应变硬化水泥基复合材料氯盐传输行为的细观数值分析

鲍玖文; 孔令艳; 张心钰; 张鹏; 秦玲; 郭伟娜

doi:10.13801/j.cnki.fhclxb.20230824.001

应变硬化水泥基复合材料氯盐传输行为的细观数值分析

doi: 10.13801/j.cnki.fhclxb.20230824.001

青岛理工大学　土木工程学院，青岛 266520

基金项目: 国家重点研发计划(2021YFB2600704)；国家自然科学基金(51922052)；山东省自然科学基金(ZR2021JQ17)；山东省高等学校青创科技创新团队项目(2021KJ019)

详细信息

通讯作者:
张鹏，博士，教授，博士生导师，研究方向为混凝土耐久性　E-mail: peng.zhang@qut.edu.cn

中图分类号: TU528；TB330.1
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出版历程
- 收稿日期: 2023-06-05
- 修回日期: 2023-07-03
- 录用日期: 2023-08-12
- 网络出版日期: 2023-08-25
- 刊出日期: 2024-04-01

Mesoscale numerical analysis of chloride ingress behavior of strain hardening cement-based composites

School of Civil Engineering, Qingdao University of Technology, Qingdao 266520, China

Funds: National Key Research and Development Program of China (2021YFB2600704); National Natural Science Foundation of China (51922052); Natural Science Foundation of Shandong Province (ZR2021JQ17); Youth Innovation Team Development Plan of Shandong Province in China (2021KJ019)

摘要

摘要: 应变硬化水泥基复合材料(SHCC)因其具有高延性、裂缝宽度可控等优点已被广泛应用于海洋腐蚀严重区域的混凝土结构加固与修复工程中。基于此，提出了海洋干湿循环作用下SHCC中氯离子传输的对流-扩散模型，并利用COMSOL仿真软件建立考虑纤维乱向分布的二维细观模型；通过开展人工室内模拟海洋浪溅区SHCC氯离子传输试验，分析了不同干湿循环比(3.0∶1、11.0∶1和85.4∶1)和不同暴露时间(30天、90天和180天)下的氯离子含量时空分布规律，对比验证了模拟氯盐传输行为的细观数值模型的有效性。结果表明：随着暴露时间的延长，SHCC氯离子峰值浓度增大，且随着干湿循环比的增加峰值浓度升高；随着渗透深度增大，氯离子浓度迅速下降并最终趋于稳定，使氯离子浓度整体表现出峰值浓度较高而传输深度较小的规律；基于Fick第二定律解析解并考虑对流区的影响，SHCC的表面氯离子浓度(C_s)和表观氯离子扩散系数(D_app)均呈现明显的时变性，干湿循环比一定时，随着暴露时间的延长而分别增大和减小；当干湿循环比为85.4∶1，暴露时间为90天和180天时C_s相较于30天分别提高了51.72%和83.45%，D_app分别降低了27.71%和48.50%；暴露时间一定时，随着干湿循环比的增加，C_s和D_app均呈现先增大后减小的趋势；最后将氯离子含量分布实测值与计算值进行对比，验证了所建立的干湿循环作用下氯盐传输的扩散-对流模型的适用性。
- 应变硬化水泥基复合材料 /
- 干湿循环 /
- 氯离子传输 /
- 细观数值模拟
Abstract: Strain hardening cement-based composite (SHCC) owning to its advantages of high ductility and controllable crack width has been widely used in the strengthening and repairing of concrete structures exposed to severe marine corrosion zones. Based on this, a convection-diffusion model of chloride transport in SHCC subjected to marine drying-wetting cycles was proposed, and a two-dimensional mesoscopic model considering the chaotic distribution of fibers was established by COMSOL simulation software. The spatial and temporal distribution of chloride content under different drying-wetting ratios (3.0∶1, 11.0∶1 and 85.4∶1) and exposure durations (30 days, 90 days and 180 days) was analyzed by conducting a simulated indoor test of chloride ingress into SHCC. The effectiveness of the mesoscopic numerical model to simulate chloride ingress behavior was contrastively verified. The results show that the peak chloride concentration inside SHCC increases with the extension of exposure time, and similarly increases with the increase of drying-wetting ratio. However, with the increase of penetration depth, the chloride concentration rapidly decreases and tends to be stable eventually, which make the chloride content as a whole show a higher peak concentration and a smaller penetration depth. According to the analytical solution to Fick's second law and considering the effect of convection zone, both the surface chloride concentration (C_s) and apparent chloride diffusion coefficient (D_app) of SHCC show obvious time-varying characteristics. At a given drying-wetting cycle ratio, the C_s and D_app increase and decrease as the exposure time increases, respectively. When the drying-wetting cycle ratio is 85.4∶1, compared to 30 days, the C_s of SHCC for exposure to 90 days and 180 days increase by 51.72% and 83.45%, and the D_app decreases by 27.71% and 48.50%, respectively. At the same exposure time, as the drying-wetting cycle ratio increases, both the C_s and D_app first increase and then decrease. Finally, the comparison between the measured data and calculated results of the chloride content distribution indicates the feasibility of the proposed convection-diffusion model under the cyclic drying-wetting action to depict the chloride transport behavior in SHCC.
- SHCC /
- drying-wetting cycles /
- chloride transport /
- mesoscale numerical simulation

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图 1 聚乙烯醇(PVA)纤维随机投放流程图

Figure 1. Flow chart of randomly distributed polyvinyl alcohol(PVA) fibers

ITZ—Interfacial transition zone

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图 2 PVA纤维随机分布的应变硬化水泥基复合材料(SHCC)模型

Figure 2. Strain hardening cement-based composite (SHCC) model with the random distribution of PVA fibers

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图 3 SHCC细观数值仿真模型

Figure 3. Mesoscopic numerical simulation model of SHCC

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图 4 不同干湿循环比下SHCC自由氯离子含量分布

Figure 4. Free chloride content distribution of SHCC under different cyclic drying-wetting ratios

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图 5 不同渗透深度处SHCC自由氯离子含量

Figure 5. Free chloride content of SHCC at different penetration depths

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图 6 SHCC自由氯离子含量计算值与试验值对比

Figure 6. Comparison between calculated value and tested data of free chloride content in SHCC

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图 7 SHCC自由氯离子含量分布云图

Figure 7. Free chloride content distribution in SHCC

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图 8 SHCC中自由氯离子含量计算值与文献[26]中试验值对比

Figure 8. Comparison between calculated value of free chloride content in SHCC and tested data in literature [26]

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表 1 干湿过程吸-脱附曲线的参数取值

Table 1. Parameters values of adsorption-desorption curves in dry and wet conditions

Duration	α/10⁻³	m	n
Drying process	1.021	0.324	1.480
Wetting process	5.159	1.874	1.874
Notes: α, m, n—Empirical parameters of adsorption-desorption model.

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表 2 PVA纤维的基本性质

Table 2. Properties of PVA fibers

Type	Diameter/ μm	Length/ mm	Elasticity modulus/GPa	Volume fraction/vol%
PVA fiber	40	12	41	2

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表 3 胶凝材料化学成分组成

Table 3. Chemical composition of cementitious materials

Chemical composition	Cement/wt%	Fly ash/wt%
SiO₂	17.04	52.00
Al₂O₃	6.08	28.68
Fe₂O₃	4.08	4.50
CaO	53.57	8.07
SO₃	2.95	1.14
MnO	0.38	—
TiO₂	0.52	—
K₂O	0.80	1.54
P₂O₅	0.14	—
MgO	—	1.18

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表 4 SHCC试件配合比

Table 4. Mix proportion of SHCC specimens

Composition	Content
Cement	550 kg·m⁻³
Fine aggregate	550 kg·m⁻³
Water	395 kg·m⁻³
Fly ash	650 kg·m⁻³
PVA	2vol%

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表 5 氯盐侵蚀的干湿循环制度

Table 5. Cyclic drying-wetting regimes of chloride ingress

α_t	One drying-wetting cycle			Number of drying-wetting cycle
α_t	t	t_d	t_w	30 d	90 d	180 d
3.0∶1	1 d	18 h	6 h	30	90	180
85.4∶1	3 d	4270 min	50 min	10	30	60
11.0∶1	6 d	132 h	12 h	5	15	30
Notes: α_t—Time ratio of drying-wetting cycle; t—Total exposure time; t_d—Time of drying period; t_w—Time of wetting period.

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表 6 SHCC表面氯离子含量C_s和表观氯离子扩散系数D_app

Table 6. Surface chloride content C_s and apparent chloride diffusion coefficient D_app of SHCC

Exposure time/d	3∶1		11∶1		85.4∶1
Exposure time/d	C_s/wt%	D_app/(mm²·s⁻¹)	C_s/wt%	D_app/(mm²·s⁻¹)	C_s/wt%	D_app/(mm²·s⁻¹)
30	1.40	3.34	1.45	4.38	1.45	4.33
90	2.10	2.70	2.21	3.19	2.20	3.13
180	2.17	1.57	2.68	2.34	2.66	2.23

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表 7 文献[26]中PVA纤维混凝土的氯离子传输模型计算参数值

Table 7. Calculated parameter values of chloride transport model for PVA fiber reinforced concrete in literature [26]

Group	α_t	One cyclic period/d	C_s/wt%	D_app/ (10⁻¹² m²·s⁻¹)
P-28	1∶1	14	0.24	2.47
P-56			0.28	2.09
P-84			0.39	1.32
P-112			0.62	0.80
Notes: P stands for PVA fiber; 28, 56, 84 and 112 represent exposure time of 28 d, 56 d, 84 d and 112 d, respectively.

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