Applied Mechanics and Materials Vols. 405-408

Abstract: Removed at authors request

Abstract: In order to estimate the impact of the degree of water saturation of concrete to chloride ion diffusion coefficient, the experimental setup allows to measure chloride diffusion coefficient through nonsaturated concrete specimens with controlled degree of water saturated. The different degrees of water saturation of concrete specimens were obtained, by using saturated solutions of NaCl and KCl controlling the relative humidity, then applied Rapid Cloride Permeability Test method to measure the cloride diffusion coefficient. The test results show that chloride diffusion coefficient depends strongly on the degree of water saturation of concrete. Beside, this relationship shows the non-linear relationship, in which, chloride diffusion coefficient reachs the maximum value in fully saturated concrete specimens.

Abstract: Capillary absorption effect is very important to the research of concrete durability. Initial surface absorption test (ISAT) method has been employed to investigate the effect of W/C, age, aggregate volume percent and concentration of NaCl solution as a transmission medium of the capillary absorption of the cement-based materials. Experiment results indicate that, the capillary absorption coefficient increases with the increasing of W/C, but decreases with the increasing of age and aggregate volume percent. Within a certain range of low concentration, the capillary absorption coefficient increases with the increasing of the concentration of NaCl solution, however when the concentration is too high, the transmission rate will be lower than pure water. This investigation provides an experimental foundation for the durability design and service life assessment of concrete structures.

Abstract: Entity structure concrete chloride ion permeability resistance change law were studied, relying on Qingdao Bay Bridge project, using entity structure concrete specimen under the same condition maintenance, using RCM method test diffusion coefficient at the age of 28d,60d,90d,1y and 2y. Different mixture concrete chloride ion permeability resistance change law were Interoperated in essence, combining with cementitious materials hydration mechanism.

Abstract: This paper displays the crack load failure pattern and influences on crack load of reinforced ceramists concrete beams in different reinforcement ratio, concrete cover thickness and diameter of rebar through the experimental study of bending anti-cracking property of 8 reinforced ceramists concrete beams, and proposes the method of calculation cracking moment of normal section for ceramists concrete beam.

Abstract: The mechanical property of the concrete under high temperature will go through great changes with much greater deformation. The uneven temperature distribution causes equilibrium temperature stress of the cross section and deformation of components, thus damaging the structure system of the concrete. This paper conducts a high-temperature test on the C25 concrete specimen with fire retardant coating, compares the test result with the test on the C25 concrete specimen without fire retardant coating, and analyzes the protective role of the surface fire retardant coating in the concrete structure buildings in case of fire.

Abstract: Fly-ash concrete used in massive concrete structure has superior advantages to reduce hydration heat. On the other hand, the fly-ash concrete has negative property of low strength development at early age because pozzolanic reaction of fly-ash activates at mature age, such as after 28 days. To investigate these characteristics of fly-ash used in concrete, the present study discusses thermal cracking possibility of fly-ash concrete by using FE analysis software. The present study employs prediction formulae proposed by Zhang and Japanese design code in the simulations. The objects in this study are normal strength concrete mixed of fly-ash up to 50% of replacement ratio to cement. The comparative investigations show that temperature effect is more significant than strength development at early age. Based on the analytical study, high volume fly-ash concretes of 30-50% of the replacement ratio can be concluded as effective and useful materials to reduce the cracking possibility in massive concrete structures. Keywords-Fly-ash concrete; Early Age, Prediction Formulae for Strength; Thermal Stress Analysis

Abstract: Nowadays, influences of concrete cracking on durability of concrete structure are widely reported. However, the influence of macro cracks on chloride diffusion of concrete is unknown under the condition of marine submergence. Therefore, the present paper adopted a notch method to study natural chloride diffusion in cracked concrete with a width of above 0.3 mm. The results show Apparent diffusion coefficient of acid soluble chloride rises from 2.66 ×10^-12 m²/s to 5.92×10^-12 m²/s with increasing crack width from 0 mm to 0.45 mm. Besides, one exponential function was used to describe the piecewise relationship between diffusion coefficient (water or acid soluble chloride) and crack width.

Abstract: In this paper, the temperature fields of concrete specimens reinforced by paste method were analyzed by experiment and ANSYS in the fire, it proved that the impact of reinforcement material on the temperature field of the specimens can be ignored, it identified that the best thickness of the fire-retardant coating is 40mm for steel-confined specimens and 50mm for CFRP-confined specimens. The calculations agreed well with the experimental results, it provides conditions for mechanical properties of the concrete reinforced by paste method at high temperature.

Abstract: In this paper, the flue gas desulfurization gypsum (FGD) generated from thermal power plant is used to produce high strength gypsum. The basic properties of super high strength gypsum prepared by FGD gypsum are investigated based on the test results of strength, thermal expansion rate, crystal appearance and size. The results indicate that the properties of high strength gypsum prepared by FGD gypsum above α50 standard. This can be a reference for gypsum-based α super high-strength gypsum related product development.