The interest in minimising fuel consumption and greenhouse gas emissions among road specialists is increasing. Thus, methods for reducing asphalt concrete mixing and compaction temperatures by a few tens of degrees Celsius without compromising the long-term performance has become a topic of significant interest. This study is focused on the analysis of warm mix asphalt (WMA) prepared with locally available materials in order to determine the suitable technology applicable to the specific traffic and climatic conditions of Romania. WMA was prepared using different warm mix additives (organic additives, chemical additive, and synthetic zeolite) at different mixing and compaction temperatures, and bitumen blends with these additives were analysed by carrying out the dynamic shear rheometer test and evaluating the penetration index. In conclusion it was noted that most additives did not lead to a significant change of bitumen`s characteristics, but the organic additive had a big influence on the bitumen`s properties. The characteristics of WMA are very similar to those of HMA. The mixing and compaction temperatures could be reduced by approximately 40 °C when WMA was blended with the additives without compromising the performance of the asphalt mixture, compared to hot mix asphalt.
The paper presents studies and laboratory tests concerning the influence of the way the natural quarry aggregates are processed upon the composition of an asphaltic concrete with a maximum grain size of 16 mm (BA 16). The research included the realization of grading curves on certain aggregates, curves lately compared to the maximum density line. This approach aims at classifying certain aspects concerning some of the physical-mechanical characteristics of the asphalt concretes determined through static and dynamic laboratory tests. The research resulted from the fact that in Romania, the elementary gradings on granular fractions from the same source, entering the composition of a certain asphalt mix, differ most of the times depending on the manipulation and the processing manner, respectively. This finding is based on the experience of the laboratory testing, where different values concerning the volume weight, apparent volume weight, voids and rigidity module were obtained on the same asphalt mix dosage prepared according to the prescription in two separate samples.Thus, in order to emphasize the impact of the processing manner (crushing) of the natural aggregates, the authors determined the percentage distribution on intermediate granular fractions of the gradings entering the composition of an asphalt concrete. Since the Romanian Standard for asphalt mixtures stipulates a large grading envelope between the standard sizes corresponding to each grading, the authors considered that there is no uniform distribution ratio depending on the size of the grains entering its composition. The study started from different research methods found in the specialized literature dealing with the calibration of the optimal grading curve. The results of the laboratory tests performed on the asphalt mixture confirm the importance of the particle size analysis in obtaining high quality physical-mechanical characteristics.
Within the last decade, much attention has been focused on determining viable techniques for producing sustainable asphalt mixtures and minimizing fuel use and greenhouse gas emissions. Thus, warm mix asphalt (WMA) has become a topic of significant interest among road specialists as it offers a potential solution for reducing the environmental impact of the asphalt mixtures due to the decreased temperatures they require for mixing and compaction compared to hot mix asphalt (HMA). The present study is focused on the Life Cycle Assessment (LCA), according to a “Cradle-to-Gate” approach, of hot mix asphalt and warm mix asphalt prepared with locally available materials and different warm mix additives such as organic additives, chemical additive, and synthetic zeolite. For the analysis of the environmental impact of the warm mix asphalts was used a dedicated software for modeling and evaluating the LCA. The WMA prepared with chemical additive or organic additive led to a decrease of the environmental impact, in the production phase, compared to HMA. The study reveals that the raw materials extraction has the greatest impact on the environment in all studied cases, followed by the actual production phase of the asphalt mixture. For WMA produced with additives there was a decrease in the global impact on the environment compared to HMA.
The compaction of bituminous layers is the operation that determines the asphalt mixtures to reduce their air voids until the desired density is obtained, at the suitable temperature and with specific equipment, in order to reach the physical-mechanical characteristics designed in well-controlled laboratory conditions. The realization of these objectives can be slightly altered by a number of factors which can intervene during the construction, such as: temperatures in the technological process (production, transportation, laying and compaction), weather conditions (atmospheric temperature, wind, humidity, transport distance), type of compactor (certain types of a single device or complex compaction equipment), thickness of the layer, alteration of the mixture during laying, etc. Most of the research concerning the compaction deals with identifying the factors affecting the site compaction and the way they can influence the realization of the designed density, starting from the premise that the reference results offered by the laboratory are those obtained in standardized conditions. The research presented in the paper aims at emphasizing the way different preparation and compaction temperatures influence the physical-mechanical characteristics of a laboratory prepared asphalt concrete. It started from the question of whether these characteristics are significantly influenced by the temperature variation or if they range between “acceptable” tolerances. For clarification, the authors prepared asphalt concrete samples for the wearing course, according to the Romanian technical standards, at different preparation and compaction temperatures, in laboratory-controlled conditions. The determined physical-mechanical characteristics were: density, voids, water absorption, Marshall stability, water sensitivity, dynamic flow and rigidity. The results obtained confirm that, for most of the determined characteristics, the temperatures used significantly influence the values obtained. Also, the paper presents a comparative study between the results obtained in the mentioned conditions in the case of three different bitumen dosages, which are 4,8; 5,2 and 5,7% binder by the weight of the asphalt mix. It was found that the variation of the binder content introduces an additional altering factor as to the preparation and compaction temperature.
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