Among all the concrete characteristics, the compressive strength is known as the most important feature and therefore, it is often utilized to quantify the quality of concretes. The assessment of concretes strength in existing constructions is important during their service life. Thus, in addition to destructive evaluation of strength, many non-destructive techniques have been adopted to assess the concretes strength. Ultrasonic Pulse Velocity (UPV) is one of the nondestructive techniques that involve measuring the speed of ultrasonic wave through concretes to predict concretes strength. According to the Griffith's theory, the strength of the material is greatly affected by the defects' existence (for example, small cracks). These cracks can be current prior to the application of any loading or could create throughout the load application. The presence of micro-cracks in concretes that generate due to the applied load may affect the UPV test results in comparison with unloaded concretes. An experimental investigation is conducted in order to assess the impact of the applied of load (ultimate load) on the measured ultrasonic wave velocity and compared with the results of compressive strength from destructive test. A total of thirty (150 mmx150mm) cube specimens have been utilized with water to cement ratios (0.45). These cubes have been examined in ultrasound without any loads and then they have been tested in the same way with applied ultimate load which is approximately equal to half of the required design load (failure load) and then inspected or tested in the normal way (destructive test). In order to assess the compressive strength of concretes using (UPV), loading condition is considered in order to study the impact of the applying load. In addition, the water absorption has been examined for thirty concretes samples under the impact of the applied loads (20%, 40% and 60%). The results of nondestructive tests of concretes samples under the influence of imposed loads (60%) have showed to be less by compressive strength 5 MPa than the results obtained from testing of unloaded concretes samples through the resulting equation and comparing them to the equation from previous research. This is consistent with the water absorption test of the specimens under the imposed loads (60%) where Absorption values have been greater than concretes models without applied loads. Copyright
In Iraq, asphalt roads suffer a lot of problems because of the high traffic and climatic conditions represented by high temperatures in the summer, which reduce the service life of the road, so it became necessary to improve the rheological and physical properties of asphalt and thus improve the performance of asphalt paving. Nanotechnology is one of the methods used for improvement has been adopted in the research. The possibility of improving the properties of asphalt was studied using Nano silica)NS) and Nano hydrated lime (NHL)with percentages (1,3,5and7)% by total weight of asphalt. Tests were performed to evaluate the enhance in softening point, penetration, kinematic viscosity and penetration index of the asphalt with penetration grade (60-70). The results of the laboratory study show the improvements in the properties of asphalt By reducing the amount of penetration and increasing the softening point of the asphalt, thus it becomes more stiffer and less sensitive to temperatures than the original asphalt, in addition to that, the results showed that an improvement in the values of viscosity and penetration index, and this in turn leads to an increase in the adhesion and cohesion of asphalt and asphalt mixture as well as the possibility of using modified asphalt with Nano-materials in areas with high temperatures and traffic load.
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