asphalt, and asphalt content in the study range of these parameters.

Hot-Mix Asphalt Segregation: Measurement and Effects

1996 ◽  
Vol 1543 (1) ◽  
pp. 97-105 ◽  
Author(s):  
R. Christopher Williams ◽  
Gary Duncan ◽  
Thomas D. White
Keyword(s):  
Thermal Imaging ◽  
Hot Mix Asphalt ◽  
Field Testing ◽  
Test Method ◽  
Pavement Performance ◽  
Air Voids ◽  
Asphalt Content ◽  
Tracking Device ◽  
Wheel Tracking ◽  
Thermal Imaging Equipment

Segregation of hot-mix asphalt (HMA) has been associated with poor pavement performance. As a result, a nondestructive test method that could quickly identify segregation and be easily included in field testing would be useful to agencies. A study was conducted of four HMA mixtures with five levels of segregation. All levels of segregation for each mix were characterized by gradation, asphalt content, density, and air voids. The segregated mixes were tested with an air permeameter and a nuclear moisture/density gauge. In addition, thermal imaging equipment was field-tested on an existing pavement, at a hot-mix asphalt plant, and at a paving project to determine its overall effectiveness in detecting segregation. Preliminary wheel-tracking tests with the PURWheel tracking device were used to evaluate segregated mixture performance.

scholarly journals The influence of chemical parameters on the in-situ metal carbonyl complex formation studied with the fast on-line reaction apparatus (FORA)

2021 ◽  
Vol 109 (4) ◽  
pp. 243-260 ◽  
Author(s):  
Yves Wittwer ◽  
Robert Eichler ◽  
Dominik Herrmann ◽  
Andreas Türler
Keyword(s):  
Metal Carbonyl ◽  
Ambient Air ◽  
Single Atom ◽  
Carbonyl Complex ◽  
Carbonyl Complexes ◽  
On Line ◽  
Carrier Gases ◽  
And Performance ◽  
Atom Chemistry

Abstract A new setup named Fast On-line Reaction Apparatus (FORA) is presented which allows for the efficient investigation and optimization of metal carbonyl complex (MCC) formation reactions under various reaction conditions. The setup contains a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes at a rate of a few atoms per second by its 3% spontaneous fission decay branch. Those atoms are transformed within FORA in-situ into volatile metal carbonyl complexes (MCCs) by using CO-containing carrier gases. Here, the design, operation and performance of FORA is discussed, revealing it as a suitable setup for performing single-atom chemistry studies. The influence of various gas-additives, such as CO2, CH4, H2, Ar, O2, H2O and ambient air, on the formation and transport of MCCs was investigated. O2, H2O and air were found to harm the formation and transport of MCCs in FORA, with H2O being the most severe. An exception is Tc, for which about 130 ppmv of H2O caused an increased production and transport of volatile compounds. The other gas-additives were not influencing the formation and transport efficiency of MCCs. Using an older setup called Miss Piggy based on a similar working principle as FORA, it was additionally investigated if gas-additives are mostly affecting the formation or only the transport stability of MCCs. It was found that mostly formation is impacted, as MCCs appear to be much less sensitive to reacting with gas-additives in comparison to the bare Mo, Tc, Ru and Rh atoms.

scholarly journals Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 228
Author(s):  
Rute Cesário ◽  
Nelson J. O’Driscoll ◽  
Sara Justino ◽  
Claire E. Wilson ◽  
Carlos E. Monteiro ◽  
...  
Keyword(s):  
Leaf Area ◽  
Elemental Mercury ◽  
Ambient Air ◽  
Tagus Estuary ◽  
Contaminated Site ◽  
Gaseous Elemental Mercury ◽  
Mercury Flux ◽  
Sarcocornia Fruticosa ◽  
Air Concentrations

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged between 1.08–18.15 ng m−3 in CN and 1.18–3.53 ng m−3 in ALC. In CN, most of the high Hg(0) levels occurred during nighttime, while the opposite was observed at ALC, suggesting that photoreduction was not driving the air Hg(0) concentrations at the contaminated site. Vegetation–air Hg(0) fluxes were low in ALC and ranged from −0.76 to 1.52 ng m−2 (leaf area) h−1 for Hp and from −0.40 to 1.28 ng m−2 (leaf area) h−1 for Sf. In CN, higher Hg fluxes were observed for both plants, ranging from −9.90 to 15.45 ng m−2 (leaf area) h−1 for Hp and from −8.93 to 12.58 ng m−2 (leaf area) h−1 for Sf. Mercury flux results at CN were considered less reliable due to large and fast variations in the ambient air concentrations of Hg(0), which may have been influenced by emissions from the nearby chlor-alkali plant, or historical contamination. Improved experimental setup, the influence of high local Hg concentrations and the seasonal activity of the plants must be considered when assessing vegetation–air Hg(0) fluxes in Hg-contaminated areas.

scholarly journals Safe and Effective Use of Ozone as Air and Surface Disinfectant in the Conjuncture of Covid-19

Gases ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 19-32
Author(s):  
Elena Grignani ◽  
Antonella Mansi ◽  
Renato Cabella ◽  
Paola Castellano ◽  
Angelo Tirabasso ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Scientific Literature ◽  
Toxic Substance ◽  
Health And Safety ◽  
Emergency Situation ◽  
Ambient Air ◽  
Public Places ◽  
Safety Measures ◽  
Effective Use

The present paper extrapolates quantitative data for ozone virucidal activity on the basis of the available scientific literature data for a safe and effective use of ozone in the appropriate cases and to explore the safety measures developed under the stimulus of the current emergency situation. Ozone is a powerful oxidant reacting with organic molecules, and therefore has bactericidal, virucidal, and fungicidal actions. At the same time, it is a toxic substance, having adverse effects on health and safety. Its use is being proposed for the disinfection of workplaces’ and public places’ atmosphere, and for disposable masks and personal protective equipment disinfection for reuse, with particular reference to the COVID-19 pandemic outbreak. Ozone can be generated in situ by means of small, compact ozone generators, using dried ambient air as a precursor. It should be injected into the room that is to be disinfected until the desired ozone concentration is reached; after the time needed for the disinfection, its concentrations must be reduced to the levels required for the workers’ safety. The optimal use of ozone is for air and surface disinfection without human presence, using a concentration that is effective for the destruction of viruses, but not high enough to deteriorate materials.

Control of Volumetric Properties of Hot-Mix Asphalt by Field Management

1996 ◽  
Vol 1543 (1) ◽  
pp. 125-131
Author(s):  
Prithvi S. Kandhal ◽  
Kee Y. Foo ◽  
John A. D'Angelo
Keyword(s):  
Hot Mix Asphalt ◽  
Linear Regression Analysis ◽  
Volumetric Properties ◽  
Production Test ◽  
Independent Variables ◽  
Dependent Variables ◽  
Preceding Work ◽  
Multiple Variable ◽  
Asphalt Content ◽  
Variable Analysis

Significant differences in the volumetric properties of laboratory-designed and plant-produced hot-mix asphalt (HMA) generally exist as demonstrated by FHWA Demonstration Project No. 74. The volumetric properties include voids in the mineral aggregate (VMA) and voids in the total mix (VTM). Guidelines for HMA contractors are needed to reconcile these differences and maintain control of volumetric properties during HMA production. The HMA mix design and field production test data (such as asphalt content, gradation, and volumetric properties) from 24 FHWA demonstration projects were entered into a data base and statistically analyzed. The objective was to identify and, if possible, quantify the independent variables (such as asphalt content and the percentages of material passing the No. 200 and other sieves) that significantly affect dependent variables VMA and VTM. The statistical analysis methods consisted of correlation analysis, stepwise multiple-variable analysis, and linear-regression analysis. On the basis of preceding work, guidelines have been developed for HMA contractors to reconcile the differences between the volumetric properties of the job mix formula and the produced HMA mix.

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