| 海水海砂混凝土无尺寸效应拉伸强度与断裂韧度的确定 |
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| 引用本文： | 于淼,杨树桐,袁源,杨松.海水海砂混凝土无尺寸效应拉伸强度与断裂韧度的确定[J].哈尔滨工业大学学报,2023,55(10):82-92. |
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| 作者姓名： | 于淼 杨树桐 袁源 杨松 |
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| 作者单位： | 中国海洋大学 工程学院,山东 青岛 266100;中国海洋大学 工程学院,山东 青岛 266100 ;青岛理工大学 蓝色经济区工程建设与安全协同创新中心,山东 青岛 266033 |
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| 基金项目： | 国家自然科学基金(51778591) |
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| 摘 要： | 海水海砂混凝土（seawater sea sand,SSC）在岛礁和临海工程建设中有广阔的应用空间。海洋环境下,混凝土容易开裂,严重影响结构耐久性。为确保该新型混凝土在海洋环境下的安全服役,对SSC的断裂力学性能研究以及断裂参数的合理确定至关重要。然而采用传统方法,基于线弹性断裂理论确定的断裂参数,由于未考虑材料非均匀性的影响,不可避免存在尺寸效应。鉴于此,本文利用基于边界效应的非线性断裂理论,考虑材料的非连续性与非均匀性,确定SSC的真实断裂参数。配制最大骨料粒径dmax为10和20 mm的海水海砂混凝土,分别进行高度为100和200 mm的三点弯曲梁试验,初始缝高比为0.1~0.7；并用淡水、河砂等质量替代海水、海砂配制普通混凝土（ordinary Portland cement,OPC）作为对照组进行试验。基于边界效应模型,通过引入混凝土平均骨料粒径,得到了SSC的真实无尺寸效应拉伸强度ft及断裂韧度KIC,进而结合正态分布分析确定两断裂参数的均值以及具有95%保证率的上下限值,并利用得到的拉伸强度成功预测任意尺寸条件下SSC试件的极限荷载。结果表明:相同骨料级配下,与普通混凝土相比,海水海砂混凝土断裂截面上骨料断裂的比例更高,SSC的拉伸强度及断裂韧度高于OPC；随着最大骨料粒径的增大,SSC和OPC骨料断裂的比例均减小,其断裂韧度KIC均增加,ft降低。所提模型及相关结果可为海水海砂混凝土实际工程设计提供参考。
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| 关 键 词： | 海水海砂混凝土 边界效应 非线性断裂力学 断裂韧度 拉伸强度 |
| 收稿时间： | 2022/7/2 0:00:00 |
Determination of size-independent tensile strength and fracture toughness of seawater sea sand concrete |
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| YU Miao,YANG Shutong,YUAN Yuan,YANG Song.Determination of size-independent tensile strength and fracture toughness of seawater sea sand concrete[J].Journal of Harbin Institute of Technology,2023,55(10):82-92. |
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| Authors: | YU Miao YANG Shutong YUAN Yuan YANG Song |
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| Affiliation: | College of Engineering, Ocean University of China, Qingdao 266100, Shandong, China;College of Engineering, Ocean University of China, Qingdao 266100, Shandong, China ;Cooperative Innovation Center of Engineering Construction and Safety in Shandong Blue Economic Zone, Qingdao University of Technology, Qingdao 266033, Shandong, China |
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| Abstract: | Seawater sea sand concrete (SSC) has a wide range of applications in the construction of islands and coastal projects. In marine environments, concrete is prone to cracking, which can significantly affect the durability of structures. In order to ensure the safe service of this new type of concrete in the marine environment, it is crucial to study the fracture mechanical properties of SSC and to determine the fracture parameters reasonably. However, the size effect is inevitably present due to the neglect of material inhomogeneity when using the determined fracture parameters based on traditional linear elastic fracture model. To address this issue, this article aims to determine the size-independent fracture parameters of SSC, utilizing a non-linear fracture theory based on boundary effect model, taking into account the material discontinuity and heterogeneity. In this paper, SSC with the maximum aggregate sizes of 10 and 20 mm were prepared. Three-point bending tests of with heights of 100 and 200 mm were carried out respectively, and the initial crack length-to-beam depth ratios were set from 0.1 to 0.7 in each group. Additionally, fresh water and river sand were used to replace seawater and sea sand in order to prepare ordinary Portland concrete (OPC) as the control group for the experiments. Based on the boundary effect model and by incorporating the average aggregate size of concrete, the size-dependent tensile strength ft, fracture toughness KIC of SSC can be obtained analytically from small and medium-sized specimens. Furthermore, the means, upper and lower limits of two fracture parameters with 95% reliability were determined based on the normal distribution analysis. The ultimate load of SSC specimens under any size condition was successfully predicted by using obtained tensile strength. Moreover, the results show that under the same aggregate gradation, compared with ordinary Portland concrete, SSC exhibits a higher proportion of aggregate fracture on the fracture surface and demonstrates higher tensile strength and fracture toughness. With the increase in the maximum aggregate size, the proportion of aggregate fracture in both SSC and OPC decreased. However, the fracture toughness KIC increased, while ft decreased. The above model and related results can provide references for the practical engineering design of seawater sea sand sea sand concrete. |
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| Keywords: | seawater sea sand concrete boundary effect non-linear fracture mechanics fracture toughness tensile strength |
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