Effectiveness of geogrids in roadway construction by large scale laboratory tests

Geogrids have been widely used in the roadway construction as reinforcement in pavement foundations. Geogrids have been effective in practice for reducing rutting damage, distributing traffic loads within the pavement foundation layers, increasing the resilient modulus of base course, improving drainage, reducing differential freeze/thaw problems, and stabilization effects on the subgrade layer. How to accurately evaluate structural benefits of geogrids in pavement foundation is a difficult issue because many factors can affect structural benefits, such as geogrid stiffness, geogrid aperture and rib shape, aperture and rib sizes, the geogrid location/depth, hot mix asphalt thicknesses, base aggregate quality, stiffness thicknesses, and subgrade stiffness. In this research, we used an Integrated Mobile Accelerated Test System (IMAS) to evaluate reinforcement effects of geogrids. The IMAS system mainly consists of a 5 ft wide and 3 ft deep rigid box and automatic loading frame. A total of eight test configurations were constructed by varying geogrid types (i.e., light-duty biaxial, heavy-duty biaxial, light-duty triaxial, and heavy-duty triaxial geogrids), geogrid locations in pavement (i.e., at the interface between base and subgrade or in the base course), and base aggregate thicknesses. The IMAS can perform cyclic load tests of pavement foundation sections to a large number of load cycles, which simulates vehicle-loading conditions expected during the service life of a pavement system to evaluate the long-term performance of the pavement structure. Testing results include resilient modulus, and permanent deformation of the pavement foundation for evaluating structural benefits of geogrids as a function of geogrid types, geogrid locations, and base aggregate thicknesses. The results of this research will help better design geogrids in roadways to improve pavement quality, extend pavement service life, and reduce life-cycle costs

Effectiveness of geogrids in roadway construction by large scale laboratory tests

Geogrids have been widely used in the roadway construction as reinforcement in pavement foundations. Geogrids have been effective in practice for reducing rutting damage, distributing traffic loads within the pavement foundation layers, increasing the resilient modulus of base course, improving drainage, reducing differential freeze/thaw problems, and stabilization effects on the subgrade layer. How to accurately evaluate structural benefits of geogrids in pavement foundation is a difficult issue because many factors can affect structural benefits, such as geogrid stiffness, geogrid aperture and rib shape, aperture and rib sizes, the geogrid location/depth, hot mix asphalt thicknesses, base aggregate quality, stiffness thicknesses, and subgrade stiffness. In this research, we used an Integrated Mobile Accelerated Test System (IMAS) to evaluate reinforcement effects of geogrids. The IMAS system mainly consists of a 5 ft wide and 3 ft deep rigid box and automatic loading frame. A total of eight test configurations were constructed by varying geogrid types (i.e., light-duty biaxial, heavy-duty biaxial, light-duty triaxial, and heavy-duty triaxial geogrids), geogrid locations in pavement (i.e., at the interface between base and subgrade or in the base course), and base aggregate thicknesses. The IMAS can perform cyclic load tests of pavement foundation sections to a large number of load cycles, which simulates vehicle-loading conditions expected during the service life of a pavement system to evaluate the long-term performance of the pavement structure. Testing results include resilient modulus, and permanent deformation of the pavement foundation for evaluating structural benefits of geogrids as a function of geogrid types, geogrid locations, and base aggregate thicknesses. The results of this research will help better design geogrids in roadways to improve pavement quality, extend pavement service life, and reduce life-cycle costs.</p

Rhodium(<scp>iii</scp>)-catalyzed diamidation of olefins <i>via</i> amidorhodation and further amidation

Rh(iii)/Co(iii)-catalyzed diamidation of amide-tethered olefins has been realized using dioxazolones and arylsulfonamides as different classes of amidating reagents.</p

Rhodium(III)-Catalyzed Enantioselective Coupling of Indoles and 7-Azabenzonorbornadienes by C-H Activation/Desymmetrization

Chiral rhodium(III) cyclopentadienyl catalysts ((CpRhIII)-Rh-X) play significant roles in asymmetric arene C-H activation. Rh/Ir-catalyzed couplings of arenes and strained rings have been well-studied, but they have been limited to racemic systems. Reported in this work is the (CpRhIII)-Rh-x/AgSbF6-catalyzed enantioselective desymmetrizative C-C coupling of N-pyrimidylindoles and 7-azabenzonorbornadienes with high efficiency and enantioselectivity. The role of AgSbF6 has been established by mechanistic studies. AgSbF6 enhances the catalytic activity by suppressing the C3-H activation of the indoles, activation which would otherwise lead to catalytically inactive species

Interaction between Aqueous Solutions of Hydrophobically Associating Polyacrylamide and Dodecyl Dimethyl Betaine

The interaction between hydrophobically associating polyacrylamide (HAPAM) and dodecyl dimethyl betaine (BS-12) is studied through surface tension, interfacial tension (IFT), apparent viscosity, aggregation behavior, and microscopic morphologies. Results show that surface and interface properties of BS-12 are largely affected by HAPAM. BS-12 critical micelle concentrations are increased with the increment of polymer concentrations. Abilities of reduced air-water surface tension and oil-water interfacial tension are dropped. The oil-water interfacial tension to reach minimum time is increased. HAPAM can form network structures in the aqueous solution. Mixed micelles are formed by the interaction between BS-12 micelles and hydrophobic groups of HAPAM in aqueous solution and self-assembly behavior of HAPAM is affected. With the increment of surfactant concentrations, the apparent viscosity, apparent weight average molecular weights (Mw, a), root mean square radius of gyration (〈Rg〉), and hydrodynamic radius of HAPAM increase first and then decline. Moreover, microscopic morphologies of the mixed system are formed from relatively loose network structures to dense network structures and then become looser network structures and the part of network structures fracture