预拌混凝土早期裂缝分级控制体系研究

发布时间：2018-05-28 12:52

本文选题：混凝土早期抗裂 + 分级控制　；参考：《兰州理工大学》2017年硕士论文

【摘要】：混凝土结构构件一般来说都是带裂缝工作的,没有不裂的混凝土,但有时由于建筑物的重要性等级和外部环境的需要,要求配制出对早期裂缝要求相对严格的抗裂混凝土;根据裂缝控制的严格程度,对抗裂混凝土实现分级,配制出不同抗裂等级的预拌混凝土,有利于对预拌混凝土实现“优质优价”,在理清现场混凝土开裂责任的同时,达到利益的最大化,同时也为施工企业节约了成本。住建部在2014年10月1日实施的行业标准JGJ/T317—2014《建筑工程裂缝防治技术规程》对预拌混凝土的抗裂性能进行了分级,其共分为五个等级,但其在应用过程中存在一些不足,针对其不足之处,本课题组尝试性的提出了新的预拌混凝土早期抗裂分级标准,在克服2014版抗裂分级标准不足之处的同时,利于新的预拌混凝土抗裂分级标准在现场工程中得到推广应用。为了更好的对预拌混凝土早期裂缝分级控制体系进行研究,本文做了如下的工作:1.通过对预拌混凝土早期裂缝控制措施的研究以及实际工程的调研,提出了预拌混凝土早期裂缝分级控制体系的概念。2.研究了水胶比、粉煤灰掺量、纤维等因素对预拌混凝土早期开裂性能的影响。试验结果表明:随着水胶比的增大,混凝土早期开裂指标逐渐变小;混凝土抗开裂性能与粉煤灰的掺量有关,两者呈非线性关系;纤维的掺入能有效抑制混凝土的早期开裂,层布式混杂纤维混凝土的抗裂效果优于整体式和单掺纤维混凝土。3.通过对各因素影响预拌混凝土早期开裂的试验结果的分析,得到了分级抗裂体系下各因素分级抗裂临界控制点的参数指标。4.在分级抗裂体系下,综合考虑现场环境情况,在现场进行平板试验。针对不同抗裂等级的混凝土,观察平板试件与混凝土构件随着龄期增长的裂缝开展情况,得到了分级抗裂体系下各级抗裂混凝土构件与平板试件早期开裂情况之间的对应关系,验证了现场条件下实施预拌混凝土抗裂分级的可行性,为后续通过现场混凝土构件的裂缝开展情况判断预拌混凝土抗裂等级提供基础支撑。5.通过对现场试验结果的分析和工程各阶段相关措施的总结,提出了适用于工程现场的预拌混凝土早期裂缝分级控制对策。
[Abstract]:Generally speaking, concrete structural members work with cracks, and there is no crack concrete, but sometimes due to the importance of the building and the need of the external environment, it is necessary to prepare crack resistant concrete which requires relatively strict requirements for early cracks. According to the strict degree of crack control, the anti-crack concrete is classified, and the ready-mixed concrete with different crack resistance grades is prepared, which is beneficial to the realization of "high quality and high price" for ready-mixed concrete, and at the same time clarifies the cracking responsibility of on-site concrete. To maximize the benefits, but also for the construction enterprises to save costs. The Industrial Standard JGJ/T317-2014 of Building Engineering crack Prevention and Control Technical Specification, which was implemented by the Ministry of Housing and Construction on October 1, 2014, classifies the crack resistance of ready-mixed concrete into five grades, but there are some deficiencies in its application. In view of its shortcomings, our group has proposed a new early crack resistance classification standard for ready-mixed concrete, which overcomes the shortcomings of the 2014 edition anti-crack classification standard. It is beneficial to popularize and apply the new anti-crack classification standard of pre-mixed concrete in field engineering. In order to better study the early crack grading control system of ready-mixed concrete, this paper has done the following work: 1. Based on the research of early crack control measures and practical engineering of ready-mixed concrete, the concept of grading control system for early crack of ready-mixed concrete is put forward. The effects of water binder ratio, fly ash content and fiber on early cracking performance of ready-mixed concrete were studied. The experimental results show that with the increase of water-binder ratio, the early cracking index of concrete becomes smaller, the anti-cracking performance of concrete is related to the content of fly ash, the relationship between them is nonlinear, and the addition of fiber can effectively restrain the early cracking of concrete. The crack resistance of layered hybrid fiber reinforced concrete is better than that of monolithic and single-doped fiber reinforced concrete. Based on the analysis of the experimental results of various factors affecting the early cracking of ready-mixed concrete, the parameter index of critical control point of graded crack resistance of each factor is obtained. The flat-plate test was carried out in the field considering the field environment under the graded anti-cracking system. For the concrete with different crack resistance grades, the crack development of slab specimens and concrete members with increasing age is observed, and the corresponding relationship between the early cracking of concrete members and slab specimens is obtained under the graded crack resistance system. The feasibility of anti-crack classification of ready-mixed concrete under field conditions is verified, which provides foundation support for judging crack development of ready-mixed concrete through crack development of in-situ concrete members. Based on the analysis of the results of field tests and the summary of relevant measures in various stages of engineering, the countermeasures for early crack classification control of ready-mixed concrete are put forward.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528.52

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