| Steel corrosion induced by chloride ion invasion is the most common,major problem of RC structural durability.The structural deterioration induced by steel corrosion not only impacts on service life,but causes substantial economic losses.Corrosion-induced cracking is the significant stage of corrosion-induced structural deterioration process.Once the crack propagates through concrete cover,the aggressive medium will penetrate into concrete and then reach the steel bar surface through the crack.As a result,the steel corrosion rate increases and the structural deterioration gets faster.Although there have been numerous models for predicting corrosion-induced cracking,few of them is satisfying for the lack of applicability.The main reason is the law and mechanisms of corrosion products filling-overflow behavior remain unclear,which have significant influences on corrosion-induced concrete cracking.Therefore,based on experimental observation,theoretical derivation and numerical simulation,the corrosion products filling-overflow behavior and the corresponding effects on corrosion-induced concrete cracking of RC structure in chloride environment are investigated.The findings can provide data support and theoretical basis for the performance assessment and life prediction of existing reinforced concrete structures.The main work of this paper can be summarized as follows:(1)Based on X-CT scanning technique and the support of image recognition algorithm,a new method for extracting corrosion-cracking data from RC structure is proposed.Compared to traditional approaches,this method offers better efficiency.It also enables the extraction of large-scale data with high accuracy,which can be further applied to study and quantify the filling-overflow behavior of corrosion products.(2)Based on the simulation of chloride-rich environment under natural condition,the characteristics of steel corrosion in RC beam-column joints specimens are investigated;the relevant factors that affect the corrosion characteristics were analyzed.The distribution of corrosion products within specimens is observed,and the filling-overflow behavior of corrosion products in different regions of concrete is revealed at mesoscopic level.The limitations of existing models,which use the range of filling area to describe the filling-overflow behavior,are elaborated.Then,the corrosion products filling-overflow index K_T is proposed to quantify the filling-overflow behavior based on elemental conservation.(3)Based on the experimental investigation and statistical simulation,the phase state of corrosion products that transport inside mortar is investigated.The law that inside cementitious materials,corrosion products could transport in the form of ions in pore fluid is detected,and the corrosion-transport-oxidation-precipitation mechanism that controlling corrosion products filling-overflow behavior is then summarized.Through quantifying the physico-chemical processes that the corrosion products filling-overflow behavior involves,combined with the evolution laws of physical fields in materials,the reactive-transport model is established for predicting the corrosion products filling-overflow behavior.By comparsion of experimental data and predicted results,the reliability of model is validated.(4)The corrosion-induced cracking of RC beam-column joints specimen in chloride-rich environment is researched,the function mapping from steel corrosion,corrosion-induced expansion to corrosion-induced cracking damage is built.With the consideration of corrosion products filling-overflow behavior,the numerical model of corrosion-induced cracking is established.Combined with the reactive-transport model,the corrosion-induced cracking can be predicted,and the law of corrosion-induced structural deterioration based on corrosion products filling-overflow behavior is proposed subsequently. |
