Study on Influence of Fiber to Stability of Asphalt Concrete Pavement

The effect of fiber in asphalt mixtures has attracted general concern. For study of this problem, four kinds of fibers are chosen in this test. Asphalt and modified asphalt are adopted in asphalt mixtures AC-16I. The road performance influenced by additional fiber was analyzed impersonally,i, e. the stability of asphalt concrete under high temperature condition, anti-crack ability under low temperature condition, the water resistance and fatigue performance. It was shown through the research that the optimum asphalt content, air void rate, clearance rate of the mineral powder, saturation degree, and the flow value were increased and the density was decreased after adding the fiber. The road performance, such as the stability of asphalt concrete under high temperature condition, anti-crack ability under low temperature condition, water resistance and fatigue performance, was obviously improved,and the high temperature stability and fatigue performance improved most evidently. The fiber asphalt mixture performance reached and even exceeded the modified asphalt mixture performance. The modified asphalt performance after adding fiber would be improved more greatly.     

Study on Resistance to Chemical Attack ofHigh Performance Concrete

The durability of concrete is always a problem of great importance while the high performance concrete raise higher requirement for durability. The authors of this paper carried out a study on resistance to chemical attack of the high performance concrete prepared with Portland cement, silica fume and superplasticizer ,which has proved that the high performance concrete offers excellent resistance to chemical attack.     

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.     

Shear Ductility of Hybrid Fiber Reinforced High Performance Concrete Deep Beams

The shear tests were conducted on 18 different groups of deep beams with steel fiber and polypropylene fiber and two groups high performance concrete deep beams without fiber according to the orthogonal experimental design. By a definition of shear ductility index shear ductility of deep beams was analyzed quantitatively. The influence of six factors on improving shear ductility of deep beams was compared by direct-viewing analysis of the orthogonal experiment. The contributory factors such as the species of steel fiber, the volume fraction of steel fiber, the length/diameter aspect ratio of steel fiber, the volume fraction of polypropylene fiber, the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement were analyzed. Results show that the volume fraction of steel fiber plays the most important role in improving shear ductility of deep beams exceeding the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement, whereas species of steel fiber has minimum effect. Hybrid fiber can be used to greatly increase shear ductility of deep beams and shear ductility is at the most increased by 40.7% although it can not change the brittleness of shear damage. The full-range shear behaviors of deep beams through ABAQUS are analyzed and the calculated results are in good agreement with test results.     

Calculation Method of Shear Behavior of Hybrid Fiber Reinforced High Performance Concrete Deep Beams

The static tests on hybrid fiber (steel fiber and polypropylene fiber) reinforced high performance concrete deep beams according to the orthogonal experimental design were conducted. The shear capacity and calculation method of deep beams were discussed as well. The contributory factors such as the characteristic parameters of steel fiber (types, volume fraction, aspect ratio), the volume fraction of polypropylene fiber, the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement were analyzed. Results show that the shear failure mode of deep beams is changed with adding a reasonable volume of hybrid fibers, and hybrid fiber can greatly increase the diagonal cracking strength and shear strength of HPC deep beams. The diagonal cracking strength is increased by 45.2% averagely while the shear strength is increased by 25.6% averagely. A satisfied result is obtained when the plasticity theory is used to analyze shear behavior of hybrid fiber reinforced HPC deep beams. The contribution of web horizontal reinforcement and web vertical reinforcement to shear strength of deep beams is not obvious but the former plays a major role. After analyzing the strengthening mechanism of hybrid fiber, a formula to calculate the shear capacity of hybrid fiber reinforced HPC deep beams is presented based on spatial strut-and-tie mode and splitting failure.     

Study on Modification of Amino-sulfonic Acid-based Water-reducer

Amino-sulfonic acid-based water-reducer is characterized by high water-reducing rate and restraining the concrete mixture from slump loss with time. The application of amino-sulfonic acid-based waterreducer in concrete mixture was restricted due to its high bleeding. Based on principles of molecular design, the traditional superplasticizer of aminosulfonic acid series was modified by the suitable functional group introduced by monomer A and monomer U. The effects of such product on the fluidity, fluidity loss with time and bleeding rate of cement paste were tested. It was found that the modifying effect of monomer A for the superplasticizer was better than that of monomer U. The dispensability and flow retainability of superplasticizer were strong and the bleeding rate of cement paste added with superplasticizer modified by 9% monomer A was reduced obviously.     

Study of Cracks on Rubber Concrete Beams Based on Fractal Theory

The flexural performances of a rubber concrete beam and a ordinary concrete beam are studied under concentrated load through the experiment. The influences of the content of the rubber powder in the rubber concrete beam on the bearing capacity and the crack width of beams are analyzed. The experimental results show that the crack distributions on two beam surfaces possess the characteristics of self-similar in statistical sense. The maximum crack width of the rubber concrete beam is less than that of the ordinary concrete beam under the same load level. The performance of anti-crack of the concrete beam is improved by adding the crumb rubber. Using the fractal theory, the fractal dimension values of the surface crack of the beams under different load grades are calculated and the relationship between the fractal dimension and the maximum crack width of the surface cracks is established.     

Preparation Technology of Fiber Toughened Self compacting High strength Concrete

Preparation technology of fiber toughened self compacting high strength concrete was tested by measuring influence of water/binder ratio, sand percentage, and steel fiber content on spread, T500 time , U shape value, and L shape value of fresh concrete. Mechanical properties were analyzed in case of different water/binder ratio, sand percentage, and steel fiber content. The test results show that suitable W/B and sand percentage were necessary to satisfy self compacting performance of the fresh concrete. With the increase of steel fiber content, the compressive strength and flexural strength were improved while workability of fresh concrete was cut down. Steel fiber toughened self compacting high strength concrete was prepared successfully with a strength grade of CF90 and a flexural strength of more than 11.0 MPa.     

Experimental Analysis on the Frost Resistance of Steel Fiber Reinforced Concrete

The frost resistance of steel fiber reinforced concrete (SFRC) was studied based on the fast freeze thaw tests in water and in a 3.5% sodium chloride solution, with different mass fraction of steel fiber in concrete at 0%, 0.5%, 1.0%, 1.5% and 2.0%, respectively. The effects of the number of freeze thaw cycles and the volume fraction of steel fiber on the mass lose rate, the splitting strength loss rate and the dynamic modulus of elasticity of SFRC were analyzed. The reinforcement mechanism of the steel fiber under the action of freeze and thaw was also discussed. Moreover, mercury intrusion method and SEM analysis were carried out to study the pore size distribution features and the performance of microstructure on the impact of frost resistance of SFRC. The results show that adding an appropriate amount of steel fiber into concrete can reduce the pore porosity and improve the compactness of concrete. Furthermore, the presence of steel fiber proves to shrink the porosity and improve evidently the frost resistance of concrete. It is also shown that the steel fiber content has a great influence on the frost resisting property of SFRC. The best performance of SFRC can be achieved when the volume fraction of steel fiber is 1.5%.     

预应力CFRP布及预紧螺栓加固RC梁试验研究

为提高碳纤维布加固RC结构的效果及其可靠性,提出了预应力碳纤维布与预紧螺栓联合加固技术。结合在役RC梁的损伤特点及目前的RC梁加固方法,分别采用不同的碳纤维布加固技术对完整梁和破坏梁的抗弯性能进行了对比试验研究。针对目前碳纤维布张拉设备的缺陷,研发了便于现场应用的新型碳纤维布布张拉设备,分析了预应力大小对加固效果的影响。结果表明,预应力碳纤维布及预紧螺栓联合加固技术是一种更可靠的桥梁加固方法,不仅能够提高RC梁正截面的抗弯承载能力及正常使用阶段的截面刚度,而且螺栓预紧锚固碳纤维布能够很好地抑制其在混凝土表面的剥离,提高碳纤维布与混凝土表面之间粘结强度,对碳纤维布施加预应力能够充分发挥其高强性能,有效抑制混凝土裂缝开裂和开展。     

活性污泥降解植物纤维容器的研究

生物可降解塑料的开发已经成为目前的研究热点之一,而活性污泥法是常用的评价高分子材料的生物可降解性的方法。以活性污泥的干燥固体总质量(TS)和活性污泥的挥发性固体含量(VS)为考察指标,分析活性污泥对于聚丙烯(PP)、纸制、植物纤维(稻壳)餐具的降解能力。实验结果表明,在降解期间(21 d),纸制餐具降解速度最快,且降解程度最大,植物纤维餐具降解程度低于纸制,而聚丙烯餐具基本不降解。增加降解物的表面积和提高活性污泥与降解物的比值,有利于降解物的降解。     

苎麻骨纤维餐具降解性能研究

为了了解苎麻骨纤维餐具的降解规律,为其规模化生产提供依据,采用活性污泥法对其生物降解性能进行了研究。以生物降解率为考察指标,分析活性污泥对于聚丙烯(PP)、滤纸、苎麻骨纤维餐具、纸浆模塑餐具和塑料淀粉餐具的降解能力。结果表明,在降解期间（28天）,滤纸降解速度最快,纸浆模塑餐具次之,苎麻骨纤维餐具降解程度低于纸制,生物降解率达到60.59%。而聚丙烯餐具和塑料淀粉餐具基本不降解。增加降解物的表面积和提高活性污泥与降解物的比值,有利于苎麻骨纤维餐具的降解。     

Online wine wearing detection device for AC contact network

For the transmission pressure 27.5 kV of the railroad AC contact network, and the non parallel (on earth) arbitrary plane for the wire wearing surface, the optic fiber was used to isolate the high voltage and to transmit the measurement signal. A remote grating type adaptive automatic machinery transducer was used to detect the AC contact network wire wearing surface with about seven meters from the ground. Based on this method, a system was designed and calibrated, achieving measurement of wire rubbing with high voltage. The actual measurements indicate that the method and the system satisfy the demand of the measurement of contact network wire wearing. The method is significant to the geometric sense measurement of the high voltage charged body.     

塑性铰区采用FRC柱试验研究及正截面承载力分析

采用简化的纤维增强混凝土应力应变关系,根据截面变形的平截面假定和截面力的平衡方程,推导出塑性铰区采用纤维增强混凝土柱在不同极限状态时的曲率。根据各极限状态点曲率,求得截面上各分布力,对截面形心轴取距,到塑性铰区采用FRC柱的开裂、屈服、峰值和极限点的弯矩表达式。与试验结果对比表明,计算值与试验值吻合较好。     

油菜秸秆纤维混凝土保温性能试验研究

(目的)为了将解决农业废弃物油菜秸秆的去向问题和新型墙材的研发结合起来,(方法)本文对油菜秸秆进行碱处理后,以砂率和不同比例的秸秆掺量为变量,制成300mm×300mm×30mm的试件,通过稳态平板导热仪测试其导热系数,使用电镜(SEM)扫描混凝土内部微观结构,从宏观和微观角度研究油菜秸秆纤维混凝土的保温性能。试验结果表明：(结果)不同秸秆掺量的各试验组及对照组,砂率为25%的混凝土相较于砂率取40%的混凝土导热系数均降低了约10%,(结论)即总体呈现砂率越高导热系数越大试件保温性能越差的趋势;(结果)不同砂率的各试验组及对照组,秸秆纤维掺量为2.5%的混凝土试件比秸秆纤维掺量为0%的混凝土试件的导热系数均降低了30%左右,(结论)即秸秆掺量越大,导热系数越小,试件保温性越好。     

Dry mixed Superfine Sand Mortar for Bonding Ceramic Tile

By modification with water retentive agents and organic bonding admixtures, one dry mixed superfine sand mortar used as ceramic tile bonding was prepared with good workability, adhesive capacity and climate resistance. The test results indicate that this mortar has excellent anti sagging characteristics, with slippage of less than 2mm, sufficient open time and bonding strength over 1 MPa after being open for 20 minutes. These traits provide the needed qualities for thin construction of ceramic tile bonding. By adding polypropylene fiber, a flexible mortar was prepared with superior crack resistance for use as a ceramic tile bonding agent. The preparation mechanism, method and performance are introduced in detail.     

Contrast Analysis of Mechanical Behavior of Confined Concrete with Stirrups and CFRP Under Axial Compression

Aiming at confined concrete with stirrups and carbon fiber reinforced plastic(CFRP) respectively, the major influence factors of mechanical behavior of confined concrete under axial compression were studied based on reported experimental data. The equations for calculating the peak stress, peak strain and ultimate strain were proposed respectively for confined concrete with stirrups and CFRP. Contrastive analysis shows that the behavior of confined concrete with stirrups is better than confined concrete with CFRP in low characteristic value, whereas the conclusion is contrary in high characteristic value.     

Analysis of Fiber Renforced Concrete Beam-Column Joints Model

Due to the large stirrup ratio and reinforcement congest in beam-column joints, the ordinary reinforced concrete beam-column joints take inconvenience to construction. Cracked fiber renforced concrete (FRC) has strong bridge ability and better tensile performance so that it can replace part or all of the stirrups. Based on previous researches on resistance mechanism of reinforced concrete joints, a new model using FRC materials in the core zone of beam-column joints is presented. It is a kind of model in which horizontal shear supported by the diagonal strut mechanism and softening truss mechanism with a certain percentage. The calculation results of the model is compared with the existing test results. It is a bit conservative to specimens with low axial load ratio. However, the results are in line with the specimens with high axial load ratio. Therefore, the results totally demonstrate the rationality of the proposed model in this paper. Meanwhile, according to the proposed model, the shear capacity of beam-column joints can be not only calculated, it also check whether FRC compressive strength in core zone of joints and horizontal stirrup ratio meets design requirements, which has a higher practicability.     

Experimental Study on Flexural Toughness and Fatigue Property of Polypropylene (PP) Fiber Reinforced Cement-stabilized Macadam

By four-point bending test and fatigue test,the authors studied the flexural toughness and fatigue property of semi-rigid base course of cement-stabilized macadam with and without polypropylene(PP) fiber.Some significant data about these two kinds of material have been obtained,such as the load-deflection curves,toughness index according to the standard methods of JCI and ASTM C1018-97,the fatigue lifetime under different stress levels and the fatigue lifetime regression equation.The results show that the reinforcing effect of the PP fiber is remarkable;the bending strength,ultimate deformability,JCI toughness index,ASTM C1018-97 toughness index and fatigue life of cement-stabilized macadam with PP fiber are increased by about 10%,150%,67.7%,36.1%~79.8%,and 126%~352%,respectively,when the volume fraction of PP fiber is only 0.077%.At the same time,the authors revealed the toughness improving mechanism and the anti-fatigue mechanism of the fiber in such material based on the fracture mechanics theory.     

Properties of Steel Fiber Asphalt Concrete and Its Application

To prevent asphalt pavement from cracking under low temperatures and prolong its fatigue life, we tested the properties of a new type of steel fiber asphalt pavement. The tests evaluated Marshall stability, dynamic ruts, and cleavage strength under both low and normal temperature conditions. We also analyzed the anti-corrosion property of steel fiber and the factors affecting the properties of the steel fiber asphalt mixture. The steel fiber asphalt pavement was installed on a highway in Chongqing, P. R. China to investigate the construction art of the steel fiber asphalt mixture and examine its effect in field use. The test results and concrete use in the field show that the cleavage strength and flexibility of steel fiber asphalt concrete increase due to the action of steel fiber. We conclude that the anti-cracking capacity of asphalt pavement under low temperature conditions can be improved by steel fiber. The construction art of steel fiber asphalt pavement is the same as common asphalt pavement without the necessity of anti-corrosion processing for steel fiber. The research results are useful for pavement material selection in low temperature regions and heavy traffic road pavement designs.