玄武岩纤维对水泥砂浆性能及水泥石微观结构的影响

以聚丙烯纤维为对比研究了新型材料玄武岩纤维(BF)对水泥砂浆的抗压、抗折强度和干缩的影响,并采用XRD、SEM及MIP现代检测技术对纤维微观作用机理进行了分析。结果表明:玄武岩连续纤维具有替代聚丙烯纤维的可行性;BF的加入提高了水泥砂浆的早期强度,但使28d强度有所降低;对早期砂浆的收缩有明显的改善效果,但28d以后对砂浆收缩的影响作用不显著;微观分析显示早期水化浆体中由于纤维-水泥石界面结合紧密和纤维乱向作用阻止了裂缝的引发与扩展,提高了水泥基材料早期力学性能。28d掺加纤维的水泥浆体在纤维-水泥石界面上产生弱界面,界面的弱化与总空隙率增加的共同作用导致掺加纤维水泥砂浆的长期力学性能下降。

Compressive properties of glue-laminated timber circular post modified by basalt fiber reinforced polymer

Glued timber structure is one of the main forms of modern wood architecture,which has gradually developed towards mid-and high-rise buildings.Glue-laminated timber(GLT)is comprised of several laminates of parallel-to-grain dimension lumber that are bonded together with durable,moisture resistant structural adhesives.GLT can be used in horizontal applications as a beam and in vertical applications as a post.So,its compressive performance has a significant impact on structural safety.Fiber reinforced polymers(FRPs)were commonly used to improve the bearing capacity of GLT components,and the structural and process parameters largely determined the reinforcement effect.This study was aimed at investigating the influence of structural and process parameters on the axial compression performance of GLT components.Three wrapping methods(middle-part,end-part and full wrapping)and three lengths(0.6,0.8,and 1.0 m)of wood post specimens were designed in this work and the axial compression performance and ductility of GLT post specimens modified by basalt fiber reinforced polymer(BFRP)were studied.The results showed that the effect of different BFRP wrapping methods on the compressive strength and elastic modulus of laminated wood was not statistically significant(P>0.05).The compressive bearing capacity of unreinforced GLT posts decreased with the increase of aspect ratio.The GLT posts with middle-part and end-part wrapping still followed this pattern,while the compressive bearing capacity of GLT posts with full wrapping showed a pattern of first decreasing and then increasing.For GLT with low aspect ratios(4.0 or 5.3),there was no correlation between the wrapping method and the compressive bearing capacity,while the compressive bearing capacity of GLT with a high aspect ratio(6.7)for middle-part,end-part and full wrapping increased by 3.5%,7.5%and 9.7%,respectively.Compared to the unreinforced group,the ultimate axial compressive strength and modulus of elasticity(MOE)of the 6-E series specimens reinforced at both ends decreased by 2.58%and 6.70%,respectively.The ultimate axial compressive strength of the 8-E specimens reinforced at both ends increased by 8.62%and the MOE decreased by 1.91%.The compressive strength of the 10-E specimens reinforced at both ends increased by 7.51%and the MOE increased by 8.14%.The failure modes of GLT with different aspects were consistent under the same BFRP wrapping,while the failure modes of GLT with the same aspect ratio were different for different BFRP wrapping methods.The ductility performance of GLT with different aspects ratio was improved by the BFRP wrapping.

Experimental study of pavement performance of basalt fiber-modified asphalt mixture

To discuss the pavement performance of basalt fiber-modified asphalt mixtures,the optimum dosages of asphalt and fibers are studied by the Marshall test and the rutting test.The results demonstrate that the optimum dosages of asphalt and fibers are 4.63% and 0.3%,respectively.Then the pavement performances of basalt（polyester,xylogen）fiber-modified asphalt mixtures are investigated through high temperature stability tests,water stability tests and low temperature crack resistance tests.It indicates that the pavement performances of the fiber-modified asphalt mixtures such as rutting dynamic stability,freezing splitting tensile strength,low temperature crack resistance and so on are improved compared with control asphalt mixture.The results show that the pavement performances of asphalt mixtures can be improved by fiber-modifiers.Besides,the improvement effects of basalt fiber are superior to polyester fiber and xylogen fiber.

Strengthening effects of BFRP on reinforced concrete beams

Reinforced concrete （RC） beams externally bonded with basalt fiber reinforced polymer （BFRP） are experimentally investigated by using different numbers of bonding plies, transverse anchorages as well as the initial conditions of strengthened beams. The performances of the BFRP strengthening are compared with those of the carbon fiber reinforced polymer （CFRP） and the glass fiber reinforced polymer （GFRP） under the same experimental condition. Experimental results indicate that the strength and ductility of the strengthened beam with two plies of the BFRP are improved remarkably than those with one ply. The strengthening effects of the BFRP lie between those of the CFRP and the GFRP. The BFRP strengthening is little influenced by pre-cracks of concrete. Most failures are caused by interfaciai debonding induced by flexural cracks in the experiment. Clamping of Uwraps along the whole beam is less efficient than endpoint anchorage for increasing the ultimate load of the strengthened beam. Finally, the models suggested by the five guidelines for predicting the debonding strain of the CFRP are extended to the BFRP and the conservative estimates of the debonding strain of the BFRP are given as well.

Experiment and simulation of creep performance of basalt fibre asphalt mortar under uniaxial compressive loadings

The creep performance of basalt fibre（BF）reinforced in asphalt mortar under uniaxial compressive loadings is investigated. The samples of basalt fibre asphalt mortar（BFAM） with different BF mass fractions（0. 1%,0. 2%, and 0. 5%） and without BF in asphalt mixture are prepared, and then submitted for the compressive strength test and corresponding creep test at a high in-service temperature.Besides, numerical simulations in finite element ABAQUS software were conducted to model the compressive creep test of mortar materials, where the internal structure of the fibre mortar was assumed to be a two-component composite material model such as fibre and mortar matrix. Finally, the influence factors of rheological behaviors of BFAM are further analyzed. Results indicate that compared to the control sample, the compressive strength of BFAM samples has a significant increase, and the creep and residual deformation are decreased. However, it also shows that the excessive fibre, i.e. with the BF content of 0. 5%, is unfavorable to the high-temperature stability of the mortar. Based on the analysis results, the prediction equations of parameters of the Burgers constitutive model for BFAM are proposed by considering the fibre factors.

Mechanical properties of polyvinyl alcohol-basalt hybrid fiber engineered cementitious composites with impact of elevated temperatures

In the present study,the mechanical properties of polyvinyl alcohol(PVA)-basalt hybrid fiber reinforced engineered cementitious composites(ECC)after exposure to elevated temperatures were experimentally investigated.Five temperatures of 20,50,100,200 and 400℃ were set to evaluate the residual compressive,tensile and flexural behaviors of hybrid and mono fiber ECC.It was shown that partial replacement of PVA fibers with basalt fibers endowed ECC with improved residual compressive toughness,compared to brittle failure of mono fiber ECC heated to 400℃.The tension tests indicated that the presence of basalt fibers benefited the tensile strength up to 200℃,and delayed the sharp reduction of strength to 400℃.Under flexural load,the peak deflections corresponding to flexural strengths of hybrid fiber ECC were found to be less vulnerable ranging from 20 to 100℃.Further,the scanning electron microscopy(SEM)results uncovered that the rupture of basalt fiber at moderate temperature and its pullout mechanism at high temperature was responsible for the mechanical evolution of hybrid fiber ECC.This work develops a better understanding of elevated temperature and basalt fiber impact on the residual mechanical properties and further provides guideline for tailoring ECC for improved fire resistance.

Experimental study on bond behavior between BFRP bars and seawater sea-sand concrete

Combining fiber reinforced polymer(FRP)with seawater sea-sand concrete(SSC)can solve the shortage of river sand that will be used for marine engineering construction.The bond performance of BFRP bars and SSC specimens is researched by pull-out test in this paper.The effects of the parameters,such as bar type,bar diameter,concrete type and stirrup restraint,are considered.It is beneficial to the bonding performance by the reduction of bar diameter.The utilization of seawater sea-sand has a low influence on the bond properties of concrete.The bond strength of BFRP is slightly lower than the steel rebar,but the difference is relatively small.The failure mode of the specimen can be changed and the interfacial bond stress can be improved by stirrups restraint.The bond-slip curves of BFRP ribbed rebar include micro slip stage,slip stage,descent stage and residual stage.The bond stress shows the cycle attenuation pattern of sine in the residual stage.In addition,the bond-slip model of BFRP and SSC is obtained according to the experimental results and related literature,while the predicted curve is also consistent well with the measured curve.

Experimental study on mechanical properties of basalt fiber-reinforced silty clay

Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering.Basalt fiber is a new kind of environment-friendly and highperformance soil reinforcement material,and the mechanical properties of basalt fiber-reinforced soil have become a hot research topic.In this paper,we conducted monotonic triaxial and cyclic triaxial tests,and analyzed the influence of the fiber content,moisture content,and confining pressure on the shear characteristics,dynamic modulus,and damping ratio of basalt fiber-reinforced silty clay.The results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its cohesion.We find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%(optimum moisture content).Similarly,we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%.The dynamic modulus is positively correlated with the confining pressure.However,the change in the damping ratio with fiber content,moisture content,and confining pressure is opposite to that of the dynamic modulus.It can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%.After our experiments,we used scanning electron microscope(SEM)to observe the microstructure of specimens with different fiber contents,and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.

The Influence of Steel and Basalt Fibers on the Shear and Flexural Capacity of Reinforced Concrete Beams

To improve the shear and flexural capacity of flexural members, the steel and basalt fibers were used in model beams tested under flexure. Three series of single span free supported model beams were prepared from SFRC （steel fiber reinforced concrete） with longitudinal steel reinforcement （steel ratio of 1.2 %） and varied spacing of steel stirrups and they were tested till failure. Another three series of BFRC （basalt fiber reinforced concrete） double-span model beams with a span of 2 mm~ 1,000 mm and cross section 180 mm ~ 80 mm were tested. During the tests till to the failure the beam reactions, vertical deflections and horizontal strains in concrete were registered, to clarify the range of redistribution of bending moments and shear forces over the span of the beams. Almost all the tested model beams failed in shear, showing visible influence of steel and basalt fibers on the shear capacity of the tested beams. The tests results confirmed that steel and basalt fibers in reinforced concrete beams can partially replace （in certain cases） the traditional steel stirrups calculated for shear.

基于长标距光纤光栅的龙尾港大桥加固监测研究

相较于其他工程结构来说,桥梁工程的安全性意义非凡。当桥梁出现损伤时,对其进行加固补救十分必要。目前已有大量成熟的加固方法用于该领域,维护保障桥梁安全。然而目前的相关研究主要集中在数值模拟和室内试验验证,对于各方法在现场实际工程应用中的效果尚未有详细的研究说明。通过对江西九江至景德镇段一座受损预应力简支空心板梁桥进行加固监测研究,来量化研究预应力钢丝绳加固法和粘贴玄武岩纤维布加固方法对桥梁梁体性能的提升效果,研究结果可以为后续研究提供参考。