Anti-cracking Performance Research Articles

Evaluating the evolution of fiber-reinforced emulsified asphalt cold-recycled mixture damage using digital image correlation

ABSTRACT The cold recycled mixture has insufficient resistance to cracking, and the process of fracture is incompletely understood. This study used digital image correlation (DIC) technology and a semi-circular bending test to investigate the anti-crack performances and fracture propagation of basalt fiber-reinforced cold recycled mixture (BFCRM). The load-displacement, full-field strain, full-field displacement, displacement rate and crack propagation map were obtained to evaluate the BFCRM’s anti-crack performances. The control cold recycled mixture without fibers was also prepared for comparison. Meanwhile, the fracture process zone (FPZ) during loading were compared and quantitatively assessed by digital image correlation analyses, and the fiber distribution and microscopic features at fracture surface was observed by scanning electron microscopy. The results show that the formation of microcracks of BFCRM takes more time than that of the control group without fiber. Based on DIC observations, the basalt fibers maintain strong anti-crack performance in cold-recycled mixtures and reduce fracture damage. The fracture surface morphology also revealed that basalt fiber exhibited adsorption, bridging, anchoring, stability, and strengthening effects at micro/nano scale, which further improved anti-crack performance e and hindered crack development of cold recycled asphalt mixtures.

Effects of Filler-Asphalt Ratio on the Properties of Lignin and Polyester Fiber Reinforced SMPU/SBS Modified Asphalt Mortar

To understand the effects of filler-asphalt ratio on different properties of lignin and polyester fiber reinforced shape memory polyurethane (SMPU)/styrene butadiene styrene (SBS) composite modified asphalt mortar (PSAM), as well as to reveal the reinforcing and toughening mechanisms of lignin and polyester fibers on PSAM, SMPU, SBS and mineral powder were first utilized to prepare PSAM. Then the conventional, rheological and anticracking properties of lignin fiber reinforced PSAM (LFAM) and polyester fiber reinforced PSAM (PFAM) at different filler-asphalt ratios were characterized. Test results indicate that the shear strength, deformation resistance and viscosity are increased after adding 0.8wt% lignin fiber or polyester fiber and increasing the filler-asphalt ratio from 0.8 to 1.2. The optimal filler-asphalt ratio of 1.0 is proposed after comprehensive performance assessments of PSAM. Polyester fiber shows a better reinforcing effect than lignin fiber, but its improvement in the thermal stability of PSAM is not significant at high temperatures. Additionally, the complex modulus, storage modulus, loss modulus and rutting resistance factor of PSAM are improved after adding lignin fiber and polyester fiber, as well as show an increasing trend as the filler-asphalt ratio is raised, but the phase angle is gradually decreased. Further, the increase of elastic components in PSAM effectively enhances the anti-deformation ability of PSAM at high temperatures, and polyester fiber more obviously improves the high-temperature deformation resistance of PSAM than lignin fiber. Finally, the anti-cracking performance of PFAM and LFAM at low temperatures is reduced by 74.2% and 46.7%, respectively, as the filler-asphalt ratio is raised from 0.8 to 1.2. The low-temperature anti-cracking performance of LFAM is lower than that of PFAM at the same filler-asphalt ratio, even lower than that of PSA. Compared with lignin fiber, the anti-cracking performance and deformation resistance of PSAM at low temperature is more greatly enhanced by polyester fiber.

Laboratory investigation on added-value application of the COVID-19 disposable mask in hot mix asphalt (HMA)

The outbreak of the COVID-19 pandemic has stimulated the demand for disposable masks to an unprecedented level, which also poses a significant risk to the natural environment from the improper treatment or disposal of waste masks. To lower such an environmental risk and maximize the added value of the waste masks, this paper proposed to recycle the waste mask fiber (MF) in combination with the waste cooking oil (WCO) for hot mix asphalt (HMA) application. A series of MF + WCO modified asphalt binders were first designed and fabricated. Their performance properties were then systematically measured. The physical-rheological test results showed that the incorporation of MF can significantly improve the high-temperature rutting resistance performance of asphalt binder. However, it may also lower the asphalt's low-temperature anti-cracking performance. The addition of WCO was found to compensate for this low-temperature performance loss effectively, and the MF5% + WCO3% was identified as the best combination. The Fourier transform infrared (FTIR) spectroscopy test results revealed that the asphalt modified by the MF + WCO involved only a physical modification. The performance test results indicated that the high-temperature permanent deformation resistance and low-temperature anti-cracking of MF5% + WCO3% modified HMA was greatly enhanced, while its moisture stability was slightly reduced but still met the specification requirement. The environmental benefit assessments proved that recycling the waste masks for asphalt paving can provide an enormous added value to pavement engineering in terms of carbon emission reduction and land resource saving.

Experimental and Numerical Study on UHPC–RC Decks within Hogging Moment Region

Steel–concrete composite continuous bridges can take full advantage of concrete and steel, but in regions with hogging moments, cracking of the concrete deck is a big issue affecting the durability of bridges. In order to solve cracking problems within the hogging moment region, this study proposes a composite deck method using ultra-high-performance concrete (UHPC) and regular concrete (RC). In this way, the layers of UHPC and RC are composited to take advantage of the high tensile strength of UHPC materials to improve the anti-crack performance of the concrete deck within the hogging moment region. Four different specimens were designed to account for different layer thickness of UHPC. Bending experiments of the UHPC–RC composite deck were undertaken and a corresponding finite element model was established to study the behavior of the UHPC–RC composite deck. The regularity of crack development in different UHPC layer thicknesses was revealed, and the load-displacement results were compared to investigate the ultimate capacity of a steel–concrete composite bridge structure using a UHPC–RC composite deck. Finally, with consideration of material cost, a reasonable UHPC layer thickness suitable for the composite deck was obtained to provide a reference for the design of a UHPC–RC composite deck.

Fracture modeling of rubber-modified binder based on Discrete Element Method

This study investigates the effects of rubber on anti-crack resistance for binders at the low temperature based on Discrete Element Method (DEM). Based on the commercial software Particle Flow Code (PFC), cohesive zone modeling (CZM) and viscoelastic modeling were combined for predicting the behavior of unmodified and Ground Tire Rubber (GTR) modified binders. A new binder fracture test was designed and further simulated in PFC to reveal the interactions between the rubber and binder particles. Then, fracture analysis was conducted in different aspects, including fracture energy, Load-CMOD curves which are mechanics indices, evolutions of crack length, crack number and fracture process zone (FPZ) etc., which are morphological indices. Results from simulations show that the rubber particles play an important role in improving the anti-crack performance of binders at the low temperature. The rubber modified binder will have a ductile failure mode rather than brittle one of unmodified binder, resulting in higher fracture energy. The evolutions of micro-cracks, FPZ and dissipated energy are significantly influenced by rubber particles, which explain the reason for better post-peak behavior, larger peak load of GTR modified binder in macro fracture tests.

Preparation and characterization of low flammable asphalt for tunnel pavements

In this study, a silane modified flame retardant blend named FRB-SC was developed to combat combustion risks faced in tunnel asphalts. FRB-SC is a composite flame retardant principally made up of four components: Expandable Graphite (EG), Magnesium Hydroxide (MH), Calcium Hydroxide (CH) and Ammonium Polyphosphate (APP). The orthogonal design and the technique for order of preference by similarity to ideal solution were used to determine the optimal dosages of these four components. KH550 silane coupling agent was then added to modify the composite flame retardant and improve its functionality and stability in asphalt. Subsequently, the basic performance, rheological properties and flame retardancy of modified asphalts containing various dosages of FRB-SC (i.e., 2, 4, 6, 8, 10 and 12%) were evaluated, and thus the optimum dosage of FRB-SC was determined. The results showed that the asphalt's limiting oxygen index increased to 24.7% with the addition of 8% FRB-SC. Also, after the addition of FRB-SC, the asphalt's penetration and ductility decreased, its softening point increased, its high temperature stability increased, and its low temperature anti-cracking performance decreased. Meanwhile, based on the oil absorption and activation index of the FRB-SC, the optimal dosages of EG, MH, CH and APP were found to be 5%, 5%, 4%, and 9% by mass, respectively, and that of the silane coupling agent determined as 1.2%. Finally, the cone calorimeter test conducted on FRB-SC modified asphalt showed that carbon monoxide emissions were significantly reduced when combustion occurred, and the amount of heat and smoke released were also noticeably decreased, establishing the flame retardant efficacy of the FRB-SC. Now, although this study’s findings have not been applied in actual tunnel mixtures, this however provides an insight to the feasibility of its use for tunnel asphalt pavements, a move which could significantly reduce the hazards of tunnel fires and accidents.

Effect of PAN fiber with bionic layered surface structure generated in situ by Fenton reaction on performance of SBS/RP asphalt binder

• Innovative application of Fenton reaction in the modification of polyacrylonitrile fibers. • Biomimetic multi-layered structure modified polyacrylonitrile fibers. • KF-PAN/SBS/RP modified asphalt had better viscoelastic performance. • KF-PAN/SBS/RP modified asphalt had better low temperature anti-cracking performance, high temperature stability and fatigue damage resistance. • KF-PAN/SBS/RP modified asphalt had better rutting resistance and high temperature adhesion performance. In this study, a surface modified polyacrylonitrile fiber (KF-PAN) with a fish-scale whisker-like biomimetic hierarchical structure was successfully prepared via in situ competition effect of Fenton reaction. The modified fibers were used as secondary modifiers to prepare fiber-reinforced styrene–butadienestyrene (SBS) block copolymers and rubber powder (RP) modified asphalt binders (KF-PAN/SBS/RP). Energy dispersive spectroscopy, scanning electron microscopy, and atomic force microscopy analyses revealed the successful construction of bionic hierarchy on the fiber surface, and confirmed rough surface of the KF-PAN fibers. The hierarchical structure of the fiber surface acted as a buffer in the asphalt and strengthened the mutual interaction of the fiber and asphalt. Dynamic rheometer shear and strip-tensile tests showed that the KF-PAN/SBS/RP modified asphalt exhibited better viscoelasticity, rutting resistance, and tensile properties than the PAN/SBS/RP modified asphalt. The linear amplitude sweep test showed that KF-PAN/SBS/RP modified asphalt had better fatigue resistance. Thermogravimetric analysis tests indicated that the surface bionic structure of KF-PAN fibers boosted thermal stability of the fibers, which in turn enhanced the thermal stability of KF-PAN/SBS/RP modified asphalt. Fluorescence microscopy analysis showed that incorporating KF-PAN fibers improved the SBS and RP microstructure inside the asphalt, forming a good mesh structure, and alleviating the stress concentration phenomenon in SBS/RP asphalt under external traffic load.

Long-term shrinkage performance and anti-cracking technology of concrete under dry-cold environment with large temperature differences

• The basic mechanical properties of long-age concrete under dry-cold environment with large temperature differences are analyzed. • The free shrinkage of long-age concrete under dry-cold environment with large temperature differences is analyzed. • The constrained shrinkage of long-age concrete under dry-cold environment with large temperature differences is analyzed. • The microstructure of long-age concrete under dry-cold environment with large temperature differences is analyzed. Shrinkage performance and anti-cracking technology of concrete in a dry-cold environment and large daily temperature differences (-20℃∼15℃) are investigated through environmental simulation tests. According to on-field practice, after 28-day standard curing, concrete specimens are placed in the simulated environment and under five different maintenance methods, which are natural exposure (NE) as reference, membrane curing (MC), coating curing (CC), curing with expansive agent (CE), and curing with both expansive and internal curing agent (CEI). A novel nano-ceramic coating is used in CC. The mechanical properties, free shrinkage rate, restrained shrinkage rate, and porosity by mercury intrusion porosimetry (MIP) of specimens after freezing age of 0 ∼ 56-d are measured. Both compressive strength ( f cu ) and tensile strength ( f t ) of NE and CE decrease evidently with freezing age, and f cu and f t for CC, MC, and CEI scenarios are slightly affected by freezing age. Both free shrinkage and restrained shrinkage are mainly due to the temperature deformation; the drying shrinkage takes only about 21 % of the total shrinkage. The cyclic temperature differences lead to accumulation of maximum restrained shrinkage stress in concrete. Shrinkage performances are highly dependent on curing methods; the order of anti-cracking performance from the best to worst is: CC, MC, CEI, CE, NE. Adding expansion agents alone (CE) is insignificant in reducing the shrinkage, which can be compensated by furthering adding internal curing agents (CEI). The moisturizing effect of internal curing agent, membrane, and coating contribute to better microstructure, strength development, and shrinkage mitigation. The thermal insulation and the bonding effect of CC further reduce the free shrinkage and restrained stress, thus presenting the strongest resistance to shrinkage and induced cracking. The porosity and most probable pore size (MPPS) from MIP tests are consistent with results of strength and shrinkage. Overall, specimens under CC show the best overall performances under simulated environment.

Laboratory Investigation of PPG-TDI Polyurethane–Modified Asphalt Binders and Mixtures

Considering the defects of insufficient low-temperature flexibility and high cost of epoxy asphalt binder, low-cost polypropylene glycol (PPG) and toluene diisocyanate (TDI) were used to synthesize two polyurethane (PU) prepolymers (PTPU) with different isocyanate group (─ NCO) contents, and the properties of PTPU-modified asphalt binders and mixtures were studied. First, the mixing parameters of the PTPU-modified asphalt binders were determined through tests, and its storage stability, high- and low-temperature creep characteristics were studied. Then the microscopic modification mechanism of PTPU-modified asphalt binders was explored. Finally, the PTPU-modified asphalt binders were used to prepare mixtures, and the application performance in bridge deck pavement was evaluated. The results showed that PTPU-modified asphalt binder has satisfactory storage stability and high- and low-temperature performance. Chemical reactions occur during the modification process which change the micromorphology of the asphalt binder, and its high-and low-temperature performance and the adhesion to the aggregates are improved. The increase of -NCO content improves the high-temperature stability and mechanical strength of the PTPU-modified asphalt binder but reduces the flexibility. Hence, the ─ NCO content in PTPU can be adjusted according to actual needs during application. The PTPU-modified asphalt mixture has a good comprehensive performance, its low-temperature anticracking performance is improved greatly compared with that of epoxy asphalt mixture, and the lower price gives it good promotion and application prospects in engineering applications.

Experimental investigation and design optimization on flexural behavior of new UHPC deck panel with longitudinal ribs reinforced by steel plates

Due to high strength and superior durability, ultra-high performance concrete (UHPC) is usually used in bridge deck panels to reduce self-weight and improve the anti-cracking capacity. In this study, two schemes of the UHPC deck panel with longitudinal ribs reinforced by steel plates were investigated basing on the Binzhou Yellow River Bridge, including the design considerations and advantages. The experiments were conducted to investigate the flexural behavior of this UHPC deck panel. The experimental results showed that the steel plate can improve the anti-cracking performance and stiffness of the deck more effectively compared to conventional measures of using steel bars. Cracks developed at the position where headed studs were placed due to the weakening of cross-section by high studs. Specimens failed with the appearance of the slightly compressive crack. In addition, the experimental test was simulated by finite element (FE) model in software ABAQUS. The cracking position, load-displacement relationship and strain response of testing specimens were verified by the FE model. For the design purpose, a numerical method was established to analyze flexural behavior including the stiffness, ultimate capacity and strain. The prediction results agreed well with the test results. Further, a parameter analysis was performed and it was clear that the narrow and high rib scheme provided superior flexural properties. Compared with UHPC tensile strength, the steel plate thickness had a more significant effect on the stiffness and ultimate capacity for the specimens. Finally, the segmental FE models were developed for the Binzhou Yellow River Bridge to obtain the actual stress state of the new UHPC deck. The calculation results indicated that the maximum longitudinal nominal stress in the UHPC deck was 7.6 MPa. In addition, when the diaphragm spacing was between 3.0 m and 5.0 m, the longitudinal stress would increase by about 12% with the diaphragm spacing increasing by 0.5 m. The comparisons between the actual stress and experimental results ensured the feasibility of the design.

Multi-scale finite element simulation of asphalt mixture anti-cracking performance

This study investigates the anti-cracking performance and cracking mechanisms of asphalt mixtures. The results of experimental tests were compared with simulated tests of asphalt mixtures based on the multi-scale finite element method (FEM). The FEM considered the mesostructure of the asphalt mixtures, the internal viscoelasticity of asphalt mortar, and the asphalt mastic-aggregate interface. Coarse aggregates were generated based on the polygonal random aggregate generation and placement method. Numerical cracking models of the asphalt mixtures were established by the multi-scale FEM and fracture tests were simulated according to the experimental test conditions. The reliability of the simulations was verified by comparison with the experimental test results. The influences on cracking behavior were investigated, with an energy-saving and economical alternative mixture—cold recycled mixture (CRM)—used for comparison. The simulations were highly accurate and could effectively simulate the asphalt mixtures’ cracking processes and mechanisms. The cracking behavior was directly related to notch length, test temperature, void content, and mixture type. A significant difference in the macroscopic anti-cracking performance of hot mixture asphalt and CRM was found. According to the simulations of crack development, there is a 'critical point' of crack propagation from the interface to the interior of the mortar. The mesoscale influences on the cracking behavior of asphalt mixtures are discussed and ranked in terms of importance.

Fabrication of SiC foam ceramics at a low sintering temperature by adding fly ash

Silicon carbide (SiC) foam ceramics (SFC) have been widely used in various industries owing to their excellent mechanical properties at elevated temperatures. However, fabricating a qualified product at a low sintering temperature is a challenge because of the strong covalent nature of the Si–C bond. In this study, we successfully fabricated a SFC at a low sintering temperature (1150 °C) by adding fly ash (FA) using the polyurethane replication method. The effects of sintering temperature and FA content on the mechanical performance of the ceramics were systematically studied. The phase composition and microstructure of the SFC were characterized using X-ray diffraction and scanning electron microscopy. At 1150 °C, an SFC with 30 wt% FA exhibited optimal properties, i.e., a porosity of 64.43%, bulk density of 0.89 g/cm3, and bending strength of 8.34 MPa. As a sintering aid, FA promoted the formation of the mullite phase at low sintering temperatures, which enhanced the anticorrosion and anti-cracking performance of the SFC. Therefore, adding FA to SiC significantly lowers the sintering temperature and reduces the fabrication cost associated with the SFC. Consequently, its commercial application is considerably enhanced.

Effect of multi-minerals on the mechanical behavior and pore structure of fiber reinforced internal-cured green concrete

In this study, multi-minerals were incorporated in fiber reinforced internal-cured green concrete (FRICC) to achieve both an improvement in concrete performance and environmental sustainability. The effect of multi-minerals on FRICC with pre-wetted lightweight fine aggregate (LWFA) and basalt-polypropylene (BF-PF) fiber was investigated through examining compressive and flexural strengths, flexural toughness, microstructure, pore structure and CO2 emissions. In comparison to ordinary concrete (mixture PO), FRICC presented good flexural performance but a decreased compressive behavior with an increase of 20.5% in flexural strength and a minor decrease of 1.6% in compressive strength. With the addition of multi-minerals, an enhancement in fiber-strengthening and anti-cracking performance was achieved, presenting a positive effect on concrete's strengths, post-cracking manner and pore structure. The internal curing of pre-wetted LWFA stimulated the pozzolanic reaction of minerals given that a denser microstructure with less porosity and more C–S–H gel effectively bound with aggregates and BF-PF fiber was identified. FRICC with a ternary mix of minerals (10% fly ash, 10% blast furnace slag and 5% metakaolin) exhibited the best mechanical performance and pore structure with an increase of 19.6% and 19.2% in compressive and flexural strength, respectively, and a decrease of 29.3% and 13.6% in porosity and mean pore diameter, respectively. Additionally, a reduction in CO2 emissions of up to 19.7% was achieved through adding multi-minerals. In general, the incorporation of multi-minerals brings positive consequences to both the performance of FRICC and environmental sustainability.

The investigation of SrCoO3-δ perovskite doping cobalt oxide thermochemical energy storage system

BackgroundThe current research of doping for metal oxide thermochemical energy storage (TCES) systems mainly focuses on the mutual doping among traditional metal oxides. However, it is too one-sided to solve the problem. In this work, SrCoO3-δ perovskite material is novelly doped into the cobalt oxide material system to solve the dehiscent problem of honeycombs, while compensating the energy storage density of materials system. MethodsSimultaneous thermal analysis (STA) is used to assess energy storage density, reaction kinetics, stability of materials. Thermo-mechanical stability assessment and thermal expansion tests are conducted to analyze the anti-crack performance of honeycombs. XRD, SEM, and XPS methods are used to analyze the characteristics of materials. Significant findingsThe mass ratio of doping of 30% exhibits the best comprehensive performance. Based on this, the attenuation of energy storage density of SrCoO3-δ doping is narrowed from 27.1% to 22.9% at least compared with Al2O3 doping for anti-crack, and SrCoO3-δ doping has no negative effects on reaction kinetics of original cobalt oxide and a better stability. Beyond that, the SrCoO3-δ doping method of this work exhibits a better balance among various performance indicators of TCES than traditional doping methods based on improving TCES performance.

Experimental and numerical study on steel-concrete composite frames with engineered cementitious composites

Engineered cementitious composites (ECC) is a type of cement-based material with the characteristics of tensile strain-hardening and multiple cracking. In this study, the structural behavior of the composite frame, whose crack resistance is improved by using ECC in the hogging moment region, was investigated. A large-scale steel-concrete composite frame with ECC at the beam end was designed and tested under vertical and lateral hysteretic loads. The test results were reported and compared with those of the traditional steel-concrete composite frame conducted by the authors in a previous study. The application of ECC notably reduced the crack width by 18%-40% in terms of the results under vertical loading cases and enhanced the ductility by 87% in the positive loading direction. The steel-concrete-ECC composite frame exhibited excellent seismic behavior with similar strength, stiffness, energy dissipation, stiffness degradation and strength degradation as the traditional steel-concrete composite frame. In addition, a nonlinear elaborate finite element (FE) model was established to simulate the tested frames, whose results agreed well with the test results. Furthermore, parametric studies on the ECC composite frames were performed via FE simulations, from which the influence of the ECC length, ECC tensile strength, ECC compressive strength and the steel beam height on the bearing capacity and cracking performance were clarified. The design method of the ECC length was also suggested. The test and FE results showed that ECC notably improved the slab anti-cracking performance. The study of this paper will provide a scientific basis for the application of ECC in steel-concrete composite frames to some extent.

Improved three-dimensional discrete modeling method and anti-cracking properties of asphalt mixture

To explore the low-temperature cracking of asphalt composite’s materials, this study used the three-dimensional module in the particle flow code (PFC3D), from which a three-dimensional numerical model of the Marshall split specimen and a three-point trabecular bending specimen was established. Second, the different contacts inside the model and parameter selection were defined, which resulted in splitting-test and bending-test simulation results for AC-13 and SMA-13 in the five temperature ranges of −15 °C, −10 °C, 0 °C, 10 °C and 15 °C. Finally, indoor trial verification simulation results were obtained, and the average error of the stiffness modulus was within 10%, so model reliability was verified. The simulation results show that the contact fracture of the aggregate, and the asphalt mastic is the chief cause of cracking. The contact between the aggregates is the maximum intensity of the pitch mixture, and the contact between the asphalt mastic and the aggregate contributes more than 90% of the asphalt mixture’s bending strength. Whether it is a splitting-power modulus or bending-power modulus, the value for AC-13 is larger than it is for SMA-13, indicating that AC-13 anti-crack performance is better than that of SMA-13. The study’s results provide a theoretical basis for the design of asphalt pavement materials.

Evaluation on long-term performance of emulsified asphalt cold recycled mixture incorporating fly ash by mechanistic and microscopic characterization

In this paper, the long-term performance of emulsified asphalt cold recycled mixture (CRME) incorporating fly ash was investigated. The dosages of fly ash included 0.75%, 1.5% and 3.0%, and the long-term service conditions of CRME were simulated by curing in an oven at 60 °C for different ages. Mechanical performance of CRME under different curing ages were obtained through indirect tensile strength (ITS), Marshall stability, low-temperature ITS and freeze-thaw ITS tests, and the microstructures were characterized by optical microscope, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) tests. The results show that, as the curing age increases, the ITS, flow value, and low-temperature indirect tensile strain of CRME with fly ash increase first and then decrease, while the Marshall stability and freeze–thaw ITS ratio (TSR) always show a gradual increase trend. By comparing the CRME with cement, the CRME with fly ash throughout the long-term curing process exhibits the higher ITS and low-temperature anti-cracking performance and the lower high-temperature stability and water stability. Optical microscope, XRD and ESEM analysis indicate that the dissolution of fly ash particles and the demulsification of asphalt emulsion particles occur simultaneously during the curing ages. After a certain curing age, a dense structure composed of asphalt binders, dissolved and undissolved fly ash particles is formed. Also, the fly ash replacing cement in CRME can effectively reduce the energy consumption and carbon emission.

Study on crack width and crack resistance of eccentrically tensioned steel-reinforced concrete members prestressed by CFRP tendons

In recent decades, steel-reinforced concrete (SRC) members under eccentrical tension have been adopted more frequently in modern buildings due to the constraints of more complex structural design/detailing that accompanying contemporary architectural creations. Crack resistance of this type of structures has become a critical design consideration but received insufficient research attention in the past. In this context, the anti-cracking performance of prestressed SRC columns reinforced with CFRP tendons under eccentric tensile loads is investigated experimentally and analytically with the following first-hand experimental validations: 1) prestressed CFRP tendons can well strengthen SRC columns under eccentric tensile load and restrain the crack propagation; 2) an increase in the load eccentricity progressively weakened the influence of prestressing tension level on the cracking load; 3) specimens with the higher prestressed tension level, larger longitudinal reinforcement diameter, and flange thickness exhibited greater crack resistance capacity. Furthermore, the plane-section assumption was also validated in this study. A test data-enhanced analytical method was proposed for determining the cracking load of PSRC columns.

Designing of an anti-rutting and High Ductility Asphalt Mixture based on mortar performance

The anti-rutting and anti-cracking performance of asphalt mixtures are a pair of contradictions that are difficult to coordinate. In order to ensure the rutting resistance of asphalt mixture to meet the requirements of the specification, while improving its deformation capacity and crack resistance. Based on the mortar performance, the Anti-rutting and High Ductility Asphalt Mixture with excellent anti-rutting performance and deformation performance was designed in this paper. With the filler-asphalt ratio as the control index, SBS modified asphalt and SHV modified asphalt was selected to design five asphalt mortars with different filler-asphalt ratios of 0, 0.5, 1.0, 1.5, 2.0. Variation laws of mortar technical indicators were investigated by rotational viscosity test, cone penetration test, and BBR test. Asphalt mixtures were prepared and a rutting test and small beam bending test were carried out to ensure the consistency of the mixture skeleton state by grouting molding. The influence of the mortar performance index on the road performance of the mixture was evaluated by conducting correlation analysis, and then an anti-rutting and high-ductility asphalt mixture was proposed based on mortar performance. The obtained results showed that the technical indicators of asphalt mortar had a good correlation with the filler-asphalt ratio, and the developed regression model could be used to determine the correlation and design of the mortars. The technical performance index of mortar was found to be directly correlated with the road performance index of the mixture. The developed anti-rutting and high-ductility asphalt mixture not only had good anti-rutting performance but also had good deformation capacity and cracking resistance. Its anti-rutting performance could meet the specification requirements, and the maximum flexural strain could reach 7161 με. The performance of asphalt mortar determines the road performance of the mixture. The rutting resistance and cracking resistance of the mixture could be coordinated by designing asphalt mortar to improve its comprehensive road performance. To guarantee that the dynamic stability of the mixture met the required specifications and the deformation ability was good, the critical value of each technical index of asphalt mortar was recommended.

Reinforcement evaluation of different fibers on fracture resistance of asphalt mixture based on acoustic emission technique

Fibers have been proven to enhance the stability and mechanical strength of asphalt mixture, but different fibers exhibited diverse characteristics of reinforcement effect. This study is set out to investigate the fiber reinforcement effect of asphalt mixture containing glass fiber reinforced asphalt mixture (GFRAM), basalt fiber reinforced asphalt mixture (BFRAM), and steel fiber reinforced asphalt mixture (SFRAM). The control asphalt mixture (CAM) was also fabricated for comparison. The fiber content was 0.5% by weight of the asphalt mixture and the specimens were manufactured following the Marshall compaction method. Indirect tensile test (IDT) and acoustic emission (AE) test at low temperature were conducted simultaneously to characterize the fracture resistance of different types of fiber reinforced asphalt mixture (FRAM). The amplitude, count, rise angle (RA), average frequency (AF), and b-value were obtained based on AE signal analysis to evaluate FRAM's reinforcement effect. The results revealed that the addition of fibers dramatically improved the strength of CAM, and the occurrence of the main fracture in FRAM emerged later than CAM. SFRAM exhibited more favorable anti-cracking performance than GFRAM and BFRAM based on the comprehensive AE signals analysis.