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Slippage cracking in asphalt overlays occurs because of bonding failure between the asphalt concrete and Portland cement concrete layers. A direct shear test was adopted to simulate common and critical bonding failures. The effects of temperature and tack coat have already been studied by previous researchers; however, the effects of texture have not been sufficiently considered. In this study, clamping shear strength was used to characterize the pure shear strength of the pavement. It is defined as the difference between the total shear strength and plane shear strength. The results indicated that the interlayer behaved in an elastic manner at lower temperatures, generating brittle failures with cracking, whereas viscoelastic behavior dominated at higher temperatures, producing ductile failure that led to slippage at the interface layer. The surface texture effects can be quantitatively characterized using the clamping shear strength. In addition, the clamping shear strength can be used to optimize the asphalt mixture to enhance the bonding performance. Key words: asphalt concrete (AC) overlay, interlayer bonding failure, clamping strength, texture, Portland cement concrete (PCC) rehabilitation. La fissuration parabolique de glissement des couches d'asphalte se produit a la suite d'une defaillance de l'adherence entre les couches de beton asphaltique (BA) et le beton de ciment Portland (BCP). Un essai de cisaillement direct a ete adopte pour simuler la defaillance d'adherence commune et critique. Les effets de la temperature et de la couche d'adherence ont deja ete etudies par des chercheurs precedents, mais les effets de la texture n'ont pas ete suffisamment pris en compte. Cette etude a utilise la resistance au cisaillement de serrage pour caracteriser la resistance au cisaillement pure dans la chaussee. Elle est definie comme la difference entre la resistance totale au cisaillement et la resistance au cisaillement normale. Les resultats ont montre que l'inter couche s'est comportee de maniere elastique a des temperatures plus basses, generant des ruptures fragiles avec fissuration, tandis que le comportement viscoelastique a domine a des temperatures plus elevees, produisant une rupture ductile qui conduit au glissement a la couche d'interface. Les effets de texture de surface peuvent etre caracterises quantitativement en utilisant la resistance au cisaillement de serrage, et cette resistance peut etre utilisee pour optimiser le melange d'asphalte dans l'amelioration des performances de l'adherence. [Traduit par la Redaction] Mots-cles : rechargement de beton asphaltique (BA), defaillance de l'adherence entre les couches, force de serrage, texture, readaptation du beton de ciment Portland (BCP)., Introduction Asphalt concrete (AC) overlay is one of the most typical pavement maintenance strategies used in Portland cement concrete (PCC) pavements to extend their service life. The life of an [...]

Reflection cracking is a critical issue in asphalt overlay pavement. Temperature variation and traffic loading are the main fracture modes acting on the material. In this paper, a multi-modal overlay tester is proposed for the evaluation of the reflection cracking resistance of an asphalt mixture, an approach that simulates three loading modes on asphalt specimens. A fine dense-grade hot mix asphalt is used as the test specimen and subjected to different loading conditions such as single Mode I, II, and III loading simulations and combined I+II and I+II+III loading simulations. Results show coefficients of variation (CVs) of 2.5%, 10.3%, and 7.4% for the Mode I, II, and III loading simulations, respectively. Furthermore, the [beta] coefficient, with a CVof 7%, is used to represent the crack resistance of the asphalt mixture. Finally, the crack propagation occurs rapidly when subjected to tension and lateral displacement prior to repeated traffic loading simulations. Key words: fatigue test, mixed loading mode, reflection cracking, asphalt overlay tester. La fissuration par reflexion est un probleme critique pour les chaussees asphaltees. La variation de temperature et la charge de roulage sont les principaux modes de rupture agissant sur le materiau. Dans le present document, un appareil d'essai de revetement multimodal est propose pour l'evaluation de la resistance a la fissuration par reflexion d'un melange d'asphalte, une approche qui simule trois modes de chargement sur des echantillons d'asphalte. Un asphalte melange a chaud a base d'agregat a haute densite est utilise comme echantillon d'essai et soumis a differentes conditions de chargement, comme des simulations de chargement en mode I, II et III simples et des simulations de chargement combinees I+II et I+II+III. Les resultats montrent des coefficients de variation (CV) de 2,5, 10,3 et 7,4 % pour les simulations de chargement des modes I, II et III, respectivement. De plus, le coefficient [beta], avec un CV de 7 %, est utilise pour representer la resistance a la fissuration du melange d'asphalte. Enfin, la propagation des fissures se produit rapidement lorsqu'elles sont soumises a une traction et a un deplacement lateral avant les simulations repetees de charges de roulage. [Traduit par la Redaction] Mots-cles : essai de fatigue, mode de chargement mixte, fissuration par reflexion, appareil d'essai de revetement bitumineux., Introduction Reflection cracking is a major problem that needs to be overcome in asphalt overlays on Portland cement concrete (PCC) pavement. Accordingly, the design of an asphalt overlay requires accurate [...]

Permeable pavement is widely used to improve the water circulation system in urban areas. The advantages of using permeable pavement are the storage of rainwater, reduction of runoff, out-flow delay, and reduction of peak discharge. The outflow characteristics of different types of permeable pavements are explained by runoff coefficients, which define the relationship between runoff and infiltration rate. This study presents a model of cumulative outflow with respect to time explaining the discharge characteristics of permeable pavement. The model can be used to explain storage capacity, delay time, peak discharge rate, and outflow of pavement structure by accumulating total discharge at the surface and subsurface relative to time. For further verification of the model, a rainfall simulation experiment was performed in the field. Based on the data analysis through the developed model, the advantages of different permeable pavements can be characterized. Key words: permeable pavement, pavement storage capacity, cumulative water flow, time and space model. Les chaussees permeables sont utilisees pour ameliorer le systeme de circulation d'eau dans les zones urbaines. Elles presentent les avantages suivants : l'entreposage de l'eau de pluie, la reduction du ruissellement, le delai des ecoulements et la reduction du debit de pointe. Les caracteristiques des rejets pour divers types de chaussees permeables sont expliquees en tant que coefficient de ruissellement, lequel definit la relation entre le ruissellement et le taux d'infiltration. Cette etude presente un modele de rejet cumulatif qui tient compte du temps, expliquant les caracteristiques de decharge des chaussees permeables. Le modele peut servir a expliquer la capacite d'entreposage, le delai, le debit de pointe et le rejet par la chaussee en accumulant, dans le temps, la decharge totale a la surface et dans la sous-surface. Pour pousser la verification du modele, une experience de simulation de precipitations a ete realisee sur le terrain. En se basant sur l'analyse des donnees par le modele mis au point, il est possible de caracteriser les avantages des diverses chaussees permeables. [Traduit par la Redaction] Mots-cles: chaussee permeable, capacite d'entreposage des chaussees, debit d'eau cumulatif, modele de temps et d'espace., 1. Introduction As urbanization continues, the convenience of the living environment has improved with efficient land utilization. The water circulation system of the city changes as ground coverage increases. The [...]

The primary objective of the present study is to assess the use of the maturity method to determine the joint sawing window and the traffic opening time on whitetopping construction in Korea. To determine the joint sawing time, it is necessary to determine the minimum strength not to have raveling and to identify the safe time of drying shrinkage. The present study found that the minimum compressive strength for joint sawing was 4.41 MPa (45 kg/[cm.sup.2]) and drying shrinkage occurred just after the concrete temperature peaked. The Nurse-Saul function was used for determining the joint sawing window and the traffic opening time because it better predicted in-place strength. The present study determined that the joint sawing window ranged from 210°C x h to 310°C x h (actual time of 6.5 to 9 h) and that the traffic opening time was after maturity values reached 390°C x h for the mix at 20°C. Key words: maturity, Nurse-Saul function, Arrhenius equation, whitetopping. Le principal objectif de la presente etude est d'examiner l'utilisation de la methode d'evaluation de la maturite afin de determiner la fenetre de coupage du joint a la scie et le moment d'ouverture a la circulation apres un resurfacage sur asphalte en Coree. Pour definir le moment de coupage du joint a la scie, il faut determiner la resistance minimale de maniere a ne pas provoquer d'arrachement et a identifier le temps adequat de retrait de sechage. La presente etude a decouvert que la resistance en compression minimale pour la coupe du joint a la scie etait de 4,41 MPa (45 kg/[cm.sup.2]) alors que le retrait de sechage est survenu une fois que le beton avait atteint sa temperature maximale. La fonction Nurse-Saul a ete utilisee pour determiner la fenetre de coupage du joint a la scie et le moment d'ouverture a la circulation parce qu'elle predisait mieux la resistance en place. Cette etude a determine que la fenetre de coupage du joint a la scie etait de 210°C-heure a 310 °C-heure (temps reel de 6,5 a 9 heures) et le moment d'ouverture a la circulation se produisait une fois que les valeurs a maturite avaient atteint 390 °C-heure pour le melange a 20°C. Mots-cles : maturite, fonction Nurse-Saul, equation d'Arrhenius, resurfacage sur asphalte. [Traduit par la Redaction], Introduction The maturity method was first applied to whitetopping construction in Korea. Because there were no reported cases of the application of maturity methods to whitetopping construction, a laboratory test [...]

Concrete block pavement (CBP) is distinct from typical concrete or asphalt pavements. It is built by using individual blocks with unique construction patterns forming a discrete surface layer to bear traffic loadings. The surface structure of CBP varies depending on the block shapes and construction patterns, so it is hard to apply a general equivalent elastic modulus estimation method to define the surface structural strength. In this study, FEM analysis and dynamic loading test were carried out to develop a deflection prediction model for CBP considering the block shapes and construction patterns. Based on the analysis results, it was found that block shapes did not have much effect on load distribution, whereas construction patterns did. By applying the deflection prediction model to the rutting model for CBP proposed by Sun, the herringbone bond pattern showed the best performance comparing with stretcher bond or basket weave bond pattern. As the load repetition increased to 1.2 million, the rutting depth of CBP constructed by herringbone bond pattern was 2 mm smaller than those constructed by the other two patterns. [ABSTRACT FROM AUTHOR]

Abstract: The effects of a V2O5 additive on the low-temperature sintering and ionic conductivity of strontium- and magnesium-doped lanthanum gallate (LSGM: La0.8Sr0.2Ga0.8Mg0.2O2.8) are studied. The LSGM powders prepared by the glycine nitrate method are mixed with 0.5–2at.% of VO5/2 and then sintered at 1100–1400°C in air for 4h. The apparent density and phase purity of the LSGM specimens are increased with increasing sintering temperature and VO5/2 concentration due to the enhanced sintering and mass transfer via the intergranular liquid phase. The 1at.% VO5/2-doped LSGM specimen sintered at 1300°C exhibits a high oxide ion conductivity of ∼0.027Scm−1 at 700°C over a wide range of oxygen partial pressure (), thereby demonstrating its potential as a useful electrolyte for anode-supported solid oxide fuel cells (SOFCs) without the requirement for any buffer layer between the electrolyte and anode. [ABSTRACT FROM AUTHOR]

The phase pure large scale synthesis, second-harmonic generation, and piezoelectric properties of a vanadium phosphate, Li2VPO6 are reported. The material has been synthesized by a standard solid-state reaction using Li2CO3, V2O5, and NH4H2PO4 as reagents. The phase purity and crystal structure of the reported material have been confirmed by powder X-ray and neutron diffractions. The material crystallizes in orthorhombic space group Pna21 (no. 33) with a=10.32581(7)Å, b=4.63728(3)Å, c=8.56606(5)Å, and Z=4. The noncentrosymmetric layered structure is composed of distorted VO6 octahedra and PO4 tetrahedra. The V5+ cations distort either along the approximate [101] or [−101] directions attributable to the alignment of distorted VO6 octahedra, resulting in a polar structure. Powder second-harmonic generating (SHG) measurements on Li2VPO6 using 1064nm radiation, indicate the material has a SHG efficiency of approximately 10 times that of α-SiO2 and is not phase-matchable (type 1). Converse piezoelectric measurements for the material reveal a piezoelectric coefficient, d 33, of 12pmV−1. [ABSTRACT FROM AUTHOR]

Abstract: A range of La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCM) powders is prepared by the carbonate coprecipitation method for use as anodes in solid oxide fuel cells. The supersaturation ratio (R =[(NH4)2CO3]/([La3+]+[Sr2+]+[Cr3+]+[Mn2+])) during the coprecipitation determines the relative compositions of La, Sr, Cr, and Mn. The composition of the precursor approaches the stoichiometric one at the supersaturation range of 4≤ R ≤12.5, whereas Sr and Mn components are deficient at R <4 and excessive at R =25. The fine and phase-pure LSCM powders are prepared by heat treatment at very low temperature (1000°C) at R =7.5 and 12.5. By contrast, the solid-state reaction requires a higher heat-treatment temperature (1400°C). The catalytic activity of the LSCM electrodes is enhanced by using carbonate-derived powders to manipulate the electrode microstructures. [Copyright &y& Elsevier]

Abstract: La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte powders suitable for use in solid-oxide fuel cells were prepared by spray pyrolysis. The powders were spherical in shape and exhibited non-aggregation characteristics. The mean particle size of the LSGM powders was 0.89μm. The powders post-treated at temperatures of 1000 and 1300°C had main crystal structure of LSGM. The powders post-treated at temperatures of 1000 and 1300°C had impurity peaks of LaSrGa3O7 and LaSrGaO4 phases. Pellets sintered at 1300 and 1400°C had relative densities of 82% and 95% and mean grain sizes of 2.3 and 3.1μm, respectively. The pellet sintered at 1400°C had a lower value than that of the pellet sintered at 1300°C. The total conductivities of the pellets sintered at 1300 and 1400°C were 1.44×10−3 and 2.89×10−3 S/cm, respectively, at a low measuring temperature of 500°C. [Copyright &y& Elsevier]