Advanced Materials Research Vols. 168-170

Abstract: The migration of ion dissolved in water is known to be main factor inducing the deterioration of porous cement-based materials in aggressive environment. Long-term tests have been carried to study the moisture diffusion in mortar with water cement ratio of 0.5 and 0.6 in different humidity, and then the inverse analysis has been done to determine the moisture diffusion coefficient D. The results indicate that the bigger water cement ratio, the faster moisture migrating in same humidity, and the moisture migration process is longer for the mortar under lower humidity. Furthermore, the results of controlled experiments carried on mortar specimens with sea sand show that the moisture migration is longer for sea sand mortar than that of river sand, and the moisture loss is bigger.

Abstract: Crumb rubber concrete (CRC) is made by adding rubber crumbs into conventional concrete, and many studies show that ultimate compressive strains for CRC are much bigger than those for conventional concrete. This article undertakes a mechanical analysis of a reinforced beam based on a proposed CRC stress-strain relationship. The results show that, assuming identical geometrical and material conditions, CRC beam can support more external moment than what conventional concrete beams can do.

Abstract: The sandstone in pavement engineering is mostly obtained by mining mountain or river way, which has brought beyond-retrieve destruction for natural environment, such as mountain bareness and ecological damage. So lightweight epoxy asphalt mixture(LEAM) incorporating different replacement percentage of granulated lightweight aggregate(GLWA) and circular lightweight aggregate(CLWA) by weight were researched. Then performances of strength, rutting resistance, moisture susceptibility of epoxy asphalt mixture incorporating GLWA and CLWA and the economical efficiency were evaluated, and results presented all performances met the specification and LEAM was more economical than the mixture without GLWA or CLWA. And the shape and replacement percentage of lightweight aggregate could improve or weaken mixture performance and the change amplitude was different. The mixture incorporating 40% CLWA replacement was determined to be the most suitable mixture for steel deck pavement of long span or special construction bridge, such as moveable bridge.

Abstract: Glass fiber reinforced plastics (GFRP) rebars / bolts are more and more being applied in construction projects with its superior corrosion resistance. To improve the economical efficiency of their application it is very significant to develop the prestressed GFRP rebars/bolts structure system. Therefore it is very valuable to probe the stress relaxation properties of GFRP rebars/bolts. With an innovation ends anchoring method for stress relaxation specimens of GFRP rebars/bolts, the stress relaxation properties has been tested in this paper. Results show that the relaxation rate of GFRP rebars/bolts increases with the initial stress increasing and with test time prolonging. It is increasing more rapidly at the beginning stage and it becomes slow after 24 hours. The relaxation law of GFRP rebars/bolts is similar to the law of CFRP and AFRP rebars/bolts. The relation between the relaxation rate and the logarithm of test time in hour follows also better linear law. The relaxation rate of GFRP rebars/bolts is bigger than CFRP ones and smaller than AFRP ones. The mechanical properties do not change obviously after 120h relaxation test.

Abstract: In this study, geopolymer was synthesized with metakaolin and tungsten-tailing as the main raw material and alkali activator composed of sodium silicate solution and alkali solution. By the contrast of the experiments with five kinds of alkali activators, the result was obtained. When the concentration of the NaOH or KOH was 10mol/L,the content of NaOH or KOH in the liquid phase was 35%,while the concentration of the Ca(OH)₂ was 3mol/L, the content in the liquid phase was 35%,the property of geopolymer was the best. For the combined alkali, when the content ratio of Ca(OH)₂ to KOH or Ca(OH)₂ to NaOH of 2:3,there was a balance between the activator of alkali and the resistance of Ca₂+.The trigger action of the alkali activator on the activity of slag was accelerated.

Abstract: In order to obtain super aerogels heat insulating composite materials with silane coupling agent on the in-situ surface treatment. The core-shell structure composite materials have been prepared by dispersion polymerization process of polystyrene grafted on the SiO₂ particles. By TEM on these samples the impact of the system components initiator polymerization parameters and dispersion process was discussed. The results showed that the system component of the greatest impact on conversion rate is the ratio of aerogels /St ,the optimum reaction temperature is 75 °C.With organic initiator KPS as initiator after a unique ultrasound technique to obtain the core-shell composite materials structure which coating is 70%.

Abstract: Based on Kirchhoff’s classical theory and adoptation the spline finite element method, three independent displacements are interpolated into the anti-symmetric angle-ply laminated plate by the spline base of the cubic spline B function, and the stiffness array and the quality array of the composite material laminated plate are derived. By using Rayleigh-Reeds method, the damping array is established; kinetic equation is derived from Lagrange equation; the response equation is expressed; the inherent frequency of the anti-symmetric angle-ply plate is found by calculation subject to the different proportions of the length to the width, the different number of the layers of the plate and different angles; and the dynamic response problems about the anti-symmetric angle-ply laminated plate are analyzed and solved. Dynamic response problems, such as the displacement, velocity and acceleration, are solved with spline collocation method, through choosing the sample strip functions as mode shape function for various boundary conditions in several numerical examples and the results are compared with Newmark’s method. And better result can be yielded. The example calculations prove the validity of the calculating ways introduced by this paper.

Abstract: The specimens of Al₂O₃/Si₃N₄ compound ceramics which contain 3%, 6%, 9%, 12%, 15%, and 18% nano-Al₂O₃ additions respectively were obtained by pressureless sintering at 1650 in the nitrogen atmosphere. The bending strength and fracture toughness (KIC) were detected. The microstructure and phase composition of the specimens were analyzed by the means of SEM and X-ray. The results show that Al₂O₃/Si₃N₄ compound ceramics can be made only using pressureless sintering. With 9-12% nano-Al₂O₃addition, the specimens have the top mechanical properties. The bending strength reach 710.86MPa, KIC reach 8.61MPa•M^1/2. These excellent properties come from many interwoven nitride distributed uniformly in the Al₂O₃/Si₃N₄ compound ceramics matrix, which composed of big and firmly plate-like β- Si₃N₄, hexagonal Sialon and sheet Si₂N₂O.

Abstract: The influences of the mesh sizes, the surface treatment and cover thickness of the textile on anti-crack and bearing capacity of the competent were investigated. Additionally, to prevent the splitting of the concrete, hanging U-shaped hook upon textiles was also experimentally studied. The experiment results indicate that sticking sand on epoxy resin-impregnated textile and reduced cover thickness are helpful to improve the mechanical performance of the component; the textile with 10mm×10mm mesh size is superior than that with 20mm×20mm mesh size regardless of in the respect of enhancing the bearing capacity of the TRC or in the respect of controlling matrix cracking; the novel method of adding U-shape iron hook not only can improve the bonding performance between the textile and the concrete, but also can enhance the shearing capacity of the concrete.

Abstract: The polycarboxylate water reducers(PCs) with different molecular structure were synthesized. The effects of molecular structure on their performance in cement paste were investigated. The results show that the PCs with a medium density of PEO side chain and/or a moderate molecular weight and its distribution have a higher dispersibility and a stronger dispersion retention stability at the same time, and that those PCs with a shorter PEO side chain exhibit a stronger dispersion retention stability. The PCs with a higher molecular weight, a lower density and/or a shorter length of PEO side chain are more easy to adsorb on the surface of cement particles. The earlier induction period is shortened while the dormant period is prolonged during the process of cement hydration in the presence of PCs. The PCs with a shorter PEO side chain show a stronger retarding effct. This effect is not very obvious with the decreasing molecular weight.