Fine aggregate angularity in Turkey in bituminous mixtures

Weight and volume of mineral aggregates used in bituminous mixtures are respectively at the rate 90-95% of mixture weight, 75-85% of mixture volume. Physical and mineralogical properties of mineral aggregates on which load bearing capacity of pavement depends affect the properties of mixture, workability of fresh mixture and performance of pavement directly. The more bituminous mixtures are workable, the more they are compactable. Easily compactable bituminous mixtures (high workability) can rut easily and quickly under traffic. In contrast, mixtures with low workability (harsh mixtures) proved to be less prone to rutting under the same conditions. Because of this reason, in recent years highway engineers in the USA and some European countries prefer less workable bituminous mixtures. Angularity of aggregate particularly that of fine aggregate is a primary factor to affect the workability of a bituminous mixture. In the eighties, SUPERPAVE in the USA and Gyratory Shear Press in France, design methods and rutting experimental studies show us that, dense graded mixtures are good for rutting and shear resistance. Also during these studies, it is determined that, angularity of aggregate and especially fine aggregate angularity (FAA) is important for rutting resistance. Because of this reason, new specifications were prepared for FAA properties. These specifications are AASHTO TP-33 and ASTM 3398 in USA, and AFNOR P18-564 in France. The aim of this study is to investigate the angularity of fine aggregate produced in Turkey and to draw the attention of the design engineers to this subject. Because of the absence of a specification for FAA in Turkey AFNOR PI 8-564 was used for them tests. FAA test were performed on different samples taken from different regions and crushed by different types of crushers, including some natural sands: In the first chapter, Fine Aggregate Angularity is defined. Definition varies depending upon country. In the following chapters, previous studies, and experimental researches are outlined. The place of this study in the literature was emphasized. Mineral Aggregates in bituminous mixtures, and mineral aggregate properties, which are related with FAA, are explained in detail. Previous design methods, which do not take into consideration FAA and the recently developed design method (SUPERPAVE), which considers FAA directly, are summarized and compared. Types of failures occurring in pavements and their reasons are explained and it is a relation between failures and FAA was searched. Then, crushers are classified. Detailed experimental specifications are explained in chapter six. It was concluded that AFNOR Specification or an eventual European Specification should be adopted in Turkey since She is a candidate to European Union. In the next part, laboratory test results performed are presented and evaluated. Finally, conclusions are drawn and suggestions are made in the last chapter. Whole study is revaluated in this section. Results obtained show that FAA depends on so many factors, which have to be considered, and it is emphasized that angularity experiments must be made in place.