Abstract: Galvanizing on the surface of reinforcing steel is an effective measure to control corrosion of reinforcing concrete structures. The corrosion behaviors of hot-dip galvanized (HDG) reinforcing steel in simulated concrete pore solution (SCP solution) with various pH and chlodride values were investigated using electrochemical impedance spectroscopy (EIS). Two equivalent circuit models corresponding to the corrosion process were proposed and the evolution feature of the corrosion parameters were analyzed. The results show that when the SCP solution was carbonated seriously (pH<11), there is hydrogen evolution phenomenon and the corrosion resistance of HDG reinforcing steel is decreased. A minute carbonation of SCP solution (11.5≤pH<12.5) favors the further passivation of the zinc layer and the corrosion resistance is enhanced. The corrosion rate of HDG reinforcing steel at pH=12.0 is minimal, around 0.59 μm/year, whereas that at pH=12.5 is approximate 1.21 μm/year. In the conditions of pH=12.5 and NaCl concentration no more than 0.5wt.%, the corrosion resistance of the passivation film on HDG reinforcing steel is good. In a serious carbonation case, the corrosion rate is increased greatly with chloride ions.
Abstract: This essay analyzed reasons of bending accidents for tower crane lifting boom in detail, and carried out mechanical analysis in different cases. The essay also mentioned the consequences caused by failure of welding, made reliable conclusion, and put forward measures to prevent such accidents.
Abstract: During the process of elastic deformation, based on first law of thermodynamics, deformation energy value equals to the work done by external forces moving through elastic deformation, which can determine the amount of elastic deformation. According to second law of thermodynamics, the true deformation energy value should be the minimum of all possible deformations, which can determine the distribution rule of elastic deformation. From this, it can be realized that there are some problems existed in the derived process of the minimum potential energy principle. The total potential energy of system remains constant in all of possible elastic deformation. Applying the two characteristics of elastic deformation, a few application problems could be solved expediently.
Abstract: With a rolling stone gathers tent hole structure as the prototype, using ABAQUS finite element software to simulate the rolling stones impact process with different impact, research rolling angle and speed impact tent hole structural dynamic mechanical response for rolling stone protection design, provide necessary basis. The results show that the rolling stones in different speed and incident angle of tents hole shocks on concrete protective structure of contact force ,displacement and injuries have great influence and for the rolling stones protection engineering design to provide theoretical reference.
Abstract: Reaches on durability of concrete has been made great advances over the past decades. However, little works have been done on the corrosion of reinforced concrete exposed to boric acid in cooling pond of heating exchange system of nuclear power plant. The purpose of this study is to experimentally investigate the behavior of reinforced concrete in such circumstance. Tests were carried out on specimens cured in a standard moisture room at a temperature of 20±3°C. Three different concentration of boric solution (2000ppm, 8000ppm, 30000ppm) were simulated to accelerate the corrosion. The compressive and splitting tensile strength,elastic modulus of concrete , mass loss rate of steel bar, bond strength and flexural bearing capacity of reinforced concrete at 60, 90, 120, 150 and 180 days were obtained respectively. The results indicate that the presence of boric acid below 30000ppm does not significantly affect serviceability of concrete. The corrosion is slight for the specimens with crack less than 0.4 mm under flexural loads. Boric acid almost has no effect on the corrosion of the steel bar and bond strength.
Abstract: Cement concrete has an increasing utilization in highway construction. However, the lower flexural tensile strength and abrasion-resistance restricted the development of concrete pavement with heavy traffic. Hence, It has highlighted the need for research on high performance concrete (HPC). The design of specific concrete normally depends on the mixing of mineral admixtures in concrete mixture. This paper presents the first experimental study on strength and abrasion-resistance enhancement admixture (SAEA) mixed with slag powder, steel slag powder and silica fume. The optimal proportion of three mineral admixture and reasonable mixed amount of SAEA were then given, and the mechanism of SAEA reacted in concrete was analyzed based on sol-gel theory. Lastly, the effect of concrete mixed with SAEA was validated and the micro-structure transformation of specimens was given by SEM.
Abstract: Boric acid (H3BO3) is often used for cooling the heat in nuclear power plant. Though the drastic measures have been taken, the potential leakage still can not be fully eliminated. Therefore, an attempt to understand the durability mechanism of RC subjected to boric acid is of vital importance. In this paper, specimens cured in a standard moist room at a temperature of 20 ±3 °C after 28days were immersed in three different concentration of boric solution (2000ppm, 8000ppm, 30000ppm) artificially simulated to accelerate the corrosion of acid environment. The hydration products are investigated. Microstructure of reinforced concrete on the surface, 2cm and 4cm away from the surface at ages of 60, 90 and 150 days are examined using X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Results indicate that main hydration product is Ca(BO2)2,boric acid corrosion to concrete surface can only be detected from the specimens in 30000ppm solutions at the ages of 150 days and its effect is slight. However, the inner part of the concrete was not affected. The results of XRD coincide with those of SEM.
Abstract: This paper is to study the sand concrete, sand is mixed with sand as fine aggregate in concrete, in recent years by large-scale applications in the coastal areas, especially in Ningbo, a coastal river sand shortage is resolved this problem, coupled with low prices, most of the commercial concrete companies are willing to play down the use of sand instead of river sand, the paper surveys and analyzes the use of sea sand in Ningbo and the physical characteristics of sea sand, on this basis, simulates sand chloride doped, dilute sea sand, not dilute sand sea sand and fly ash concrete mortar strength was measured to analyze the strength of law, by comparison analysis, the presence of chloride in the early strength concrete sand.
Abstract: This paper mainly explain and expounded folding compressive strength of the different types of sea sand mortar , fly ash to the sea sand concretes mortar intensity influence as well as the chloride ion content to the sea sand concretes mortar intensity influence. The pulverized fly ash has the postponement function to the sea sand concretes early strength, the chloride ion has the promoter action to the sea sand concretes early strength. 20% pulverized fly ash be good to the sea sand concretes long-term strength development influence, can achieve the goal which enhances the sea sand concretes the long-term strength . The chloride ion is greater to the concretes early strength influence, especially in previous 3 days. Along with the time development, the chloride ion influence weakens, but the pulverized fly ash enlarges to the concretes intensity's influence factor. A two-phase arrived, the final concrete strength values close to each other.
Abstract: Based on the large deformation theory and considering the axial extension of the beam, the governing equations of post-buckling of a simply supported elastic FGM beam subjected to conservative and non-conservative distributed forces were established. In the analysis, it was assumed that the material properties of the beam vary continuously as a power function of the thickness coordinate. By using shooting method, the nonlinear boundary-value problem was solved numerically and the equilibrium paths as well as the post- buckling configurations of the deformed beam were presented. A comparison between the results of conservative system and that of non-conservative systems were given. The results shows that the features of the equilibrium paths of the the functionally graded beam under non-conservative are evidently different from those to a conservative one.