脱硫石膏—粉煤灰胶凝体系性能研究

发布时间：2018-09-01 06:18

【摘要】：脱硫石膏和粉煤灰是能够被广泛利用的工业废渣，脱硫石膏经煅烧可以制备建筑石膏，建筑石膏与粉煤灰复合可以制备一种新的胶凝体系，该胶凝体系既具有建筑石膏轻质、快硬、体积稳定的特点，又由于粉煤灰受硫酸盐激发后生成水硬性水化产物，而具有耐水、后期强度高的特点，但目前该复合胶凝材料体系尚无系统研究。本文对脱硫石膏-粉煤灰胶凝体系的浆体流动性、凝结时间、强度及耐久性进行了系统研究，并对不同外加剂（激发剂、减水剂、缓凝剂）以及玻璃纤维对脱硫石膏-粉煤灰复合胶凝体系性能的影响规律进行了探讨。在此基础上，研究了脱硫石膏-粉煤灰-水泥三元胶凝体系的特点，并通过XRD、SEM及水化热等测试，探讨了二元体系及三元体系的水化机理。主要研究内容及结果如下：首先，本文研究了脱硫石膏-粉煤灰胶凝体系的性能特点及水化机理：粉煤灰加入到脱硫石膏体系中，会提高胶凝体系的流动性能，延长凝结时间。减少胶凝体系的放热量。由于前期粉煤灰较少参与水化反应，粉煤灰的加入会降低胶凝体系的早期强度；不同类型的激发剂（石灰、碱、硫酸盐、硅酸盐、氯盐）对二元体系的强度有一定的激发作用。对二元体系最有效的复合激发剂为石灰、氯化钙和硫酸铝钾复掺；减水剂的掺入能提高胶凝体系的强度，增加流动性能。且萘系减水剂对二元体系强度提高效果好于聚羧酸减水剂，但聚羧酸减水剂对体系的流动性能增强效果更好；柠檬酸和三聚磷酸钠能够延缓该胶凝体系的凝结时间，柠檬酸对二元胶凝体系的凝结时间延缓效果更好，且凝结时间延缓的越多，对于强度的损失就越大。玻璃纤维的加入能够提高二元胶凝体系的抗折强度，但掺量过多后，会损害抗折强度。10mm玻璃纤维较20mm的玻璃纤维更适合此体系，且掺量为1%的10mm玻璃纤维能使胶凝体系的强度性能达到最优。其次，本文研究了脱硫石膏-粉煤灰-水泥胶凝体系的性能特点及水化机理：水泥加入到脱硫石膏-粉煤灰体系中，会提高胶凝体系的流动性能，缩短凝结时间，并提高胶凝体系的强度；不同类型的激发剂（石灰、碱、硫酸盐、硅酸盐、氯盐）对三元体系的强度有一定的激发作用。对三元胶凝体系激发效果最好的复合激发剂为石灰、氯化钙、硫酸钠复掺；减水剂的掺入能提高胶凝体系的强度，增加流动性能。且萘系减水剂对三元体系强度的提高效果好于聚羧酸高效减水剂，但聚羧酸高效减水剂对流动性增强效果更好；柠檬酸和三聚磷酸钠对胶凝体系的凝结时间有延缓作用。柠檬酸对三元胶凝体系的缓凝效果更好。与纯石膏胶凝体系相比，脱硫石膏-粉煤灰-水泥胶凝体系具有较好的耐水性，经过25次冻融循环后，三元胶凝体系试件的质量随着脱硫石膏掺量的增加而增大；在CO2浓度为75%的气体中，由于体系中OH-的匮乏，，此复合胶凝体系的碳化速度较快；由于石膏的微膨胀性，可抵消一部分水泥体系自身不可避免的收缩，因此，与纯水泥胶凝体系相比，三元胶凝体系体积变化率较小，体积稳定性较好。以上研究结果表明，脱硫石膏-粉煤灰二元胶凝体系和脱硫石膏-粉煤灰-水泥三元胶凝体系能在大量利用工业固体废弃物的同时，形成性能独特的复合胶凝体系，具有良好的应用价值。
[Abstract]:Desulfurization gypsum and fly ash are industrial waste residues that can be widely used. Desulfurization gypsum can be calcined to prepare building gypsum. A new cementing system can be prepared by compounding building gypsum and fly ash. The cementing system not only has the characteristics of light weight, fast hardening and stable volume of building gypsum, but also produces water after being stimulated by sulfate. In this paper, the fluidity, setting time, strength and durability of desulfurized gypsum-fly ash cementitious system are systematically studied, and different admixtures (activator, water reducer, retarder) and glass fiber are also studied. On the basis of this, the characteristics of desulfurized gypsum-fly ash-cement ternary cementitious system were studied. The hydration mechanism of binary system and ternary system was discussed by XRD, SEM and hydration heat test.
First of all, the performance characteristics and hydration mechanism of desulphurization gypsum fly ash cementitious system are studied.
Adding fly ash to the desulfurization gypsum system will improve the flowability of the cementitious system, prolong the setting time and reduce the heat release of the cementitious system. Lime, calcium chloride and potassium aluminium sulfate are the most effective compound activator for binary system, and the addition of water reducer can improve the strength and fluidity of binary system, and naphthalene water reducer can improve the strength of binary system better than Polycarboxylic Water reducer, but polycarboxylic water reducer can improve the body. Citric acid and sodium tripolyphosphate can delay the setting time of the binary cementitious system. Citric acid has a better effect on the setting time of binary cementitious system, and the more the setting time is delayed, the greater the loss of strength.
The addition of glass fiber can improve the flexural strength of binary cementitious system, but excessive dosage will damage the flexural strength. 10mm glass fiber is more suitable for this system than 20mm glass fiber, and the 10 mm glass fiber with 1% dosage can make the strength performance of the cementitious system reach the optimum.
Secondly, the performance characteristics and hydration mechanism of desulphurization gypsum fly ash cement cementing system are studied.
When cement is added to the desulfurized gypsum-fly ash system, the fluidity of the cementitious system will be improved, the setting time will be shortened, and the strength of the cementitious system will be enhanced. Different types of activators (lime, alkali, sulfate, silicate, chloride) have certain excitation effect on the strength of the ternary system. Lime, calcium chloride and sodium sulfate are used as hair additives, and the addition of water reducer can improve the strength and fluidity of the cementitious system. The setting time has a delayed effect. Citric acid has better retarding effect on the cementing system of three yuan.
Compared with the pure gypsum cementitious system, the desulfurized gypsum-fly ash-cement cementitious system has better water resistance. After 25 freeze-thaw cycles, the quality of the ternary cementitious system specimen increases with the increase of the dosage of desulfurized gypsum; in the gas with 75% CO2 concentration, the carbonization rate of the composite cementitious system is due to the lack of OH-in the system. Because of the expansion of gypsum, it can counteract the inevitable shrinkage of some cement systems, so the volume change rate of ternary cementitious system is smaller and the volume stability is better than that of pure cement cementitious system.
The results show that the desulfurized gypsum-fly ash binary cementitious system and the desulfurized gypsum-fly ash-cement ternary cementitious system can form a composite cementitious system with unique properties and have good application value.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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