| Summary: | 碩士 === 國立宜蘭大學 === 土木工程學系碩士班 === 106 === This study explores the use of building materials for multiple-barrier structures with high levels of radioactive waste. Most countries use bentonite with waterproof properties to protect storage tank. Underground structures are influence by slow penetration of groundwater, Portland cement penetration pore water pH value was between 12.0 to 13.0 will affect bentonite dense waterproof properties. Sweden, Finland and Japan and other countries using low-alkali-cement-based materials to maintain the bentonite properties and the mechanical and durability properties of construction materials are not affected. Pozzolan materials can effectively reduce the pH value of the pore water infiltration below 11.0. The reason for the decline in the pH value is calcium silicon ratio reduce. This study found that calcium silicon ratio below 0.8 has a decline pH effect.
In this study, the low-alkali-cement-based materials of various countries to design the ratio, the first part used silica fume cement to replace from 0% to 60% and fly ash, furnace stone, silica fume and other three kinds of pozzolan materials mixing ratio of 40% to 80% instead of the amount of cement for 13 groups of preliminary analysis. The second part is for the previous match ratio, select two groups to study and explore the best ratio. Hard-hardening properties include compression tests, tensile tests, bending tests and ultrasonic tests that mechanical properties of mortars; durable nature of saturated water absorption test, resist chloride ion penetration test, rapid chloride migration test, shrinkage test, cyclic shrinkage test and reinforcement corrosion test for pore structure of chloride ion behavior and volume stability analysis; chemical properties of the test to determine the value of pH, X-ray fluorescence analysis test, X-ray diffraction test for calcium and silicon ratio and hydrate composition analysis; the microscopic nature of the mercury intrusion porosimetry test and electron microscopy observations. The results are as below, mechanical behavior in the age of 91 days presented, 40% silica fume ratio replacement has the best results and based on long-term mechanical behavior to enhance the selection of 20% silica fume and 40% fly ash ratio; durable nature found that the selection of the ratio have resistance against chloride ions have excellent results, volume stability found, large amount of material used as a small proportion of pozzolan materials, C-S-H colloid converted to the major proportion by the hydration reaction, as the result pore volume contraction caused by poor stability; the chemical nature of the pH value by calcium silicon ratio, it is mentioned in the literature that when the ratio of calcium to silicon is less than 0.8. It makes the value of pH below 11 consistent. In general, hard-setting properties and chemical properties both can meet the requirements of low-alkali-cement-based materials, chemical and micro-properties can establish the actual situation of hydration products, durability properties for practical applications still need to improve the dimensional stability.
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