微生物修复水泥基材料早期裂缝研究

发布时间：2018-03-20 02:17

  本文选题：水泥基材料　切入点：微生物　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：混凝土材料是当今世界上用途最广、用量最大的建筑材料之一。但是混凝土材料脆性大,易开裂,在其服役的过程中遭受外界介质侵蚀,致使混凝土材料的性能不断降低,对建筑物的耐久性造成严重的危害。因此,混凝土裂缝修复技术引起研究界广泛关注。本文围绕微生物诱导矿化修复水泥基材料裂缝这一中心问题,采用一种新型微生物,利用全新修复机理,实现对水泥基材料早期裂缝的修复,并通过数值模拟和试验结合的方式,揭示微生物诱导矿化修复早期裂缝的机理。通过对高碱环境中微生物生长特性、存活率以及酶化活性的研究结果表明,微生物能够在短时间内存活于高碱环境,在pH值为10左右的水泥基材料裂缝水溶液中仍具有较好的酶化活性；修复剂掺量的增加会影响水泥基材料性能,造成流动性下降,水泥凝结时间延迟,强度损失等,但在合适的掺量范围内不会对水泥基材料性能造成明显影响：在钙盐溶液中,微生物能够高效诱导CaCO3沉积,这是诱导矿化修复裂缝的关键,对早期宽度小于0.3mm的小裂缝修复效果显著,证明了微生物修复早期水泥基材料裂缝的可行性。进一步研究不同影响因素下裂缝修复效果表明,裂缝修复效果随裂缝宽度增大呈下降趋势,在一定范围内,裂缝修复效果并不随修复剂用量增加而无限提高,对于宽度在0.3mm以下小裂缝而言,较低的修复剂用量即可获得较好的修复效果,对于大裂缝而言(宽度1.0mm左右),即使增加修复剂用量也无法达到较高修复水平。低温环境(低于10℃)不利于裂缝修复,30℃左右温度可获得最佳修复效果。采用土工布覆盖洒水湿养护无法实现裂缝修复,但试验证明了干湿循环或泡水养护可以获得较好的修复效果。修复剂对后期(60d)产生的裂缝修复效果不佳,可通过载体固载细菌的方式来提高后期修复率。基于CO_2在混凝土中扩散传输理论和Ca~(2+)溶蚀理论可揭示微生物诱导矿化修复水泥基材料早期裂缝机理。通过计算模拟CO_2在裂缝中浓度分布,并引入微生物吸收转化CO_2过程,揭示矿化沉积修复的演化过程。通过Ca~(2+)溶出试验研究水泥基材料内部Ca~(2+)向裂缝中的迁移,确定了不同宽度裂缝Ca~(2+)最大溶出深度和修复剂中Ca~(2+)溶出率,提出有效Ca~(2+)概念,基于有效Ca~(2+)概念对不同宽度裂缝下CaCO3沉积深度进行了预测,并通过试验验证了预测结果的准确性,最终解释了裂缝修复只能发生在表层的原因。
[Abstract]:Concrete material is one of the most widely used and used building materials in the world nowadays. However, the concrete material is brittle and cracking, and is eroded by external media in the course of its service, which causes the performance of concrete material to decrease continuously. Therefore, the repair technology of concrete cracks has attracted wide attention in the field of research. In this paper, a new type of microorganism is adopted to repair the cracks in cement based materials. Using the new repair mechanism, the early crack repair of cement based materials is realized, and the mechanism of microorganism induced mineralization to repair the early crack is revealed by numerical simulation and experiment. The growth characteristics of microorganism in high alkali environment are studied. The results of survival rate and enzymatic activity showed that microorganism could survive in high alkali environment in a short time, and still had good enzymatic activity in cracked aqueous solution of cement based material with pH value of about 10. The increase of the amount of repair agent will affect the properties of cement-based materials, such as the decrease of fluidity, the delay of cement setting time, the loss of strength, etc., but it will not have a significant effect on the properties of cement-based materials within the appropriate dosage: in calcium salt solution, Microbes can efficiently induce CaCO3 deposition, which is the key to induce mineralization and repair cracks, and has remarkable effect on small cracks whose width is less than 0.3 mm in early stage. It is proved that it is feasible to repair the cracks of early cement based materials by microorganism. Further study on the effect of repairing cracks under different influence factors shows that the effect of repairing cracks tends to decrease with the increase of crack width, and in a certain range, The effect of crack repair is not infinitely improved with the increase of the amount of repair agent. For the small crack with width below 0.3 mm, the lower amount of the repair agent can obtain a better repair effect. For large cracks (width of about 1.0 mm), even if the amount of repair agent is increased, it can not reach a higher level. Low temperature (less than 10 鈩，

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