Advanced Materials Research Vols. 821-822

Abstract: This paper presents the theoretical analysis of capillary absorption dynamics for cemementitious material. Fractal theory is applied to analyse tortuosity of capillary pores in cementitious material and a definition of tortuosity is given. The dynamic equation of capillary absorption considering water evaporation and tortuosity of capillary pores is derived. Based on the dynamic model, the capillary coefficient and sorptivity of concrete are explained theoretically. In absorption test, water evaporation is one of the main reasons caused variations from linearity between water absorption height and the square root of time, or between water amount absorbed and the square root of time. In cementitious material, the evaporation rate is very small compare to capillary flow velocity at the initial time of absorption test. For simplification of testing procedure, there is no meaning to modify absorption test.

Abstract: The strength and durability are the main design parameters of high performance concrete. Concrete should be strict attention to the requirements of various raw materials and mix proportion design in the production process. Engineering example shows that high performance concrete has good durability, economy and environmental protection.

Abstract: Red mud is a kind of fine particles which with a strong alkalin value. The paper used red mud powder to prepare red mud-rubber composite for the feasibility of recycling about red mud. XK-160 open-mixing machine, QLB Series vulcanizing machine, multifunction electronic tensile machine, JC-1086 rotary roller, fluorescence spectroscopy analyzer, BT-9300 laser particle size distribution analyzer etc were used for test. The results showed that red mud in rubber composites played as beneficiations added in rubber significantly.

Abstract: The structures of reinforced concrete has been extensively increased with rapid development of industrial society. Furthermore, these reinforced concretes are often exposed to severely corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Thus, the corrosion problem of a steel bar embedded in the concrete is very important in terms of the safety and economic points of view. In this study, a multiple mortar test specimen (W/C:0.4) that had six types of cover thickness was prepared and immerged in flowing seawater for five years. And the effects of cover thickness and immersion years on the corrosion properties of the steel bars were investigated using electrochemical methods such as measuring corrosion potential, anodic polarization curve, and impedance. At the beginning of immersion (0 year), corrosion potentials exhibited increasingly nobler value with increasing the cover thickness. However, after being immersed for 5 years, the corrosion potentials conversely shifted in the positive direction with decreasing the cover thickness. As a result, the relationships between corrosion potential and cover thickness were not in good agreement with each other after 5 years. In addition, after 5 years, the thinner cover thickness, the higher value of impedance at 0.01Hz. It is considered that corrosive products deposited on the surface of the steel bar embedded in mortar specimen in the case of thinner cover thickness played the role as a resistance polarization which resulted in decreasing the corrosion current density. Consequently, it seemed to be somewhat problem that evaluation on the corrosion property in reinforced steel would be estimated by only the corrosion potential measurement. Therefore, it is suggested that we should take into account various parameters such as cover thickness, corrosion potential, and immersed years etc. for its accurate assessment. Keywords : Cover thickness, Corrosion potential, Anodic polarization curve, Impedance, Resistance polarization

Abstract: Polyester fabric is prone to static charging. Its decay rate is small and static phenomenon is serious. Therefore, the polyester products are usually modified. Polyaniline (PANI) is a conductive polymer and it has many advantages. Polyester (PET) fabric was treated with alkali and low temperature plasma. Polyaniline/Poly (ethylene terephthalate) composite conductive fabric was prepared though an in-situ polymerization process using aniline as monomer. The structural properties of PANI/PET composite conductive fabric were studied and characterized. After alkali deweighting and low temperature plasma, a film made of PANI on the surface of PANI/PET composite conductive fabric was formed easily.

Abstract: Thermal control coatings (TCCs) play an important role in thermal management of spacecrafts and satellites by their thermo-optical properties. In this research, the novel TCCs were prepared by incorporating the self-made strontium silicate and zinc oxide into the potassium silicate binder. The effects of strontium silicate on phase composition, microstructure and optical performance of TCCs were studied using scanning electron microscope and spectroreflectometer. The results show that: strontium silicate can improve near infrared band (1000~2400nm) spectra reflectance. Compared with traditional zinc oxide TCCs, the novel composite coatings enhance the reflectance , and improve the optical properties.

Abstract: Porous composite ceramics was manufactured from ordinary paper by sol-gel techniques, and SiC/Si ceramics composite with laminated or tubular structure were also prepared by biomimetic design. The results show that the amorphous carbon remained after carbonizing of the ceramic paper had changed into β-SiC after silicon infiltrating in the vacuum environment. The bending strength of SiC/Si ceramic composite was up to 200MPa, and it behaved as non-catastrophic fracture behavior.

Abstract: The influence of two kinds of polymer emulsions on the flexure strength of armid fibers reinforced cementitious composites has been investigated. The morphology of fractural interface of modified composites is conducted by scanning electron microscopy (SEM). Our experiment results indicated that the early flexural strengths of the epoxy emulsion and EVA emulsion modified aramid fiber reinforced cementitious composites have been improved significantly in comparison with that of unmodified composites, that is, an increase of 34.21%, 133% observed versus pristine samples curried for 28 d, respectively. The microscopic analysis on the interface between fibers, cement and aggregates revealed a novel rupturing and stripping mechanism. The efficacy of EVA emulsion modified samples is higher than that of epoxy modified ones.

Abstract: The gray analytic hierarchy process (GAHP) can be used to find the reasonable substitute of the expensive or much needed composite materials in the market, thus avoiding the subjectivism and one-sidedness of choosing the substitute materials by experience. This paper introduces the basic principle and analysis steps of GAHP and the application cases in the substitute selection of composite materials. As is proved in practice that the evaluation process is reasonable and objective. At the same time, due to the accurate evaluation results, it avoids the subjectivity and one-sidedness otherwise being unavoidable for judging by experience.Its an effective method to solve the substitute of composite materials with GAHP. The evaluation results can accurately reflect the performance of the substitute.

Abstract: Based on four-terminal network theory, a multilayered model for reflective electrical thickness measurement system is presented in this paper. Using the simulation method of finite element, two crucial parameters of the measurement system are given. One parameter is the distance between the inner surface of composite and reflective mold, the other is the outer surface of composite and horn antenna aperture. This work will guarantee the design of the electrical thickness measurement system of composite.