Advanced Materials Research Vols. 838-841

Abstract: The Poly(vinylidene fluoride)(PVDF)/Cyclic Butylene Terephthalate (CBT)/carbon black (CB)/graphite (GR) composites were prepared by melting blend method and were studied by milliohmmeter and material testing machine. The results showed that due to the formation of CB and GR conductive network, the volume electrical resistivity of PVDF/CBT/CB/GR composites linearly decreased as graphite content increased at below 4 wt% of graphite, but it in turn increased when graphite content was higher than 4 wt%. Flexural strength showed an increase at below 1.6 wt% of GR and gradually decreased as GR content increased further. Differently, flexural modulus of composites declined as GR content increased. In all composites, the flexural strength was more than 25 MPa, which satisfied with the requirements of bipolar plates.

Abstract: The effect of calcium sulfate whisker (CaSO₄) on mechanical property, melting, crystallization and rheological properties of polyamide 1012 (PA1012) was studied by differential scanning calorimeter (DSC), rheometer and material testing machine. It was shown that CaSO₄ had no influence on melting temperate of PA1012, but can effectively enhanced nucleation ability of PA1012, which indicated that CaSO₄ was good nucleation agent for PA1012. The viscosity and storage modulus of PA1012 firstly increased and then decreased as CaSO₄ content increased. The results showed that CaSO₄ had little effect on tensile strength, but impact largely flexural strength.

Abstract: Cyclic Butylene Terephthalate (CBT)/carbon black (CB)/aluminum composites were prepared by melting blend method and their conductivity and mechanical property were studied by Milliohmmeter and material testing machine. The results showed that at below 1.6 wt% of flake aluminum（Al）, volume electrical resistivity and flexural strength of composites increased with Al content increases and reached the maximum value at 1.6 wt% of Al. Composites containing 18.4 wt% of CB and 1.6 wt% of aluminum exhibited excellent comprehensive performance (electrical resistivity, 20.3 Ω.cm; flexural strength, 40.0 MPa).

Abstract: The steel rebar inside reinforced concrete structures is susceptible to corrosion when the chloride content at the surface of the steel exceeding the critical chloride concentration. Stainless steel reinforcements have proved to be the most reliable methods to assure the durability of reinforced concrete structures in marine environment for the compact passive films forming on its surfaces and higher critical chloride concentration. In the present work, the compactness of passive film on 2205 stainless steel in simulated concrete pore solution (SPS) is compared with carbon steel (Q235). the critical chloride concentration of Q235 and 2205 stainless steel reinforcement are discussed. Results indicate the slope(k) of double-log plot of current time for 2205 stainless steel is higher than Q235 , the k value is related with the compactness of passive film, the critical chloride concentration of 2205 stainless steel is much higher than Q235 steel in SPS.

Abstract: The application of Carboxylmethyl Cellulose Sulfate (CMC-S) in cement paste was studied. The effect of CMC-S on the setting time of cement paste was investigated. Hydration heat of specimens with different cured age was measured via the Hydration Heat Tester (HHT), and hydration process was recorded via Differential Scanning Calorimeter (DSC). The results indicated that CMC-S was a kind of set-retarding and water-reducing agent; its retarding properties appeared at early age, but after three days, the hydration process of cement paste was even improved.

Abstract: In recent years, with the urbanization in our country speeding up, the phenomena of wasting concrete due to the demolition and renovation are very common. For our country, resources are very scarce. How to reuse the waste concrete, so as to keep the sustainable utilization of building resources, is a topic worthy of deep thinking. In order to realize the full use of recycled concrete, this paper points out that the use of recycled concrete is the key to keep the sustainable utilization of natural resources. Based on this, it discusses the work performance, mechanical properties, durability properties, shear properties, seismic performance of recycled concrete and its performance evaluation.

Abstract: The foundry industry has greatly increased in many parts of the world, and their generation of enormous amounts of waste foundry sand is a major environmental concern. Such waste may be classified as hazardous, requiring special precautions for its management, which may include disposal in landfills for hazardous waste. However, this waste can be used as a partial substitute for the sand in a concrete aggregate. Slump flow, water absorption, concrete compression strength, and index void tests were performed to study the properties of fresh and hardened concrete made by substituting 10% and 20% of the sand by weight with foundry sand as concrete aggregate. Image analysis by optical microscopy was also performed in the present study. The results showed that the replacement of the waste foundry sand is technically feasible under the conditions studied and that both the substitutions studied increase the compression strength of the concrete.

Abstract: Based on the consequences of abundant relevant literatures, this essay expounded the latest mechanical properties research results of the concrete reinforced with CBF and its application on building structure reinforcement studied by the domestic and foreign scholars. Research suggests that the new composite material of concrete reinforced with CBF has many excellent engineering application characteristics such as good crack resistance, durability, permeability resistance, high temperature resistance and fire retardancy. CBF is a kind of good reinforcement materials with so many advantages including simple construction, favorable reinforcement effect and low cost. We can infer that CBF can be widely used in underground engineering port, deep-water wharf, cross-sea bridges and tunnels, cold region and other fields based on the good mechanical properties and durability of the concrete reinforced with CBF in the future.

Abstract: An experimental investigation was carried out to assess the effect of metakaolin (MK) on the compressive strength, flexural strength and porosity of cement mortar. The cement was partially substituted with MK at 0-30% replacement levels. The results show that the strengths and porosity of mortar containing up to 20% were superior to that of control (0% MK). The Balshin equation fits the experimental results of compressive strength and porosity of the specimens containing MK and there is a strong quantitative relationship between compressive strength and porosity of the specimens.

Abstract: In this paper, an elevator safety gear wedge with surface metal-ceramic composite coatings is proposed. After composite coating, the friction performance of the elevator safety gear wedge is very stable at high temperature, because of high hardness and high temperature oxidation resistance of coating material. And the friction coefficient becomes small by coating ceramic. In this research, six samples with different coating are prepared. These samples are installed in elevator safety system, and related speed parameters and stopping distance of elevator are tested. A conclusion can be drawn that sample 4 with 45# steel substrate and NiCrBSi-60 coating has a suitable friction coefficient, and the deceleration of elevator is controlled in the range of 0.2 to 1.0g when sample is installed in safety gear system.