The paper presents the influence of laboratory aging simulation on fracture properties determined on 150 variants of asphalt mixtures. The fracture properties were determined by two different test approaches—semi-circular bending test (SCB test) and three-point bending test on beam specimens (3-PB test). The aging was simulated according to one of the methods defined in EN 12697-52 (storage of test specimens in chamber at temperature of 85 °C for 5 days). The evaluated group of variants covered asphalt mixtures for all road layers. The group was further divided according to used bituminous binder (unmodified vs. modified) and reclaimed asphalt content. The results showed that strength parameters (flexural strength and fracture toughness) increase with aging. It further shows that fracture work provides more complex information about the cracking behavior. For the aging indexes, it was found that for mixtures with modified binders and mixtures which did not contain reclaimed asphalt (RA), the values were higher. The aging indexes for fracture work showed different results for both performed tests.

Recently, environmental concerns have become a primary driving force in most countries and industries dealing with natural resources. As a part of this category, asphalt pavement industry is trying to implement more green and sustainable features in its products, while maintaining the mechanical and performance-based properties of the resulting asphalt mixtures. Among potential recycled materials, vehicle tires and aged asphalt pavement have been demonstrated to show economic, ecological, and behavioral improvements in the mixtures. However, mixtures with a high content of reclaimed asphalt (RA) and crumb rubber present some limitations. Therefore, using another group of additives, i.e., a warm mix asphalt (WMA) additive, has been considered. The presented paper investigates the use of an elevated content of RA with different crumb rubber modified binders and (in some mixtures) a warm mix additive in an asphalt concrete (AC) binder mix. Regular empirical tests have been conducted and more advanced performance or functional characteristics, i.e., stiffness, thermal induced cracking, resistance to permanent deformation, complex modulus have been determined and evaluated. Selected results are presented in the paper.

High-modulus asphalt concrete is a specific type of asphalt mixture which is used for several decades in pavement engineering. It was originally invented as a solution which should help to minimize the effects of permanent deformation caused mainly by heavy traffic and mainly during the periods with elevated temperatures. These mixtures are used either in binder or base courses, whereas for base courses, it is important to combine reasonably the high stiffness with good fatigue life to avoid premature pavement failures not caused by rutting but by fatigue cracking. In this respect, various types of HMAC used and designed in the Czech Republic were tested first and foremost to determine stiffness. The stiffness modules were tested according to EN 12607-26, test method IT-CY, at selected temperatures representing cold, moderate and high service temperatures. The susceptibility to temperature change can be shown by thermal susceptibility for each mixture. In the parallel test, specimens were laboratory age to identify the changes in stiffness caused by thermo-oxidative ageing. This allows calculating a simple measure of the ageing index. Not presented in this paper but performed as a very last test was resistance to crack propagation.

High modulus asphalt concrete (HMAC) presents a concept of an asphalt mixture with advanced performance which is suitable mainly for heavy loaded pavement structures. The mix concept was developed more than 25 years ago in France and became a standard in many countries. In the Czech Republic this type of asphalt mixtures is used since the early years of this millennium, when original technical requirements have been set. After almost 20 years a volunteer technical assessment started to validate whether the technical requirement set mainly for stiffness values and partly also for flexural strength or resistance to crack propagation are still up-to-date or if some reasonable modification is needed like was done several years ago in France when high modulus asphalt concrete of so called EME II or GP5 generation were brought to the practice. Based on this a study with focus on stiffness determination for more than 40 different HMACs was started. The stiffness was tested at different temperatures. At the same time virgin and aged asphalt mixtures were compared. Results from this study are presented by the paper.

No abstract