Applied Mechanics and Materials Vols. 99-100

Abstract: Twelve PVC tubed short concrete columns and four columns without PVC tube confined were tested under axial load to investigate mechanical properties of axially loaded PVC tubed short concrete columns . The principal influencing factors such as concrete strength, loading condition and ratio of height to diameter were studied. Test results indicated that strength and deformation performance of core concrete increased as a result of the confinement of PVC tube. The PVC tube confinement effect on concrete will decrease with an increase in strength of concrete. Load- carrying capacity and deformation of short composite columns with different loading condition made some difference. As the ratio of height to diameter increases, load- carrying capacity and plasticity of short composite columns decreased gradually.

Abstract: This paper presents the results of experimental study on the effects of addition of excessive volume of fly ash on the strength characteristics of concrete. Crushed stone aggregate concrete with the replacement ratio of fly ash to Portland cement of 0, 10%, 20%, 30%, 40%, 60% and 80% were tested for compressive strength and modulus of elasticity at the ages of 7 days, 28 days and 91 days. The test result indicated significant reduction in compressive strength with the increase of fly ash content, indication 90% reduction at 80% fly ash replacement. Reduction in modulus of elasticity was found to be less than those of compressive strength, indicating 60% reduction at 80% fly ash replacement.

Abstract: For calcium leaching and loaded concrete in engineering structures, defining the initial damage state as basic state, the damage model of calcium leaching and loaded concrete is established using damage mechanical theory and principle of strain equality. It is shown that the mechanical properties of calcium leaching and loaded concrete are determined by calcium leaching, load and coupling effect. For calcium leaching and loaded concrete, the influence factors to stress at any point are elastic modulus, maximum strain, strain at this point and the degree of calcium leaching.

Abstract: For better understanding on adhesive ability and action mechanism of asphalt mortar, a series of mortar based on Zhong-hai asphalt were prepared and evaluated by the method used in high molecule composite materials. Some influencing factors including temperature, filler-binder ratio and asphalt type were discussed on interface adhesive ability. And some conclusions were conducted. The interface adhesive ability between asphalt and mineral filler will decline as temperature fall, until the glass transition or interface phase break appears in mortar system. To the same mineral filler and asphalt, interface adhesive ability of mortar will declines as filler-binder-ratio increases under a certain temperature, and beyond this temperature, high filler-binder-ratio will upgrade the interface adhesive ability and the whole binding performance of mortar.

Abstract: The portland cement clinker was successfully produced using pumice as the principal materials. Effects of different calcine temperature on cement clinker were studied. Phase compositions of clinker were confirmed by combining the phase diagram with X-ray diffraction. Microstructures of clinker were analyzed by scanning electron microscope. From the result of mechanical property showed that the compression strength of clinker can be reached 35MPa. The result of scanning electron microscope showed that the main hydrating products were CSH gels, AFt and CH crystals, the morphology of which were normal. With the prolongation of hydrating age, the hydrating products were richer and the cement paste was densified.

Abstract: By evaporable water test and compressive strength test, this paper studies on the influence of lime dust on pore structure and compressive strength of fly ash-cement paste. The test results show that: 1) With the volume of lime dust as cement replacement increasing, porosity and big pore to total volume ratio of fly ash-cement paste are gradually raising .However, with the volume of lime dust as fly ash replacement increasing, porosity of fly ash-cement paste decreases gradually, while big pore to total volume ratio firstly increases, and then decreases. 2) Substituting lime dust for isometric cement, compressive strength of fly ash-cement paste containing over 5% lime dust reduces gradually when the proportion of lime dust replacing cement raises. Whereas, substituting lime dust for isometric fly ash, the influence of lime dust content on compressive strength of fly ash-cement paste within less than 6% lime dust is not obvious. But When lime dust content is 9%, the compression strength of fly ash-cement paste increases by 20.0% around.

Abstract: The magnetic water can increase the strength of concrete, which can infer that the impermeability of concrete has been improved. According to the reason of permeation of concrete and on the basis of the study of magnetic water concrete by the predecessors, the effects such as hypothesis of the mechanism, action of the cement hydration, concrete workability, water ratio of the concrete, setting time and hardening process on impermeability of magnetic water concrete was studied in this issue. And the mechanism of impermeability of magnetic water concrete is also analyzed.

Abstract: The influence of stone dust content on chloride diffusion coefficient in C60 grade concrete were investigated by means of the natural immersion test, XRD test, MIP test and TGA test, respectively. The experimental results showed that the chloride diffusion coefficient increased with increasing the stone dust content in manufactured sand, and the chloride diffusion coefficient increased little when the stone dust content increasing from 7% to 13%. The hydration degree for cementitious and compressive strength for concrete was slightly promoted by using stone dust replacing cementitious at a low level. But the porosity and average pore size of concrete increased with increasing the stone dust content from 3% to 13%, and the concrete pore structure was the main factor that influences the changes of chloride diffusion coefficient in concrete.

Abstract: Fick’s second law and its analytical solution were usually used for analysis of chloride diffusion in concrete. But discretization of the continuous variables is more appropriate in modeling and discrete model is more suitable for engineering applications. In this paper, Difference Equation equivalent to partial differential equation was established with the difference method, and three-dimensional differential equation of Fick's second law was resolved. Based on this study，the convergence conditions of difference Equations for one-dimensional, 2D and 3D diffusion was given.

Abstract: In this study, concrete prisms were made with three mineral admixtures: fly ash, blast furnace slag or silica fume and with three water-to-binder ratios(w/b). Chloride penetration was measured by the rapid chloride permeability test (RCPT)-ASTM C1202, 150-days ponding test and alternate wetting and drying test by cyclic loading with salt solution and oven drying, and the results by the three test methods were compared. This paper discussed the effects of mineral admixtures and w/b on the concrete chloride permeability. Blending concrete with blast furnace slag, fly ash or silica fume was beneficial with regard to the resistance against chloride ion penetration. Concrete specimens with lower w/b showed lower chloride permeability.