Advanced Materials Research Vols. 168-170

Abstract: In this paper, in order to investigate impact-mechanics property of basalt fiber reinforced concrete (BFRC), impact test on BFRC with four kind of volume content (0, 0.1%, 0.2, 0.3%) was carried out using 100mm-diameter split hopkinson pressure bar (SHPB) device. Obtained dynamic stress-strain curves and testing data. Testing results were analyzed. The testing results showed that BFRC has favorable impact-mechanics properties, strain rate and fiber volume content have large effects on impact-compression strength and toughness of BFRC; impact-compression strength and toughness show strain rate strengthening effect, strain rate sensitivity of impact-compression strength is stronger and the impact-compression strength and toughness are higher relatively when fiber volume content is 0.1%; there is approximate linear function relation between the dynamic strength increase factor and the strain rate logarithm, there is approximate quadratic polynomial function relation between the peak strain and the strain rate logarithm.

Abstract: This paper reports experimental study of 17 high strength aluminium alloy specimens of type of 6082-T6 under axially compressed load including I-section column, rectangular hollow section. The general-purpose non-linear finite element analysis software ABAQUS is adopted to simulate the mechanical performance and overall buckling of aluminium alloy columns. The feasibility of finite element method has been verified through the comparison between the simulation results and the test finding. Finally, based on the experimental data and numerical calculation results, a useful column curve formulation to calculate the coefficient of stability of 6082-T6 aluminium alloy columns loaded by axial compressive load is derived. Comparison between column curves from proposed formulation and different code and test results has been presented, from which the validation of the proposed formulation has been verified.

Abstract: Low elastic modulus of aluminum alloy gives prominence to lateral and local buckling of members, especially when thin walled sections are adopted to save material usage. Under certain conditions of loads and constraint, local buckling would occur in aluminum beams. A numerical study to assess the local stability of aluminum I section beams is presented in this paper. The study focused on two aspects: the local buckling of aluminum flange plate under compression, the local buckling of aluminum web plate under bending and shear. An extensive parameter analysis including width-to-thickness ratio, initial imperfection, material constitutive relation and restriction effect from adjacent plates was carried out with the purpose of extracting several governing parameters and investigating their effects on the local buckling of aluminum plate. Based upon the results of finite element analysis (FEA), a new design method in connection with the local stability of aluminum I section beams has been developed. By virtue of the proposed design method, three key indicators that include the critical value of width-to-thickness ratio to prevent local buckling of aluminum flange plate under compression, the local stability of aluminum web plate under bending/shear and the bearing capacity of aluminum I section beams under the condition that the post buckling strength of web is taken into account, could be obtained to provide more rational and efficient designs. The proposed design method is different from the current Eurocode but acts in accordance with Chinese code for design of steel structures (Chinese steel code) in order to satisfy applicability.

Abstract: The stress-strain characteristics of the fly ash blended with curing agent was studied using uniaxial and triaxial compression tests. Curing agent JNS-2 was used as the stabilizing agents in sample preparation. Four curing agent JNS-2 contents of 3%, 6%, 9% and 12% were selected for sample preparation. UU triaxial compression tests were conducted in a range of confining pressures from 100 kPa to 300 kPa. The experimental results obtained from the laboratory tests showed that curing age, mixture ratio, compaction degree and confining pressures had significant influence on the shape of curves. Uniaxial stress-strain test results demonstrated that the latter strength and deformation characteristics of the fly ash blended with curing agent grew little and with the increase of curing agent amount and compaction factor, the curve of uniaxial stress-strain changed significantly. On the other hand, triaxial stress-strain test results indicted that the failure strain showed a partial negative growth trend with the increase of curing agent amount, and the failure stress showed a partial positive growth trend with the increase of curing agent amount. When the curve was at high confining pressure, it showed hardening type, when at low confining pressure it showed softening type.

Abstract: This manuscript makes experiments on the macroscopic concrete strength improvement of fly ash activation at early age. At the same time we test the microstructure of fly-ash waste residue concrete cementious materials and calculus, analyzing HPC preliminary mechanism tentatively. The mechanism of improving the early concrete strength by fly ash activation is expatiated, which improves activation mechanism and technology of fly ash.

Abstract: Sintering glass-ceramics, a new type material for architectural decoration, belong to CaO-Al₂O₃-SiO₂ system (CAS) without nucleation agent. Combined by Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscope (TEM), phase evolutionary process of CaO-Al₂O₃-SiO₂ system glass and glass-ceramic was investigated. According the relation between heat treatment schedule and microstructure, the glass system has a very wide temperature range of crystallization. The crystalline phase is β-CaSiO₃ (β-wollastonite) and there is no other crystalline phases precipitated in these glass-ceramics. The influences of various heat treatment systems on the structure and properties of the glass-ceramics were investigated simultaneously. The optimal heat treatment schedule, microstructure and bending strength of the CAS glass ceramic were gained.

Abstract: In order to find out the long-term deformation behavior of MgO concrete,the nearly 10 years prototype observation data of Dongfeng arch dam foundation is analyzed. The results show that the MgO concrete has excellent delayed micro-expansion character, and its long-term expansive deformation always tends to stable level without any trend to contraction or infinite expansion, and by adding appropriate MgO expanding agent which was calcined at some high temperature into concrete, the cracking resistance of the concrete is improved. It is an effective way to construct dams excellently, efficiently and economically by using MgO concrete technology.

Abstract: The temperature field distribution and thermal stress distribution in concrete has been studied by finite elements method to establish the relationship between the thermal stress and the temperature in this paper. The results show that the maximum thermal gradient and the maximum thermal stress in the concrete appears on the direction of greater structural dimension, and the thermal stress value is positively correlated with thermal gradient or saying temperature difference and elastic modulus, and is negatively correlated with the water content and air content.

Abstract: Characteristics of aluminum alloys such as light weight, high strength-to-weight ratio and favorable corrosion resistance have brought about a bright application prospect in building structures. Wrought alloys are applicable to common beams and columns, while casting alloys can be fabricated as connectors in point-supported glass curtain wall and joints in spatial latticed structures on account of easy implement of moulding. Because of high strength, outstanding castability and remarkable mechanical properties after heat treatment, ZL111 in aluminum-silicon alloys is regarded as a desirable option. However, aluminum alloys are non-linear materials and their properties vary with casting and heat treatment modes. It is the well-marked distinction between aluminum alloy and ordinary carbon steel that special study on mechanical and fatigue performance is required. ZL111 raw materials were selected, with alloying agent and fabrication processes meeting the requirement of GB/T 1173-1995 standard. After T6 heat treatment process, test coupons were obtained by machining from raw materials. By utilization of electronic universal testing machine and cryogenic box, tensile tests at room temperature and low temperatures were performed. High-circle fatigue tests were carried out to obtain the fatigue performance of the material. Scanning electron microscope (SEM) was introduced to observe morphology of tensile and fatigue fractures. The tests revealed the relationship between mechanical property index and temperature, which indicated that the ZL111-T6 would increase in strength and plasticity. The microstructure of fractures validated and explained the macroscopic results. Furthermore, material strength at room temperature or low temperatures, stiffness and fatigue performance could satisfy bearing and normal serviceability requirement. Because of non existence of ductile-brittle transition temperature, superior corrosion resistance and outstanding castability, ZL111-T6 material is prone to fabricate complicated elements and joints withstanding cryogenic environment instead of carbon steel.

Abstract: Full-automatic concrete pressure machine and 100-mm-diameter split Hopkinson pressure bar (SHPB) apparatus were used to investigate quasi-static and dynamic energy absorption property of ceramic fiber reinforced concrete (CRFRC) subjected to various high strain rates, which is compared to carbon fiber reinforced concrete at the same volume fraction of 0.1%, 0.2% and 0.3%. And the absorbing mechanism of CRFRC is analyzed. The results show that the quasi-static energy-absorption property of CRFRC increases with the volume of ceramic fiber and the relation presents linear approximations; the specific energy absorption of ceramic fiber reinforced concrete is strain rate-dependent dynamic strength-dependent under impact load, and the effect can be expressed by linear approximations. And the strain rate is more distinct when volume fraction of ceramic fiber increases. The energy absorption property of ceramic fiber reinforced concrete is superior to plain and carbon fiber reinforced concrete, especially at higher strain rate and volume.