Wasit Journal of Engineering Sciences

Warm mix Asphalt (WMA) could be mixed and used in paving at low temperatures to minimize the consumption of energy and the emissions of greenhouse gas. Recycled Asphalt pavement (RAP) could save Asphaltic cement and aggregate, which could achieve the better effects of recycling. However, both of the two WMA and RAP technologies have some deficiencies. Warm mix Asphalt and Reclaimed Asphalt pavement (WMA-RAP) technique may solve these issues and deficiencies when they are utilized together. This study investigated the implementations of WMA-RAP and its impacts on the performance of the Asphalt mixture. Under the framework of this study, four percentages of RAP (0%, 20%, 30%, and 40%) were added to the hot mix Asphalt (HMA) and WMA containing 4% Sasobit to study the impact of increasing RAP content on Marshall stability and moisture resistance of Asphalt mixtures. In summary, the Marshall stability of HMA and WMA mixtures is higher than the control mixtures. A small decrease in moisture resistance of both (HMA and WMA) containing RAP comparing to control mixtures Asphalt was observed, as shown by reduced the tensile strength ratios (TSR), but it is still much higher than the minimum of 80%.

Recently, polymer -nanocomposites were used to manufacture durable asphalt mixtures to replace the polymer modified binder, because of the remarkable properties and unique features of nanomaterials compared to conventional materials, such as their wide surface area and small dimensions, making it possible to be utilized as an additive for asphalt paving. Nanosilica particles (NS) are one of the latest minerals which likely integrate useful characteristics, such as huge surface area, good distributions, high absorption levels, high stability, and a high level of purity. Therefore, this paper is interested in studying the characteristics of nanocomposite-polymer modified asphalt. In laboratory work, a pure asphalt 60-70 penetration grade, has been modified separately with waste polypropylene polymer (WPP), and nanosillica composite polypropylene (NS/WPP) at different concentrations. As a result, two modified binders: waste polypropylene polymer- modified asphalt (WPP-MA), and nanosillica composite polypropylene modified asphalt (NSCPMA) were obtained. Traditional asphalt binder tests were performed for pure and modified binders such as penetration, ductility, flash and fire point test, softening point, and rotational viscosity. Also, storage stability test has been conducted to ensure the storage stability of binders at high temperatures. The results showed an improvement in physical properties and increase in mixing and compaction temperature due to the increase in stiffness of (NSCPMA). The results also indicated that the nanosillica composite polypropylene modified asphalt binders have good storage stability at high temperatures.

The angle of internal friction value (φ) is used to describe the soil resistance to shear failure. It is estimated experimentally either from Direct Shear Test or Triaxial Stress Tests. Because of the high cost needed for conducting field tests, it has become essential to find alternative and practical methods to predict soil characteristics for non-spatial data areas. The objective of this study is to specify the best interpolation method to predict the angle of internal friction and use it to produce geotechnical maps for parts of An-Najaf province-Iraq; these parts are the city centre An-Najaf and Kufa city. Furthermore, the study describes the strength and type of soil strata. The results show that the Local Polynomial Interpolation (LPI) is the ultimate and the most significant method to interpolate the angle of internal friction. Moreover, the angle of internal friction φ values is ringing between (20-46) degrees, which represent medium to dense soil resistance to shear, while the mean values of φ ranged between 34.3 - 36.18 and represent good resistance to shear failure. This indicates that the Density of Sand is medium to dense, and N60 values range from 10-50. This kind of map would ease the engineers and decision-makers to decide the suitability of the construction site to carry loads, and the selection the foundation type. The benefits also extend to selecting urban expansion alternatives and for the delimitation of future trends for land-use-development processes in the metropolitan area of An-Najaf city, mainly at local and regional scales.

Reliability has been considered of magnificent importance in engineering design specially in geotechnical engineering due to the unpredictable conditions of soil layers. It is essential to establish well- designed failure modes that could guarantee safety and durability of the proposed structure. This study aims to suggest a reliability analyses procedure for retaining walls by the mean of a reliability index β using the specifications of AASHTO Bridge Design 2002, Eurocode 7, and DIN EN 1993-5 norms. Two failure modes; Tensile failure of tendon (G1) and Failure by bending (G2) were studied and compared by using equation of the Design Limit State (DLS) and by taking some basic geotechnical parameters as Random Variables RV. The analyses demonstrated that the reliability index β and probability of failure Pf are the most important parameter in the reliability analysis. Also, the suitable height (H) for the retaining structure (for all angles ϴ) equals to 6 m and the most critical angle is ϴ= 45º to prevent the failure by tensile of tendon. While the bending failure reliability analysis shows that all heights of retaining structure are suitable. After comparing the two cases it was found that (G1) is more dangerous than (G2).

The air conditioning system performance is significantly affected by temperature rise which causes continuous increase in electricity consumption and pollution problems to environment. Evaporative cooling systems are characterized by their low energy consumption so that they represent successful potential alternatives to traditional vapor compression air conditioning systems. This study investigates the performance of multi-stages evaporative cooling systems experimentally and theoretically. The experimental set-up is mainly composed of two parts: indirect unit to decrease the air temperature and direct unit to moisturize the air. The system is installed and equipped with temperatures, humidity, and air velocity sensors. The experimental tests were run continuously to monitor the system performance at various weather conditions between to in June and July months. A mathematical model for the system components was developed and implemented in the Engineering Equation Solver (EES) program to simulate the performance of multi-stages evaporative cooling systems. The results showed that the heat flux increases with the increase in the Reynolds number Re of inlet air, velocity fraction extracted air for sensible cooling, air temperature at the product-in , air velocity at the product-in , and the adiabatic efficiency . But, it is decreasing with increasing the spacing between the heat exchanger plates and the relative humidity at the product-in . Optimum performance was obtained with very small space between plates which was bout 5mm. Good agreement have been shown between experimental and predicted data, where the results. Uncertainty of experimental data was within the range 4.14 to 6.15.