【作者】 刘畅； 王振波； 韩宇栋； 左建平； 张子山；

【Author】 Liu Chang;Wang Zhenbo;Han Yudong;Zuo Jianping;Zhang Zishan;School of Mechanics and Civil Engineering,China University of Mining and Technology;Central Research Institute of Building and Construction,MCC Group Co.,Ltd.;

【机构】 中国矿业大学(北京)力学与建筑工程学院； 中冶建筑研究总院有限公司；

【摘要】 我国海洋工程基础设施建设已进入飞速发展时期,混凝土材料被越来越多的应用到桥梁、海底隧道、海上油气钻采平台等海工结构。海工混凝土服役过程中不仅遭受化学腐蚀,在潮汐区、浪溅区还将经历干湿交替的加速劣化。传统混凝土性脆易裂,缝宽不可控,这极大地限制了海洋工程结构的服役寿命。高延性水泥基材料(ECC)因其超高的拉伸延性及突出的缝宽控制功能而被看作是提升海工结构耐久性的潜力材料。作为实际情况的模拟,干湿循环硫酸盐侵蚀环境下ECC的力学破坏测试是最具代表性的耐久性研究手段之一,但仅仅依靠力学实验难以有效追踪材料内部性态的变化规律。作为一种新型的无损检测手段,超声波法可以用于材料强度的检测,并对材料内部缺陷进行动态表征。本文采用超声脉冲技术,同步实施单轴压缩试验,分析了侵蚀实验中ECC的脉冲时域参数及其与力学性能的相关性。结果表明:在侵蚀早期,ECC的初始横、纵波波速变化幅度较小,侵蚀至第8周期(120d)时波速突降,相较于侵蚀实验前横、纵波速均降低75%左右,并且初始波速与弹性模量的发展趋势类似;随着侵蚀龄期延长,ECC横、纵波幅值发展趋势均为先增大后减小,材料抗压强度呈现出类似的变化规律,同时在第6周期(90d)达到峰值,相较于侵蚀前,横、纵波振幅提高约90%,峰值强度提高约45%,超声脉冲幅值与峰值强度之间存在明显的正相关性。比较实验中横、纵波的时域参数,发现综合利用横波波速和纵波幅值可有效推定ECC的内部结构演化过程,揭示干湿循环硫酸盐侵蚀ECC的受力破坏机制。更多还原

【Abstract】 As the rapid development of marine engineering infrastructure in our country,concrete is increasingly used in bridges,undersea tunnels,offshore oil and gas drilling platforms and other marine structures.In tidal and wave splash areas,marine concrete is exposed to not only chemical erosion but also the accelerated deterioration of drying-wetting cycles.However,traditional concrete is easy to crack and its width is not controllable,which greatly limits the service life of marine engineering.Engineered Cementitious Composites(ECC) is considered promising material for improving the durability of marine structures due to its ultra-high tensile ductility and prominent crack width control functions.As a simulation of the real condition,mechanical test of ECC under sulfate attack in drying-wetting cycle serves as a typical method to evaluate its durability,but it is difficult to effectively detect the variation of internal damage based on mechanical experiments alone.Ultrasonic pulse technology can be used not only to the measure of material strength,but also to characterize its internal defect. In this paper,the time domain parameters of ECC and their correlation with mechanical properties are investigated by ultrasonic pulse and uniaxial compression test.The results show that at the early stage of erosion,the initial P wave velocity and S wave velocity of ECC keep almost unchanged.However,the wave velocities suddenly drop in the eighth cycle(120 d),resulting in a75% lower value than that prior to erosion.It is noted that the initial wave velocity is closely related to the Young’s modulus.As the erosion age extends,the amplitude of P wave and S wave both increase and then decrease,and the compressive strength of ECC shows a similar developing trend,arriving at the peak value at the sixth cycle(90 d)simultaneously.Compared with P wave and S wave prior to erosion,the amplitude increased by about 90%,and the peak strength increased by about 45%.It can be concluded that there is a good positive correlation between ultrasonic pulse amplitude and compressive strength.The combination of S wave velocity and P wave amplitude can effectively identify the dynamic evolution of internal structure of ECC and disclose the failure mechanism of ECC under sulfate attack in drying-wetting cycles.更多还原