Long-life concrete pavements require less frequent repair and rehabilitation and contribute to highway safety and congestion mitigation. The Federal Highway Administration, American Association of State Highway and Transportation Officials, and National Cooperative Highway Research Program sponsored a scanning study to identify design philosophies, materials requirements, construction procedures, and maintenance strategies used in Europe and Canada to build long-life concrete pavements. The scan team observed that concrete pavements in the countries visited are designed for 30 or more years of low-maintenance service life. The countries are responding to pavement-tire noise issues in urban areas by using exposed aggregate surface. Some use catalog designs for pavements and geotextiles as a separator layer between the cement-treated base and concrete pavement. Team recommendations for U.S. implementation include using two-lift construction to build pavements, developing pavement design catalogs, using better-quality materials in pavement subbases, paying greater attention to cement and concrete mixture properties, using a geotextile interlayer to prevent concrete slabs from bonding to the cement-treated base, and using exposed aggregate surfaces to reduce noise.

Long-Life Concrete Pavements in Europe and Canada

For testing the bond between asphalt pavement layers quite a variety of methods were proposed and used during the last 30 years. In many publications some of these test methods and devices were described by presenting photographs and sketches. Often photographs show the functioning of the devices only insufficiently and detailed information regarding the test devices (e.g. gap width) and test conditions (e.g. loading function, normal force) are difficult to retrieve. The following paper summarises the test methods and devices for the determination of the bond between asphalt pavement layers regarding shear testing. Direct and simple shear tests from all over the world are presented and their mode of operation shown. Furthermore, the range of applications is described and information regarding test evaluation and results are given.

https://bjrbe-journals.rtu.lv/article/download/1822-427X.2009.4.186-195/2180

Evaluation of Interlayer Shear Bond Devices for Asphalt Pavements

Aim of this study was to evaluate the response of bone to novel biodegradable polymeric composite implants in the femora of growing rats. Longitudinal observation of bone reaction at the implant site (BV/TV) as well as resorption of the implanted pins were monitored using in vivo micro-focus computed tomography (µCT). After 12, 24 and 36 weeks femora containing the implants were explanted, scanned with high resolution ex vivo µCT, and the surface roughness of the implants was measured to conclude on the ingrowth capability for bone tissue. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe changes on the surface of Polyhydroxybutyrate (PHB) during degradation and cell ingrowth. Four different composites with zirconium dioxide (ZrO2) and Herafill(®) were compared. After 36 weeks in vivo, none of the implants did show significant degradation. The PHB composite with ZrO2 and a high percentage (30%) of Herafill® as well as the Mg-alloy WZ21 showed the highest values of bone accumulation (increased BV/TV) around the implant. The lowest value was measured in PHB with 3% ZrO2 containing no Herafill®. Roughness measurements as well as EDX and SEM imaging could not reveal any changes on the PHB composites׳ surfaces. Biomechanical parameters, such as the adhesion strength between bone and implant were determined by measuring the shear strength as well as push-out energy of the bone-implant interface. The results showed that improvement of these mechanical properties of the studied PHBs P3Z, P3Z10H and P3Z30H is necessary in order to obtain appropriate load-bearing material. The moduli of elasticity, tensile strength and strain properties of the PHB composites are close to that of bone and thus promising. Compared to clinically used PLGA, PGA and PLA materials, their additional benefit is an unchanged local pH value during degradation, which makes them well tolerated by cells and immune system. They might be used successfully for personalized 3D printed implants or as coatings of rapidly dissolving implants.

Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications.

Interlayer Bonding of Binder, Base and Subbase Layers of Asphalt Pavements : Long-Term Performance

During the past thirty years, interface bonding between pavement layers has been a topical subject worldwide to research. In this context, many researchers have developed and utilized their own devices to investigate the properties of pavement interfaces. In the absence of an international standard procedure for interface bonding, it is inevitable that testing results are not comparable in all cases. In addition, various conducted studies reveal that parameters such as temperature, loading conditions, materials and so on exert an influence on interface properties. This paper aims to deal with the matter effectively via a thorough and comprehensive review of interface bond testing to lay the groundwork for standardization procedure. For this purpose, first, a general overview of interface bond function and its impact on pavement performance is presented. Then, different types of interface bond test methods according to loading conditions are explained; furthermore, the configuration of various setu...

State-of-the-art review of interface bond testing devices for pavement layers: toward the standardization procedure

The authors focus on crack resistance and bond behavior assessment and testing in regard to asphalt-concrete interfaces tested at different temperatures, necessary for, with so-called whitetopping technology, rutted asphalt pavement rehabilitation. Different interface pretreatments were performed: using only synthetic dispersion, using a synthetic dispersion and cement grout combination, or using cement grout. Determination of mechanical and fracture mechanical properties were done through the wedge splitting test and the pullout test at temperatures of 22, 10, 0, and -10° C (71.6, 50, 32, and 14° F).

Mechanical and Fracture-Mechanical Properties of Asphalt-Concrete Interfaces

For the rehabilitation of rutted asphalt pavements white topping and ultra thin white topping turned out to be adequate methods. The force-fit bonding between asphalt and concrete is a pre-condition for the functioning and durability of this method. Little attention is paid on testing of the bonding; in the majority of the cases the adhesive tensile strength is tested. The wedge splitting test is much more appropriate for the testing of the interface. It delivers mechanical and fracture mechanical properties of the interface. In a comprehensive test programme different surface treatments of the milled asphalt were investigated by means of this method. The usage of bonding agents lead to no improvement of the interface, the most important influencing factors on the interface are cleaning of the milled asphalt surface and mainly the correct surface design for the milling of the asphalt corresponding to the top size of the concrete aggregate. (Author)

J. Steigenberger

Papers

Mechanical and Fracture-Mechanical Properties of Asphalt-Concrete Interfaces

White topping - assessment of asphalt concrete interfaces