偏高岭土对水泥砂浆中钢筋钝化的影响

李闯; 范颖芳; 李秋超

doi:10.13801/j.cnki.fhclxb.20200305.001

偏高岭土对水泥砂浆中钢筋钝化的影响

doi: 10.13801/j.cnki.fhclxb.20200305.001

大连海事大学　交通运输工程学院，大连 116026

基金项目: 国家自然科学基金面上项目(51578099)；大连海事大学基础性学科经费

详细信息

通讯作者:
范颖芳，博士，教授，研究方向为混凝土结构耐久性　E-mail：fanyf@dlmu.edu.cn

中图分类号: TU528.33
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- 文章访问数: 1629
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- 被引次数: 0
出版历程
- 收稿日期: 2019-12-27
- 录用日期: 2020-02-22
- 网络出版日期: 2020-03-05
- 刊出日期: 2020-11-15

Influence of metakaolin on passivation of reinforcing steel in cement mortar

College of Transportation Engineering, Dalian Maritime University, Dalian 116026, China

摘要

摘要: 利用电化学阻抗谱、循环动电位极化、阴极极化、热重和XRD等方法，研究了偏高岭土(MK)掺量(占MK/水泥总质量的20wt%、30wt%、40wt%)对钢筋-MK/水泥砂浆中钢筋钝化膜形成及其耐蚀性能的影响。结果表明：在一般环境中，钢筋在不同MK掺量的钢筋-MK/水泥砂浆中均可以形成稳定的钝化膜；在质量分数为3.5wt%的NaCl溶液环境中，MK掺量过多会使钢筋-MK/水泥砂浆中钢筋的钝化膜稳定性降低，耐蚀性能下降。从钢筋钝化膜稳定角度考虑，在氯盐环境中，水泥基材料中MK掺量应予以限制。
- 偏高岭土 /
- 水泥砂浆 /
- 钢筋 /
- 钝化 /
- 电化学阻抗谱 /
- 极化曲线
Abstract: The effect of metakaolin (MK) amount (accounting for 20wt%, 30wt% and 40wt% of the total mass of MK/cement mortar) on the passivation film formation and corrosion resistance of passivation film of reinforcing steel in MK/cement mortar was studied by eletrochemical impedance spectroscopy, cyclic potentiodynamic polarization, cathodic polarization, thermogravimetric analysis and diffraction of XRD. The results indicate that the reinforcing steel can form stable passivation film in steel-MK/cement mortar with different MK contents in general environment. In the solution environment of 3.5wt% mass fraction of NaCl, excessive amount of MK reduces the stability of passive film and the corrosion resistance of reinforcing steel in steel-MK/cement mortar. Considering the stability of passive film, the content of MK in cement-based materials should be limited in chloride environment.
- metakaolin /
- cement mortar /
- reinforcing steel /
- passivation /
- electrochemical impedance spectroscopy /
- polarization curve

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图 1 MK的XRD图谱

Figure 1. XRD pattern of MK

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图 2 MK和水泥的粒径分布

Figure 2. Particle size distribution of MK and cement

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图 3 钢筋-MK/水泥砂浆的几何尺寸

Figure 3. Geometry of reinforcing steel-MK/cement mortar

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图 4 28 d内钢筋-MK/水泥砂浆的腐蚀电位

Figure 4. Corrosion potential of reinforcing steel-MK/cement mortars in 28 d

M0—Reinforcing steel-MK/cement mortar-0; M20—Reinforcing steel-MK/cement mortar-20; M30—Reinforcing steel-MK/cement mortar-30; M40—Reinforcing steel-MK/cement mortar-40

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图 5 3.5wt% NaCl溶液浸泡前后钢筋-MK/水泥砂浆的腐蚀电位

Figure 5. Corrosion potential of reinforcing steel-MK/cement mortars before and after immersion in 3.5wt% NaCl solution

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图 6 养护1 d和28 d 后钢筋-MK水泥砂浆的电化学阻抗谱

Figure 6. Eletrochemical impedance spectroscopy plots of reinforcing steel-MK/cement mortars for 1 d and 28 d

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图 7 经3.5wt%NaCl溶液浸泡后钢筋-MK/水泥砂浆的电化学阻抗谱

Figure 7. Eletrochemical impedance spectroscopy plots of reinforcing steel-MK/cement mortars after immersion in 3.5wt% NaCl solution

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图 8 钢筋-MK/水泥砂浆电化学阻抗谱的等效电路

Figure 8. Equivalent circuit of eletrochemical impedance spectroscopy of reinforcing steel-MK/cement mortar

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图 9 钢筋-MK/水泥砂浆在3.5wt% NaCl溶液中的阴极极化曲线

Figure 9. Cathodic curves of reinforcing steel-MK/cement mortars in 3.5wt% NaCl solution

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图 10 循环动电位极化曲线示意图

Figure 10. Schematic diagram of cyclic potentio dynamic polarization curve

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图 11 养护28 d和经3.5wt% NaCl溶液浸泡后钢筋-MK/水泥砂浆的循环动电位极化曲线

Figure 11. Cyclic potentiodynamic polarization curves of reinforcing steel-MK/cement mortars after curing 28 d and after immersion in 3.5wt% NaCl solution

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图 12 MK/水泥净浆的XRD图谱(28 d)

Figure 12. XRD patterns of MK/cement pastes (28 d)

P0—MK/cement paste-0; P20—MK/cement paste-20; P30—MK/cement paste-30; P40—MK/cement paste-40

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图 13 MK/水泥净浆的TG和DTG曲线(28 d)

Figure 13. TG and DTG curves of MK/cement pastes (28 d)

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图 14 经酚酞溶液浸润后MK/水泥净浆颜色变化(28 d)

Figure 14. Color variation of MK/cement pastes after soaking with phenolphthalein solution (28 d)

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表 1 水泥化学组成

Table 1. Chemical composition of cement

wt%
SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	SO₃	Na₂O_eq	f-CaO	Cl^–	Ignition loss
21.88	4.31	3.47	62.39	1.72	2.56	0.23	1.52	0.016	1.42
Notes: Na₂O_eq—Content of volatile alkaline; f-CaO—Free CaO^[10].

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表 2 水泥物理力学性能

Table 2. Physical and mechanical properties of cement

Density/ (g.cm^–2)	Standard consistency/%	Compressive strength of 3 d/MPa	Flexural strength of 3 d/MPa	Setting time/min
Density/ (g.cm^–2)	Standard consistency/%	Compressive strength of 3 d/MPa	Flexural strength of 3 d/MPa	Initial setting	Final setting
3.15	25	26.6	5.3	186	248

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表 3 偏高岭土(MK)化学组成

Table 3. Chemical composition of metakaolin(MK)

wt%
SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	SO₃	K₂O	N₂O	Ignition loss
49.40	43.88	0.51	0.27	2.66	0.14	0.23	1.52	0.59

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表 4 钢筋-MK/水泥砂浆和MK/水泥净浆的配合比

Table 4. Mix proportions of reinforcing steel-MK/cement mortar and MK/cement paste

Sample	MK/ wt%	Cement/ wt%	Mass ratio of water to binder	Mass ratio of binder to sand	Water reducer/ wt%
Reinforcing steel-MK/cement mortar-0	0	100	0.4	1∶3	0
Reinforcing steel-MK/cement mortar-20	20	80	0.4	1∶3	0.13
Reinforcing steel-MK/cement mortar-30	30	70	0.4	1∶3	0.26
Reinforcing steel-MK/cement mortar-40	40	60	0.4	1∶3	0.36
MK/cement paste-0	0	100	0.4	0	0
MK/cement paste-20	20	80	0.4	0	0.13
MK/cement paste-30	30	70	0.4	0	0.26
MK/cement paste-40	40	60	0.4	0	0.36

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表 5 钢筋-MK/水泥砂浆的电化学测试过程

Table 5. Electrochemical test process of reinforcing steel-MK/cement mortar

Stage	Time/d	Environment	Electrochemical test
1	1–28	General environment	E_corr, EIS, CPP
2	32	3.5wt% NaCl solution	E_corr, EIS, CPP, CP
Notes: E_corr—Corrosion potential; EIS—Electrochemical impedance spectroscopy; CPP—Cyclic potentiodynamic polarization; CP—Cathodic polarization.

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表 6 钢筋-MK/水泥砂浆的等效电路元件参数

Table 6. Parameters of equivalent circuit of reinforcing steel-MK/cement mortars

Sample	R_ct/(kΩ·cm²)			Y₀/(10⁵ Ω⁻¹·cm⁻²·sⁿ)			n			C_app/(μF·cm⁻²)
Sample	1 d	28 d	3.5wt% NaCl	1 d	28 d	3.5wt% NaCl	1 d	28 d	3.5wt% NaCl	1 d	28 d	3.5wt% NaCl
M0	2 012.0	6 462.2	6 452.2	3.40	2.43	2.46	0.90	0.93	0.90	54.8	35.9	42.7
M20	1 012.5	7 632.7	6 462.0	3.53	2.27	2.35	0.92	0.89	0.90	48.1	41.8	40.7
M30	423.4	3 972.5	2 844.7	3.00	2.42	2.28	0.91	0.93	0.92	40.6	34.9	32.9
M40	407.3	4 633.4	650.8	3.68	2.36	4.13	0.91	0.90	0.75	48.3	40.6	126.6
Notes: R_ct—Charge transfer resistance on surface of reinforcing steel; Y₀—Base admittance; n—Index of constant phase angle; C_app—Apparent interfacial capacitance.

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表 7 钢筋-MK/水泥砂浆的循环动电位极化曲线电化学参数

Table 7. Electrochemical parameters of cyclic potentio dynamic polarization curves of reinforcing steel-MK/cement mortars

Sample	E_pit/mV		E_rep/mV		i_p/(μA·cm⁻²)
Sample	28 d	3.5wt% NaCl	28 d	3.5wt% NaCl	28 d	3.5wt% NaCl
M0	662	682	674	716	0.073	0.078
M20	705	680	740	728	0.075	0.077
M30	680	695	726	744	0.076	0.075
M40	690	717	733	−66	0.080	0.222
Notes: E_pit—Pitting potential; E_rep—Repassivation potential; i_p—Current density of passivation.

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表 8 28 d时MK/水泥净浆的化学结合水含量

Table 8. Chemical bound water contents of MK/cement pastes for 28 d wt%

Sample	C-S-H	Ca(OH)₂	CaCO₃
P0	7.27	4.36	1.75
P20	11.68	1.65	—
P30	12.00	0.95	—
P40	12.12	—	—
Note: C-S-H—Calcium silicate hydrate.

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