DETERMINING THE ELASTIC PROPERTIES OF LIGHTWEIGHT EXPANDED SHALE AND CLAY AGGREGATES OF IRAN

Due to application of articially lightweight aggregates in various industries, the property of these aggregates is very important. According to their physical nature and the lack of bedrock, the elastic properties of arti- cially lightweight aggregates have a special complexity. At present, lightweight expanded shale aggregates or Liapor and expanded clay aggregates or LECA are the most important articially lightweight aggregate in Iran. Expanded shale or Liapor is produced using expansible shale by a dry process, and expanded clay or Leca is produced using expansible clay by a wet process and by cooking in horizontal rotary kilns. The major dierence between these two types of aggregate production is in the method of their agglomeration, which causes signicant dierences in the nal product. Products often contain zero to 25 mm diameters, increase porosity by increasing diameter, and their densities are reduced. Since the standard for the direct determination of the elastic properties of the aggregate is absent, a combination of experimental methods and a theory of composite materials are used to determine these parameters. In the section of the theory of composite materials, using the micromechanical method and the inverse Mori- Tanaka homogenization model, the elastic properties of the inclusion of the according to matrix and composite material properties are determined. Paying attention to nature of the aggregates, their shape is assumed to be a complete sphere in this research. In the laboratory work, two groups of quaternary ordinary and structural Leca, and one group of trinary Liapor aggregates, each group being produced under identical conditions, are used. By a combination of each type of aggregate with cement sand mortar, and by building standard cylindrical samples of composite materials, the elastic properties of the matrix and composite samples are determined. Then, using experimental results and relations obtained from the Mori-Tanaka model, the elastic properties of the aggregate are determined. The results show an exponential relation between the elastic modulous and particle density, and a linear relation between the elastic modulous and the crushing resistance for LECA and Liapor aggregates.