The Impact of Rice Husks Ash on Some Mechanical Features of Reactive Powder Concrete with High Sulfate Content in Fine Aggregate

The sulfate issue in fine aggregate grows with time and it is not easy to gain a fine aggregate with sulfates amount within the specifications of Iraqi standard. Internal sulfate attack is regarded as a significant problem in concrete construction in Iraq and the Middle East countries. One of the modern generations in ultra-high performance concrete is Reactive powder Concrete (RPC) that has been prepared for cemented materials using microstructure improvement methods. RPC has gained attention from both academia and engineering fields with extensive applications. This study presents an experimental research on the impact of Rice Husks Ash (RHA) as replacement percentage of cement upon some mechanical features of RPC with high sulfate content in fine aggregate (Three percentages of SO3 = 0.16, 0.5 and 1.2%). Three percentages of RHA (0, 10 and 15%) as a partial substitution of cement weight have been used in this research. The compressive and the flexural strengths have been adopted to attain the impact of adding RHA. The outcomes have showed that the incorporation of RHA has an important influence on the compressive-strength for both with and without internally sulfate attacking. The result has indicated that using 10% of RHA as a partial cement substitution has increased the effectiveness of RPC by its mechanical features (compressive and flexural-strengths) without internal sulfate attacked

Studying the Impact of Imposed Actual Loads on the Non-Destructive Test Results for Evaluating the Compressive Strength and Other Properties of Concrete

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 non-destructive 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 mm × 150mm) 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 non-destructive 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