Influence of admixtures on hydration process of magnesium oxychloride cement(PDF)
长安大学学报（自然科学版）[ISSN:1006-6977/CN:61-1281/TN]
- Issue:
- 2019年05期
- Page:
- 1-10
- Research Field:
- 道路工程
- Publishing date:
Info
- Title:
- Influence of admixtures on hydration process of magnesium oxychloride cement
- Author(s):
- FENG Chao; GUAN Bowen; ZHANG Ben; CHEN Huaxin; FANG Jianhong
- (1. School of Materials Science and Engineering, Changan University, Xi‘’an 710061, Shaanxi, China; 2. Engineering Research Center of Transportation Materials, Ministry of Education Chang‘an University, Xi‘’an 710061, Shaanxi, China; 3. Qinghai Research Institute of Transportation, Xining 810000, Qinghai, China)
- Keywords:
- -
- PACS:
- -
- DOI:
- -
- Abstract:
- To further enhance the rapid hydration rate and short setting time of magnesium oxychloride cement (MOC), suitable polycarboxylic acid water reducer and an acid retarder was added to the MOC to improve its workability. Firstly, the hydration process of a standard sample of MOC was explored, and the hydration stage was analyzed through the hydration heat test. The main control factors at different hydration stages were investigated using the method of hydration kinetics. Furthermore, the effects of admixtures on MOC hydration heat release, hydration rate, hydration product type, and morphology were then analyzed. Kinetic equations were used to compare the changes in the MOC hydration process under the action of admixtures. Finally, the rotational viscosity test was used to characterize the changes in the MOC hydration process under the action of admixtures, and the ratio of mechanical strength before and after immersion was used to characterize the water resistance under the action of admixtures. The results show that the MOC hydration process is similar to that of Portland cement and can be divided into initial period, induction period, acceleration period, deceleration period, and stable period. The hydration rate in the acceleration phase is completely controlled by crystal nucleation and crystal growth under acceleration period, after then the phase boundary reaction and diffusion factors gradually affect the hydration rate. Therefore, the crystallization nucleation and crystal growth rate directly affect the setting time of MOC, and a major way to reduce the hydration rate of MOC is to control the crystallization rate. The hydration product of MOC is unaltered by adding a water reducing agent and retarder, but admixtures change the crystal morphology and improve the water resistance. The immersion test shows that the improved crystal morphology is better for water resistance. The water reducing agent improves the fluidity of the slurry. The retarder effectively prolongs the hydration induction period, and postpones the acceleration period for approximately 2 h, but the mechanical strength of MOC is slightly reduced. The rotational viscosity test shows that admixtures are beneficial for improving the fluidity of MOC. 4 tabs, 15 figs, 33 refs.
Last Update: 2019-10-16