Advanced Materials Research Vols. 261-263

Abstract: Secondary effluent and reclaimed water reusing as mixing water in concrete production is studied in this paper. The research mainly focuses on the influences of mixing water on the mixture ability of concrete, basic mechanical properties of concrete, concrete admixture (water reducing) and the aging resistance ability of concrete. The experiment shows that the abilities of concrete mixed with the reused secondary effluent and reclaimed water has no obvious difference from concrete mixed with drinking water, and actually it displays better function in terms of certain abilities than the latter.

Abstract: Salt-frost action is one of the main causes that induced the decrease of force resistance behavior of concrete structure in cold areas. By the freezing and thawing cycles of 0, 50, 100 and 200 times for the reinforcement concrete beam specimens in saline solution, the effects of freezing and thawing cycles on the bond behavior between steel bar and concrete are studied. The results show that: with the increase of freezing and thawing cycles, the bond strength and the bond stiffness trend to degenerate. The co-operating capacity between steel bar and concrete falls down. The ductility of the specimens reduces, and the bond failure presents brittle. The degradation speed of bond strength after salt-frosting is relevant to the size and stirrup ratio of specimens, the larger the specimen’s size is, and the higher the stirrup ratio is, The stronger the capacity of resisting freezing-thawing cycle is, the more slowly the bond property degenerate, the study using small specimens will probably underestimate the frost resistance of actual structure.

Abstract: Based on the method of electricity migration, the characteristics of the stainless steel in concrete structure are researched on in stray current and chlorate coupling environment. Test results show that stray current could make the stainless steel in concrete structure corrosion in a short time; The corrosion feature of stainless steel is different from the common steel obviously on the surface, which shows uniform pitting corrosion mainly; In static current and constant voltage conditions, the corrosion time of concrete sample with stainless steel to crack is shorter than that with common steel; In static current and constant voltage conditions, the theoretical corrosion amount is well related to the actual one, but is higher than the measured value clearly.

Abstract: Acceleration penetration tests of chloride ion were conducted for typical diurnal and semidiurnal tidal types in China with consideration of various values of soaking time. It was found that the content of chloride ion from shallow area near the surface of concrete to the pure diffusion area of concrete reduced more significantly with the depth than that in the pure diffusion area of concrete. Based on Fick’s second law, the variation laws of chloride ion content at the edge of the pure diffusion area and chloride ion diffusion coefficient in the pure diffusion area under different soaking time ratios were identified by using the chloride ion content distributions that were established based on the test results of concrete in the pure diffusion area. It was found that the chloride ion content and the apparent chloride ion diffusion coefficient in pure diffusion area may be very high when the ratio of soaking time ratio is between 0.3 and 0.42 or 0.6 and 0.7 for diurnal tidal type and 0.83 for semidiurnal tidal type, which will cause severe erosion in concrete structures in tidal zone.

Abstract: The form factor of abrasion particles is one of the most important Influencing factors of abrasion resistance of concrete. In order to evaluate the serves life of concrete, a relationship about the form factor of abrasion particles and the wear degree of abrasion resistance of concrete should be established. In this paper, wear process of basalt on concrete was studied under the flow velocity form 1.7m/s to2.4m/s by a improved under water method test equipment. Meanwhile, an image acquisition method was used to get the form factor of basalt to measure the influence of form factor of basalt on wear degree of concrete. The result shows: the abrasion rate of concrete is higher when the flow velocity is faster and the particle form is sharper, and there is an exponential function relationship between particle forms and abrasion rate.

Abstract: Recycled concrete which are made by waste concrete has significance of environmental protection and saving natural resources. But there are different study results of recycled concrete of domestic and foreign scholars, so it is necessary to do the further study of recycled concrete. Compressive strength test of 225 concrete standard cube specimens have been done by Hydraulic Type Universal Testing Machine, and the relationships among recycled concrete compressive strength, age and recycled coarse aggregate replacement ratio have been studied. The results show: the growth rate of early strength of recycled concrete is smaller than natural concrete of the same gradation and the growth rate of later strength of recycled concrete is faster than natural concrete; when the recycled coarse aggregate replacement ratio increases the compressive strength of concrete decreases, and when the recycled coarse aggregate replacement ratio is over 70%, the decrease ranges more apparent.

Abstract: Corrosion is one of the major factors affecting the durability of recycled concrete structures. Through experimental test of seven recycled concrete columns with corroded rebars, issues were discussed concerning the failure patterns, the effects of the degree of rebar corrosion on the ultimate load and axial deformation of recycled concrete columns. The test results show that the ultimate load decreases and the axial deformation increases as the degree of rebar corrosion increases.

Abstract: In this paper, a method for measuring carbonation depth of cracked samples was introduced, and experiments have been carried out to determine the extent of carbonation through a crack. Comparison of the carbonation in sound concrete and in cracked concrete has been suggested. The experiment conducted to demonstrate that crack will accelerate the carbonation of concrete, and increasing crack width allows more penetration of the carbonation reaction for three kinds of penetration mentioned in the paper. Carbonation depth penetration into the sample from exposed face increase rapidly, when the crack width increases from 0 to 0.1 mm. Carbonation degree of the cracked sample is greater than that of the sound sample at the same site according to the results of calcium carbonate contents.

Abstract: In this paper, the creep experiment of UEA expansive concrete is performed. Based on the creep experiment results, the creep model of UEA expansive concrete is gotten by Curve Fitting function supplied by ANSYS. By comparing the residual error, the modified time hardening equation is recommended to simulate the primary stag constitutive relation of UEA expansive concrete and the primary + secondary time hardening equation is recommended to simulate the whole constitutive relation of UEA expansive concrete. Besides, when calculating by ANSYS, the suggestions about the selection of the expansive concrete element type are given.

Abstract: In order to study the durability of Polypropylene fiber concrete, indoor artificial methods were used to simulate dry-wet cycle and deicer-frost damage. The results indicated that amounts of polypropylene fibers increase the flexural strength of concrete slightly. The chloride penetration depth increased as the cycles of dry-wet was increased, adding 0.1% PPF into concrete have the prefect resistance of Cl^- penetration. Under salt freezing cycle, the deicer-scaling resistance of concrete is reduced by the addition of Polypropylene fiber. The corner of concrete has the largest Cl^- penetration area.