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Due to the wide range of concrete in radioactive waste disposal sites, the use of cement materials is very important, especially when the groundwater penetrates into the concrete. The Ordinary Portland Cement (OPC) releases the pore fluids of the pH 12-13. In the high pH environment, the pore water leakage after the encounter buffer material, it will make the buffer material with the expansion of the main components of montmorillonite dissolution rate which increases the pH. Therefore, the use of low-alkali cement material after the pozzolanic reaction, the consumption of calcium hydroxide solution (CH), will reduce the pH value that ensure the buffer material are safety.
In this study, the micro-characteristics, engineering properties and durability of the same cementing ratio of cement paste, mortar and concrete were replaced by low pH cement silica and fly ash. According to the references, the measurement of pH method are found that Ex-Situ leaching method is established for laboratory testing whichis easily and capabilities. To explore the use of different mineral admixture of silica fume and fly ash replace of cement, it will reduce the pore fluids of the pH value effectively.
The results show that the addition of Pozzolan material to the cement can reduce the pH value of the pore solution by adding silica fume. To achieve the requirements of the concrete plug sealing, it needs to control the amount of cementitious materials, when 40% silica fume replace of cement, the pH of mortar and concrete samples in the 90-day is lower than 11. Because of the silica fume is more expensive than fly ash and when the more silica fume is added, the workability is in bad condition, it needs add some plasticizer to improve the workability. Therefore, the silica fume and fly ash were replaced by cement weight 35 % and 20% respectively, it can achieve the requirements of quality of low pH concrete plug sealing. | en_US |