The requirements imposed on road pavements are ever increasing nowadays, necessitating the improvement of the properties of paving materials. The most commonly used paving materials include bituminous mixtures that are composed of aggregate grains bound by a bituminous binder. The properties of bitumens can be improved by modification with polymers. Among the copolymers used for modifying bitumens, styrene–butadiene–styrene, a thermoplastic elastomer, is the most commonly used. This article presents the results of tests conducted on bitumens modified with two types of styrene–butadiene–styrene copolymer (linear and radial). Two bitumen types of different penetration grades (35/50 and 160/220) were used in the experiments. The content of styrene–butadiene–styrene added to the bitumen varied between 1% and 6%. The results of the force ductility test showed that cohesion energy can be used for qualitative evaluation of the efficiency of modification of bitumen with styrene–butadiene–styrene copolymer. The determined values of the cohesion energy were subjected to the original analysis taking into account the three characteristic elongation zones of the tested binders. The performed analyses made it possible to find a parameter whose values correlate significantly with the content of styrene–butadiene–styrene copolymer in the modified bitumen. With smaller amounts of added modifier (approximately 2%), slightly better effects were obtained in the case of linear copolymer styrene–butadiene–styrene and for larger amounts of modifier (5–6%) radial copolymer styrene–butadiene–styrene was found to be more effective. This is confirmed by the changes in the binder structure, as indicated by the penetration index (PI).
The benefits of the use of cold recycling mixtures (CRMs) in pavement rehabilitation are associated with both the reduction of natural resource consumption by replacing them with recycled materials and the reduction of energy consumption during their production and paving. The evolution of the stiffness of CRMs in road construction and the fatigue life of pavements with CRM base layers are still being investigated. In this paper, CRMs with 1% cement content, called bitumen-stabilized materials with bitumen emulsion (BSM-Es), were examined. Mixtures that were differentiated in terms of Reclaimed Asphalt Pavement (RAP) content, as well as the amount and type of bitumen emulsions, were subjected to indirect tensile stiffness modulus (ITSM) tests at 5 °C, 13 °C, and 20 °C. The thermal sensitivities of the BSM-E mixtures were analyzed. BSM-E mixture stiffness modulus levels at various temperatures were determined using a statistical approach. On the basis of the results obtained, a discussion on the mechanistic-empirical design of flexible pavements with BSM-E base layers is presented. The potential benefits of using BSM-E materials in road construction in certain aspects of pavement life are indicated.
Sustainable development is a basic principle of modern world society. One of important aspects of sustainable development is care of natural resources, To achieve this goal it is obligatory to use within building materials those from recycling. In terms of road engineering it refers to all reclaimed materials from pavement construction, however, one of the most valuable of them is reclaimed asphalt pavement (RAP). Its use in production of new hot mix asphalt (HMA) is promoted due to environmental issues but it also causes concerns among road administrators. Aged bitumen, being an ingredient of RAP, poses a threat to new HMA, decreasing its cracking resistance regardless of its source. Aged bitumen is more brittle than the` virgin one, thus high RAP content may lead to the same sort of problems within HMA. To enable high RAP content in HMA there are additives (rejuvenators) introduced onto aged bitumen (RAP) to restore its characteristics. Choice between applied rejuvenators is crucial task along with its content in accordance to amount of aged bitumen. The aim of the paper is to pinpoint differences between effects obtained after use of different rejuvenators on mix consisting of 100% RAP. The effect was shown on void content determination and Marshall stability test. Results showed significant differences between 4 rejuvenators of different types, making some of them more effective in comparison to others. Tests confirmed possibility of further investigation on 100% RAP mixes made of confirmed-quality RAP.
The research focuses on the analysis of potential use of microwave radiation as alternative Reclaimed Asphalt Pavement (RAP) heating method. Material characteristics and the microwave heating possibility for the production of Hot Mix Asphalt (HMA) were verified. The research focused on testing HMA with different content of RAP and RAP of different moisture containing unmodified bitumen and modified bitumen with styrene-butadiene-styrene (SBS) polymer. Tests for density, bulk density, air void content and the Indirect Tensile Strength were carried out. The test results confirmed the possibility of using microwaves to heat the HMA without adversely affecting its basic properties. The research also shows the possibility of heating the RAP in the process of HMA production, especially with the RAP of a moisture content above 3%. In addition, the tests of HMA did not reveal any negative impact of microwave heating in the case of using moist RAP for the production of HMA. The susceptibility of the SBS polymer to microwave radiation was indicated by comparing the behavior of the two HMA types under its influence. HMA containing modified bitumen appears to achieve higher temperatures than HMA with unmodified bitumen after the same time of microwave heating.
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