Advanced Materials Research Vols. 450-451

Abstract: The effect of aggregate shape on the chloride diffusivity of concrete is studied. To represent the heterogeneity of concrete, a three-phase composite ellipse model is constructed and the relative dimensions are determined by calculating the area fraction of interfacial transition zone in a numerical manner. The height of each bar in the lattice mesh is derived analytically. The lattice method is then used to estimate the chloride diffusivity of concrete. After the validity of the numerical method is verified with experimental results, the effect of aggregate shape on the chloride diffusivity of concrete is evaluated in a quantitative manner.

Abstract: Seaweed house is special tradition at Jiaodong Peninsula, it has good ecological characteristics. This has much to do with the properties of the roof materials and the way of roofing construction. This text analyzes and discusses the components and bio-structure of seaweed (eelgrass), and the measures of these roofs, to reveal the contribution of seaweed materials on the seaweed house.

Abstract: We consider the positive definite solution of the nonlinear matrix equation . We prove that the equation always has a unique positive definite solution. The iteration method for the equation is given.

Abstract: At steam curing and moist curing conditions, the mechanical properties of concrete with different fineness and different proportions ultrafine fly ash-slag composite were studied. The experimental results indicated that the addition of ultrafine fly ash-slag composite had improved the long term mechanical properties of steam-cured concrete. The concrete with ultrafine fly ash-slag composite has lower drying shrinkage and creep compared to that of control concrete.

Abstract: Through splitting tensile tests on 30 plain concrete and polypropylene fiber concrete specimens with the dimensions of 100mm × 100mm × 100mm , studied the influence of the different scales of polypropylene fiber and hybrid fiber on concrete splitting tensile strength and splitting tensile deformation. The results showed that: the splitting tensile strength of concrete for single-doped fine fiber had increased 7%~31%,for single-doped coarse fiber had increased 7%~39%,and mixing-doped coarse-fine fiber had increased 2%~50%. Doped-fiber can improve the concrete splitting tensile toughness, it's enhancement sort: mixing-doped coarse-fine fiber concrete > single-doped coarse fiber concrete > single-doped fine fiber concrete> plain concrete

Abstract: Spherical sponge iron (SSI) with high activity and intension could be prepared through direct reduction by hydrogen. To optimize the reduction technology, reductive kinetics of SSI was analyzed on the basement of unreacted core model. In the light of the single reaction surface theory, the ratio of internal diffusion resistance fI and chemical reaction resistance fR was calculated according to the weight loss curve of SSI reduction. Under different temperature, both fI and fR increased with the reaction time, especially the radium of unreacted core was small after a period of reaction time. Compared the ratio of fI and fR, it concluded that SSI reduced by hydrogen was controlled by the chemical reaction, combination of chemical reaction and the internal diffusion, the internal diffusion under the temperature being lower than T3, from T3 to T4, more than T5, respectively.

Abstract: Uniaxial tensile strength is one of the important strength parameters of concrete. In this study, two test methods were applied to determine direct tensile strength, splitting tensile strength and flexural strength of fly ash concrete specimens with the same cross section and different strength grades. Relationship among the uniaxial tensile, splitting tensile and flexural strength of concrete were researched. Furthermore, the influence of concrete strength and age to the three tensile strengths were specifically analyzed in the paper.

Abstract: In this study three-dimensional X-ray computed tomography (X-ray CT) is used to investigate the testing results differences of cement paste and mortar before and after drying. It can be found that the mean gray values of paste and mortar before drying are bigger than after drying, and the impact of drying on cement paste is more serious than mortar. In addition, the porosity of non-drying cement paste and mortar is 1.10% and 0.43%, while that of drying cement paste and mortar is 1.55% and 0.70%, respectively. So, the porosity of paste and mortar markedly increases after drying process. The numbers of pores of paste and mortar sharply increase after drying process in particular between 0.01mm3 and 0.1mm3. The impact of drying on smaller pores is more serious than bigger pores.

Abstract: For saving costs and improving the durability of concrete, the superplasticizer was often added into the modern concrete. Since the superplasticizer was used, many apprehensions have occured, e.g. slump loss, segregation of concrete, entraintment of air, etc. Namely, there is the compatibility problem of superplasticizer and cement. Many researchers have studied on these factors which have an effect on the compatibility of superplasticizer and cement. These factors include the physical and chemical property of cement, the property of superplasticizer and other factors. Various factors which have an impact on the compatibility of superplasticizer and cement were summarized in the paper.

Abstract: The urethane reaction kinetics of 1,2-propanediol with phenyl isocyanate is monitored with in-situ FT-IR with xylene as solvent. Triethylamine is used as catalyst and its amount effect is investigated. Rate constants for the reaction with different concentrations of triethylamine are worked out. The urethane reaction has been found to be a second order reaction and the reaction is largely accelerated with the increase of catalyst concentration. Furthermore, when triethylamine is used as catalyst, the rate constants are different between initial stage and final stage, which belong to different hydroxyls in 1,2-propanediol. However, the rate constant is the same when there is no catalyst, which shows no reactivity difference for hydroxyls in 1,2-propanediol.