Study of Structurizing Capacity of Mineral Filler of Different Origin

Abstract

Introduction. Mineral filler is an important component of asphalt mixture which plays an important role in ensuring the quality of asphalt mixtures. The specific surface of mineral filler is about 90 % of the specific surface of aggregates in asphalt mixture. Being a part of asphalt mixture, mineral filler performs two roles: it fills the pores between fine grained and coarse-grained aggregate and structurizes bitumen. Recently, a significant amount of works has been devoted to the study of industrial waste as a raw material for the production of mineral filler. First of all, these studies are related to the evaluation of the direct effect of mineral filler mainly on the volumetric properties of asphalt concrete or on its strength properties. Since one of the purposes of mineral filler is structurizing of bitumen, it is reasonable to pay considerable attention when studying the alternative raw materials, to the structurizing ability of the obtained mineral filler, as insufficient structurizing ability of mineral filler can cause plastic deformations, and too high structurizing ability causes the decreasing of its low-temperature crack resistance. Problem statement. In order to evaluate the structurizing ability of the mineral filler, the «ring and ball method» is preferably used, in which the structurizing ability is evaluated by ane increase in the softening point of bitumen after mixing with the mineral filler. However, this method characterizes only the effect of mineral filler on the properties of bitumen at high operating temperatures, but it does not consider the possible change in the properties of bitumen at low operating temperatures and at process temperatures. Objective. This study explores the evaluation of the effect of mineral filler of different origin on the structuring of bitumen at low and high operating temperatures, as well as at process temperatures for the production of asphalt mixtures. Materials and methods. Mineral filler of limestone, granite, quartzite, fly ash, mechanically activated fly ash, the ash from hydraulic waste disposal, blast furnace slag and cement had been used for research. Results. The results of researches showed a significant effect of the mineral filler origin on its structurizing capacity. The structurizing capacity of mineral filler increases with growing temperature; so at low operating temperature mineral filler has almost no effect on the properties of bitumen, and with the increase of temperature to the values of high operating temperature and process temperatures of asphalt mixtures production, the effect of mineral filler on bitumen properties becomes much more significant. Conclusions. Studies of the structurizing capacity of mineral filler of different origins by changing the softening point had shown the possibility of using the raw materials of different origins for the production of mineral filler namely: raw materials from rock (sedimentary, erupted and metamorphic), raw materials from industrial by-products (fly ash, ash from hydraulic waste disposal, blast furnace slag), and also practically finished construction product (cement). For evaluation of the effectiveness of mineral filler, it is possible to study its structurizing capacity by changing the brittleness temperature, as during determination of this indicator, it is possible to evaluate the effect of structuring, which consists in maintaining the homogeneity of asphalt binder during the preparation of plates.