Salt resistance reliability evaluation of magnesium cement recycled fine aggregate reinforced concrete based on two-parameter weibull distribution
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摘要: 针对盐湖地区建筑结构受到恶劣气候环境和腐蚀性离子双重侵害现象,采用镁水泥再生细骨料钢筋混凝土来缓减构筑物寿命退化速度。通过掺加不同量的再生细骨料并将其埋置在盐渍土中进行恒电流通电加速试验,借助电化学工作站、超声波无损检测技术及SEM、XRD分析微结构演变机制,最后引入两参数Weibull分布函数退化过程对评价指标腐蚀电流密度icorr、相对动弹性模量建模进行可靠度评价。结果表明:掺入质量比为15%、30%和45%的细骨料时,Cl−、CO3 2−和SO4 2−侵蚀性离子随着再生细骨料掺量的增多侵入试件几率增大,内部结构损伤程度更加显著;大片、块状的锈蚀产物逐渐疏松内部结构导致劣化程度加深,15%、30%掺量试件低腐蚀程度,45%掺量试件则处于严重腐蚀;以动弹模量作为退化参数得到15%、30%、45%再生细骨料掺量试件的服役寿命分别为10000天、7500天、6000天;以腐蚀电流密度icorr得到45%掺量试件的工作寿命为4000天,钢筋腐蚀电流密度耐久性退化相对动弹模量更加敏感,对于镁水泥再生细骨料钢筋混凝土构件的日常维护与检测具有可观的指导意义。
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关键词:
- 镁水泥再生细骨料钢筋混凝土 /
- 腐蚀电流密度icorr /
- 相对动弹模量 /
- 两参数Weibull分布 /
- 可靠度
Abstract: In view of the fact that the building structure in the salt lake area is subjected to the double damage of harsh climate environment and corrosive ions, which leads to the phenomenon of shortened life. Magnesium cement recycled fine aggregate reinforced concrete was used to slow down the life degradation speed of the structure. The galvanostatic accelerated test was carried out by adding different amounts of regenerated fine aggregate and burying it in saline soil. With the help of electrochemical workstation, ultrasonic non-destructive testing technology, SEM and XRD, the evolution mechanism of microstructure was analyzed, Finally, the degradation process of the two-parameter Weibull distribution function was introduced to evaluate the reliability of the evaluation index corrosion current density icorr and relative dynamic elastic modulus modeling. The results show that: When mixed with mass ratios of 15%, 30% and 45% fine aggregates in the accelerated test environment, aggressive ions such as Cl−, CO3 2− and SO4 2− invade the interior of the specimen with the increase of the content of recycled fine aggregates. The probability increases, and the degree of damage to the internal structure is more significant. The large and block corrosion products gradually loosen, which makes the internal structure deteriorate further. The specimens with 15% and 30% dosage have low corrosion degree, and the specimen with 45% dosage is in serious corrosion. The dynamic elastic modulus is used as the degradation parameter to obtain 15%, 30%, 45% regeneration. The service life of the samples with fine aggregate content is 10000 days, 7500 days and 6000 days, respectively. The working life of the specimen with 45% dosage obtained by the corrosion current density icorr is 4000 days. The corrosion current density durability degradation of steel bars is more sensitive to the dynamic elastic modulus, which has considerable guiding significance for the daily maintenance and inspection of magnesium cement recycled fine aggregate reinforced concrete components. -
表 1 再生细骨料物理性能指标
Table 1. Physical properties of recycled fine aggregates
Performance Water
absorption/%Ignition
loss/%Activity
index/%Apparent
density
/(kg·m−3)Bulk
density
/(kg·m−3)Particle size
range/mmIndex 3.9 4 60 2482 1260 0.16-0.5 表 2 镁水泥再生细骨料混凝土配合比
Table 2. Mix proportion of reinforced concrete with magnesium oxychloride cement
(kg/m3) MgO Water reducer Water resistant agent Fly ash Stone MgCl2 Water Sane Regenerated fine
aggregate content/%388.96 16.02 4.58 68.64 1162 147.81 135.59 531.25 15 388.96 16.02 4.58 68.64 1162 147.81 135.59 437.5 30 388.96 16.02 4.58 68.64 1162 147.81 135.59 343.75 45 表 3 镁水泥再生细骨料钢筋混凝土锈蚀状态与腐蚀电流密度icorr 的关系[19]
Table 3. Relationship between corrosion state and corrosion current density icorr of magnesium cement recycled fine aggregate reinforced concrete[19]
(μA·cm−2) Corrosion current density icorr<0.1 0.1≤icorr<0.5 0.5≤icorr<1.0 icorr≥1 Rust state Not corroded Low corrosion Moderate corrosion Severely corroded 表 4 不同掺量再生细骨料钢筋混凝土的腐蚀电流密度值icorr
Table 4. Corrosion current density values of reinforced concrete with different contents of recycled fine aggregate icorr
(µA·cm−2) t/d Recycled fine aggregate content (mass ratio) 15% 30% 45% 0 0.0249 0.0367 0.0793 90 0.0183 0.0221 0.1367 180 0.0311 0.1215 0.6946 270 0.0943 0.1951 1.5337 360 0.0744 0.2510 1.3725 450 0.0756 0.3608 2.3702 540 0.1336 0.3953 3.4219 630 0.2920 0.4359 2.7995 720 0.3431 0.4901 3.1545 Note: t—Power-on time. 表 5 镁水泥再生细骨料钢筋混凝土相对动弹模量评价参数
Table 5. Evaluation parameters of relative dynamic elastic modulus of magnesium cement recycled fine aggregate reinforced concrete
t/d Recycled fine aggregate content (mass ratio) 15% 30% 45% 0 1 1 1 1-90 1.1951 0.7821 0.8473 2-180 1.0894 0.6998 0.6728 3-270 1.1891 0.7961 0.7466 4-360 1.1039 0.7360 0.6660 5-450 1.1388 0.7221 0.6962 6-540 1.1295 0.7582 0.7198 7-630 1.0588 0.6703 0.5754 8-720 0.8169 0.4474 0.3270 表 6 中位秩法参数估计值
Table 6. Estimated values of median rank method parameters
Evaluation parameters Dosage Estimated parameter $ M({t_i}) = \dfrac{{n({t_i})}}{{n + 0.4}} $ $ M({t_i}) = \dfrac{{n({t_i}) - 0.3}}{{n + 0.4}} $ $ M({t_i}) = \dfrac{{n({t_i}) - 0.5}}{n} $ $ M({t_i}) = \dfrac{{n({t_i}) - 0.375}}{{n + 0.25}} $ Dynamic modulus 15% m −57.7578 −46.7735 −58.9149 −57.5832 η 857.3885 855.2996 945.9229 886.8786 30% m −41.8435 −32.5912 −42.4287 −41.2342 η 683.3401 683.5395 781.1129 716.2332 45% m −18.4942 −19.9327 −14.0796 −20.9632 η 547.1807 593.3212 644.7079 590.8916 icorr 45% m −21.8989 −22.4775 −23.8497 −23.8537 η 409.5679 393.7802 441.9369 392.1016 Notes: n(ti)—Time corresponding to specimen loss; n—Sample size; M(ti)—Median rank. 表 7 极大似然法参数估计值
Table 7. Maximum likelihood method parameter estimates
Evaluation parameter Dosage Estimated parameter Value Dynamic modulus 15% m −57.3905 η 813.3148 30% m −40.7319 η 639.5112 45% m −18.5544 η 535.4391 icorr 45% m −20.8969 η 366.3250 -
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