Experimental Investigation on Contribution of CFRP Attachment to Durability of Reinforced Concrete Structure Subjected to Chloride Attack

The function of externally-bonded carbon fiber reinforced polymer （CFRP） in preventing chloride from entering into concrete is verified by experiment. The results show that externally-bonded CFRP can be considered as a part of corrosion prevention system of strengthened concrete structures subjected to chloride ingress, and the contribution of CFRP should be considered in evaluation of durability of reinforced concrete structures with externally-bonded CFRP. With the effective shielding function of CFRP considered, an equation for residual lifetime prediction of concrete structures with externally-bonded CFRP is derived from Fick＇s dispersion law. CFRP has two functions for coastal concrete structures, including strengthening and increasing durability as part of corrosion prevention system.     

混凝土抗氯离子渗透性能试验研究

应用电通量法和氯离子扩散系数法,研究不同配合比的铁路混凝土抵抗氯离子渗透的能力。对于同一组试件,采用这2种试验方法所得数据均能满足相关技术指标要求。电通量法和氯离子扩散系数法所得数据分布区间分别在170?C~1?194?C和0.5×10-12?m2/s?~3.5×10-12?m2/s范围内。试验结果表明,这2种方法均可对铁路混凝土抵抗氯离子渗透能力进行定性分析,电通量法能更好地反映不同配合比混凝土抵抗氯离子渗透能力的差异。     

海排灰的氯盐含量对三灰结合料微观机理影响研究

对基于海排灰的三灰结合料水化产物的微观机理进行研究,揭示氯离子对底基层材料强度形成的影响.研究表明:水泥、石灰材料对海排灰中的氯离子有固化作用,海排灰中适量的氯离子对底基层材料有益.     

海排灰基层结合料中氯离子固化特性的研究

分析普通水泥、石灰等结合料对海排灰中氯离子固化能力的影响,揭示水泥海排灰、水泥石灰海排灰混合料结合氯离子的固化特性。采用测定氯离子固化含量的水溶盐化学分析法、氯离子的固化理论方法,对水泥海排灰和水泥石灰海排灰固化氯离子特性进行深入研究。试验结果表明,对于水泥海排灰结合料,当氯离子含量超过混合料中海排灰含量2%时,各个龄期的氯离子固化率不再增加。而水泥石灰海排灰结合料,氯离子含量越多,固化率越高。对海排灰基层结合料中氯离子固化研究表明,含适量的氯盐的海排灰可以用做道路基层材料。     

硅灰增强混凝土抗氯离子渗透性能研究

硅灰掺入到混凝土中,由于其微粒充填效应、火山灰活性效应、晶核效应、流变效应等而使混凝土的密实度得以改善,提高混凝土的抗渗性,降低氯离子的渗透系数,提高混凝土的抗氯离子侵蚀能力。。     

Analysis of corrosion risk due to chloride diffusion for concrete structures in marine environment

The chloride-induced steel corrosion is one of the main causes of deterioration for reinforced concrete structures exposed to marine environments. The chloride ingress into reinforced concrete structures is even more complex since it depends on random parameters linked to transport and chemical properties of materials, which results in variability of corrosion initiation. This variation raises the need of statistical approaches to evaluate the risk of corrosion initiation due to chloride ingress. To address this issue, we use sensitivity analysis to identify the influence of input parameters on critical length of time before corrosion initiation predicted by our chloride diffusion model. Exceedance probabilities of corrosion initiation time given that input parameters exceed certain thresholds were also calculated. Results showed that the corrosion initiation time was most sensitive to: chloride effective diffusion coefficient D_e in concrete, that is a parameter controllable by relevant stakeholders; surface chloride concentration C_s, a non-controllable parameter depending on surrounding conditions. Reducing the chloride diffusion coefficient enables us to postpone the maintenance of structures. However, the interaction between controllable parameters and non-controllable surrounding conditions was revealed influential on the reliability of results. For instance, the probability that corrosion initiation time exceeds 15 years given an effective diffusion coefficient (D_e) equal to 0.1 × 10⁻¹² m²⋅s-1 can vary from 19 to 41% according to stochastic variations of chloride concentrations (C_s) values. Postponing the corrosion initiation time was combined with a decreasing probability of its occurrence.     

在海洋与化冰盐环境中钢筋混凝土构筑物的钢筋防锈技术对策

针对处于海洋与化冰盐环境中的工程因氯盐引起钢筋锈蚀大幅度降低普通钢筋混凝土结构使用寿命的主要问题，综述了有关防锈技术措施、结构寿命与高耐久混凝土技术要求，并介绍了近5年内建成的4座设计使用寿命为100-120年海洋桥梁的混凝土技术标准。     

Degradation of bond strength and deformation between TRC-confined seawater sand concrete and BFRP bars under chloride corrosion environment

The interfacial bonding performance between seawater sand concrete and basalt fiber reinforced polymer (BFRP) bars were tested under different textile reinforced concrete (TRC) confinement layers, confinement sequences and chloride salt dry-wet cycles. The results show that TRC confinement can change the failure mode of the specimen and improve the ductility of specimens. With the increase of corrosion age, compared with the specimens with the same restrained layers in the conventional environment, the ultimate bond strength of restrained specimens before corrosion gradually decreases, and the slip value when reaching the ultimate bond strength also slightly decreases. The bond strength of the pre-restrained corroded specimens has the same development trend. Based on the bond-slip model of deformed steel bars and concrete proposed by Eligehansen for the first time in 1983—BPE model, under the control of TRC confinement and corrosion age, the relationship between the TRC confinement layer and the ultimate bond strength and slip of seawater sand concrete and BFRP steel bar is established. By fitting and predicting the ultimate bond strength, corresponding slip value, and corrosion age control of different TRC confinement layers, it is found that the confinement effect will not be significantly improved when the confinement layers exceed 4 layers. Under long-term chloride corrosion, the failure mode of the specimen may still change into splitting failure when the number of restrained layers is small.