Ultrasonic pulse velocity investigation of steel fiber reinforced self-compacted concrete.

摘要

Concrete is a basic material used for a number of applications in civil engineering projects. Structural concrete is brittle material under normal conditions. Therefore, by adding short and randomly distributed steel fibers, it is possible to improve the ductility and other basic properties of concrete. However, the addition of steel fibers results in loss of workability of the concrete, especially in self-compacted concrete. Therefore, in this study, ADVA-140 high range water reducer (HRWR) superplasticizer was added to improve the workability of self-compacted (SC), steel-fiber-reinforced concrete (SFRC). The amount of superplasticizer varied with the volume percentage of fiber for the beams; however, it was kept constant for the cylinder, as shown in Tables 4-2 and 4-3, respectively. Other admixtures, such as fly ash and silica fumes, were also added to improve the concrete properties. Type II deformed steel fibers with a diameter of 0.023 in and length of 0.75 in were added to the mix. The amount of steel fibers varied from 0-4% for the beam samples and from 0-2% for the cylinder samples. The samples were self-compacted to allow for self-setting without applying vibration in order to avoid materials segregation and bleeding.;A total of 18 beam samples and 5 cylindrical samples were investigated in this experiment. The ultrasonic pulse velocity (UPV) method was applied to detect flaws and characterize the properties steel fiber reinforced self-compacted concrete. This method is used to measure the time required for the ultrasonic wave to travel through the test material and energy attenuation. Knowing the time of flight, it is possible to calculate the wave velocity through the material. This study investigated the effects of steel fiber volumes, curing periods, wet and dry conditions (saturation), and fiber and aggregate orientations on UPV. The result showed that by controlling measurement errors and environmental factors, the UPV is a very promising method to detect concrete flaws and to estimate design properties in concrete structures.