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The results of in-plane static cyclic lateral loading tests conducted on unreinforced masonry walls retrofitted with trowelling engineered cementitious composites (ECC) are presented in this paper. Six 1/2 scale testing specimens including unretrofitted and retrofitted walls were constructed. The first and second unretrofitted masonry walls were control specimens. The third and fourth walls were retrofitted applying ECC with strip type and the other two walls were retrofitted with ECC coatings. Every batch of tested walls was constructed with two different mortar strengths. The failure modes, lateral strength, ductility, stiffness, and the energy dissipation capacity of the tested walls were examined and compared. Furthermore, the experimental envelope curves were idealized and reasonable overstrength factors of the retrofitted walls were obtained. The results indicated that these retrofit techniques can effectively improve the lateral strength and the displacement ductility of unreinforced masonry (URM) walls, convert the brittle failure mode to a more ductile one, and provide an effective constraint for the walls, resulting in preserved integrity of the wall at large lateral displacements. Finally, the calculation methods for each retrofitting scheme were proposed to estimate the ultimate lateral strengths of ECC retrofitted masonry walls. [ABSTRACT FROM AUTHOR]

• The hydration products of pure C 3 S and nano-SiO 2 at 80℃ were studied. • The optimum amount of silicon material at 80℃ differs from that at high temperature. • Decalcification will decrease the Ca/Si of hydration products. • Hight Ca/Si products can be converted into low Ca/Si products by nano-SiO 2. The hydration products of G-grade oil well cement can affect its overall performance, which is currently enhanced by nano-silica (nano-SiO 2). However, the hydration process and products of silica nanoparticles and cement have not yet been fully clarified. This study focused on tricalcium silicate (C 3 S), the main component of oil well cement, and analyzed the effects of nano-SiO 2 on the hydration products of C 3 S using 1H low-field NMR, XRD, SEM-EDS, TGA, FTIR, and 29Si MAS NMR at 80 °C. The results showed that after seven days of maintenance and the addition of more than 34% nano-SiO 2, due to the agglomeration and adsorption of nano-SiO 2 , the content of C S H decreases obviously. The added nano-SiO 2 reacted with both the volcanic ash of CH and the high Ca/Si products from C 3 S hydration, resulting in the formation of a large amount of low Ca/Si hydration products and a denser microstructure of the specimen. In addition, the decalcification reaction of nano-SiO 2 facilitated the polymerization of C S H and increased the chain length, but the agglomeration of nano-SiO 2 and decalcification shrinkage increased the porosity of the specimens. [ABSTRACT FROM AUTHOR]

To investigate the influence of bolt pre-tightening force and hole-bolt spacing on the mechanical responses and failure characteristics of rock-like materials with hole-bolt composite structures, a comprehensive set of physical tests was carried out. The findings suggest that enhancing the pre-tightening force improves the peak stress and elastic modulus of the material. However, these properties initially increase and then diminish with widening hole-bolt spacing. An increase in pre-tightening force results in more fractures around the hole, altering the material's failure mode from tensile-shear to purely tensile. Additionally, as the hole-bolt spacing expands, the tensile crack positioned above the hole progressively shifts away from the bolt, leading to a transition in failure mode from tensile to tensile-shear. Field tests confirm that the bolt force proximate to the pressure relief hole remains significantly greater than that at a distance, establishing hole-bolt spacing as a critical factor in anchorage stability. • The mechanical response and failure behavior of hole-anchor composite rock-like materials was investigated. • The physical test considers the pre-tightening force and hole-bolt spacing on the influence of the rock-like material. • The failure process of the rock-like material are successfully captured by the Digital Speckle Correlation Method (DSCM). • The bolt force is influenced by the distance from the pressure relief in the physical test and verified through the field test. [ABSTRACT FROM AUTHOR]

• Asphalt mixture containing high-proportion RAP was prepared by SMC regenerant. • The failure strength master curve of high-content RAP asphalt mixture was obtained. • The fatigue performance of high-proportion RAP asphalt mixture was studied. Reclaimed Asphalt Pavement (RAP) is a cleaner production widely used in road engineering. In order to investigate the failure strength and long-term performance of high-proportion RAP asphalt mixture, this research prepared two high-content RAP recycled asphalt mixtures (50% and 60% RAP-RAM) with the gradation of AC-20 based on Styreneic Methyl Copolymer (SMC) regenerant. Firstly, indirect tensile (IDT) strength tests were implemented on 50% and 60% RAP-RAM at four temperatures and six loading rates. Secondly, IDT fatigue tests at six stress levels were carried out. The relationships of strength and temperature, strength and loading rate were obtained based on strength test results. The master curve model of indirect tensile strength and loading rate of high-proportion RAP recycled asphalt mixture was established by linear and Sigmoidal functions. On the basis of the Sigmoidal strength master curve equation, the fatigue stress ratio was calculated. Finally, this paper established the fatigue equation of the high-content RAP recycled asphalt mixture based on the fatigue stress ratio. The analysis results show that 50% and 60% RAP-RAM based on SMC regenerant show favorable strength and fatigue properties. In addition, increasing the proportion of RAP improves the strength of the mix while reducing the loading rate sensitivity of strength. However, the fatigue performance of the mix reduces by increasing RAP content. The fatigue equation based on the fatigue stress ratio takes the factors of temperature and loading rate into account, reflecting the mix's fatigue performance more realistically. The strength and fatigue performance results verify the reliability of the high-content RAP recycled asphalt mixture based on SMC regenerant and provide a reference for the effective utilization of RAP which can generate environmental benefits of saving aggregate and asphalt and reducing energy consumption and carbon emissions. [ABSTRACT FROM AUTHOR]

• Mechanical properties of LCGB as a function of interface geometry parameters. • Effects of interface geometric parameters on damage evolution of LCGB. • Failure mode of LCGB is affected by interface geometric parameters. • Dynamic crack evolution law of LCGB during loading. Subsequent backfilling of widespread goaf generally necessitates multiple fillings to enrich the goaf, resulting in the layered structure of cemented gangue backfill. Therefore, it is of great significance to study the mechanical properties of layered cemented gangue backfill (LCGB) with different interface geometric parameters to ensure the stability of underground engineering. In this paper, the effects of interface roughness and interface angle on the mechanical properties and damage evolution of LCGB were comprehensively explored using uniaxial compression test, acoustic emission (AE) and digital image correlation (DIC). A numerical model of LCGB was built using simulation software (PFC2D) to demonstrate the dynamic crack evolution of LCGB during loading. The results demonstrate that LCGB's compressive strength and elastic modulus have positive linear and quadratic relationships with interface undulating angle and interface angle respectively, and that the rupture angle, which represents the worst mechanical properties of LCGB, is between 45° and 60°. Increasing the interface undulating angle can enhance the strain hardening characteristics of LCGB during the post-peak deformation stage and release more active AE signals. As the interface angle approaches the rupture angle, the peak stress of LCGB continues to deteriorate, and its AE signal appears more concentrated in the post-peak deformation stage. The surface principal strain of LCGB rises as the interface undulating angle increases, while it reduces first and then increases with the interface angle increases. The simulation process reveals that shear cracks mainly extend along the interface, whereas tension cracks propagation and coalescence the adjacent interface along the axial stress loading direction, and they converge to generate macroscopic defects that cause LCGB unstable failure. [ABSTRACT FROM AUTHOR]

• Textile grids level and PVA fibers content dominate the tensile behavior of TR-HDC. • Ultimate tensile stress is slightly affected by the matrix category. • Proposed constitutive laws and tensile capacity calculation formulas are suitable. Textile-reinforced concrete (TRC) is a cement-based material reinforced with textile grids and could be an alternative to fiber-reinforced polymers (FRPs) whose scope of application is impracticable. Under tension, the TRC matrix generally exhibits brittleness and is prone to peeling and slipping between the textile mesh. This study shows the uniaxial tensile tests of high ductile fiber-reinforced concrete (a cement-based composite reinforced with short synthetic fibers) embedded in basalt textile grids to exhibit the technique for overcoming the deficiencies in TRC. The mixed material was renamed as TR-HDC, and thirty-two groups of ninety-six tensile specimens were tested to investigate the mechanical properties of this composite material. The variable parameters included short-fiber volume fraction, matrix category, and textile grid level. The test results indicated that the short-fiber volume fraction and textile grid level dominated the tensile behavior of TR-HDC, while the types of substrates had a relatively small impact; in addition, by replacing the matrix of TRC with HDC, the reorganized compounding material exhibited superior mechanical properties. Finally, based on regression analysis of the experimental results, this study presents a formula to compute the ultimate uniaxial tensile strength of TR-HDC and provides related analytical models to describe the stress–strain behavior of such composites. [ABSTRACT FROM AUTHOR]

• Two kinds of bio-oils are used together in pavement materials to improve the utility. • The response surface method is used to determine the optimal dosage of modifiers. • The properties of bio-asphalt are evaluated from the macroscopic and microscopic perspectives. Bio-asphalt is a potential pave material in road engineering. In order to realize comprehensive utilization of a variety of bio-oils and improve the road performance of bio-asphalt, this study chose two different sources of bio-oil for effective utilization. First, vegetable oil was used to prepare mixed bio-asphalt through high-speed shearing. Polyurethane and castor oil were added to the bio-asphalt for modification to obtain castor oil-based polyurethane-modified bio-asphalt (CPBA). Based on the Box-Behnken Design, the penetration test and softening point test of the CPBA were carried out to evaluate its conventional performance. Temperature sweep, multiple stress creep recovery test, and bending beam rheometer test was conducted to evaluate its macroscopic rheological properties. Fourier transform infrared reflection (FTIR) was shown to reveal its modification mechanism. Scanning electron microscopy (SEM) was performed to observe its microscopic morphology and verify the effect of polyurethane modification. The results manifest that castor oil-based polyurethane can increase the high-temperature properties of bio-asphalt. However, when the amount of castor oil is too high, it will also weaken the high-temperature properties of CPBA. The high-temperature properties of CPBA depend on castor oil content, polyurethane content, and stress level. Vegetable oil and castor oil can improve the low-temperature properties of asphalt. Instead, the chemical reaction production of polyurethane or polyurethane and castor oil with asphalt negatively influences the low-temperature properties of asphalt. The optimal polyurethane content, castor oil content, and vegetable oil content determined using the response surface method were equal to 20.00%, 33.61%, 8.38%. FTIR results manifest that polyurethane can chemically react with castor oil but not with vegetable oil. Vegetable oil mainly plays a role in improving the compatibility of CPBA. SEM results also show that under the action of vegetable oil, the appearance and structure of the reaction products of polyurethane and castor oil have been greatly improved. The polyurethane application in bio-asphalt makes a variety of bio-oil used, improving bio-asphalt performance and availability. [ABSTRACT FROM AUTHOR]

• The yield surface of Miller at different loading rates was established. • A new stress ratio of fatigue was proposed. • The fatigue models under different test methods were normalized. Fatigue strength is the core of pavement structure design. For semi-rigid base asphalt pavement, the anti-fatigue design of cement stabilized macadam is the key to the entire pavement design process. However, the structural layer of cement stabilized macadam is in a complex stress path, and the traditional S-N fatigue equation is various in different stress paths. Single S-N fatigue equation cannot truly reflect the actual pavement's stress path (three-dimensional structure), thus bringing challenges to make selections in engineering design. This study aims to accurately perform the cement stabilized macadam's fatigue characteristics in structural design. First, the specimens were prepared under vibration mixing and vibration molding, and the uniaxial compression, bending, and indirect tensile mechanical properties were studied. Then, based on test results and Miller yield criterion, the strength yield surfaces of cement stabilized macadam were established with an increase in loading rates. Finally, the generalized shear stress strength ratio is proposed to unify fatigue performance under different test methods. The results show that the strength rises with an increase in loading rates, and the yield surface is a parabola. Miller yield surface referrings as fatigue damage surface comprehensively describes the failure characteristics of cement stabilized macadam. The new fatigue equation curves based on the Miller yield surface are significantly closed in different stress paths and pass-through points (1, 1). Using one equation can represent the fatigue feature of cement stabilized macadam thoroughly. It realizes the unified characterization of fatigue performances and eliminates the effect of test methods and conditions on fatigue results. This study solves the long-standing problem: the fatigue equations obtained by different test methods are various, which improves the design accuracy of the semi-rigid base pavement. [ABSTRACT FROM AUTHOR]