Evolution of distribution and content of water in cement paste by low field nuclear magnetic resonance
来源期刊：中南大学学报(英文版)2013年第4期
论文作者：SHE An-ming(佘安明) YAO Wu(姚 武) YUAN Wan-cheng(袁万城)
文章页码：1109 - 1114
Key words：cement water; distribution; water-to-cement ratio; pore; nuclear magnetic resonance
Abstract: the low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c ratio) during early and later hydration stages. From the water distribution spectrum deduced from relaxation time distribution in paste, it is suggested that the water fills in the capillary pores at initial period, and then diffuses to the mesopores and gel pores in hydration products with the hydration proceeding. The decrease of peak area in water distribution spectrum reflects the transformation from physically bound water to chemically bound water. In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores were also measured. The results demonstrate that it is influenced by the formation of pore system and the original water-to-cement ratio in the paste. Consequently, the relative content of capillary water is dropped to less than 2% in the paste with low w/c ratio of 0.3 when being hydrated for 1 d, while the contents are still 16% and 36% in the pastes with w/c ratios of 0.4 and 0.5, respectively.
SHE An-ming(佘安明)1,2, YAO Wu(姚 武)1, YUAN Wan-cheng(袁万城)2
(1. Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education (Tongji University),
Shanghai 201804, China;
2. State Key Laboratory of Disaster Reduction in Civil Engineering (Tongji University), Shanghai 200092, China)
Abstract:the low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c ratio) during early and later hydration stages. From the water distribution spectrum deduced from relaxation time distribution in paste, it is suggested that the water fills in the capillary pores at initial period, and then diffuses to the mesopores and gel pores in hydration products with the hydration proceeding. The decrease of peak area in water distribution spectrum reflects the transformation from physically bound water to chemically bound water. In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores were also measured. The results demonstrate that it is influenced by the formation of pore system and the original water-to-cement ratio in the paste. Consequently, the relative content of capillary water is dropped to less than 2% in the paste with low w/c ratio of 0.3 when being hydrated for 1 d, while the contents are still 16% and 36% in the pastes with w/c ratios of 0.4 and 0.5, respectively.
Key words:cement water; distribution; water-to-cement ratio; pore; nuclear magnetic resonance
