The Impact of Sample Compaction Temperatures on the Characteristics of Bituminous Concrete

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.