Abstract:The effect of dry wet cycle time ratio(3∶1 and 854∶1) and exposure time(30,90d) on chloride resistance of strain hardening cementitious composites(SHCC) was investigated through the artificially simulated marine tidal zone test. Combined with the classical Ficks second law, the time dependent behaviors of the surface chloride content and diffusion coefficient were further analyzed. The results indicate that the mechanism of dry wet cycles has a significant influence on the behavior of chloride ingress into concrete. The time varying behavior of surface chloride content conforms to the variation of inverse model. The apparent chloride diffusion coefficient is markedly greater than that of instantaneous coefficient, and the age attenuation coefficient of SHCC is greater than that of C30 ordinary concrete.

Abstract:Yield stress and consistency of cement limestone powder pastes were measured by RHEOLAB QC rotational viscometer. The relationship between particle size distribution, packing density and rheological properties was studied. The results show that the addition of limestone powder makes the particle distribution wider and improvement of the state of particle accumulation. The linear correlation between particle size distribution coefficient and yield stress and consistency is not close, the correlation coefficient is only 060061 and 069962 The correlation coefficient between the packing density and the yield stress and consistency is 083058 and 084654, which is closer than that of the particle size distribution coefficient. The relationship between water film thickness and rheological properties cannot be described by linear function, among which the yield stress and consistency of the cement paste with 411m2/kg limestone powder are decreased and the water film thickness is increased. The yield stress and consistency of the cement paste adding limestone fineness powder of 807, 1007m2/kg decrease, the water film thickness first increases and then decreases, and the yield stress, consistency and water film thickness decrease simultaneously.

Abstract:Based on the theory of fracture mechanics and micromechanics of concrete, a flexural property prediction method for steel fiber PVA fiber reinforced strain hardening cementitious composite(SF PVA/SHCC) was developed by considering the effect of hybrid fibers on the flexural properties of strain hardening cementitious composite(SHCC). In order to verify the effectiveness of the proposed method, a series of flexural tests for SF PVA/SHCC were performed. The influence of fiber type and fiber content on the flexural strength, ultimate flexural deflection and load deflection curves of SHCC was studied. The results show that the proposed method can well predict the flexural strength and ultimate flexural deflection of SHCC containing steel fiber and PVA fiber.

Abstract:Investigations on the residual uniaxial compressive behaviors of strain hardening cementitious composites with high volume of fly ash(HVFA SHCC) subjected to elevated temperatures were carried out. Specimens with dimension of 40mm×40mm×160mm were exposed to different temperatures（100，200，400，600，800℃）. Residual compressive strength, stress strain curves, compressive toughness, elastic modulus and failure mode were determined after two cooling methods(natural cooling and water cooling). Scanning electron microscope(SEM) was used to analyze the degradation mechanism of HVFA SHCC at mesoscale level. Experimental results indicate that the temperature has little effect on the mechanical properties and mass loss of HVFA SHCC when temperature is lower then 200℃. At 400800℃, the internal micro structures of HVFA SHCC specimen become loose and the residual mechanical properties deteriorate seriously. When the temperature is higher than 800℃, the average residual compressive strength, the elastic modulus and the toughness index of the samples is only 399%, 323% and 590% of that at room temperature, respectively. And the mass loss rate is increased to 155%. Meanwhile, the effect of cooling method on residual mechanical properties is significant. The specimens cooled in water exhibit superior residual mechanical performance. Finally, based on the test results, the uniaxial compressive constitutive relationship of HVFA SHCC after high temperature is proposed.

Abstract:Early age hydration behavior of Portland cement containing liquid alkali free accelerators was studied by early age hydrated strength development, released ionic concentration, isothermal calorimetry, hydration phase analysis and microstructure analysis. The results show that the initial hydration heat rate of Portland cement containing liquid alkali free accelerators rises sharply due to the fast crystallization of massive ettringite prisms. The fluoride present in alkali free accelerators promotes C3S dissolution and C S H gel generation, leading to better quick setting effect and improved compatibility with superplasticizers. However, the hardening strength of cement paste hydrated 24h is declined notably with fluorine containing alkali free accelerator, mainly due to the crystallization of plate like CaF2, which absorbs and intercalates into the C S H gel structure and induces delayed hydration process.

Abstract:The general moving object(GMO) method was used to simulate the motion and static segregation of fresh self compacting concrete(SCC) considering the fresh self compacting concrete as a two phase solid liquid medium. The effect of yield stress and viscosity of mortar on aggregate movement process was studied. Based on this, the movement behavior of three groups of self compacting concrete coarse aggregates with different gradation in mortar was studied. The results show that the yield stress of mortar has an obvious effect on the static segregation of concrete, while the viscosity has little effect. The segregation behavior of different aggregate gradations under the same conditions is different, but it still shows certain regularity. Under the same conditions, gradation with less content of large particle size aggregate and more content of small particle size aggregate is relatively stable.

Abstract:The nano modified concrete was prepared based on coating aggregate with nano SiO2 enhanced technology. The rheological properties of paste, the compressive strength, the mass loss and the relative dynamic modulus of concrete were tested. The microstructure of the interface transition zone and the pore structures were studied by scanning electron microscope（SEM） and mercury porosimeter（MIP）. The results show that the viscosity of the paste is significantly increased and the coated aggregate with nano SiO2 is strengthened The mechanical and frost resistance of the concrete with aggregate coated by nano SiO2 are enhanced, because the strength loss and the quality loss are lower than that of the ordinary nano modified concrete. The interface transition zone becomes denser and the harmful pores are reduced by 101% while the harmless pores are increased by 147%, compared with the ordinary nano modified concrete.

Abstract:An alkali corrosion test on basalt fiber was carried out to analyze alkali corrosion mechanism by comparing micro morphology, elemental composition and molecular structure of basalt fiber before and after alkali corrosion. And the alkali corrosion model of basalt fiber in NaOH solution was explored. Then the accelerated aging test and bending test regarding basalt fiber textile reinforced concrete(BFTRC) slabs were conducted to evaluate the strengthening effect of the textile on concrete via aging coefficient(Ac) and enhancement coefficient(Ec). The results show that the alkali resistance of basalt fiber is comparable to that of alkali resistant glass fiber. For basalt fiber after alkali corrosion, the diameter becomes smaller, the typical structure is composed of fiber core, gel layer and deposition layer, and the dissolution kinetics can be expressed by zero order model and contracting cylinder model. The Ac and Ec of flexural strength and energy absorption for BFTRC slabs are decreased with time, and the Ec is greater than 1 In particular, the Ec for energy absorption still amounts to 2900 after aging treatment for 14d. The reduction coefficient of bearing capacity should be considered for the design of BFTRC members because of alkali corrosion of fiber textile in the concrete matrix.

Abstract:In order to improve the strength and toughness of high strength lightweight aggregate concrete(HLAC), 05% to 20% volume fraction of micro fine, end hook and corrugated steel fibers were mixed into HLAC respectively. The mechanical properties of steel fiber reinforced high strength lightweight aggregate concrete(SFHLAC) such as compression, splitting tensile, flexural and shear strength were studied. The characteristics of material toughness such as toughness factor and bearing capacity variation coefficient of SFHLAC were also analyzed. The results show that except for the corrugated steel fiber reinforced high strength lightweight aggregate concrete with 20% volume fraction of corrugated steel fiber, the strength and toughness of SFHLAC increase with the increase of the steel fiber volume fraction; the micro fine steel fiber has the best reinforcement and toughening effect on HLAC; the improvement effect of the end hook steel fiber and the micro fine steel fiber on flexural strength of the HLAC is similar, but the improvement of other mechanical strength and toughness is not as good as that of micro fine steel fiber; the effect of corrugated steel fiber on the strength and toughness of HLAC is poor; after comprehensively considering the working performance of the fresh mixture, the recommended volume fraction for engineering applications of three typical steel fibers are given.

Abstract:The influences of stress level(0, 03, 05, 07) and replacement ratio(0%, 30%, 50%, 100%) of recycled aggregate on capillary water absorption of recycled aggregate concrete was studied. Based on the unsaturated flow theory and the obtained experimental results, the predicted model of water distribution within concrete considering the influence of stress level and recycled aggregate replacement ratio is established using the Boltzmann variable and the exponential law of hydraulic diffusivity. The results indicate that capillary water absorption mass and sorptivity for recycled aggregate concrete show an increasing trend with the increase of recycled aggregate replacement ratio and stress level. Under a given stress level, the depth of water penetration into concrete increases with increasing recycled aggregate replacement ratio of recycled aggregates.

Abstract:The effects of different fly ash contents on chloride ion content, chloride ion binding capacity and capillary water absorption properties of coral aggregate concrete(CAC) was investigated. In addition, the hydration products, theoretical total pore volume and bound water content in CAC were analyzed by X ray diffraction(XRD) and thermogravimetry(TG DTG). The results indicate that the total chloride ion content increases with curing age. At early ages, the total chloride ion content in CAC containing fly ash is lower than that without fly ash; however, it increases at later ages. The change in the free chloride ion content with curing age is just opposite. The addition of fly ash improves the chloride binding capacity of CAC. Fly ash has little effect on the capillary water absorption of CAC for 28d; however, it can significantly reduce the absorbed water and sorptivity at 60days. Adding 20% fly ash decreased the secondary sorptivity of CAC for 28d and 60d by 61% and 154%. Fly ash has little influence on the types of hydration products formed, but it can reduce the content of Ca(OH)2 in CAC and lead to Friedels salt.

Abstract:Fly ash self compacting concrete(SCC) was prepared by replacing 40% cement with fly ash. Its workability, basic mechanical properties and axial compression deformation properties with the volume fraction of steel fibers were studied. The results show that the workability of fly ash SCC decreases with the increase of the volume fraction of steel fibers. When the volume fraction of steel fibers is more than 075%, the workability decreases most remarkable. The change of the volume fraction of steel fibers has slight effect on the compressive strength of fly ash SCC, but it can significantly improve its splitting tensile strength and flexural strength. When the volume fraction of steel fibers is 100%, the splitting tensile strength and flexural strength are increased by 14% and 12% respectively compared with SCC without steel fiber fly ash. The addition of steel fibers can significantly improve the axial compressive deformation properties of fly ash SCC. When the volume fraction of steel fiber is 050%, its ultimate stress, peak strain, strain energy and relative toughness are increased by 3%, 35%, 53% and 49% respectively compared with SCC without steel fiber fly ash.

Abstract:In order to study the effect of mineral composition on the early compressive strength of geopolymer and geopolymer gel structure, and to obtain the best mineral composition range. The geopolymer gel structure model was established by using Materials Studio(MS) software, and the early compressive strength formation mechanism of the geopolymer was investigated by scannint electron microscopy(SEM), X ray diffraction(XRD) and molecular dynamics(MD) simulation. The results show that n(CaO)/n(Al2O3) directly determines the development of early compressive strength. Increasing n(CaO)/n(Al2O3) can improve the internal atomic bond mode and diffraction peak shape of the gel, forming a more stable geopolymer structure.

Abstract:Previous studies showed that porcelain tile polishing residue was able to effectively inhibit alkali silica reaction(ASR) expansion. However, due to its high alkali content, it is necessary to further study the inhibition of ASR expansion in different alkali environments. Then the inhibitory mechanism of porcelain tile polishing residue on ASR was investigate. The mortar samples were prepared by using porcelain tile polishing residue as mineral admixture to replace part of cement, and their expansion ratios in KOH solution were measureed. SEM analysis of the near aggregate area of the mortar samples were carried out, and the experimental data in NaOH solution were compared. Experimental results show that porcelain tile polishing residue is able to effectively inhibit the ASR expansion of cementitious materials in NaOH or KOH solution. When the content of porcelain tile polishing residue is lower, the expansion ratio of samples is smaller in NaOH solution. When the content of porcelain tile polishing residue is larger, the expansion ratio of samples is smaller in KOH solution. In the two alkali solutions, potassium and aluminum are enriched in the near aggregate area simultaneously, and non expansive scaffold aluminosilicate KAlSiO4 is formed. The high content of SiO2 and Al2O3 and low content of CaO in porcelain tile polishing residue play an important role in inhibiting the expansion of ASR.

Abstract:The microwave absorption properties of porous microwave absorption functional aggregate and mortar prepared by template sintering were studied by using shale, organic matter(rice) and Mn Zn ferrite. The results show that in this system, the porous microwave absorption functional aggregate with controllable pore structure and compressive strength of 65MPa can be prepared after sintering at 1000℃ for 30min. When the pore diameter is 245833μm and the content of organic matter is 25%, the temperature rise of functional aggregate and functional mortar irradiated by microwave for 30s is the highest, which can rise from room temperature to 2188℃ and 1194℃ respectively, and the melting time of functional mortar is 485s. The porous structure can improve the impedance match between functional aggregate and free space, absorb more microwave, significantly enhance the microwave absorption capacity of functional aggregate and functional mortar, and increase the temperature rise of microwave irradiation.

Abstract:Based on monotonic direct shear tests, the effects of normal stress and shear rate on the interface properties such as shear stress, shear displacement, shear strength and shear modulus of interface between non water reacted polymer geotextile and polymer sand were studied. The test results show that, under the same mormal stress and shear rate, with the increase of shear displacement, the polymer geotextile interface and the polymer sand interface show shear softening characteristics. The mormal stress has a significant effect on the shear strength and shear modulus of the polymer geotextile interface. The mormal stress increases from 50kPa to 150kPa and the shear strength of the polymer geotextile interface increases from 15kPa to 46kPa at the shear rate of 2mm/min. Under the same mormal stress, with the shear rate increases from 1mm/min to 3mm/min, the shear strength and the shear modulus of the fluctuation of two kinds of shear interface only is in a small range. The shear rate has little effect on the friction angle of the polymer geotextile interface under monotonic direct shear condition, which indicates that the shear rate has a little influence on the shear strength and shear modulus of the polymer geotextile interface and the polymer sand interface.

Abstract:The off axial trapezoid tearing tests of six different types of coated fabrics were carried out, mainly considering 13 off axis angles：from 0 to 900° with interval of 75°. The trapezoid tearing strengths of all kinds of membrane materials at different off axis angles were obtained. The results show that the relevent curves of tearing strength of all membrane materials and different off axis are symentrical at 450° angles, from 0 to 450° and from 450 to 900°,the tearing strength firstly decreases and then increases, the maximum tearing strength is achieved at 450°, the minimum value is at 150° or 225° and 750° or 675°; the off axial trapezoid tearing strength was determined by the strength and the breaking elongation of yarns. Abaqus software is used to conduct finite element method(FEM), the displacement curves before the onset of tearing can be simulated by FEM. The result is fits well with those obtained from tests, and the initial loads of tearing obtained by FEM is also close to those obtained by tests.

Abstract:Bending beam rheometer test(BBR) and semi circular bend test(SCB) were conducted to study the low temperature performance of terminal blend(TB) crumb rubber composite styrene butadiene styrene(SBS) modified asphalt and its mixture with different contents of TB crumb rubber and SBS. The correlation of different low temperature performance indexes was analyzed. The results show that compared with the matrix asphalt, TB crumb rubber modified asphalt has excellent low temperature performance, and with the increase of the TB crumb rubber content, the low temperature PG of TB crumb rubber modified asphalt decreases, the thermal stress of asphalt decreases, and the low temperature crack resistance of mixture is enhanced; the low temperature performance of TB crumb rubber composite 3% SBS modified asphalt and its mixture is better than that of matrix asphalt, and with the increase of the TB crumb rubber content, the improvement effect of low temperature performance of composite modified asphalt is more significant, but is not better than that with the corresponding content of TB crumb rubber modified asphalt; with the increase of SBS content, the low temperature performance of 10%TB crumb rubber composite SBS asphalt does not change significantly, and the low temperature crack resistance of the mixture becomes poor; the low temperature PG grade of TB crumb rubber modified asphalt can well reflect the low temperature performance of asphalt and its mixture, while the low temperature performance of TB crumb rubber composite SBS modified asphalt cant be evaluated by a single low temperature PG index, which needs to be evaluated together with other indexes.

Abstract:The adhesion and self healing properties of five kinds of modified asphalt were evaluated by using pull out test. The influences of dry and wet healing conditions and modifier contents were investigated. Based on pull out test, the samples of damaged healing redamaged asphalt were analyzed by Fourier transform infrared spectroscopy(FTIR) test, and the correlation between self healing performance and molecular structure of asphalt was explored. The results show that：the bonding properties of liner styrene butadiene styrene(SBS) modified asphalt, crumb rubber modified asphalt, TB rubberized asphalt and high density polyethylene(HDPE) modified asphalt are lower than that of base asphalt, while that of gilsonite modified asphalt is much better than that of base asphalt; HDPE moditified asphalt, crumb rubber modified asphalt and gilsonite modified asphalt with suitable content of gilsonite have more excellent self healing ability. The recommended contents for linear SBS, crumb rubber, TB rubber, HDPE and gilsonite are 3%, 18%, 10%15%, 8%, 12%20% respectively. There is a strong correlation between the self healing performance of asphalt mixture and the molecular selective adsorption of asphalt with less branched chain structure by aggregate surface pores.

Abstract:The low temperature performance of basalt fiber asphalt mortar（BFAM）and mixture was studied by tensile test and bending test, and the correlation of low temperature performance between BFAM and mixture was analyzed. The phase change of BFAM and the microstructure of asphalt mixture were tested and characterized, and the mechanism of improving the low temperature performance of BFAM and mixture by basalt fiber was thoroughly analyzed. The results show that the low temperature performance of BFAM and mixture has a close correlation, and the tensile fracture energy of mortar at -20℃ has the greatest correlation with the bending strain of mixture. Based on the low temperature performance, the optimal content of basalt fiber is recommended to be 04%. The tensile fracture energy of the BFAM with the optimal content of basalt fiber is 46 times that of the ordinary asphalt mortar at -20℃, and the bending strain of mixture is 190% and 250% higher than that of the ordinary asphalt mixture at -10℃ and -20℃. BFAM has good low temperature performance and thermal stability. The glass transition temperature of mortar is 375℃ lower than that of ordinary asphalt mortar, and the heat absorption increases by 01525J/g during the transition from high elastic state to viscous flow state. The internal connection of ordinary asphalt mixture is weak. Basalt fiber enhances the integrity of mixture and restrains the crack propagation, thus improves the crack resistance of asphalt mixture.

Abstract:A novel warm mix additive Siligate with inorganic silica gel as the main ingredient was developed specifically for cold areas. In order to investigate the influence of this warm mix additive on asphalts, styrene butadiene styrene triblock copolymer(SBS) modified asphalt was selected as the test asphalt. Two kinds of warm mix additives that have been widely used in China, Sasobit and Evotherm M1, were used as the comparison. Rotational plate viscosity test, double edge notched tension test, calculation of critical cracking temperature at low temperature(Tcr), quantitative test of characteristic environmental emissions were respectively used to test the changes of construction temperature, fatigue resistance, low temperature crack resistance and characteristic emissions during mix of SBS modified asphalt. The results show that 6% Siligate, 3% Sasobit and 08% Evotherm M1have similar effect in construction temperature decreasing, which can effectively reduce the mixing temperature of asphalt by 13℃ and the compaction temperature by 14℃. Based on above dosage, Siligate can significantly reduce the critical cracking temperature at low temperature(Tcr) and optimize the low temperature performance of asphalt, which are not available in traditional products. In addition, Siligate can also improve the fatigue resistance of asphalt and significantly reduce the emissions of carbon based compounds.

Abstract:The rheological parameters and microscopic indexes of the original, short term aging, long term aging and regenerated asphalts were tested by dynamic shear rheometer（DSR）, bending beam rheometer(BBR), infrared spectrometer(IR）and scanning electron microscope（SEM）. The relationship of rheological parameters and microscopic indexes was established by grey correlation analysis, combined with Comsol numerical analysis results, the regeneration mechanism of microwave sensitive asphalt rejuvenate agent was studied. The results show that the correlation degree between storage modulus, loss modulus, complex shear modulus and component and functional groups change of asphalt is greater than 08, and the correlation degree between m value and bitumen resin is 0743, the correlation degree is better. Microwave sensitive asphalt rejuvenate agent can restore the proportion of the aged asphalt component and the number of functional groups by component adjustment, and the microwave heating material and the emulsion system accelerate the fusion of the regeneration agent and the aged asphalt.

Abstract:In order to study the effect of the amount of steel bars and the wrapping method of carbon fiber reinforced plastic(CFRP) sheets on compressive stress strain relationship of rectangular timber columns, based on the test results of 27square and 9 rectangular timber columns under axial compression, the strength calculation method of rectangular timber columns confined by CFRP sheets was proposed, calculation formulas of the bearing capacity for combined strengthening rectangular timber columns were obtaind. Then a trilinear compressive stress strain model of rectangular timber columns strengthened with combination of near surface mounted steel bars and lateral CFRP sheets was recommended. The calculated stress strain curves based on this recommended model are in good agreement with the test values of timber columns, which verifies the applicability of the trilinear compressive stress strain model of rectangular timber columns strengthened with combination of near surface mounted steel bars and lateral CFRP sheets.

Abstract:Experimental study of eccentric compression of 36steel bamboo combination box columns was carried out by mechanical parameters of the eccentricity, aspect ratio and with or without screw. The destructive pattern, lateral deflection, deformation and bearing capacity of the combination column were analyzed and the main factors affecting mechanical performance under eccentric compression of them were also discussed. There gives a nonlinear whole process program analysis using nonlinear analysis program based on fiber model method. The results show that the damage of the different eccentricity specimens with smaller aspect ratio is caused by the splitting of the bamboo and the buckling of the steel. The damages of the lange aspect ratio specimens are caused by the splitting of bamboo in the middle of the column. Within the design parameters, the eccentricity has a great influence on the mechanical properties of the composite column. The screw reinforcement connection has a certain effect on the yield bearing capacity and ultimate bearing capacity of the specimens. The change of aspect ratio has certain effect but no obvious regularity. The calculation results obtained by the program agree well with the experimental results, their errors are within 10%, which indicates that the established calculation method has high accuracy.

Abstract:In order to explore the influence of replacing river sand with aeolian sand on filling effect and voidage of fine aggregate, the optimal replacement rate of aeolian sand for river sand with different fineness modulus in different grade distribution areas was determined. This work was accomplished through the following two aspects. The first was comparative analysis of the data of voidage, which was obtained by the replacement of aeolian sand to 9 groups of river sand with different grade distribution areas under different replacement rates. The second was simulation of fine aggregate which was operated by PFC3D discrete element software. In addition, the river sand with the same gradation as Kubuqi aeolian sand was used to carry out similar test and simulation exploration. By comparing the previous test results, the influence factors of the grain shape of the aeolian sand in the Kubuqi desert on the voidage of fine aggregate under different fineness modulus river sand and different replacement rates were determined.

Abstract:The effects of hydroxyethyl methyl cellulose(HEMC) with high and low substitution degrees on the properties of sulphoaluminate cement mortar under fixed fluidity were studied. Test results show that water demand and setting time increase significantly while wet density and strength decrease significantly with the increase of HEMC content. Flexural strength is less influenced than compressive strength by HEMC content. Compared with the low substitution degree HEMC, high substitution degree HEMC to some extent leads to lower water demand and wet density together with lower strength and similar setting time of sulphoaluminate cement mortar. Incorporation of HEMC slows down the acceleration of sound velocity at early stage which is in favor of pot life, and leads to the decrease of final sound velocity. Moreover, the acoustic wave propagation speed is affected by the content and the degree of substitution of HEMC. The strength of HEMC modified sulphoaluminate cement mortar has good liner correlation with both sound velocity and wet density.

Abstract:Ceramsite foam concrete was produced by mixing fast hardening sulphoaluminate cement with precast foam and ceramsite. The effects of foam concrete density and ceramsite particle size on the failure mode, compressive strength(peak stress), densification strain and energy absorption of ceramsite foam concrete subjected to static uniaxial compression was investigated. The experiment results indicate that remarkable non interfacial failure is observed with higher density of foam concrete and larger particle size of ceramsite, from which the density range of foam concrete with matched strength of the three corresponding ceramsite is determined. With increasing density of foam concrete, the compressive strength and energy absorption of ceramsite foam concrete are remarkably improved, while the densification strain decreases. In addition, with increasing ceramsite particle size, the densification strain decreases first then increases, the compressive strength increases first then decreases, and the energy absorption capacity gradually increases.

Abstract:The explosive spalling behaviour of 15 groups of fibre reinforced ultra high strength concrete(FRUHSC) specimens with cubic compressive strength of 116143MPa was investigated subject to ISO834 standard heating condition. The effect of water binder ratio, porosity, fibre type, fibre content, and dimention of specimens on spalling was investigated. Test results show that the UHSC with water binder ratio of 015 has lower porosity and higher strength than that with water binder ratio of 018 and which is more likely to undergo spalling. The addition of 100% corrugated ultra fine steel fibre in volume, which is intended for improving the ductility of concrete at room temperature， cannot prevent spalling. The spalling of both 100× 200mm specimens and 300× 300mm specimens can be prevented by the addition of 015% polypropylene fibre in volume. No spalling is observed when UHSC with water binder ratio of 0.15 encased steel columns with 050% short steel fibre and 015% polypropylene fibre in volume are subject to loadings in fire condition. The fire tests reveal that the spalling of UHSC in the loaded element can be prevented as long as following the proposed addition of hybrid fibres.

Abstract:Using recycled engine oil bottom(REOB) as asphalt rejuvenator, the aging performance was studied from three combinations：REOB, REOB rejuvenated asphalt and REOB rejuvenated asphalt mixture. The change of quality and viscosity of REOB rejuvenated asphalt, RA5 rejuvenated asphalt and matrix asphalt were measured after extended thin film oven tests(TFOT)(aging times were 5, 10, 15, 20, 25h), and the low temperature performance of three aged asphalts was evaluated by bending beam rheological tests. The corresponding three combinations of asphalt mixtures were used to design and pave surface layers of a full scale indoor test road. A self developed rotary accelerated loading test system(RALT) was used to carry out accelerated loading tests at room temperature and high temperature to evaluate the long term fatigue performance of indoor asphalt pavement. The results show that the short term aging resistance(TFOT aging time less than or equal to 10h) of REOB rejuvenated asphalt is better than that of RA5 rejuvenated asphalt but worse than that of matrix asphalt, whereas the long term aging resistance(TFOT aging time greater than or equal to 15h) of REOB rejuvenated asphalt is the worst among the three tested asphalts. After long term aging, REOB rejuvenated asphalt is prone to cracking at low temperatures because of its rapid increase in stiffness and sharp decrease in stress relaxation performance. High temperature aging significantly aggravates the increase of deflection value of REOB rejuvenated asphalt pavement under long term loading of RALT, which makes it most prone to fatigue failure among the three pavements. It is shown that when REOB is used in the rejuvenated asphalt pavement, it will easily cause premature and excessive damage to the pavement.