Thermo-piezo-rheological characterization of asphalt concrete

The linear viscoelastic (LVE) properties of asphalt concrete is investigated in this paper using a controlled-strain triaxial dynamic modulus test over wide frequency, temperature, and confining pressure ranges. The time–temperature-pressure superposition principle (TTPSP) is applied to validate the thermo-piezo-rheological simplicity of the tested materials using triaxial master curves. The LVE response is found highly stress-dependent at intermediate and high temperatures. The Prony series modeling of time-domain properties ascertains that confining pressure strongly correlates with long-term relaxation modulus, the absolute maximum slope of the relaxation modulus, and viscoelastic damage parameter. The stress triaxiality ratio concept is applied, and a new shift model is proposed that takes the triaxiality ratio as an internal state variable in the TTPSP. The model prediction agrees well with the experimental data. Moreover, a relationship between the long-term relaxation modulus and the triaxiality ratio is established. The triaxiality ratio coupled with TTPSP can accurately describe the stress-dependent response of asphalt concrete in the LVE domain.publishedVersionPaid open acces

Advances in Permanent Deformation Modeling of Asphalt Concrete—A Review

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Permanent deformation and fatigue damage interaction in asphalt concrete using energy approach

The interaction of fatigue and permanent deformation is very complex phenomenon and little attempt is made on this topic. This paper presents an investigation on the interaction of the two damages using the energy approach. Laboratory tests were conducted for both fatigue and permanent deformation on two different asphalt concrete in a sequential test procedure. A new failure criterion is proposed based on the dissipated energy ratio (DER). The proposed criterion for permanent deformation gives more damage indicator (inflection points) than the conventional flow number/strain rate criterion. The sequential test procedure is also found economical that can be standardized. From the study, strain hardening (pre-deformed) accelerates fatigue cracking susceptible. Similarly, high fatigued samples are more prone to permanent deformation than new samples. The energy approach is convenient for potential coupling of fatigue and permanent deformation interactions.publishedVersio

Environment-Friendly Construction Materials

Construction materials are the most widely used materials for civil infrastructure in our daily lives. However, from an environmental point of view, they consume a huge amount of natural resources and generate the majority of greenhouse gasses. Therefore, many new and novel technologies for designing environmentally friendly construction materials have been developed recently. This Special Issue, “Environment-Friendly Construction Materials”, has been proposed and organized as a means to present recent developments in the field of construction materials. It covers a wide range of selected topics on construction materials

Reliability of Calculation of Dynamic Modulus for Asphalt Mixtures Using Different Master Curve Models and Shift Factor Equations

To develop a mechanistic-empirical pavement design system for Norwegian conditions, this paper evaluates the influence of the adoption of different models and shifting techniques on the determination of dynamic modulus master curves of asphalt mixtures. Two asphalt mixture types commonly used in Norway, namely Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA) containing neat bitumen and polymer-modified bitumen, were prepared by the roller compactor, and their dynamic moduli were determined by the cyclic indirect tensile test. The dynamic modulus master curves were constructed using the standard logistic sigmoidal model, a generalized logistic sigmoidal model and the Christensen–Anderson–Marasteanu model. The shifting techniques consisted of log-linear, quadratic polynomial function, Arrhenius, William–Landel–Ferry and Kaelble methods. The absolute error, normalised square error and goodness-of-fit statistics encompassing standard error ratio and coefficient of determination were used to appraise the models and shifting methods. The results showed that the standard logistic sigmoidal model and the Williams–Landel–Ferry equation had the most suitable fits for the specimens tested. The asphalt mixtures containing neat bitumen had a better fit than the ones containing polymer-modified bitumen. The Kaelble equation and log-linear equation led to similar results. These findings provide a relevant recommendation for the mechanistic-empirical pavement design system.publishedVersio

Comparative study of indirect tensile test and uniaxial compression test on asphalt mixtures: Dynamic modulus and stress-strain state

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Molecular markers for cervical cancer screening

This review gives an overview of current screening practices for cervical cancer. In the introduction, we will cover approaches of population screening focusing on high-risk Human Papilloma Virus (hrHPV) and the need for a better triage assay. We will further assess the impact of current vaccination programs on screening. Subsequently, the review will cover various technological aspects of nucleic acid- and protein-based biomarker assays. We will then detail different molecular markers in view of their use in triage assays, emphasizing epigenetic and protein markers. Finally, we will place this in the context of cost-effectiveness considerations in view of their implementation in high- as well as in low- to middle-income countries. Introduction: Cervical cancer remains a significant healthcare problem, notably in low- to middle-income countries. While a negative test for hrHPV has a predictive value of more than 99.5%, its positive predictive value is less than 10% for CIN2+ stages. This makes the use of a so-called triage test indispensable for population-based screening to avoid referring women, that are ultimately at low risk of developing cervical cancer, to a gynecologist. This review will give an overview of tests that are based on epigenetic marker panels and protein markers. Areas covered: There is a medical need for molecular markers with a better predictive value to discriminate hrHPV-positive women that are at risk of developing cervical cancer from those that are not. Areas covered are epigenetic and protein markers as well as health economic considerations in view of the fact that most cases of cervical cancer arise in low-to-middle-income countries. Expert opinion: While there are biomarker assays based on changes at the nucleic acid (DNA methylation patterns, miRNAs) and at the protein level, they are not widely used in population screening. Combining nucleic acid-based and protein-based tests could improve the overall specificity for discriminating CIN2+ lesions that carry a low risk of progressing to cervical cancer within the screening interval from those that carry an elevated risk. The challenge is to reduce unnecessary referrals without an undesired increase in false-negative diagnoses resulting in cases of cervical cancer that could have been prevented. A further challenge is to develop tests for low-and middle-income countries, which is critical to reduce the worldwide burden of cervical cancer

Produksjon og bruk av overskuddsmasser - Beste praksis og vegen videre

Kortreist Stein har hatt en arbeidspakke konsentrert mot Produksjon og anvendelse. Som et utgangspunkt for forskningsaktivitetene, er det det laget detaljerte oversikter over de mest relevante anvendelsesområdene for kortreist stein og hvilke tekniske egnethetskrav som må tilfredsstilles ut fra dagens regelverk. Prosjekter i Norge og andre land hvor overskuddsmasser har blitt nyttiggjort, er presentert. Prosjektet har sett nærmere på hvordan man kan optimalisere knuseprosessen i mobile anlegg ut fra utgangsmateriale og med mål om mest mulig høyverdig anvendelse av kortreist stein. I Arbeidspakken Produksjon og anvendelse er det gjort detaljerte studier i laboratorium og felt rettet inn mot bruk av tunnelmasser i veg, asfalt og betong, og hvor effekt av knusing og annen prosessering også har vært fokusert. Forskningsarbeidene har inkludert Master- og PhD-arbeid. Flere studier har spesielt vært rettet mot utnyttelse av svake steinmaterialer i ulike anvendelser. Flere arbeider utfordrer dagens metodikk for kvalitetsvurdering av tilslagsmaterialer, og der mange funn demonstrerer nytteverdien av funksjonstesting for bedre konklusjon om egnethet og bruksoppførsel og slik sett bedre utnyttelse av kortreist stein. Arbeidet har resultert i forslag til forbedringer og videre forskning, som både er relevant for utnyttelse av overskuddsmasser fra infrastrukturprosjekter og bergverk, generelt for forhold rundt tilslagsproduksjon og tunnel- og anleggsdrift. Foreliggende rapport oppsummerer arbeider, resultater og anbefalinger. I teksten gis referanser til hvilke publikasjoner funn er hentet fra, og en egen referanseliste følger til slutt i rapporten. Hovedbudskapet fra arbeidspakken Produksjon og anvendelse er som følger: • Etabler en helhetlig produksjons- og bruksstrategi som tar utgangspunkt i hvilke lokale og kortreiste steinmasser man kan nyttiggjøre i eller fra et infrastrukturprosjekt. Dette vil føre til en bedre massebalanse, og en mer kortreist, høyverdig bruk av overskuddsmasser fra infrastrukturprosjekter. • Det ligger flere optimaliseringsmuligheter for å få til dette, både når det gjelder • Utgangsmaterialet og kunnskap om dette • Driveteknikk • Prosessering og mobile anlegg • Materialteknologi og anvendelser Riktig og tidlig fokus kan gi forbedret ressursforvaltning og -utnyttelse, miljø og bærekraft og økonomi.publishedVersio