Mechanical Properties and Durability of Extruded Fiber Reinforced Cement Mortar Board and Its Composite Beam

The effect of water to cement ratio, fiber types and content, cement types on the bending performance of the extruded fiber reinforced cementitious board were studied. And it was found that polyvinyl alcohol (PVA) fibers can significantly improve the ductility of the board compared with polypropylene (PP) fibers. As PVA fiber content achieved 1.7%, the strain hardening and multiple cracking were occurred on the extruded board, while strain softening were shown on PP fiber reinforced cement board. The difference between the two kinds of board was from the differences of the mechanical properties of the two fibers. In addition, taking the fiber reinforced extruded board as base, the ultimate bending strength, as well as and the corresponded deflection and the resistant to chloride iron penetrating, was improved for a composite beam with fiber board and concrete compared with those of traditional concrete beam.     

Review of Research on Damage of Corrod Reinforced Concrete

The research result shows that the corrosion of reinforcement is one of the dominating factor for decreasing the durability of reinforced concrete structures. In this paper, the significance of the research of corroded reinforced concrete is presented, and an attempt is made to integrate the latest development with regard to the mechanical behaviors of reinforcement corrosion, the damage of concrete due to corroded bars, bond relationship between corroded bars and concrete, as well as the load capacity of corroded reinforced concrete flexural member and compressive member and the seismic behavior of corroded reinforced concrete element. And the trend of its development in future is discussed as well.     

Mechanical Properties of Concrete Cylinders Confined with CFRP Sheets Subjected to Axial Compression

Based on Drucker-Prager criterion with non-associated flow rule, numerical analysis of mechanical properties of concrete cylinders were carried out by using non-linear finite element method. The effect caused by various parameters such as wrap thickness, fiber orientation and concrete strength on axial mechanical properties of concrete cylinders is discussed. The results show that the results calculated by non-associated flow rule conform to that in the test. It is demonstrated that there is significant enhancement both in compressive strength and ductility of cylinders with the increase of wrap thickness. Moreover, the gain in axial compressive strength is observed to be higher for lower strength concrete and be highest in the cylinders wrapped with the hoop orientation.     

Deformation Analysis of Thermo Elastic Plastic on ReinforcedConcrete Structure Subjected to Fire

To investigate the mechanical behavior of reinforced concrete structure subjected to fire, the incremental thermo elastic plastic creep constitutive equations of steel and concrete in consideration of temperature and creep deformation were obtained based on different yield rules and the elastic plastic theories. The nonlinear analysis for reinforced concrete simply supported slab was carried out with consideration the variation of the mechanical properties of steel and concrete with temperature. The effectiveness and applicability of the constitutive equations were verified with the test results from relevant literature. The nonlinear analysis was employed for one bay one storey reinforced concrete frame under fire and the variation of displacement at partial nodes was analysed. It was found that the reinforced concrete structure at a high temperature would have a significant deformation. And the displacement change curves of beam column joints of reinforced concrete frame were not monotonous trend and there were inflexion points. The vertical displacement values of beam column joints were less than those at midspan of cross beam.     

Influence of Fine Recycled Aggregate on Physical and Mechanical Properties of Concrete

Based on a series of recycle process, waste concrete can be made into fine recycled aggregate which can be used completely or partly to compound concrete as a substitute for natural sand. But the special properties of fine recycled aggregate make the performance of concrete with fine recycled aggregate different from normal concrete. Characteristics of fine recycled aggregate and its influence on physical and mechanical properties of concrete are studied. On this basis, the influence of fine recycled aggregate on gas permeation properties, chloride permeability, and carbonation resistance of concrete are also studied. It is found that fine recycled aggregate produces a lot of defects in crushing preparation. And the compressive strength, the chloride permeability and the carbonation resistance of the concrete with fine recycled aggregate as substitution show difference from that of normal concrete.     

Mechanical and Chloride Diffusion Behavior of Kaolinite Clay Modified Cement-Based Material

The effects of kaolinite clay on the microstructure (pore structure, internal structure) and mechanical properties (workability, early-age and long-term flexural strength, chloride diffusion property) of the cementitious composites were tested. It is shown that the addition of clay improves the micro-pore structure in the cement paste and limits the introduction of chloride ions. As a result, it is suggested that the kaolinite clay would act as both filler and accelerator of cement hydration. Compared with the control specimen, the flexural strength of cement paste with 1% kaolinite clay increased by 30.41%, 39.04%, 36.27% and 38.32% at 1, 3, 7 and 90 curing ages, respectively. The 28-day flexural strength increased slightly. It is observed that the clay modified cement mortar has lower chloride diffusion coefficient values compared to the plain mortar, and the 28-day DCl of cement mortar decreased by 53.03% with 5% clay. Compared with the controlled sample, the increase in compressive strength and the reduction in chloride diffusion coefficient of the concrete with 5% clay addition is 28.4% and 18.87% respectively. The chloride diffusion coefficient of concrete decreases with the amount of clay addition exponentially. The 28-day compressive strength increases linearly with the chloride diffusion coefficient of the concrete.     

改性竹筋混凝土受弯构件力学性能试验研究

针对竹筋混凝土结构存在的问题,提出了多种对竹筋的改性方法。在此基础上,对12根采用不同配筋和不同改性方法的受弯构件(11根竹筋混凝土梁和1根钢筋混凝土梁)进行了试验研究,分析了不同改性方法和不同配筋率竹筋混凝土受弯构件的力学性能、破坏形态及其影响因素。研究结果表明：竹筋能有效提高混凝土受弯构件的承载能力;经过适当方法改性后的竹筋能确保竹筋和混凝土之间的有效粘结,其正截面强度计算可以采用平截面假定;竹筋混凝土受弯构件的破坏均为脆性破坏,其破坏形态与其截面配筋率有关。     

再生混凝土抗碳化性能试验研究及理论分析

通过快速碳化试验,以再生骨料掺量、水灰比、水泥用量、原始混凝土强度和矿物掺合料为影响因素,对再生混凝土的碳化性能进行研究。试验结果表明：再生混凝土的碳化深度随水灰比、再生骨料掺量的增加而减小,随原始混凝土强度的增大和水泥用量的增加而增大,适量添加矿物掺和料能降低再生混凝土的碳化深度,提升其抗碳化性能。在已有的普通混凝土碳化模型研究基础上,结合本试验和中国其他学者的试验数据,建立了再生混凝土碳化深度预测模型,模型预测结果与试验值吻合较好。     

Study on Mechanical Properties of High-Performance Concrete

In this paper the high-performance concretes with 56-day compressive strengths of 60 to 100 MPa (with or without silica fume) have been studied experimentally in order to develop information about the mechanical properties of high-performance concrete. Results and discussions are presented regarding compressive strength gain with time,effect of drying. A linear equation of static modulus of elasticity has been derived.The static modulus of elasticity and Poisson's ratio are calculated by regression with testing data of 20 specimens.     

Meso-scale numerical investigation on the crack process of concrete cover induced by rebar non-uniform corrosion

Concrete cover cracking induced by corrosion of steel reinforcement is a major influencing factor for durability and serviceability of reinforced concrete structures. In order to investigate the cracking process of concrete cover induced by rebar corrosion, the heterogeneity of concrete meso-structure and non-uniformity of rebar corrosion are accounted for. The undamaged concrete is assumed to be a three-phase composite material composed of aggregate, mortar matrix and the interfacial transition zone (ITZ). And a concrete random aggregate structure is established for the study on the mechanical behavior of the non-uniform radial corrosion expansion. In the present simulations, non-uniform radial displacement is adopted to simulate the non-uniform corrosion of the rebar; the plasticity damaged model is used to describe the mechanical behavior of the mortar matrix and the ITZ, and the aggregate is assumed to be elastic. The cracking of concrete cover due to the non-uniform corrosion of the middle located rebar is numerically simulated. The comparison of the analysis and the test result on failure pattern of cover concrete shows fairly good agreement. And then the failure patterns under uniform corrosion and non-uniform corrosion obtained from the macro-scale homogeneous model and the meso-scale heterogeneous model are compared. Furthermore, the influences of concrete cover thickness and rebar diameter on the failure pattern of concrete cover, the expansive pressure and the corrosion rate of the rebar when cover concrete cracks are investigated.     

A Review of Concrete Damage Constitutive Models

The existing constitutive models of concrete are mainly based on the framework of the classic elastic -plastic models which are rigorous on mathematics, but not coordinated with the failure mechanism of concrete. Researchers of different countries proposed various kinds of damage constitutive models based on the irreversible thermodynamics theory to describe the damage behavior of concrete. This paper presents a review of different models for concrete,analyzes the characteristics of each representative model and studies the scope of their application. On the basis of the review of existing concrete damage models, some new methods can be provided for further research on damage constitutive models.     

Mechanical Properties of Marble at High Temperature

为进一步优化超声波提取胡萝卜中β-胡萝卜紊的工艺条件,在超声功率、超声时间、提取温度、物料粒度、料液比及提取次数6个单因素试验结果的基础上,采用二水平部分因子析因设计（2—level fractional factorial design）法,筛选出了影响β-胡萝卜素提取的主要因素为提取时间（p=0．0145）、温度（p=0．0189）、料液比（p=0．0180）和提取次数（p=0．0114）。     

THE ORGANIZED DEVELOPMENT TREND OF CEMENT CONCRETE

Cement concrete is the building material which is widely and lar-gely used.Congenital deficiency of cement concrete is brittleness.Adding a little polymer into cement concrete can improve its brittleness and function and even provide concrete with new function.This is an organized development trend of cement concrete.     

早龄期混凝土蠕变模型比较

针对早龄期混凝土的蠕变松弛特性,以配比、强度以及不同加载龄期的混凝土蠕变试验数据为依据,对比研究了CEB-FIP模型、Muller模型、B3模型与笔者所建立变系数四参数Burgers模型的蠕变预测差异。研究结果表明:常用经验模型中,CEB-FIP模型具有较好的适应性,Muller模型对于高强混凝土的蠕变预测较好,基于固化理论的B3模型对于早龄期混凝土的蠕变预测值偏大,准确性较差。对比研究验证了变系数四参数Burgers模型中参数的物理意义与经验取值范围及其合理性与适用性。     

The Study on Intelligent Experimental System of Bio-soft Tissue

According to the especial mechanical properties of bio-soft tissue materials, we design a mechanical test system of bio-soft tissue moterials which is controlled by microcomputer and can execute the post-processing for bio-soft tissue materials. The system can solve better the problems of reliability and accuracy appearing in the test of the mechanical properties for bio-soft tissue materials,and the test is convenient as well as speedy,and provides an effective experimental means for the study of biomechanics.     

Application of ultrasonic detection for partial discharge to cable terminals

The mechanical properties, phase change energy storage, environmental protection, and recycling of building materials are extensively studied, but few studies focus on the mercury adsorption of different building materials. Five types of cement brick powder including foam concrete, red brick, aggregate and gravel as well as several standard concrete blocks were exposed to gaseous mercury in constant temperature to determine most vulnerable building material to mercury contamination and the contamination depth of concrete blocks.Results showed that small particle contributed to large mercury adsorption, however different performance was found amongvarious materials. Red brick was the likely to have strong adsorption capacity followed by foam concrete and gravel. For concrete block,the pollution mainly concentratedat the 0~1.5cm of the surface. As a result, for some seriously mercury polluted factories and workshops, mercury pollution can be removed by peeling the skin of the buildings before demolition, renovation process.     

THE DETERMINATION OF A CRACK IN STEEL FIBRE REINFORCED LIME-SAND CONCRETE

This paper studies the determination of a crack in steel fibre reinforced lime-sand concrete and its precision by acoustic emission(AE).The main AE paramters which influencethe precision of the determination of a crack are introduced,The properties of the lime-sand concretecan be increasted greatly with the steel fibre,The result in this paper can be used in the study of fi-bre re inforced cement concrete.     

高温下钢管约束型钢混凝土柱的受力性能

火灾下无防火保护的结构构件温度会迅速上升,从而造成钢材和混凝土的强度明显下降。为了研究火灾下钢管约束型钢混凝土柱的受力性能,考虑火灾下钢管约束型钢混凝土柱的不均匀温度分布及温度对材料力学性能的影响,提出了火灾下受轴心荷载作用的钢管约束型钢混凝土柱承载力的计算方法。利用有限元软件ABAQUS对提出的计算方法进行了验证,结果吻合较好。进而采用该计算方法对影响高温下承载力的参数进行了分析,研究表明：随着构件截面尺寸的增加以及混凝土强度和钢材强度的提高,构件的承载力逐渐增加,而钢管壁厚的改变对承载力并无太大影响。利用有限元软件ABAQUS分析了荷载比、构件尺寸、钢管壁厚等因素对构件耐火极限的影响,发现耐火极限随着荷载比和钢管壁厚的增加而减小,随着构件尺寸的增加而增大。     

A STUDY ON REINFORCED BEAMS OF HIGH STRENGTH ALKALI-SLAG CONCRETE

In This paper,the characteristics and mechanical prop-erties of high strength and super-high strength concrete(60-120MPa)based on slags and alkaline components are presented.This type ofconcrete can be produced as rapid hardening or super rapid hardeningwith high durability,energy saving and low cost.Based on experimentswith reinforced beams of this type of concrete,its deformation properties,process and characteristics of disruption are described.     

建筑垃圾细料生产流动化回填材料的性能

以灰砂比0.03、0.05和0.08,粉砂比0、0.05、0.1、0.15和0.2为设计参数,对建筑垃圾回填材料进行设计。通过试验对回填材料的流动性(流动度、泌水率)、无侧限抗压强度以及应力应变曲线、本构关系模型和弹性模量等进行研究。研究结果表明:回填材料的流动度受水固比影响较大,两者接近线性关系;流动度在200~250 mm范围,泌水率在4%~8%之间;回填材料抗压强度与灰砂比和水固比之间存在很好的幂指数关系;回填材料应力应变曲线形状与普通混凝土的相似,在此基础上提出回填材料的本构关系模型;回填材料无侧限抗压强度与弹性模量之间存在很好的指数关系。