Advanced Materials Research Vols. 261-263

Abstract: In this study, we studied on the durability of restorative cement mortar for deteriorated concrete at complex deteriorated conditions as variation of temperature and of humidities. We made a comparison between restorative materials with insulation function and restorative materials without insulation function in items of compressive and bending strength and permeability of water, durability for carbonation, salt damage, diffusion coefficient of salt at complex deterioration conditions like change of temperature, change of humidity, For insulation, we used close-pore type Alumino-Silicate lightweight aggregate and substituted 12 wt% and 15 wt% out of original restorative cement mortar without insulation function.As a result, it was found that original restorative cement mortar without insulation function fail to meet Korean Standard on polymer modified cement mortar for maintenance in concrete structure, but restorative cement mortar with insulation function is in contentment Korean Standard to meet excellent than restorative materials without insulation function for durability at complex deteriorated conditions.

Abstract: A three-part model (mortar, original concrete and ITZ) was established in this study to analyze the chloride coefficient of the new interfacial transition zone (ITZ) in recycled aggregate concrete (RAC). Based on this model, a formula for calculation was derived from the chloride transport characteristics in the steady state. Two types of RAC were used to study the properties of ITZ by steady-state migration test and Scanning Electron Microscope (SEM) method. The results indicate that the chloride diffusion coefficient of new ITZ in RAC is about 1 to 4 cm²/year, and that the addition of superfine phosphorous slag (PHS) not only reduces the chloride diffusion coefficient of mortar but also decreases the thickness and the chloride diffusion coefficient of new ITZ in RAC due to its pozzolanic reaction effect. The chloride permeability of mortar containing 20% PHS is only 1/5 of that in normal RAC. The chloride diffusion coefficient of ITZ in normal RAC is about 10 times greater than that of ordinary mortar. When modified with PHS and superplasticizer, the permeability of chloride in new ITZ is 3 to 7 times greater than that in the ordinary bulk cement paste. Furthermore, the mechanism and the effects of superfine phosphorous slag (PHS) on the resistivity of chloride permeation were discussed on basis of the experimental results and the images of SEM.

Abstract: A new method for fatigue test is developed for semi-rigid pavement materials in this paper, which is much more reliable than the current method in domestic. The max deflection and max tensile strain among different specimens are compiled in flexural bending strength test. And the fatigue equation for lime fly-ash treated aggregate (LFTA) is established.

Abstract: Since high strength of lightweight aggregate concrete leads to increased brittleness, fiber reinforcement should be considered for improving strength and ductility. 5 groups of SFLWC specimens with different steel fiber volumes including 0.0%, 0.5%, 1.0%, 1.5% and 2.0% were tested to investigate the effect of steel fiber content on the static mechanical properties and impact resistance of lightweight aggregate concrete. The static mechanical properties include the prismatic compressive strength, splitting tensile strength, first-crack flexural strength, flexural strength, and flexural toughness, etc. The experimental results indicated that addition of steel fiber can greatly improve such mechanical properties as the splitting tensile strength, flexural strength, flexural toughness and impact resistance, but leads to a little effect on compressive strength. Further more, the author suggests the feasible volume ratio of this kind of steel fiber is 1-1.5%.

Abstract: This paper is supported by National 863 Plans Projects and Sub-project of Science and Technology Department of Sichuan Province, through experimental research on flexural behavior of non-crack recycled concrete one-way slabs reinforced with CFRP, research the ultimate bearing capacity and maximum deflection of it, and comparative analysis the results with recycled concrete one-way slabs which is not been reinforced and reinforced with CFRP after post-cracking. The results show that, the ultimate bearing capacity is higher than the non-crack reinforced concrete slabs, at the same time the deflection is smaller. The ultimate bearing capacity of non-crack recycled concrete one-way slab reinforced with CFRP is lower than post-cracking recycled concrete one-way slab reinforced with CFRP, at the same time the deflection is greater. But found bearing capacity and deflection is lower than that post-cracking recycled concrete one-way slab reinforced with CFRP when experimental on flexural behavior of non-crack recycled concrete one-way slabs reinforced with CFRP, and do a preliminary analysis for this phenomenon.

Abstract: Construction field has experienced a growing interest in Fiber Reinforced Concrete (FRC) due to its various advantages. The disposal of industrial waste especially non biodegradable waste is creating a lot of problems in the environment. In the present investigation, an attempt has been made by using non biodegradable waste (polyester fibers) in the concrete to improve the crack resistance and strength. Concrete having compressive strength of 25MPa is used for this study. Samples were prepared by using various fiber contents starting from 0 to 6% of with an increment of 0.5% for finding Compressive strength, split tensile strength and flexural strengths. It is observed that, compressive strength, split tensile strength and flexural strengths of concretes is increasing as the fiber content is increased up to some extent.

Abstract: Pseudo dynamic test and pseudo static test were carried out on 1/2 scale model of light composite structure. By experimental research, hysteretic curves of base shear force and top displacement of the model structure were got, which come from various sections of pseudo dynamic test and pseudo static test, and through hysteretic curves of base shear force and top displacement of the model structure, skeleton curve of base shear force and top displacement of the model structure can be got. Outside line of all skeleton curves was skeleton curve of the light composite structure model. By analyzing and simplifying of the skeleton curve, finally restoring force model of the model structure was obtained, so reasonable dynamic analysis method of seismic design of the model structure can be offered. Research shows that as peak acceleration of inputting seismic wave continuously grows, especially when the peak acceleration reaching 800 gal, after the model structure reached plastic stage and in the stage of pseudo static test, the hysteretic curves become fuller and fuller, which shows that, with continuous emerging and propagation of crack, the structural rigidity losses gradually, and its energy dissipation capacity increases gradually. So earthquake fortification level of not collapse when hit by rarely occurred earthquake will achieve.

Abstract: Based on the coupled thermal-fluid pipe element, a numerical computation method for concrete temperature field with pipe cooling is proposed in this paper. This method has both the high efficiency of equivalent negative heat source method and the high precision of cooling pipe discrete element method. The theory and detailed steps of the method are introduced. Then the validity and accuracy of the proposed method are demonstrated by an engineering example of concrete ship lock which is better consistent with the measured results.

Abstract: Geopolymer has been attracted world attention as a potentially revolutionary material that is one of the ideal substitutes of portland cement. Fundamental studies on geopolymer are increasing rapidly because of its potential commercial applications. However, little work has been done on its erosion resistance of sulfate. In this paper, slag and metakaolin as source materials, different modules of water-glass as activator were used to prepare slag-based geopolymer which was then prepared to make slag-based geopolymer concrete. Linear expansion rate and mass loss of concrete were used as indicators to explore different erosion rules of slag-based geopolymer concrete which was long-term immersed in the 5% ( by mass ) Na₂SO₄ solution. Comparative experiments were also done between slag-based geopolymer concrete and ordinary cement concrete. The results showed that geopolymer concrete had excellent sulfate resistance performance, linear expansion rate and mass loss rate of geopolymer were 0.024% and 0.58% respectively at the soaking age of 49d as the water glass modulus was 1.4 and the water-glass content was 4%. It was also found that the anti-sulfate ability of geopolymer concrete is much better than that of ordinary concrete with the same strength grade.

Abstract: Proposed is a simple analytic model that can simulate the chloride diffusion distribution in a modeled recycled aggregates concrete (RAC). In this paper, on the one hand, the RAC is divided into three phases such as normal aggregates, new mortar and old attached mortar; on the other hand, a single aggregates RAC model was built, finite element method (FEM) is used to simulate chloride diffusion process based on the parameters of diffusivities summarized or derived from other literatures. It is found that the chloride concentration distribution in the RAC shows a band-like profile instead of a smooth curve for a homogeneous medium by ten years diffusion, with the bandwidth undulating and narrowing as the diffusion depth increases. The concentration of chloride distribution can be indicated by the different colors and, therefore, the proposed model allows more accurate realization of diffusion process.