预固化条件对加砂固井水泥高温性能演变规律研究OA

Objective The effects of low-temperature pre-curing temperature and duration on the evolution of hydration products and the physicomechanical properties of silica-blended well cement cured at 240℃were systematically investigated to elucidate the mechanism by which pre-curing conditions affect the high-temperature mechanical performance of cement.Method Mercury intrusion porosimetry,X-ray diffraction,thermogravimetric analysis,and scanning electron microscopy were employed to characterize the phase composition and microstructural evolution of cement under different pre-curing conditions.Result As the pre-curing temperature increased from 20 ℃ to 80℃,the compressive strength increment of cement stone during 90 days curing at 240℃increased from 0％to 85％,accompanied by significant refinement of the microstructure.Meanwhile,the formation of tobermorite increased,whereas the content of xonotlite decreased markedly,and the chemically bound water content tended to stabilize.Although specimens pre-cured at 80℃for 2 days and 14 days exhibited similar trends in mechanical property development,their pore structures differed substantially.In the 14-day pre-cured specimens,harmful pores gradually transformed into smaller pores,and the structures of calcium silicate hydrate and tobermorite exhibited greater stability.Conclusion Optimized pre-curing conditions can effectively regulate the high-temperature hydration reaction pathway of cement stone,promote the formation of stable hydration products,and suppress pore structure coarsening,thereby enhancing the structural compactness and long-term mechanical performance of cement stone.