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Maintenance works in an asphalt pavement for removing and replacing the wearing course produce large amounts of milled material. Following the sustainably-sourced resource principle, this material is recirculated and, in this case, utilized in new mixtures, chiefly in cold recycled mixes. Since it is derived from surface course rehabilitation, its particle size is up to 10 mm. To ensure the most beneficial parameters of so produced cold mix asphalt, the properties of the binder have to be optimized. The binder used in the tests was composed of CEM I 32.5R, hydrated lime and by-product fines. Various combinations of binder components were tested in this study to obtain the optimal parameters of the recycled mix. Foamed bitumen 70/100 was used. Void characteristics were evaluated, and a particular focus was on the resistance to moisture and frost-induced damage, i.e., ITSR, TSR, and RWWM according to ASSHTO T283. A series of tests enabled the determination of the composite binder composition to ensure proper resistance of a cold recycled fine-graded mixture to moisture and frost. [ABSTRACT FROM AUTHOR]

Air void content is one of the key parameters determining such properties of asphalt mixtures as resistance to permanent deformation, resistance to moisture damage, stiffness, resistance to fatigue and resistance to cracking. Adequate levels of air void content in pavement layers are prerequisite for obtaining durable and long-lasting pavements. In the asphalt mix design, laboratory testing is used to evaluate the properties of the formulations and to assure the quality of the paved material. Laboratory testing usually involves relatively small samples with unfavourable dimension to nominal maximum aggregate size ratios. Compaction in laboratory conditions also introduce edge effects which are due to small mold dimensions and non-uniform, rapidly changing temperature distribution during compaction. Non-uniform air-void distribution may directly impact the results of the performance tests carried out on laboratory samples and contribute to inadequate characterization of the pavement material. These effects are typically, to some degree, combated using adequately large samples and sample trimming. The density of asphalt mixtures can be evaluated using a variety of well-established methods, including those involving the water displacement principle (saturated-surface dry method, paraffin and parafilm method, vacuum sealing method), nuclear density gauge and non-nuclear density gauge. Some of these methods are more suited for laboratory use, while others (nuclear and non-nuclear density gauge methods) are intended for field evaluation of compacted later density. The common characteristic of all mentioned methods is the fact that they provide a bulk result, without the possibility of providing the spatial distribution of the air voids in the samples without planned and intended cutting involved. Such prospect arises from the use of the computed tomography technique, in which the scanned samples and obtained data regarding the distribution of air voids can be evaluated non-destructively. The paper concerns the evaluation of the distribution of air voids in laboratory produced samples of asphalt concrete using the water displacement method and computed tomography. [ABSTRACT FROM AUTHOR]

Currently, efforts are being made to use ecological and eco-friendly technologies in road construction aimed at reducing CO2 and other compounds emissions to the atmosphere. It can be achieved by using various additives lowering technological temperatures of asphalt mixtures or by using appropriate technologies. One of the technologies for reducing the production temperature of asphalt mixtures is the technology of foaming the binder with water. This technology enables the production of mixtures using warm mixed asphalt. The aim of the research was to evaluate the properties of 50/70 paving grade bitumen and polymer modified bitumens: 45/80-55, 45/80-80 intended to produced warm mix asphalt. These binders were subjected to standard tests: penetration at 25°C, softening point, Fraass breaking point and dynamic viscosity in different temperatures: 90°C, 110°C and 135°C. These parameters were evaluated both before and after foaming process by adding water. In addition, tests of the foamability of these binders were performed in terms of amount of foaming water and the temperature of the bitumen binder. The important role of the binder temperature in the foaming process results, first of all, from the strong relationship between the temperature and viscosity of asphalt binders, as well as from the need to evaporate the foaming water by transferring thermal energy. Therefore, the experimental plans for the foaming tests of the analyzed bitumen binders were implemented, taking into account the assessment of the influence of the binder temperature and the amount of foaming water on the maximum expansion ratio ERm and half-life T1/2 values. The analyzed amounts of foaming water ranged from 1% to 3%, while the temperature range of the binder during foaming was from 140°C to 170°C for 50/70 road bitumen and 155°C to 185°C for polymer modified binders (45/80-55,45/80-80). Optimization was performed to determine the optimal foaming water content for each type of bitumen binder. The analysis of the results showed that the optimal foaming water content was in the range of 1.6%-2.0%, while for polymer modified bitumens it was found to be in the 1.8% to 2.4% range. [ABSTRACT FROM AUTHOR]

The subject of the research is to evaluate the influence of the composition and quantity of the hydraulic binder on the stiffness modulus of the recycled subbase, made of a mineral-cement-emulsion mixture (BE-RCM). Road subbases made in the technology of deep cold recycling are a proven method for the construction of the construction layer of the road surface. Among the many advantages, it is necessary to indicate the reuse of materials obtained during the demolition of a degraded pavement. There is also a real possibility of reducing the costs and time of reconstructing the road infrastructure. It is extremely important to choose the right hydraulic binder for the recycled mixture. The subbase must be a durable and load-bearing layer. It should be noted that the use of too much binder, in the form of Portland cement, may lead to the stiffening of the layer and the appearance of uncontrolled reflected cracks. Cracks of this type are initiated precisely in the hydraulically bound base layer. Currently, attempts are being made to modify the binder composition to avoid the occurrence of undesirable effects. The paper presents the results of research on the stiffness modulus of the recycled BE-RCM subbase depending on the measurement temperature and the composition of the hydraulic binder. Portland cement I class and a modifier in the form of a redispersible polymer powder with a polymer base (polyethylene-co-vinyl acetate) EVA were used as a binder. The impact analysis was performed using the assumptions of the Box-Behnken experiment plan in which three variables are controlled. The variables in the experiment were the content of: polymer, cement and asphalt emulsion in the mixture. The mentioned ingredients were dosed with a step of 1.5% of the percentage share in the mixture composition. EVA redispersible polymer powder and Portland cement were dosed from 0.5% to 3.5%. In contrast, the pure asphalt that came from the asphalt emulsion added to the mix was 0.0%, 1.5% and 3.0%, respectively. The obtained test results may be an impulse to optimize the binder composition of recycled cold mixes with asphalt emulsion. There is a chance to reduce the Portland cement content in BE-RCM mixes thanks to the use of a polymer modifier. The subbase made in this way has the appropriate parameters and values of the stiffness modules. The introduced polymer allows to reduce the occurrence of uncontrolled cracks in the foundation. [ABSTRACT FROM AUTHOR]