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Non-uniform corrosion of rebar leads to the cracking of the concrete cover, which reduces the reliability of structures and increases maintenance costs. In this paper, we present a coupled phase-field model at the mesoscale to investigate the time-dependent process of non-uniform corrosion-induced cover cracking. This model couples chloride and oxygen diffusion, electrochemical reaction, and concrete cover cracking. A time-dependent non-uniform corrosion model is established based on chloride diffusion and electrochemical theory by considering the cracking effect. The cracking behavior of the concrete cover is described using a phase-field regularized cohesive zone model. The model was verified against several experiments available in the literature. Parametric studies were conducted to observe the effects of the crack and chloride diffusion coefficient, the interaction between the corrosion of multiple rebars, and the crack characteristics in three dimensions. • The non-uniform corrosion model is based on chloride diffusion and electrochemical theory. • The effect of corrosion-induced cracks on the diffusion process is considered. • The characteristics of rebar corrosion and concrete cracking in 2D and 3D are studied. [ABSTRACT FROM AUTHOR]

Non-uniform corrosion of rebar in reinforced concrete will lead to concrete cover cracking, thus significantly reducing the durability of structures. A 2D mesoscale phase field model was developed to explore the failure behaviors of corrosion-induced cracking. The expansion of rust was described by a time-dependent non-uniform corrosion model. The phase field regularized cohesive zone model was employed to study the cracking pattern. The proposed model was validated by available experimental results in publications. The effects of several geometric parameters, such as concrete cover thickness, rebar diameter, and clear spacing, on the crack pattern and crack width of single and multiple rebar models were investigated. Finally, the influence of the ratio of cover thickness to rebar diameter on the failure pressure was discussed. • A mesoscale phase field model is developed to study the time-dependent non-uniform corrosion. • Crack pattern, crack width and failure pressure of concrete are investigated. • Effects of the cover thickness, rebar diameter, clear spacing and cover-to-diameter ratio are investigated. [ABSTRACT FROM AUTHOR]

Abstract: A partially encased composite I-girder with flat or corrugated web has been proposed to improve the structural performance of continuous composite girder under hogging moment. The flexural behavior of such structure under two points symmetric loading has been experimentally and analytically investigated. Static flexural loading tests showed that the partially encased girder improved bending strength in comparison to steel I-girder, as local bucking of steel flange was restricted by encased concrete. Especially for the corrugated web girder, the ultimate bending strength was improved about 20%, and the ductility also increased about 3 times. In addition, the limitation of width-to-thickness ratios for steel and concrete-encased composite I-girders with corrugated web were suggested to prevent premature failure due to local buckling of compressive flange. Moreover, the analytical methods of flexural strength under service and ultimate state for partially encased composite girder were proposed and verified with experimental results. It was found that the analytical bending strengths agreed well with the experimental ones at both service and ultimate state, which means the proposed analytical equations can be applied in predicting flexural strength accurately for such encased composite girder with flat or corrugated web. [Copyright &y& Elsevier]

Abstract: This paper proposed a novel cost-effective movable hybrid GFRP and concrete deck consisting of corrugated pultruded GFRP plate with T-upstands for the tension part and concrete with reinforcing bars for the compression part. First, the strength and stiffness of GFRP plate serving as formworks for concrete casting under construction stage was verified by sand filling test. Then, static tests on six full-scale models with different penetrating bars and surface treatment under sagging moments were conducted to evaluate the load-carrying capacity and failure modes of proposed hybrid deck. The load and displacement relationship, ultimate flexural resistance, strain distribution on GFRP plate and concrete slab were measured during the test. Experimental results indicated that both surface treatment and penetrating bars improve the connection between GFRP plate and concrete, and promote the ultimate strength and rigidity of hybrid deck. In addition, the concrete used for encasing corrugated pultruded GFRP plates not only increases its stiffness, but also prevents local buckling failure of the GFRP plate with T-upstands. The comparison of experimental and theoretical ultimate strength results showed ACI 440 flexure and shear equation can effectively predict the ultimate capacity for the hybrid deck. The overall investigation showed the presented hybrid GFRP and concrete concept is a better alternative for beam-and-slab bridges. [Copyright &y& Elsevier]

The effect of the aggregate morphology on the chloride diffusivity of concrete was evaluated from the perspective of the physical tortuosity of the diffusive path at meso-scale. Three morphological indices, i.e., convexity, aspect ratio and circularity, were defined. A novel method by using the Fourier transform was proposed to simulate the meso-scale model of concrete. The physical tortuosity was defined based on the chloride diffusive streamline at meso-scale. The effects of aggregate morphological indices on the physical tortuosity were analysed by the multiple linear regression. The results show that: (1) the physical tortuosity increases when: (1) the area fraction of the aggregate increases; (2) the circularity decreases while the convexity and aspect ratio of aggregates increase; 3) the ITZ diffusivity decreases. (2) the area fraction and circularity of the aggregate have the first and second dominant effects on the physical tortuosity, while the effects of the convexity and aspect ratio are ignorable. (3) The chloride diffusivity of the interfacial transition zone between the cement paste and aggregate has a noticeable effect on the physical tortuosity. Based on the results, analytical models were proposed to fast evaluate the physical tortuosity. • The meso-scale model of the concrete is simulated by the Fourier transform. • The effect of the aggregate morphology on the physical tortuosity is studied. • The aggregate content and circularity have dominant effects on the tortuosity. • Analytical models of the physical tortuosity are developed. [ABSTRACT FROM AUTHOR]

Predicting the failure of reinforced concrete structures due to rebar corrosion is significant in maintaining the service life of concrete structures. This paper presents a multi-phase-field framework at the mesoscale to investigate the time-dependent process of non-uniform corrosion and concrete cracking. The evolution of the corrosion morphology and cracking pattern were described by a phase field corrosion model and a phase field regularized cohesive zone model, respectively. The diffusion-corrosion coupling and corrosion-fracture coupling were achieved by corrosion-induced current density and expansion-induced strain, respectively. The diffusion-crack interaction and the rust-concrete confinement were included in the model. The numerical results of each model component were compared with three separate experimental data. The effects of interface thickness and length scale on corrosion and fracture behaviors were investigated. Two numerical experiments were conducted to demonstrate the feasibility of studying the evolution characteristics of corrosion and cracking under localized corrosion and non-uniform corrosion in 3D. [ABSTRACT FROM AUTHOR]