【作者】 王鑫；

【导师】 关新春；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2021， 硕士

【摘要】 超高性能混凝土(UHPC)作为优良的修补材料大量用于修复加固工程,有力地保证了既有结构的安全性和耐久性。但是由于UHPC早期收缩大,与旧混凝土变形不协调,造成修补系统失效。为了更好地控制修补系统的可靠性,UHPC的早期收缩行为应该被提前预知。UHPC的早期收缩通常是胶凝材料水化、湿热以及应力耦合作用的结果。本研究借助已有的水化-湿-热-力耦合模型建立偏微分方程组,通过试验得到方程组所必要的参数,最终利用有限单元方法求解方程组,从而获得UHPC的早期收缩性能,达到预测的目的。本文开展的具体工作如下:(1)根据UHPC早期的水化反应—相对湿度—温度—应力间相互作用的特征,借助普通混凝土的水化-湿度-温度-力学耦合模型,建立了UHPC的耦合偏微分方程组。(2)进行了压汞测试分析,研究了不同龄期不同收缩能力UHPC早期的孔结构变化;进行了热重测试分析,研究了不同龄期不同收缩能力UHPC早期的水化反应程度;根据早龄期UHPC孔结构的演化和水化反应之间的对应关系,给出了求解耦合方程组所需的UHPC细孔隙体积分数与水化反应程度之间的函数关系;给出了不同收缩能力UHPC的细孔隙体积分数与水化反应程度的机理。(3)联合试验得到的函数关系以及所建立的耦合方程组,利用有限单元法求解了5种不同工况的耦合方程组,得到了相应工况UHPC的收缩性能。结果表明,在各种工况下,本文的多物理场耦合模型均能较好地预测早龄期UHPC的收缩性能;针对实际修复加固工程中常见的约束收缩,给出的基于损伤程度的评价方法具有一定的实际应用价值,可以用于预测修补工程中的修复加固材料的可靠度。更多还原

【Abstract】 Ultra-high performance concrete(UHPC)as an excellent repair material is widely used in repair and reinforcement projects,which effectively guarantees the safety and durability of the existing structure.However,due to the large early shrinkage of UHPC,it is incompatible with the deformation of the old concrete,causing the repair system to fail.In order to better control the reliability of the repair system,the early contraction behavior of UHPC should be predicted in advance.The early shrinkage of UHPC is usually the result of the coupling of hydration,damp heat and stress of the cementitious material.This study uses the existing chemical-moisture-heat-mechanical coupling model to establish partial differential equations,obtains the necessary parameters of the equations through experiments,and finally uses the finite element method to solve the equations,so as to obtain the early shrinkage performance of UHPC and achieve prediction the goal of.The specific work carried out in this paper is as follows:(1)According to the early UHPC hydration reaction-relative humiditytemperature-stress interaction characteristics,with the help of the temperaturehumidity-chemical reaction-mechanical coupling model of ordinary concrete,the UHPC coupled partial differential equations are established.(2)Conducted mercury intrusion test analysis to study the early pore structure changes of UHPC at different ages with different shrinkage capacity;conducted thermogravimetric test analysis to study the early hydration reaction degree of UHPC at different ages with different shrinkage capacity;The corresponding relationship between the evolution of the UHPC pore structure and the hydration reaction at ages,the functional relationship between the volume fraction of UHPC pores and the degree of hydration reaction required to solve the coupled equations is given;the UHPC with different shrinkage capacities The mechanism of the volume fraction of fine pores and the degree of hydration reaction.(3)The functional relations obtained in the joint test and the established coupling equations are solved by using the finite element method to solve the coupling equations of 5 different working conditions,and the shrinkage performance of the UHPC under the corresponding working conditions is obtained.The results show that under various working conditions,the multi-physics coupling model in this paper can better predict the shrinkage performance of UHPC at the early age;for the common constrained shrinkage in actual repair and reinforcement projects,an evaluation based on the degree of damage is given The method has certain practical application value and can be used to predict the reliability of repair and reinforcement materials in repair projects.更多还原