基于毛细管负压理论的纤维混凝土早期水平收缩试验  

Experiment on Early Horizontal Shrinkage of Fiber Reinforced Concrete Based on Negative Capillary Pressure Theory

作　　者：何化南[1] 代向阳 HE Hua-nan;DAI Xiang-yang(State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology,Dalian 116024,Liaoning,China)

机构地区：[1]大连理工大学海岸和近海工程国家重点实验室,辽宁大连116024

出　　处：《建筑科学与工程学报》2020年第3期73-80,共8页Journal of Architecture and Civil Engineering

基　　金：国家重点基础研究发展计划(“九七三”计划)项目(2015CB057703)。

摘　　要：为了研究聚丙烯纤维不同参数对混凝土早期水平收缩的影响,基于毛细管负压理论,进行了水平收缩试验。分别采用水势张力计及万用表测试了混凝土内部早期毛细管负压及电阻的发展,得到了混凝土早期毛细管负压及电阻发展的全过程曲线,将毛细管负压和电阻发展曲线结合在一起,得到混凝土早期毛细管负压的空气进入值Paev,并探索了纤维不同参数与Paev之间的关系,给出了综合考虑纤维体积率和纤维长度的参数G与Paev之间关系的表达式;另外,利用高精度激光位移传感器测试了混凝土早期的水平收缩变形发展过程。结果表明:聚丙烯纤维加入混凝土后有效地减缓了混凝土内部早期毛细管负压的发展速率,并显著降低了毛细管负压的极限值,从而抑制了混凝土早期的水平收缩变形,同时提高了混凝土早期毛细管负压的Paev值,即提高了混凝土早期的抗裂强度;当纤维体积率为0.1%,纤维长度为18 mm时,混凝土早期毛细管负压的空气进入值Paev达到41.1 kPa,抵抗局部开裂的能力最强,同时早期水平收缩变形得到较好地抑制,水平收缩最大值相比素混凝土降低72.6%。In order to research the influences of different parameters of polypropylene fiber on early stage horizontal shrinkage of concrete, based on negative capillary pressure theory, the horizontal shrinkage tests were carried out. The developments of both negative capillary pressure and electric resistance in the early stage of concrete were measured by water potential tensiometer as well as multimeter respectively, and the whole process curve of the development of negative capillary pressure and electric resistance in the early stage of concrete was obtained. By combining the development curves of negative capillary pressure and electric resistance, the air-entry value Paev of negative capillary pressure was obtained. Meanwhile, the relationship between different parameters of polypropylene fiber and Paev was discussed and a comprehensive formula to express the relationship between parameter G and Paev was given. Parameter G synthesized fiber volume fraction and fiber length and Paev. In addition, the development process of early horizontal shrinkage deformation of concrete was tested by high-precision laser displacement sensor. The results show that the adding of polypropylene fiber into concrete can effectively slow down the early development rate of negative capillary pressure in concrete and significantly reduce the limit value of negative capillary pressure, thereby inhibiting the early horizontal shrinkage deformation of concrete. Meanwhile, the Paev value of negative capillary pressure in the early stage of concrete is increased, which improves the early cracking resistance strength of concrete. When the fiver volume fraction is 0.1% and the fiber length is 18 mm, the Paev value of the negative capillary pressure of the concrete reaches 41.1 kPa, which has the strongest early resistance to local cracking of concrete. At the same time, the early horizontal shrinkage deformation of concrete is well controlled, and the maximum horizontal shrinkage is 72.6% lower than that of plain concrete.

关 键 词：纤维混凝土 空气进入值 早期水平收缩 毛细管负压理论 激光测距 局部开裂 

分 类 号：TU528.572[建筑科学—建筑技术科学]