| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 101 === There are many researches to study the resistant ability of cement as building materials in the complex environments, and the study of sulfate resistance is one of the most important subjects. American Society for Testing and Materials (ASTM) uses the expansion coefficients and uniaxial compressional strengths of the cements as indices to define the resistant ability of cement in the sulfate environment. In this study, the uniaxial compressional strengths and mode I fracture tougthnesses were used to record the mechanical behavior of cement samples in the sulfate environment. In addition, the P wave and S wave velocities were measured by the ultrasonic testing. These results were discussed and compared in this study.
In this study, three different amounts of fly ash and blast slag(FABS) were selected for testing. They are 0%, 15%, 30% in weight, respectively. The Portland cement samples were mixed with these ingredients. Four different sulfate enviroments were prepared for curing. They are 0%, 5%, 10%, 15% of Na2SO4 in weight of solution. The testing periods was recorded at 0, 7, 14, 28, 56, 84 days, respectively. In each time interval, the uniaxial compressional tests, mode I fracture tougthnesses test, and the ultrasonic testing were performed.
The experimental results show that both the uniaxial compressional strengths and mode I fracture tougthnesses increase as the curing time increases up to 28 days. After 28 days, both the uniaxial compressional strengths and mode I fracture tougthnesses reach stable values. It is found that the strengths of samples with 15% FABS reach maximum in 10 % of Na2SO4 in weight of solution. The results from the ultrasonic testings show that P and S wave velocities become greater as the time increases up to 28 days. However, after 28 days, these values become stable.
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