Applied Mechanics and Materials Vols. 174-177

Abstract: The carbonation of concrete is one of the factors that weaken the durability of the concrete. Accelerated carbonation method was utilized to study the strength and carbonation resistance of cement paste containing different contents of layered double hydroxides treated in different ways. The results show that the LDH improves the carbonation resistance of the cement paste obviously. With 2% addition of the LDH, cement paste shows enhanced carbonation resistance in early age. When LDHs is added, the strength of cement paste decreases to some extent.

Abstract: Some low-titanium aluminum alloys were prepared and the effect of titanium elements on microstructure and wear property of zinc-aluminum alloy was investigated. The test results showed that addition of titanium is an effective way to refine the grain size of zinc-aluminum alloy. As the titanium content is 0.04 wt%, the grain size becomes to be a minimum value. The wear resistance is also improved with the decrease in the grain size. This can be attributed to the grain boundary strengthening of the test alloys leading to strain hardening. SEM photomicrographs of the worn surfaces shows that the test alloys with and without grain refinement exhibit similar wear mechanism. However, the grain-refined sample of the alloy exhibited a more stable friction coefficient than that of the untreated ones under the same test conditions.

Abstract: Frost Resistance of rapid hardening sulphoaluminate cement was modified with redispersible powders. Frost resistance and strength of sulphoaluminate cement mortar were tested. With the help of SEM and mercury porosimetry, the morphology of the hydrates and the micro-structure of the mortar were observed. The frost resistance mechanism of redispersible powders in the mortar is analyzed. The results show that the frost resistance of sulphoaluminate cement mortar could be improved significantly by mixing redispersible powders. The optimal content of redispersible powders is 0.9%.

Abstract: With the fast freeze-thaw test method, the c50 steel fiber self-compacting concrete was carried out 300 tests of freeze-thaw cycle. In the process of freeze-thaw cycles, it determined by the quality of the concrete specimen, dynamic elastic modulus and strength, and analyzed the steel fibers and their different contents on frost resistance of self-compacting concrete impact. The results showed that: steel fiber self-compacting concrete in freeze-thaw cycle can play constrained role in the quality loss, dynamic elastic modulus and intensity, and can significantly improve the self-compacting concrete frost resistance. Within a certain range, the more steel fiber, the stronger of frost resistance.

Abstract: This study aims to introduce an alternative design method for unbound pavement layer materials based upon shakedown theory. The kinematic shakedown theorem that describes the ultimate response of an elastic/plastic structure to cyclic loads is used to predict whether stable behaviour in the unbound granular materials layer occurs or excessive rutting will develop. This method seeks the mechanism, from within a class of mechanisms that minimises the shakedown limit load for pavements consisting of layers of Mohr-Coulomb material obeying the associated flow rule. The basic concepts are outlined together with the most recent calculations of the critical design shakedown load. The influence of the of design parameters such as, the strength, stiffness and depth of the base-course material as well as the consequences of load distribution are discussed.

Abstract: Reinforced concrete core walls have become major lateral force structure units in high-rise building. Base on fiber model, the process simulation of a seismic behavior testing on reinforced concrete core walls is presented. The Perform-3D software is adopted to perform static pushover analysis for reinforced concrete core walls, and results from the simulation match well with those from the tests. It is shown that the fiber model is valid for numerical simulation analysis of core walls. Damage development sequence of core wall specimen and yielding condition of each member are analyzed which coincide well with the experimental results. On this basis, effects of more design parameters on bearing capacity and deformation performance are systematically analyzed, and conclusions which is valuable for theoretical research and engineering design are obtained. The influence of axial compression ratio, height-width ratio, reinforcement ratio of coupling beam and span-depth ratio of coupling beam on the seismic performance of core walls are analyzed systemically.

Abstract: Analysis and research the composition and properties of sugar mud and city sludge and add other materials to make the permeable material. Research results show that the main crystal phase with Mullite, Quartz and Calciclase when the mass percent respectively of sugar mud, fly ash, clay, waste ceramic, city sludge, glass powder are 15%, 20%, 35%, 20%, 5%, 5%, the optimal sintering temperature is 1100°C and the holding time is 0.5h. The water absorption of permeable material is 24.50%, the porosity is 34.81%, the flexural strength is 14.33MPa, the range of aperture size is 5μm ~30μm.

Abstract: The mixture proportion of recycled concrete was discussed by orthogonal design method. The influence of water-cement ratio, recycled aggregate quantity on workability, cube compressive strength of recycled concrete was analyzed. The experimental results indicated that，Recycled concrete mix proportion design should consider the impact of the water absorption of recycled aggregate. Unit water amount of recycled concrete should be plain concrete unit water consumption and recycled aggregate additional amount of water. Sand ratio should increase in the corresponding ordinary aggregate concrete sand ratio on the basis of 1 to 3 percent. When the water-cement ratio is 0.36 and construction waste content of 40% slag content of 20%, 28d compressive strength of concrete is 48.1MPa, slightly higher than the reference concrete (48.0MPa).

Abstract: The nanosized TiO₂ was prepared by microemulsion process in the system of cyclohexane/[Span80 combine with Tween40]/water with TiOSO₄ as raw material. The synthesis process of the powder was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and laser particle size analysis (LPSA). The results showes that TiO₂ with the average size of 19.5nm and narrow size distribution was prepared under these conditions of Span80 of 8g and Tween40 of 2g as the emulsifier, water/oil mass ratio of 1/4, amount of TiOSO₄ of 10mL with the consistency of 0.8mol/L, calcination temperature of 480 °C for 20min.

Abstract: In order to notably improve the mechanical properties and durability of low-grade cement-based material, superfine silica fume was used to modify the cement-based composite based on special perfomance and effects of nano powder. The mechanical performance and durability were investigated.Then the phase compositions,microstructure and morphologies of as-received cement-based composite were studied by X-ray Diffractometer、TGA-DTA and SEM. The results show that： the best formula of raw materials is 1:1:0.025:0.015, and hydration can be accelerated and increasing of hydration products is observed after modification. In the hardened cement matrix, microstructure is very compacted and C-S-H gel forms densed structure, so the structure defect is notably reduced. This means that both strength and durability of cement-based composite are notably improved by the addition of superfine silica fume.