Preliminary Studies On The Effect Of Water Content And Pore Water Pressure On The Concrete Strength

The strength of concrete is directly related to its water content and to the loading rate. Inthis paper, the concrete specimens were soaked in water for its free water absorption to formatsamples with different water content. Its strength was tested by applying different loading rateand the ultrasonic instrument was used to measure the wave velocity. After that, how theconcrete strength was influenced by its water content was researched. According to workingenvironment of the high dam concrete in the water, Concrete standard test cube happenosmosis when they were applied periphery hydraulic pressure. The mechanical properties ofC15and C20concrete was affected by pore water pressure, action time, largest aggregatediameter which was very important, so influencing rule of concrete strength change combinedwith high permeability pore water was reviewed.(1) The water content of concrete test cube increased with soaking time. At the beginning,the water content increased rapidly and then very slowly. The stable water content wasaround3.9percent. Concrete block ultrasonic wave velocity was increased after soaked, thetime needed for ultrasonic penetrating across concrete specimen section became shorter. Theincreasing range of ultrasonic wave velocity was not significant, when water content wasbelow3.5percent. But the increasing rate of ultrasonic wave velocity was obviouslybecoming bigger, when the moisture content was more than3.5percent.(2) Under the same water content, the compressive strength increased rapidly, and thengradually became stable, with increasing loading rate. Under the same loading rate, thecompressive strength gradually reduced with increasing water content. When the loading ratewas over1.0MPa/s, the strength basically reached to a stable value. The change trend oftensile strength with the loading rate was similar with concrete compressive strength.(3) With increasing pore water pressure, the compressive strength damage valuegradually increased. Under same pore water pressure, the lower the concrete strength gradewas, the greater the damage value was. The bigger the largest-aggregate diameter was, thegreater the damage value was. The concrete splitting tensile strength of damage value presentthe change trend that the value increased progressively with increasing pore water pressure,and concrete splitting tensile strength of damage value was affected by its strength grade. The higher the strength grade was, the smaller the splitting tensile strength of damage value wasat the same pore water pressure.