Applied Mechanics and Materials Vols. 446-447

Abstract: The present paper deals with the applicability of Impact-echo acoustic method to testing of cement-based composites prepared from a mix of cement mortar and quartz sand, which were intentionally degraded by high-temperature treatment (in the temperatures range from 200°C to 1200°C). Changes in the the bulk density and the flexural tensile strength were monitored during the degradation for comparison.

Abstract: The paper deals with the study of dominant frequencies of an Impact-Echo method response signal obtained from a reinforced concrete beam with a steel rod diameter of 8 mm. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Dominant frequencies of the response signal will be the main criterions for the reinforced concrete rebar corrosion progress. The article presents the results of measurements obtained after 12 months controlled degradation in aqueous NaCl solution. The results were compared with measurements of electrical resistance of reinforcing steel by using the Thomson double bridge.

Abstract: In order to make the pressure safe, a new method and material for reinforcing pipelines is introduced, that is carbon fiber reinforced polymer sheet. In the experiment, the metal pipelines that wrapped with different layers of CFRP sheets respectively are carried loads by hydrostatic burst test. The results show that this method can be a substantial reinforcement in the bearing capacity of the metal pipelines. According to the test data and the thin wall cylinder stress calculation theory, the design formula of reinforcing layer thickness of CFRP was presented in the elastic and plastic state of metal material. Based on the plastic solution of thick wall cylinder in the polar coordinates, the strength checking formulas of repair system was presented in different mechanical states. The presented formulas without iterative calculation have practical value in the production practice.

Abstract: By means of eccentric compressive tests of Concrete-filled Steel Tubular Columns, to research the mechanical properties and failure modes of Concrete-filled Steel Tubular Columns without yield point. Research shows that, the failure modes of axial compressive Concrete-filled Steel Tubular Columns without yield point, as well as axial compressive short columns, have the same trend of oblique shear failure.

Abstract: The purpose of this paper is to focus on studying its flexural behavior after different damages pre-stressed concrete hollow slab is strengthened with CFRP. By the experimental method, twelve residential pre-stressed concrete hollow slabs are tested under concentrated force at the two points of the symmetrical load in order to analyze both flexural behavior and effects factored by different bonding modes. The conclusion can be drawn that the flexural behavior of pre-stressed concrete hollow slabs strengthened with CFRP is well-tried. It provides design suggestions and reference for pre-stressed concrete hollow slabs strengthened with CFRP, and also provides an experimental basis for the repairing and reinforcing practical engineering application in Wenchuan disaster area.

Abstract: The high performance cement concrete mixture design for pavement was studied through a series of laboratory experiments based on an actual project program. We analyzed the data by principal component analysis and tested the concrete performance of strength, shrink and freeze-resistance. The results of a series of experiments indicated that the dry-shrink rate was reduced obviously by using expanding agent. The flexural elastic modulus increased as the flexural strength increasing. Adding air-entraining agent could improve the air content of the concrete, and as a result, the flexural elastic modulus was reduced and freeze-resistance performance was enhanced greatly.

Abstract: Roadway borehole pressure relief and let the pressure anchor combined support technology were based on using the new pressure high strength bolt instead of ordinary bolt ,Combined with the borehole pressure relief principle, aim at releasing high stress of surrounding rock of roadway ,Complying with the deformation characteristics of supporting technology of the surrounding rock. In this paper, we used scaled numerical simulation technology —— ADINA to analyze the roadway borehole pressure relief and let the pressure anchor coupling support technology. To the tunnel, we used the method of numerical simulation of let the pressure bolt support independently, drilling pressure relief, and borehole pressure relief and let the pressure anchor coupling support three kinds of the comparison numerical simulation. The advantages of coupling supporting effect was elaborated, It was instructive for the deeply roadway engineering in the future.

Abstract: An efficient way to repair the damage of concrete is to enable the concrete adapt to the surrounding environment actively and have self-repair capabilities. In this paper, a type of concrete beam with embedded glass fibers filled with adhesive capable of crack self-repair was investigated. The capacity of self-repair cracks in concrete beams was verified by bending tests, and the influence of the layout of glass fibers on crack self-repair was studied. Test results show that the stiffness of concrete beams increases after crack repair. The glass fibers can be arranged according to the average crack spacing of reinforced concrete beams. In addition, the influence of the levels of crack repair on properties of concrete beams was analyzed with the finite element analysis software ANSYS.

Abstract: A kind of new warm mix additive called SAP was proposed in this paper. The principle is using foam to lower the operating temperature of asphalt mixtures. The mixing and molding temperature of SAP warm mix asphalt mixture were measured by viscosity method and void ratio method, which are almost 20°C lower than that of HMA. Considering the engineering applications and test accuracy, the void ratio method is considered to be the better way to measure the operating temperature of asphalt mixtures.

Abstract: The water immersion technique is conducted to increase the surface area of the triple base propellant. In order to investigate the influence of water erosion on triple base propellants, the SEM and material tester were used to observe the surface texture and test the mechanical property at different temperature .The result shows that the effect of water erosion on structure is superficial, the erosion depth is about 50~150 μm after 60 minutes,which does not impact the interior structure. The tests of mechanical property indicate that the mechanical property declines with the time of water erosion increasing, the decrease at room temperature is less than the decrease at high and low temperature.