Numerical simulation of chloride diffusion in cementitious materials by lattice type model

The chloride ingress is one of the most significant problems to reinforced concrete structures in coastal areas and cold regions where the de-icing salt is commonly used. In this paper, the lattice type model which has been widely used in fracture analysis of brittle materials is applied to simulate the chloride diffusion process in cementitious materials. The theoretical background of the lattice type model in solving the mass transport problem is briefly presented. The analytical solution of the Fick’s law is adopted to theoretically validate the developed lattice type model. After that, two typical case studies are included to demonstrate the application of the lattice type model in the chloride ingress issue. In the first case, the tortuosity effect of the aggregates on the chloride diffusion front at meso-scale is studied by the lattice model. In the second case, the lattice model is applied in the simulation of the chloride diffusion in cracked concrete. The results show that the lattice type model can be a useful tool to simulate the chloride ingress in the cementitious materials

Auditor of State Mary Mosiman today released a reaudit report on the Mason City Community School District (District) for the period July 1, 2014 through June 30, 2015. The reaudit also covered items applicable to the years ended June 30, 2016 and June 30, 2017.

Auditor of State Mary Mosiman today released a reaudit report on the Mason City Community School District (District) for the period July 1, 2014 through June 30, 2015. The reaudit also covered items applicable to the years ended June 30, 2016 and June 30, 2017

Primer registro de anomalía intersexual gonadal de Trachurus mediterraneus (Steindachner, 1868) desde el Mar de Alborán.

El objetivo principal de este trabajo es dar a conocer el primer registro de una anomalía intersexual gonadal de Trachurus mediterraneus desde el mar de Alborán (Mediterráneo occidental). Este espécimen es el primer registro de intersexualidad para un jurel en el mundo.Postprin

Effect of Seasonal Characteristics of Temperature and Relative Humidity on Chloride Diffusion Process in Concrete: A Preliminary Theoretical Study

The chloride diffusion process can be greatly affected by the temperature and relative humidity. Annual average temperature and relative humidity are often adopted in analytical models to calculate chloride profiles. These models, however, cannot consider the seasonal characteristics of temperature and relative humidity. This paper presents a theoretical study to solve the above problem. The temperature and relative humidity in several major cities in China are first collected. Then, the governing equation of one-dimensional chloride diffusion is solved by both analytical and numerical methods using the annual and monthly average temperature and relative humidity, respectively. Based on these two methods, a parameter called “seasonal correction coefficient” is introduced into the analytical models. The values of the coefficient for major cities in China are obtained. Based on the results, it is found that: (1) the analytical solution with annual average temperature and relative humidity is questionable to calculate chloride profiles for typical cities, (2) the seasonal correction coefficient is independent on the apparent chloride diffusivity, affected slightly by the activation energy of chloride ions during diffusion and greatly by the critical relative humidity for common water-to-cement ratios of ordinary Portland cement (OPC) mortar and concrete

Numerical simulation of chloride diffusion in cementitious materials by lattice type model

The chloride ingress is one of the most significant problems to reinforced concrete structures in coastal areas and cold regions where the de-icing salt is commonly used. In this paper, the lattice type model which has been widely used in fracture analysis of brittle materials is applied to simulate the chloride diffusion process in cementitious materials. The theoretical background of the lattice type model in solving the mass transport problem is briefly presented. The analytical solution of the Fick’s law is adopted to theoretically validate the developed lattice type model. After that, two typical case studies are included to demonstrate the application of the lattice type model in the chloride ingress issue. In the first case, the tortuosity effect of the aggregates on the chloride diffusion front at meso-scale is studied by the lattice model. In the second case, the lattice model is applied in the simulation of the chloride diffusion in cracked concrete. The results show that the lattice type model can be a useful tool to simulate the chloride ingress in the cementitious materials

A study on image-processing based identification of aspect ratio of coarse aggregate

The mesoscopic simulation of behaviours of cementitious materials under different conditions has become a hot topic in academic research, as it provides more details to the mechanism study and structural design. To conduct a mesoscopic simulation, the meso-scale model of cementitious materials must be built. To ensure the precision of the aggregate shape in the simulated meso-scale model, key shape parameters of real aggregates should be identified. In this paper, an image-processing based method is proposed to detect the aspect ratio of a polygonal aggregate. The procedure and used algorithms are demonstrated in detail. As an application, totally about 1000 coarse aggregates from the Xinjiang, China are selected to identify the aspect ratio. It is found that the aspect ratio of coarse aggregates is a random variable following the Generalized Extreme Value (GEV) distribution. The published data by using the X-ray technique is also adopted as a comparison, and the results are almost the same as each other, which indicates that the aggregate source does not have an obvious effect on the probabilistic characteristics of the aspect ratio

Engineering practices on surface damage inspection and performance evaluation of concrete bridges in China

This paper mainly demonstrates some experiences in China regarding surface damage inspection and performance evaluation of reinforced concrete (RC) bridges. To begin with, the mechanisms of the major damages of RC bridges such as chloride attack, concrete carbonation, and rebar corrosion are briefly reviewed. A statistical result of concrete cracking that exists in (prestressed) concrete bridges is presented as well. Second, the inspection practices of surface damages such as crack by using computer vision and deep learning on the RC pylons of the Jiang-Yin Yangtze River bridge are demonstrated. Third, the specifications used in China for the performance evaluation of RC bridges are introduced. Its general philosophy and framework are explained. The Xia-Men bridge is taken as an example to illustrate how to conduct a quantitative performance evaluation by following the instructions in China specifications. Finally, some perspectives on more advanced and efficient inspection techniques and performance evaluation methods are provided

Forecasts for the fish Migration and Fishing time under Marine Environment Changes based on the ARIMA model

The validation of using ARIMA model to predict temperature is proved based on the global ocean temperature date monthly from1960 to 2019. According to ARIMA(1,1,0), bootstrap method is used to simulate 10000 possible prediction cases by MATLAB code, which lays a great foundation to predict the migration of fish. Then based on the 10000 temperature change samples generated by bootstrap method in model, migration situation of each sample is simulated to identify the most likely locations of the fish. It was finally shown that the fish are mainly distributed in the area between Iceland and the Faroe Islands 50 years later. Due to technical shortcomings of small fishing companies, if fishing vessels are too far from the continental shelf, they will face problems such as insufficient energy, low safety, and difficulty in keeping fish fresh. Finally, we estimate the elapsed time until the fishermen are unable to catch these two types of fish in their fishing area based on how fast the temperature changes, with the best, worst, and most likely scenarios