【作者】 吴伟明；

【导师】 吴胜兴；

【作者基本信息】 河海大学 ， 结构工程， 2006， 硕士

【摘要】 现代混凝土结构中,泵送混凝土被大量使用。泵送混凝土使得施工输送混凝土能力大、速度快、效率高、缩短工期、降低费用,同时减轻工人的劳动强度。但是,泵送混凝土的特点也导致了工程出现一些问题,比如现浇楼板裂缝,已经成为常见的质量通病。 作为江苏省“六大人才高峰”资助项目(A类)“现代混凝土裂缝机理及成套控制技术”的一个子课题,本文运用圆环约束法试验装置,结合泵送混凝土的基本性能测试,分析泵送混凝土早期开裂性能。首先,测试龄期分别为1、2、3、5、7、14天的泵送混凝土抗拉强度、弹性模量,并用Origin7.5数据拟合软件进行分析,用公式表达混凝土抗拉强度、弹性模量随龄期发展曲线;弹性模量测试方法包括压力机测试和超声波测试,本文也分析了两种方法得到的试验结果之间的区别和联系。同时,模拟混凝土圆环中的混凝土干燥情况,测试泵送混凝土早期自由收缩,并用Origin7.5数据拟合软件拟合收缩随龄期变化曲线,得出泵送混凝土收缩随龄期发展公式。其次,运用圆环约束法试验装置,通过观测约束钢环内表面应变变化,衡量泵送混凝土约束收缩性能。最后,运用弹性力学方法,对混凝土约束收缩试验装置进行理论分析,计算泵送混凝土环中理论应力和实际应力的发展,并结合泵送混凝土的抗拉强度试验,评价泵送混凝土的约束收缩开裂可能性,以及泵送混凝土的应力松弛性能,实现泵送混凝土的早期开裂性能评价。 改变泵送混凝土的泵送剂掺量、单方混凝土用水量、水泥用量,本文设计了8个配合比的泵送混凝土,研究泵送剂掺量、用水量、水泥用量对泵送混凝土早期开裂性能的影响。研究发现:相对于基准混凝土,泵送剂掺量、用水量、水泥用量的改变,都会影响泵送混凝土的早期开裂性能。因此,选择合适的泵送剂掺量、用水量、水泥用量,可以有效控制泵送混凝土早期开裂。更多还原

【Abstract】 Pumping concrete is very popular in the construction of modern concrete structures, it makes the construction more rapidly and more efficiently, and it can alleviate the labor intensity of the workers. Hoeever, pumping concrete brings on many problems to the projects, such as the early age cracking of cast-in-place floor, which has already become the common quality fault.By testing concrete with ring specimens and other tests for mechanical properties of pumping concrete, this paper analyzed early age cracking properties of pumping concrete.Firstly, the pumping concrete were tested at 1, 2, 3, 5, 7, and 14 days after casting to determine the splitting tensile strength and elastic modulus, and the data were analyzed using the software Origin 7.5. The relation between tensile strength and age of the concrete was described using formula gained from the analysis with Origin 7.5. At the same time, the pumping concrete specimens in the similar drying condition as the ring specimens were tested for early age free shrinkage. The data of shrinkage were analyzed by software Origin 7.5, and the relation between shrinkage and age was described in the form of a formula. Then, ring tests were used in this paper to measure the inside surface strain of the steel ring. At last, the test setting was theoretically analyzed by mechanics of elasticity, and the theoretical stress and actual stress of ring specimens were calculated. In combination with the test of tensile strength, evaluation on cracking potential and stress relaxation of ring specimens was made. With all the above, the evaluation on cracking characteristics of pumping concrete at early age is realized.Concrete specimens with different constituent materials were tested in this paper. Test result indicated that the quantity of pumping agent, water, and cement used in concrete influenced the cracking properties of pumping concrete. The quantity of pumping agent, water, and cement should be properly chosen in construction.更多还原