Environment conservation and diminishing natural resources caused an increase in popularity of the application of renewable bio-origin resources for the construction of road pavement. Currently, there are known additions of bio-origin materials for bitumen modification. Such material is also used as a flux additive for bitumen or as a rejuvenator once working with reclaimed asphalt pavement (RAP). This paper presents research dealing with asphalt mixtures with RAP modified with a bio-agent of rapeseed origin. The main idea of the conducted research was to apply more RAP content directly to the batch mix plant without extra RAP heating. The RAP used in this study was milled from a base asphalt layer; the addition of RAP stiffens new asphalt mixtures. A bio-agent, due to its fluxing action, was used to support the asphalt mixing process and to decrease the over-stiffening of the mixture caused by RAP addition. This research includes bitumen and mixture tests. For the bitumen study, three different bitumens (35/50, 50/70, and 70/100) were tested in a dynamic shear rheometer (DSR) for complex modulus G* and for phase angle |δ| in the temperature range 0–100 °C. The reference mixture and mixtures with 2.5% bio-agent were tested to assess the influence of RAP and the bio-agent addition on the asphalt mixture properties. Low temperature behavior (TSRST), stiffness, and fatigue resistance (4PB) were tested. Based on the bitumen test, it was determined that even a low rate of bio-agent (2.5%) beneficially changes bitumen properties at a low temperature; moreover, polymerization processes occurring in the second stage of the process improves bitumen properties at a high operational temperature. The research with these asphalt mixtures demonstrates that the bio-origin flux acts as a rejuvenator and allows for an application of 30% cold RAP. Thermal cracking resistance of the mixture with RAP and 2.5% bio-agent improved. The bio-agent removes unfavorable stiffening of RAP and increases the fatigue resistance of the asphalt mixture.

The topic of this article is the evaluation of the fatigue life of asphalt concrete mixtures with reclaimed asphalt pavement (RAP). The evaluation was carried out in relation to asphalt concrete mixtures AC22P and high modulus asphalt concrete ACWMS16 with 50% contents of RAP, greater than currently permitted by technical regulations in Poland. The first stage consisted of the evaluation of laboratory results, which was followed by a mechanistic analysis of the designed life of pavement structures with reclaimed asphalt. The evaluation included the results of laboratory tests (i.e., the air voids content, effective asphalt content, properties of recovered asphalt (penetration, softening point), stiffness, and resistance to fatigue of bituminous mixtures). Calculations of the design life of the structure were made using the criteria according to the 2004 AASHTO specifications for fatigue life and the Asphalt Institute for subgrade deformation. In addition, calculations were carried out using the French method. The analyses allowed for a comprehensive evaluation of the asphalt concrete mixture in the analyzed scope. The evaluation of the fatigue life of AC22P and ACWMS16 mixtures with 50% content of reclaimed asphalt as well as the results of the calculations of design life of the structure indicated positive effects. The tests have been carried out within the framework of the research project dedicated to hot recycling entitled “Reclaimed asphalt pavement: Innovative technology of bituminous mixtures using material from reclaimed asphalt pavement”.

Recycling of bituminous pavements is an issue increasingly being discussed in Poland. The analysis of domestic and foreign experience indicates a need to develop this technology in our country, in particular the hot feeding and production technologies. Various steps are being taken in this direction, including research projects. One of them is the InnGA project entitled: "Reclaimed asphalt pavement: Innovative technology of bituminous mixtures using material from reclaimed asphalt pavement". The paper presents the results of research involving the design of bituminous mixtures in accordance with the required properties and in excess of the content of reclaimed asphalt permitted by the technical guidelines. It presents selected bituminous mixtures with the content of RAP of up to 50% and the results of tests from verification of industrial production of those mixtures. The article discusses the details of the design process of mixtures with a high content of reclaimed asphalt, the carried out production tests and discusses the results of tests under the verification of industrial production. Testing included basic tests according to the Polish technical requirements of WT- 2 and the extended functional testing. The conducted tests and analyses helped to determine the usefulness of the developed bituminous mixtures for use in experimental sections and confirmed the possibility of using an increased amount of reclaimed asphalt up to 50% in mixtures intended for construction of national roads.

The goal of the work was to describe properties of asphalt-cement concrete (ACC) with reclaimed asphalt pavement (RAP), Portland cement, sand, and rubber powder (RP), as a material to base courses of road pavements. The mixtures were designed with the RAP in the amount of 75, 80, and 85% (m/m) and chosen cement-sand-rubber (CSR) mortar. Three CSR mortars were composed with cement CEM 42.5 R in the amount 29% (m/m); washed sand 0/2 mm in the amount 29, 35, or 41%; rubber powder of granulation 0/1 mm in the amount of 18, 24, or 29% (m/m); and water in the amount 12% fulfilled w/c = 0.4. The optimum moisture content of the selected ACC with CSR mortar determined in the modified Proctor compaction test was approximately 6% and maximum dry density 2.000 g/cm³. Laboratory tests of indirect tensile strength, stiffness modulus (IT-CY and 4PB-PR), water resistance, fatigue life, and complex modulus (E*) at different temperatures were conducted and analyzed. The test results are presented, among others, in the form: the isotherm of complex modulus, Black curve, the master curve, and the Cole-Cole plot.

The principles of the circular economy are the basic determinants of the sustainable development of road construction. This paper presents a field study with a new concept of asphalt pavement structure with ecologically oriented attributes, significantly reducing the asphalt pavement carbon footprint while achieving a level of long-term performance comparable or greater than that of conventional pavement structures. The sustainable pavement consists of the introduction of a BIO-additive that allows for the integration of higher percentage of reclaimed asphalt pavement (RAP) as an alternative to the traditional asphalt mixtures. In the sub-base the use of construction and demolition waste was adopted. The results were obtained from a full-sized test section of the road structure divided for reference and eco-innovative cases. Mechanistic analyses were performed for materials and pavement structure based on laboratory tests and on-site assessment. The new eco-design solution was subjected to a comprehensive LCA and LCCA analysis and summarised by SWOT assessment.