Seracettin Arasan

Hydraulic conductivity of compacted clay liners permeated with inorganic salt solutions

Due to their low permeability, geosynthetic clay liners (GCLs) and compacted clay liners (CCLs) are the main materials used in waste disposal landfills. The hydraulic conductivity of GCLs and CCLs is closely related to the chemistry of the permeant fluid. In this study, the effect on the hydraulic conductivity of clays of five different inorganic salt solutions as permeant fluid was experimentally investigated. For this purpose, NaCl, NH4Cl, KCl, CaCl2, and FeCl 3 inorganic salt solutions were used at concentrations of 0.01, 0.10, 0.25, 0.50, 0.75 and 1 M. Laboratory hydraulic conductivity tests were conducted on low plasticity (CL) and high plasticity (CH) compacted raw clays. The change in electrical conductivity and pH values of the clay samples with inorganic salt solutions were also determined. The experimental test results indicated that the effect of inorganic salt solutions on CL clay was different from that on CH clay. The hydraulic conductivity was found to increase for CH clay when the salt concentrations increased whereas when the salt concentrations were increased, the hydraulic conductivity decreased for the CL clay.

Correlation between Shape of Aggregate and Mechanical Properties of Asphalt Concrete

ABSTRACT The importance of the shape of aggregate particles on their mechanical behavior of bituminous materials is well recognized. In asphalt concrete, the shape of aggregate particles affects the durability, workability, shear resistance, tensile strength, stiffness, fatigue response, and optimum binder content of the mixture. In recent years, DIP techniques are widely used to analyze the shape indexes of aggregate. In this study, the shape characteristics such as aspect ratio, elongation, flatness, form factor, roundness, shape factor, and sphericity were determined by DIP technique. The coarse aggregate was proportioned into three size fractions, namely, 19 to 12.5 mm, 12.5 to 9.5 mm, and 9.5 to 4.75 mm. Coarse Aggregate sizes of 19 to 12.5 mm and 12.5 to 9.5 mm were selected by hand as three categories of flat, elongated, and spherical. In addition, a control mixture containing all of aggregate shapes was prepared. ImageJ Java program was used as the image analysis program. This program measures a lot of geometrical values such as area, perimeter, length and angle. Asphalt concrete specimens were fabricated in accordance with ASTM D 1559. Marshall stability and flow values were determined and volumetric properties of all Marshall specimens were calculated. The test results indicated that there is a good correlation between some shape indexes of aggregate and asphalt concrete properties. The DIP was shown to be a useful tool for quantifying the morphological characteristics of coarse aggregates. Therefore, DIP technique proposed in this study may be used instead of some mechanical asphalt concrete tests which are cumbersome and time consuming. However, further studies may lead to use the DIP technique in aggregate quality assurance and quality control procedures and stability and flow values for HMA concrete can be predicted using DIP. It should also be pointed out that further studies on the image analysis system are needed to make more useful and practical method for DIP.

Effect of Freeze-Thaw Cycles on Strength Behavior of Compacted Chicken Quill-Clay Composite in Undrained Loading

ABSTRACT A large number of studies have been conducted recently to investigate the influence of randomly oriented fibers on some engineering properties of cohesive and cohesionless soils. However, few studies have been carried out on fine-grained soils reinforced with natural fibers. In this study, a series of triaxial testing (unconsolidated-undrained) and freeze-thaw tests were conducted in laboratory environment in order to investigate the effects of chicken quills dispersed randomly in high plasticity clay on freeze-thaw behavior. Chicken quill percentage was chosen as 0.5%, 1%, and 1.5% of the total dry weight of the reinforced soil. The numbers of freeze-thaw cycles were taken as 5 and 10. As a result of the experiments, it was determined that, the dzeviatoric stress of unreinforced samples caused a decrease when the freeze-thaw cycles increased. However, the deviatoric stress remarkably increases with increasing fiber ratio in different confining pressures, for 5 and 10 freeze-thaw cycles.