This paper proposes a design for a testing program for accelerated life testing of reinforced concrete in the sulfite saline soil area. According to the situation of saline soil area, a constant current was used to accelerate the corrosion of steel rebar, and the wet sand with complex salt solution was used as electrolyte. The accelerated life testing was carried out, and a certain amount of accelerated life data was collected using electrochemical technique. By using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS), the microstructure and composition of corrosion products were analyzed. According to present codes, the critical corrosion current density of reinforced concrete was obtained. The linear model and exponential model were used to fit the average value of data corresponding to each time point respectively. Furthermore, based on the Wiener stochastic process, a reliability model for the degradation of reinforced concrete was established, and the accelerated life of reinforced concrete specimens was predicted. The results showed that the experimental scheme can effectively simulate the natural corrosion state of steel rebar in the sulfite saline soil area of western China. Corrosion current density can be used as the key factor for the durability deterioration of reinforced concrete specimens, and it can be used to judge the corrosion state of the reinforced concrete. Wiener stochastic process can effectively describe the durability degradation process of reinforced concrete specimens. By integrating the life data of the degradation process, the accelerated life reliability function established by this method can directly reflect the accelerated life of the specimen. The method is simple in calculation, and has certain value of popularization and application.
Raw earth bricks made from river sediments and natural fibers are essentially environmentally friendly bricks. They are made from river sediment waste and natural fiber waste, both of which are renewable resources. Sediment-based bricks have been formed from river sediment and flax fibers, the latter being considered as waste. Both types of waste are available in the same region. The study focused on the definition of water content by means of a miniature Proctor test, on the incorporation of short flax fibers of 2, 3 and 4 cm at various dosages and on the shaping by dynamic compaction of bricks of reduced size of 4 cm × 4 cm × 16 cm, dimensions similar to mortar specimens. The air-drying kinetics of the specimens were monitored from manufacture through to stabilization of their mass. The effects of water content, fiber content and fiber length were analyzed. Recommendations are given for the manufacturing and drying of green bricks and natural fibers.
1 January 2018 in Advances in Civil Engineering Materials
To predict the failure lifetime of reinforced concrete, a current accelerating corrosion test was performed on concrete by simulating the environment in an area with saline soil. To study the concrete’s process of deterioration under these conditions, this study selected the corrosion current density of the steel bars and the ultrasonic velocity of the concrete as the main factors in accelerated corrosion degradation. Then, by using the Weibull distribution function to model the degradation process, the study obtained the reliability function of the accelerated failure. The results showed that the corrosion current density of the steel bars and the ultrasonic velocity of concrete can be used as degradation factors of reinforced concrete, but the corrosion current density is more stable, which is propitious for modeling. Further, the Weibull distribution function can describe the durability degradation process of reinforced concrete effectively. Because of the high content of corrosive ions in saline soil, the reinforced concrete cover fails first.