再生石膏性能变化及外加剂影响研究

发布时间：2018-02-22 20:47

本文关键词： 再生品位性能机理外加剂　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：石膏在我国应用广泛,但生产石膏的技术落后导致每年废弃的石膏堆积如山。废弃石膏经一系列工艺后成为再生石膏。对再生石膏的性能进行研究,找到性能变化的规律和内在原因,并对外加剂对再生石膏的影响进一步探讨,可以为废弃石膏再利用提供一定的理论依据,找到再生石膏性能下降的行之有效的解决办法,最终实现废弃石膏可循环利用。课题对不同品位、不同成分(天然和化学)石膏及其再生石膏性能变化的规律和机理,变化规律对比,聚羧酸减水剂、三聚磷酸钠和柠檬酸缓凝剂对原生和再生石膏的影响进行了一系列研究。研究表明,原生和再生半水石膏的标稠需水量和强度都是随着品位的降低而减小,再生石膏的性能下降与品位有关,强度降低幅度随品位的降低而增大,抗压强度降幅相比抗折更大。化学石膏下降幅度磷再生天然再生脱硫再生,磷再生石膏强度降幅约为其余二者的一半,这与磷石膏本身晶型差,强度不高,结构稳定有关。排除比表面积的影响,探究再生石膏性能下降的其它原因。再生半水石膏晶体粒径较小,以比表面积一致测平均粒径,对比平均粒径一致的情况下测得的比表面积,可知再生半水石膏颗粒粗糙,有很多缺陷。对原生石膏和再生石膏向其半水石膏转变做热分析和XRD分析,再生石膏的转变温度低于原生石膏,再生半水石膏的结晶度差。减水剂在小掺量(低于0.12%)下,随着减水剂掺量的增加,减水效果快速增加,再生石膏与原生石膏的强度增加幅度都在不断的变大,但原生石膏要小于再生石膏的强度增加幅度。当达到0.12%以后,减水效果虽继续增加但趋于平缓。聚羧酸减水剂掺量为0.12%时,原生石膏结晶最多,晶体颗粒数目多,颗粒搭接最为密集。在再生半水石膏中直接掺加聚羧酸减水剂时,形成的硬化体与原生掺减水剂相比,棒状颗粒明显增加,几乎排列在一起,棒状晶粒有团聚趋势,呈簇状,几乎没有孔隙。原生半水石膏掺加减水剂后,经工艺处理,再生石膏中减水剂成分未发生脱附,减水效果仍然存在。原生石膏中加入三聚磷酸钠后,标稠需水量有略微升高,凝结时间随掺量的增加而显著地延长,强度则是先升高后降低,且升高的幅度不大,再生石膏的性能变化与之相反。三聚磷酸钠掺量对石膏凝结时间和早期强度的影响有一个临界值0.10%。原生石膏晶体多为柱状和长棒状,掺加三聚磷酸钠缓凝剂后再生石膏多为短棒状。柠檬酸缓凝效果比三聚磷酸钠要好。
[Abstract]:Gypsum is widely used in our country, but the backwardness of gypsum production technology leads to the accumulation of waste gypsum every year. Waste gypsum becomes regenerated gypsum after a series of processes. The performance of regenerative gypsum is studied. Finding out the law and internal cause of performance change, and further discussing the influence of admixture on regenerative gypsum, can provide certain theoretical basis for the reuse of abandoned gypsum, and find an effective solution to the deterioration of reproducing gypsum performance. Finally, the waste gypsum can be recycled. The subject of different grade, different composition (natural and chemical) gypsum and its reclaimed gypsum performance change law and mechanism, change law contrast, polycarboxylic acid water reducer, The effects of sodium tripolyphosphate and citric acid retarder on primary and regenerated gypsum were studied. The decline of the properties of regenerated gypsum is related to its grade. The decreasing range of strength increases with the decrease of grade, and the decrease of compressive strength is greater than that of flexural strength. The decrease of the strength of phospho-regenerated gypsum is about half of that of the other two, which is related to the poor crystal form, low strength and stable structure of phosphogypsum, excluding the influence of specific surface area. Other reasons for the deterioration of the properties of regenerated gypsum are explored. The average particle size of regenerated gypsum crystal is smaller, the average particle size is measured consistently with the specific surface area, and the specific surface area measured under the condition of the same average particle size shows that the regenerated hemihydrate gypsum particle is rough. There are many defects. Thermal analysis and XRD analysis of the conversion from original gypsum and regenerated gypsum to its hemihydrate gypsum show that the transition temperature of regenerated gypsum is lower than that of original gypsum, and the crystallinity of regenerated hemihydrate gypsum is poor. With the increase of the amount of water reducing agent, the water reducing effect increases rapidly, and the strength of regenerated gypsum and original gypsum increase continuously, but the strength of original gypsum is smaller than that of regenerated gypsum. After 0.12%, When the amount of polycarboxylic acid superplasticizer is 0.12, the primary gypsum crystallizes the most, the number of crystal particles is large, and the particles overlap most intensively. When the polycarboxylic acid water reducer is added directly into the regenerated semi-hydrate gypsum, the polycarboxylic acid superplasticizer is added directly into the regenerated semi-hydrate gypsum. Compared with the original superplasticizer, the hardened body formed is obviously increased and almost arranged together. The rod-shaped grain has the tendency of agglomeration, and has almost no pores. After the addition of water reducer, the primary hemihydrate gypsum is treated by the process. After adding sodium tripolyphosphate into the original gypsum, the standard thickening water requirement increased slightly, and the setting time was significantly prolonged with the increase of the amount of water added. The strength was increased first and then decreased, and the increase was not significant. The effect of sodium tripolyphosphate on the setting time and early strength of gypsum has a critical value of 0.10. After adding sodium tripolyphosphate retarder, gypsum is mostly short rod. Citric acid retarding effect is better than sodium tripolyphosphate.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ177.3

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