Advanced Materials Research Vol. 893

Abstract: To explore the feasibility of the approach of "interfacial toughening in concrete", the 2D concrete model which possesses the characteristic of random distribution of spherical aggregates was used to simulate the relations between interface material and toughness of concrete containing flexible interfacial material. The influence of interfacial material on the toughness of concrete was calculated with elastic modulus, thickness and the displacement at peak load for variables. And the results show that: The peak width of the concrete's load-displacement curve is increased evidently with the ultimate displacement also improved evidently upon replacing the normal ITZ with flexible interface phase material; the concrete's peak load, the displacement at peak load and the fracture energy increase gradually with the increase of the elastic modulus of interface phase material. When the elastic modulus exceeds 50MPa, the concrete's peak load will exceed that of normal concrete promptly with the displacement at peak load and the fracture energy all reaching the maximal value; With the gradual increase of the thickness of interface phase material, the concrete's peak load declines gradually while the displacement at peak load increases gradually; The concrete's fracture energy and ductility coefficient approximately increase first and then decline with the change of thickness. When the thickness is 0.2mm, the concrete's fracture energy and ductility coefficient reach the optimal value in setting scope. With the gradual increase of the interface phase material's displacement at peak load, the concretes peak load increases gradually while its fracture energy and ductility coefficient increase first and then decline. When the displacement at peak load is 0.05, the two reach the optimal value; when the displacement at peak load exceeds 0.05, the cracks will extend from the aggregates-mortar base debonding to the mortar matrix. The results have certain exploration value for developing concrete toughening technology.

Abstract: An experimental investigation was conducted to evaluate the compressive, tensile strength and modulus of elasticity of two-stage concrete (TSC) at different water-to-cement ratios. The primary objectives were to measure the elastic modulus, compressive strength and splitting tensile strength of TSC and to determine if there is a quantifiable relationship between compressive and tensile strength. Behavior of TSC in compression has been well documented, but there are little published data on its behavior in tension and modulus of elasticity. This paper presents the experimental results of preplaced, crushed granite aggregate concreted with five different mortar mixture proportions. A total of 48 concrete cylinders were tested in unconfined compression modulus of elasticity and splitting tension at 28 and 90 days. It was found that the modulus of elasticity and splitting tensile strength of two-stage concrete is equivalent or higher than that of conventional concrete at the same compressive strength. Splitting tensile strength can be conservatively estimated using the ACI equation for conventional concrete.

Abstract: This paper used the environmental simulation curing system to cure the concrete specimens, and studied the mechanical properties of the concrete specimens under varying temperature histories, resulting in some suggestions regarding the same curing condition of mass concrete.

Abstract: Two full scale frames were tested on a shaking table to investigate seismic performance and fracture mechanism of fiber reinforced concrete in contrast to the plain concrete. The information about acceleration response, the maximum strain value as well as the time to reach it, the typical strain - time curves and the crack development of two test frames were presented. Test results indicate that reinforced concrete did not crack during the test; the fiber reinforced concrete could better absorb or consume energy in the process of stress redistribution after peak acceleration; maximum strain and maximum acceleration did not occur at the same time; structure came into being deformation even failure when the seismic energy in the structure gone up to certain extent, and the dynamic failure would be their main failure modes.

Abstract: Yield stress and plastic viscosity are two basic parameters to describe the rheological characteristics of self-compacting concrete which would reflect the workability of self-compacting concrete quantificationally, the relationship between workability test results and rheological parameters was summarized, and the influence of superplasticizer and water cement ratio on rheological characteristics and of self-compacting concrete was studied by series experiments, the optimum water cement ratio and mixing amount of superplasticizer was proposed, this would guide the design and application of self-compacting concrete.

Abstract: To improve the seismic performance of existing residential buildings, strengthening methods for T-shaped walls are evaluated through the performance tests. Almost damaged three specimens are strengthened by aramid fiber sheet and additional reinforcement. Cyclic lateral loads are applied to the top of the specimen with constant axial load. From these, strengthened wall by aramid fiber sheet and additional reinforcement shows the almost 100% strength and deformation capacity recovery comparing the undamaged wall. For the convenience of wall strengthening method in a residential state, using of aramid fiber sheet is recommended from this performance test results.

Abstract: This paper investigates the static mechanical properties and flexural impact properties of reactive powder concrete (RPC) reinforced by the basalt fiber through various experimental works. The results indicate that the highest flexural and compressive strength can be obtained when the fiber content is 3kg/m³. Length and diameter of basalt fiber both influence the mechanical properties. The basalt fiber of 25mm long and 18μ in diameter can have an ideal strengthening effect. The static mechanical properties and flexural impact resistance can be improved to a considerable extent.

Abstract: Timber-concrete composite structures, which use advantages of both materials, are suitable for new works and reconstructions of civil and residential buildings. There are described many methods of joining between timber beam and concrete slab in technical literature. Joints are more and more sophisticated which brings higher demands on work control and technology. Main goal of the paper is in design technologically low demanding method of joining with steel plates and nails, to test its shear strength and to compare it with other similar joining .

Abstract: The aim of this paper is to investigate the time dependence distribution of workpiece cutting temperature in milling process. An experimental system used to achieve a measurement of cutting temperature in high speed milling is designed by use of the thermocouple and infrared thermal imager. The general regularity of temperature distribution is concluded, and the influence of the process variables such as cutting speed, cutting depth, etc. on the temperature distribution was investigated in detail. All the experiment results can be effective used to develop a new non-contact soft-sensing method for high speed cutting temperature prediction.

Abstract: Superalloy GH4169 as one of high temperature structural material is widely used in aviation industry. Isothermal compression of superalloy GH4169 has been conducted on Gleebe-1500D hot simulation at the deformation temperatures ranging from 950°C to 1100°C,the strain rates ranging from 0.01s^-1 to 10s^-1, and the height reduction of 50%. Effect of processing parameters ,i.e. deformation temperature, strain rate and strain, on the hot deformation behaviors of superalloy GH4169 was studied. The research shows that the fine dynamic recystallization grains could be obtained at the condition of high deformation temperature and low strain rate. Constitutive equation of superalloy GH4169 was established by experimental data. Error analysis showed that calculated stress values by the established constitutive equation were coincident with experimental data well, and it provided the theory basis to optimize forging processing of superalloy GH4169.