Advanced Materials Research Vols. 1065-1069

Abstract: The objective of this work was to examine the relationships that may exist between porosity and thermal conductivity with particular reference to normalized cement mortar which is most commonly found in civil engineering. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity and 20% CO₂ concentration. We investigated the evolution of the total porosity measured by hydrostatic weighing and of the thermal properties measured by Hotdisk method. This experimental campaign allowed relating the total porosity and the thermal conductivity before and during carbonation. These results can be used for further studies which can propose models predicting the thermal conductivity if changes in porosity are known. Moreover, the results indicated that the thermal conductivity of a cement material is directly related to the density and inversely related to porosity. Finally, this study showed that a characteristic coefficient can be deduced for two states of material: non-carbonated and carbonated. This coefficient is therefore proper to a specific material and can be used not only for modeling the relationship between porosity and thermal properties but also for other microstructural studies of cement materials.

Abstract: Studying on the modified asphalt foaming characteristic, the energy indexes of the actual maximum expansion ratio and the foam index influencing on the modified asphalt foaming effect is analyzed reasonably by varying moisture content. The results show that the half-life of modified foamed asphalt decay sharply with the decrease of SBS content (modified asphalt viscosity),the moisture being mainly applied to modified asphalt foaming is proved with actual max expansion ratio index and evaporated vastly with the decrease of SBS content (modified asphalt viscosity), the modified foamed asphalt stored energy internally is reflected by the foam energy and corrected according to the viscosity.

Abstract: The physical and mechanical properties and microstructure of Q₂ loess are of great theoretical and practical significance. Through studying these properties which Q₂ loess samples are taken in the Xi'an city of Lin-tong District of Mount Li, the results show that: (1)Natural water content, wet density, liquid and solid index, shear strength, collapsible coefficient compressive modulus; (2)By means of the scanning electron microscope to study the picture of the loess micro-structure, there are some preliminary understanding of micro-structure’s basic characteristics; (3)Using scanning electron microscopy techniques to observe the loess micro-structure, As the performance of the loess micro-structure’s basic unit-body and its arrangement form, the loess micro-structure is the reflection of its physical and mechanical properties, Meanwhile the change of physical and mechanical properties also show the unstability of the loess micro-structure.

Abstract: Based on pullout test, shear test, tensile test strip, studied the influence of three fibers and glass fibers of different lengths on mechanical properties of synchronization plus fiber stone layer. Test results show that, glass fiber and polyacrylonitrile fiber has little effect on the interfacial bonding performance difference compared with no fiber, polyester fiber has greater impact on the interfacial bonding performance; Adding fiber, crack resistance significantly enhanced, including glass fiber and polyacrylonitrile fiber are most obvious, considering, determined glass fiber as the best choice , 60mm as the optimum length.

Abstract: The harmful chloride ion in sea sand concrete is the main issue that hinders its application, proposing a method using fly ash the active mineral, chloride ion content of harmful curing of sea sand concrete, to improve the durability of sea sand concrete. The experiment studies the influence of sand in the chlorine ion and fly ash on the strength of concrete, and analyzes microscopic structure and hydration products of concrete. Research results show that: the sea sand concrete with 20% fly ash prepared has good mechanical properties and durability; the existence of Cl- on the early strength of sea sand concrete has a positive promoting role, but has negative effective on the later development.

Abstract: Through the different rolling and normalizing methods to study the variation of microstructure and mechanical properties of eight groups of steels ,based on the low carbon micro alloy steel as the research object, The results show that, the main structure of steel are ferrite, bainite and a small amount of M-A island group, and granular bainite is helpful to improve the test fire resistance steel; with the increasing of normalizing temperature, the ratio of YS increased gradually, the test steel has high good fire resistance at 790 °C; the faster the cooling speed after rolling, has better fire-resistant .

Abstract: Using the fast freeze-thaw test method, we tested the loss modulus and compressive strength of steel slag-limestone powder concrete after 0,25 times,50 times,75 times,100 times freeze-thaw cycle,studied the mechanical properties and frost resistance performance after the freeze-thaw cycle. The results showed that adding a certain amount of steel slag-limestone powder does not affect the anti-frost property of concrete; established different dosage of steel slag concrete freeze-thaw damage model: y = a + bx + cx2, degree of fitting is better; large quantity of steel slag used in concrete shall be a wider range of research.

Abstract: Adsorption of Cu(Ⅱ) onto natural attapulgite was investigated with respect to temperature, initial concentration and contact time. The adsorption process can be well described by the pseudo-second-order kinetic model, and the equilibrium adsorption isotherm was closely fitted with the Freundlich model. Enthalpy change(△H⁰), entropy change(△S⁰) and Gibbs free energy change(△G⁰) were calculated from the temperature dependent sorption data, and the results indicated that the sorption of Cu(Ⅱ) on attapulgite was a spontaneous process, and the sorption was endothermic.

Abstract: The same batch reactive powder concrete specimens were obtained with same raw materials and curing process, uniaxial compressive strength test had been done on the specimens after hot water curing placed in laboratory for seven days , three months and three years. The test results showed that seven-day strength and three-month strength of plain reactive powder concrete after hot water curing are almost equal. Strength of plain reactive powder concrete has not degradation within three months after hot water curing. While strength of plain reactive powder appears serious degradation phenomenon after placed in Laboratory for three years. Comparing uniaxial compressive strength test results of plain reactive powder concrete at three-month with three-year after hot water curing ,we find that strength of plain reactive concrete at three-year decrease about 27 percent than the strength of plain reactive powder concrete placed at laboratory for three months, and elasticity modulus increases about 71 percent, axial peak strain decrease about 62 percent respectively .With the passage of time, plain reactive powder concrete appears more Brittle Features and less toughness.

Abstract: Fracture is a kind of effect of common reinforced concrete structure, concrete structure crack is the most common in the industry, is difficult to avoid the phenomenon of cracks, heavy then endanger the safety of the structure, and the use of the normal concrete light will influence the housing life. This paper classifies the cracks from different angles, and the forming reason of crack analysis.