混凝土振动搅拌机理和工业应用研究

发布时间：2018-07-31 08:28

【摘要】：目前，原材料级配、性能及新拌混凝土成型等是国内外有关混凝土研究的焦点，而搅拌过程却往往被忽视和研究不够。究其原因，主要是因为搅拌过程涉及多学科交叉领域，如搅拌设备、施工材料和生产工艺等，认知起来比较困难，研究过程中易相互脱节。所以，相关研究至今仍停留在宏观尺度上。致使混凝土微观匀质性较差，界面粘结强度较低；搅拌工作装置的线速度较低，搅拌时间长；搅拌过程存在速度梯度和搅拌低效区等现象长期得不到根本解决。本文提出利用振动与普通静力搅拌相结合的新方法，利用动力学原理设计振动器，置于圆形拌筒的中心，振动器埋在混合料中，振动能量直接被混合料吸收。在两种方式共同作用下，混凝土微观结构和力学性能得以改善，搅拌设备综合性能得以提升。论文首先分析了新拌混凝土结构-流变特性，为确定振动搅拌设备工作机构的几何、运动参数提供理论依据，指出各参数的选取需以保证搅拌筒内混合料结构的完全破坏为目标；进一步分析了混凝土搅拌过程及目前普遍采用的普通静力搅拌所存在的不足。分六大方面，论文重点对混凝土振动搅拌方式改善搅拌过程及混凝土性能的机理进行了详细阐述，包括：振动搅拌对混凝土结构-流变特性的影响机理；振动搅拌对新拌混凝土中水泥团粒的破坏机理；振动搅拌对新拌混凝土中粗骨料表面的净化及其粘结强度的增强机理；振动搅拌对新拌混凝土中气相生成物的影响机理；振动搅拌对搅拌过程—低效区的改善机理；振动搅拌对多材料的适应性机理。理论分析认为，振动搅拌可综合提高搅拌设备及混凝土各项性能。在理论分析的基础上，设计了两台试验样机：振动与静力搅拌相结合，但振动与搅拌工作装置分离的立轴式振动搅拌机，以及振动与静力搅拌工作装置相结合的一体式双卧轴振动搅拌机；进行了振动搅拌对普通混凝土、RCC、SFRC、CA砂浆等材料的适应性试验研究。初步得出了振动搅拌各参数的合理取值及匹配关系，为振动搅拌设备的工业化提供依据。试验结果表明：振动搅拌对多材料具有较好的适应性，，各项性能指标均优于普通静力搅拌；立轴振动搅拌更适宜于骨料颗粒普遍较小的CA砂浆等材料的搅拌，双卧轴振动搅拌更适宜于较大粒径骨料的混凝土搅拌。在理论分析和大量试验研究的基础上，针对现行搅拌设备评定指标体系的不合理性进行了试验证明和分析，并对修改现行搅拌设备评定指标提出了若干建议，给出在不同场合下需要增加的检验指标，旨在完善现行搅拌设备评定指标体系。将理论及试验研究成果与工业实际相结合，试制了1m3双卧轴振动搅拌工业样机，并进行了工业化研究。研究表明：工业样机工作过程稳定可靠，各项指标满足国标要求，能耗较低，搅拌时间为45s；其他条件相同的情况下，工业样机生产的混凝土比普通静力搅拌机生产的混凝土强度提高15%以上，且新拌混凝土匀质性更好；工业样机在减少水泥15%时，混凝土性能仍满足设计要求，节约水泥效果明显。本课题研究受到国家自然科学基金项目“混凝土振动拌和机理研究”（50678026）、陕西省重大科技创新专项资金项目“高效混凝土搅拌机的工业化研究”（2008ZKC01-16）资助。
[Abstract]:At present, the grading of raw materials, properties and the molding of fresh concrete are the focus of concrete research at home and abroad, and the stirring process is often ignored and not enough. The main reason is that the agitation process involves multi disciplinary cross fields, such as mixing equipment, construction material and production technology, which are difficult to understand and have been studied. Cheng Zhongyi is separated from each other. Therefore, the related research still remains on the macro scale. It causes the poor micro uniformity of the concrete, the low interfacial bonding strength, the low line speed of the stirring device, the long agitation time, the existence of the velocity gradient and the low efficiency agitator in the agitation process for a long time. A new method of combining vibration with static static mixing is used to design the vibrator by the principle of dynamics. The vibrator is placed in the center of the circular cylinder. The vibrator is buried in the mixture. The vibration energy is absorbed directly by the mixture. Under the joint action of the two ways, the microstructure and mechanical properties of the concrete can be improved and the comprehensive performance of the mixing equipment can be improved.
The paper first analyzes the structure and rheological properties of new mixed concrete, and provides a theoretical basis for determining the geometry and motion parameters of the working mechanism of vibratory mixing equipment, and points out that the selection of the parameters should be aimed at ensuring the complete destruction of the mixture structure in the mixing cylinder. There is a shortage of force stirring.
In six major aspects, the paper focuses on the mechanism of concrete vibration mixing to improve the mixing process and the concrete performance, including the mechanism of vibration agitation on the concrete structure and rheological properties, the destruction mechanism of the cement pellets in the fresh concrete by vibration stirring; the vibration agitation on the coarse bone in the fresh concrete The mechanism of the purification of the material surface and the strengthening of the bond strength; the mechanism of the influence of vibration agitation on the gas phase in the fresh concrete; the improvement mechanism of the stirring process - the low efficiency zone; the adaptability mechanism of the vibration agitation to the multi materials. The theoretical analysis shows that the vibration agitation can improve the various properties of the mixing equipment and the concrete. Yes.
On the basis of theoretical analysis, two test prototype is designed, which combines vibration and static mixing, a vertical vibration mixer which is separated from vibration and stirring device, as well as a one type double lying shaft vibrating mixer which combines vibration and static stirring device. The vibration agitator is used for ordinary concrete, RCC, SFRC, CA mortar. The reasonable value and matching relation of various parameters of vibration agitation are preliminarily obtained. It provides a basis for the industrialization of vibration stirring equipment. The experimental results show that vibration agitation has good adaptability to multi materials, and all performance indexes are superior to ordinary static stirring; vertical shaft vibration agitation is more suitable for bone. The stirring of materials such as CA mortar with smaller particle size is more suitable for concrete with larger particle size.
On the basis of theoretical analysis and a large number of experimental studies, this paper proves and analyzes the irrationality of the current agitator evaluation index system, and puts forward some suggestions to modify the evaluation index of the current mixing equipment, and gives the test index which needs to be increased in different situations, aiming at improving the current evaluation index body of the mixing equipment. Department.
Combining the theoretical and experimental research results with the industrial practice, the industrial prototype of 1m3 double lying shaft vibrating agitation is tried and manufactured. The research shows that the working process of the industrial prototype is stable and reliable, the indexes meet the requirements of the national standard, the energy consumption is low, the mixing time is 45s, and the industrial prototype is produced under the same conditions. The concrete strength of concrete produced by concrete is 15% higher than that of ordinary static mixer, and the homogenization of new concrete is better. The performance of concrete is still satisfied with the design requirement and the effect of cement saving is obvious when the industrial prototype can reduce the cement 15%.
The research is funded by the National Natural Science Fund Project "Research on the mixing mechanism of concrete vibration" (50678026) and the capital project of the major scientific and technological innovation of Shaanxi Province, "the industrialization of high efficiency concrete mixer" (2008ZKC01-16).
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU642;TU528.062

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