Applied Mechanics and Materials Vols. 584-586

Abstract: Typically, the selection of large aggregate particle size is mainly determined by the thickness of structures and the thickness of protective layer. The greater the aggregate diameter is, the smaller the specific surface is, and the smaller coating materials demand will be without specific requirements. It will affect the concrete flowability directly if there are too much big size of aggregates or the particle size is too big for forming a certain stable packing skeleton structure. The strength of the large diameter recycled self-compacting rock-fill concrete is low so that the primary cause of its failure mechanism is bond failure and bond slip in aggregate. Shear failure in aggregate is not easy to happen due to the strength of the aggregate is too low. For this reason, we put forward the general selection requirements for large diameter aggregate.

Abstract: The effect of very low temperature on high performance concrete (HPC) mechanical properties is studied by using a reasonable testing method. The results show that the compressive strengths of concrete are increasing with lower temperatures. Fly ash (FA), compared to ground granulated blast-furnace slag (GGBFS), is positive to the compressive strength increasing at low temperature. The splitting tensile strengths of concrete appear a maximum at-40°C~-80°C. The compound replacement by GGBFS and FA makes the splitting tensile strength present the extreme value at higher temperature. At very low temperature, the single or compound replacement by mineral admixtures can result in the difference of the relationship between compressive strength and splitting tensile strength, and the degradation of concrete subjected to cold-thermal shocks.

Abstract: In this paper, FGD gypsum mixed with fly ash (FA) and ground granulated blast furnace slag (GGBFS) was used as a composite binder. The strength experiments of range analysis and analysis of variance (ANOVA) showed that the optimal proportion of FGD gypsum, FA and GGBFS was 6:3:4. The study of microstructure of hardened paste proved that the hydration product was mainly C-S-H gels and ettringite, and some ettringite crystals grew from C-S-H gels.

Abstract: The penetration resistance to chloride ions of concrete is one of the important factors affecting the durability of concrete structures. The penetration resistance to chloride ions of concrete is measured with the increasing substitution amount of silica fume in this paper. For the low water-binder ratio of 0.28, 0.30 and 0.32, compared with the reference concrete, with the increase of age, the penetration resistance to chloride ions of concrete can be enhanced with the increasing substitution amount of silica fume, but the increased range is smaller. The penetration resistance of chloride ions of concrete is not necessarily improved by gradually decreasing the water-binder ratio. Considering the substitution amount of silica fume, water-binder ratio and concrete age, the best mix proportions are that the substitution amount of silica fume is 9% or 12% when the water-binder ratio is 0.28 and the substitution amount of silica fume is 12% when the water-binder ratio is 0.30.

Abstract: The PEEK/PEI/PES plastic alloys were processed by twin-screw extruder at 370°C separately with five mass ratios of 70/30, 70/25/5, 65/30/5, 60/30/10. The flame retardant of plastic alloys were investigated by experiments, their results showed that, the oxygen index declines when PES was added, the oxygen index of plastic alloy with mass ratios of 70/30 is higher than that of pure PEEK or PES, lower than that of pure PEI, which the oxygen index is 37.1%. The volume resistivity plastic alloy with mass ratios of 60/30/10 is 3.72×10¹⁷Ω·cm, which is higher than that of pure PEEK and PES for two orders of magnitude, and the insulation performance of PEEK is improved significantly by alloying.

Abstract: Forming three groups concrete of different gelled material systems, the effecting of HPI hydrophobic compound hole plug on concrete compressive strength, chloride ion permeability resistance and water absorption performance were studied taking CALTITE and 3CC for example. Studies have shown that this kind of polymer can reduce compressive strength, but can improve chloride ion permeability resistance and hydrophobic property of concrete.

Abstract: Replacement rate is an important factor that affects the mechanical properties of recycled concrete. In order to study the influence of replacement rate on triaxial mechanical performance of recycled concrete, 20 recycled concrete cylinder specimens for conventional triaxial loading test with recycled aggregate replacement rate as changing parameters were designed. The results show that replacement rate has a great influence on peak stress of recycled concrete specimens under uniaxial stress, but the effects of replacement rate gradually decreased with the increase of lateral confining pressure. The influence of replacement rate on peak strain is larger than peak stress, the impact of replacement rate on peak strain gradually decreased with the increase of lateral confining pressure. The elastic modulus of recycled concrete specimens changes with different replacement rate, and the fluctuations is in the range of 20%. The results will provide reference for further theoretical study of recycled concrete.

Abstract: Using the ANSYS thermal analysis module to do steady thermal analysis of given heat-insulating bricks. The results show that this kind of bricks can achieve better insulation in both sides; when the thermal conductivity of the heat insulating material in the hole space are less than 0.3 W/(m·K), the bricks can obtain the good insulation effect; the smaller the heat conductivity coefficients of the bricks materials and filling materials are, the better insulation bricks can achieve.

Abstract: The activity index of steel slag-GGBS composite mineral admixture with different steel slag contents at the W/B of 0.3, 0.4, and 0.5 was investigated. The results show that the activity index of the composite mineral admixture with higher GGBS content is larger, and this phenomenon is more obvious at later ages. At lower W/B, the gap of activity index of different composite mineral admixtures is smaller. The activity index of each composite mineral admixture is higher at lower W/B and at later age. The steel slag-GGBS composite mineral admixture is more suitable to be used in high strength concrete than in low strength concrete. As far as the long-term properties of concrete are concerned, the activity index of the composite mineral admixture at the late age should be adopted.

Abstract: New building wall materials is a kind of material which is not at the price of consuming cultivated land, destruction of ecology and environmental pollution, adapting to the construction industrialization, construction mechanization, reducing wet construction operations at the site, improving the function of modern building construction. Presently, as for our country stage, new building wall materials is including all building wall materials except for clay solid brick building wall materials. In our country, the production of new type wall materials has been increasing rapidly and its quality and product has been improved obviously, what’s more, the technology and equipment level also rises fast which created very convenient advantages for the development of exterior wall thermal insulation technology. Presently, there are mainly three kinds which are the out-cell heat preservation, a polystyrene board and wall body casting molding at a time and polystyrene particles insulation pulp outer wall heat preservation.