Manfred N. Partl

ADVANCED TESTING AND CHARACTERIZATION OF INTERLAYER SHEAR RESISTANCE

The performance of multilayered pavement systems depends strongly on interlayer bonding. To guarantee good bonding, tack coats (also called bond coats) are usually applied at various interfaces during pavement construction or overlay. The effectiveness of the tack coat can be assessed with the use of several devices arranged by different laboratories to evaluate interlayer shear resistance. This paper shows how interlayer shear resistance may be evaluated through the Ancona shear testing research and analysis (ASTRA) device. ASTRA results, expressed in units of maximum interlayer shear stress (τpeak) highlight the effects of various influence parameters such as type of interface treatment, curing time, procedure of specimen preparation, temperature, and applied normal load. Moreover, this paper compares the τpeak results obtained by two different shear test devices: the ASTRA tester designed and developed in the Polytechnic University of Marche (Italy) and the layer-parallel direct shear tester created by...

Advances in Interlaboratory Testing and Evaluation of Bituminous Materials

A background on RILEM interlaboratory testing is presented with some comments regarding general development and objectives for advanced testing, providing also a general overview on requirements and needs. It is emphasized that development of today is driven by the evaluation of performance based material behavior, moving more and more from semi-empirical to fundamental test methods. Given this background, an updated version of the RILEM methodology for testing of bituminous pavement materials is presented with a short discussion of basic elements. This framework is the basis for this report on the achievements of RILEM technical committee TC 206-ATB on “Advanced Testing and Characterization of Bituminous Materials”. Furthermore, main principles and key elements for planning of interlaboratory tests are summarized containing points that proved also relevant for the interlaboratory tests presented and discussed in the following chapters of this book. This summary is intended as general checklist and practical tool for initiating and conducting future interlaboratory tests. 1.1 Background of RILEM interlaboratory tests

Gyratory Compaction Analysis with Computer Tomography

ABSTRACT In this study, the change and differences in homogeneity and isotropy in asphalt concrete specimens during gyratory compaction is investigated. The study was carried out by using both standard air-void content determination (AV) and X-ray Computer Tomography (CT), focusing on experimental aspects. It is intended to serve as a basis for laboratories and producers to optimize compaction procedures and devices.

Construction and Maintenance Practices for Permeable Friction Courses

This report recommends design, construction, and maintenance guidelines for permeable friction courses (PFCs). It presents recommended practices for (1) design and construction of PFCs and (2) PFC maintenance and rehabilitation. The report will be of immediate interest to public and private sector engineers with responsibility for the specification, construction, and maintenance of PFCs.

Investigation of porous asphalt microstructure using optical and electron microscopy.

Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom‐up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well‐performing mixes used polymer‐modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well‐performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in‐service use.

Comparison of Laboratory Compaction Methods using X-ray Computer Tomography

ABSTRACT Changes and differences in homogeneity of asphalt concrete specimens during Marshall and Rolling-Wheel compaction are investigated by means of standard air-void content determination (AV) and X-ray Computer Tomography (CT). Following an earlier study on Gyratory compaction with the same objective and material, this study, again, focuses on experimental aspects serving as a basis for laboratories and producers to optimize compaction procedures and devices. The results demonstrate that X-ray CT is a powerful tool leading to a better understanding of compaction mechanisms. In this way, X-ray CT may be considered very suitable for developing improved laboratory compaction methods and procedures.

Mechanical Testing of Interlayer Bonding in Asphalt Pavements

Steadily increasing requirements on pavement performance properties, in terms of bearing capacity and durability, as well as new innovative developments regarding pavement materials and construction, are observed worldwide. In this context interlayer bonding at the interfaces of multi-layered bituminous systems is recognized as a key issue for the evaluation of the effects, in terms of stress-strain distribution, produced by traffic loads in road pavements. For this reason a correct assessment of interlayer bonding is of primary importance, and research efforts should be addressed in order to improve the lack of correlation and/or harmonization among test methods. Following this principle RILEM TG 4 organized an interlaboratory test in order to compare the different test procedures to assess the interlayer bonding properties of asphalt pavement. The results of the experimental research are presented with a preliminary overview of basic elements, test methods and experimental investigations on interlayer bonding. Then the RILEM TG 4 experimental activities, based on the construction of three real- scale pavement sections, are presented in detail. Each pavement section was composed of two layers, and three different interface conditions were chosen. The first pavement was laid without interface treatment and the others with two different types of emulsion. Fourteen laboratories from 11 countries participated in this study and carried out shear or torque tests on 1,400 cores. The maximum shear or torque load and the corresponding displacement were measured, and the shear or torque strength was calculated as a function of the following parameters: diameter, test temperature, test speed, stress applied normal to the interface and age of the specimen. The results of this study are presented in terms of precision and correlations regarding the parameters which results in useful information on asphalt pavement interlayer bond tests.

Fatigue Evaluation of Porous Asphalt Composites with Carbon Fiber Reinforcement Polymer Grids

Porous asphalt (PA) has been widely used in many countries because of its positive benefits, such as efficient water drainage, improved safety in wet weather conditions, and noise reduction. However, the attractive features of PA do not last long because of clogging, stripping, and accelerated aging. Application of fiber reinforcement materials can be a possible solution to the structural weakness in PA pavements. Fatigue of fiber-reinforced PA composite systems was investigated with a model mobile load simulator (MMLS). Carbon fiber reinforcement polymer (FRP) grids were used to strengthen the fatigue resistance of PA. FRP grids were placed between two asphalt layers as a reinforcement interlayer. The dynamic fatigue traffic loadings were applied on the top surface of reinforced specimens to investigate the performance improvement by reinforcement materials. These fatigue tests were conducted under four different conditions: absence and presence of reinforcement at dry conditions and wet conditions. The stiffness difference between unaged and aged specimens was 25% at minimum and 55% at maximum. The surface deflection of PA was successfully reduced by 23% at dry and by 48% at wet conditions by using interlaid carbon FRP grids. In addition, the reinforcement layer could increase the fatigue life by 23% at dry and by 27% at wet conditions based on MMLS test results.

Numerical and Experimental Analysis for the Interlayer Behavior of Double-Layered Asphalt Pavement Specimens

Bonding characteristics between pavement layers have an important influence on responses of pavement structures. This paper deals with this subject by analyzing the interlayer behavior of double-layered asphalt DLA specimens taken from an in-service motor- way using a coaxial shear test CAST and a layer-parallel direct shear LPDS test. To analyze and model the influence of the interlayer condition, finite-element simulations of CAST DLA specimens were conducted. In the models, both idealized fully bonded and no- bonding assumptions were used to characterize the interlayer behavior of DLA specimens. Experimental results presented for CAST and LPDS tests demonstrate that there is a strong influence of temperature in the interlayer bonding mechanism. At lower temperatures, there is an increase on the bonding strength produced by the binder stiffening and aggregate interlocking. Further, it was observed that comparisons of CAST experimental and numerical results indicate that the interlayer can be close to the fully bonded condition at low temperatures below 20°C while the interlayer, at higher temperatures, behaves between fully bonded and no-bonding idealized conditions. DOI: 10.1061/ASCEMT.1943-5533.0000003 CE Database subject headings: Asphalt pavements; Finite element method; Numerical analysis; Experimentation. Author keywords: Interlayer; Double-layered asphalt; CAST; LPDS; Finite element.

Use of Reclaimed Asphalt in Porous Asphalt Mixtures: Laboratory and Field Evaluations

AbstractMaintenance and reconstruction of road pavements involve the production of huge amount of discarded material, such as reclaimed asphalt (RA), every year. As a consequence, issues related to RA stockpiles and disposals are dramatically increasing. At the same time, the growing importance of environmental and economic matters has led researchers and engineers to promote reusing milled materials rather than using valuable and nonrenewable natural resources (bitumen and aggregates). Road pavement maintenance and construction usually involve the use of porous asphalt (PA) mixtures, in particular in the case of motorways and highways. In fact, PA mixtures are widely employed as pavement surface layer thanks to their ability in reducing traffic noise and enhancing safety in wet conditions. In this sense, the reuse of RA into PA should be strongly encouraged. Unfortunately, technical specifications adopted in many countries do not allow any recycled materials in porous asphalt surface layers yet. Thus, re...