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Polyurethane grouting is a commonly employed technique for seepage prevention and reinforcement during tunnel construction. Gaining insights into the propagation behavior of polyurethane grout within rock fractures holds importance in guiding grouting operations. To investigate the effects of fracture aperture on the propagation of self-expanding polyurethane grout, experimental studies were first conducted to examine the polyurethane propagation characteristics in homogenous fractures. Subsequently, propagation mechanisms of polyurethane grout and cement grout were compared and analyzed by numerical simulation. Finally, the scanning electron microscope (SEM) tests were performed to analyze the effect of fracture aperture on the microscopic characteristics of filled polyurethane grout. The experimental results demonstrate that, larger fracture apertures result in smaller maximum propagation distances and shorter propagation time. Besides, in fractures with a large aperture, a noticeable pressure drop occurs after grout gelation. The simulation results demonstrate that an increase in the aperture is inversely proportional to the polyurethane filling rate, whereas it is directly proportional to the cement filling rate. This disparity is attributed to different injection modes and driving force sources for these two grouting materials. In addition, the SEM test results show that larger fracture apertures correspond to greater microscopic pore diameters and fewer pore numbers in filled polyurethane grouts, which provides a microscopic explanation for the observed pressure drop during experimentation. The outcomes of this study offer valuable experimental and theoretical foundations for enhancing the understanding of self-expanding polyurethane grouting in rock fractures. • The tests on polyurethane grouting in fractures with variable aperture are conducted. • The propagation and pressure of polyurethane grout in fractures are measured. • The propagation mechanism of cement and polyurethane grouts in fracture is compared. • The microscopic properties of filled polyurethane grout in fractures are investigated. [ABSTRACT FROM AUTHOR] more...

Cement grout is a fundamental material used in diverse engineering applications, such as mining, civil engineering, geothermal energy, and oil and gas industries, due to its role in stabilizing rock masses and sealing wellbores. Despite its widespread usage, grout's susceptibility to cracking, particularly under tensile stress, remains a major concern, compromising structural integrity and long-term performance. This study investigates the micro-cracking behavior of cement grout under tensile loading to gain a deeper understanding of the mechanisms governing fracture initiation and propagation. By employing acoustic emission monitoring and analyzing fracture surface characteristics, this research reveals the complex interplay between microcracking mechanisms and macro-fracture morphology. The results reveal significant differences in fracture behavior between the two loading regimes. Brazilian tests exhibited higher tensile strength due to the dominance of non-tensile microcracking mechanisms, such as compaction and shear, which enhance strength and dissipate more energy. These specimens showed smoother, less tortuous fracture surfaces, corresponding to lower with tensile strengths. In contrast, direct tensile tests, governed by tensile microcracks, produced lower strength and rougher, more tortuous fractures, highlighting the distinct influence of microcracking mechanisms on fracture morphology. Correlation analyses indicated consistent roughness characteristics across different fracture orientations and underscored the link between smoother surfaces and non-tensile microcracks. This study offers new insights into the interplay between microcracking mechanisms, fracture surface roughness, and tensile strength, emphasizing the impact of loading conditions on the fracture behavior of grout. The findings provide a deeper understanding of grout fracture processes, contributing to enhanced design and performance of grout-based structures in engineering applications. Future research could further explore the role of material microstructure on fracture development, aiming to improve the durability and reliability of cement grout in critical infrastructure. • Microcracking mechanisms significantly influence the tensile strength and fracture behavior of cement grout. • Different loading methods (direct tension vs. Brazilian tests) create distinct microcracking patterns and fracture morphologies. • Microcracks play a crucial role in initiating and propagating larger-scale fractures. • Fracture surface roughness analysis reveals energy dissipation mechanisms and the impact of microcracking on roughness. [ABSTRACT FROM AUTHOR] more...

Grouting is an effective way to prevent water inrush in underground engineering, with cement grout commonly used at ambient temperature. However, its properties change remarkably under high temperature. Existing research on this is inconsistent and limited. Thus, focusing on ordinary Portland cement, this paper investigated the basic properties and water plugging capacity of grout at various temperatures (20℃-95℃) and different water-cement mass ratios. Moreover, using a self-designed testing system, the grout retention ratio under dynamic water was explored. The influence mechanism of temperature on cement stone was studied through scanning electron microscopy, X-ray diffraction and thermogravimetric analysis as well. Here we show that as the temperature rose from 20℃ to 95℃, the grout fluidity, bleeding ratio, setting time and grout retention ratio under dynamic water all exhibited a downward trend. For the grout with a water to cement mass ratio of 1.0, when the temperature rose from 20°C to 95°C, the fluidity dropped by 30.2 %, the bleeding ratio by 73 %, the final setting time by 75 %, and the grout retention ratio by 84 %. The cement stone strength first increased and then decreased with rising temperature, peaking at 80°C for 1-day curing, 50°C for 3-day curing, and 35°C for 7-day curing. Beyond 65°C, ettringite decomposed, calcium hydroxide depleted, and monosulfoaluminate crystals fractured and distorted, reducing the compactness and compressive strength of the cement grout stone at high temperatures. • Laws of water plugging properties of grout under high temperature were studied. • A retention ratio test in dynamic water at high temperature was conducted. • A microscopic explanation for grout properties at high temperature was proposed. [ABSTRACT FROM AUTHOR] more...

Revealing the load transfer and failure mechanisms of the bolt-grout interface is crucial for the stability control design of rock mass engineering. Based on laboratory experiments, this study employs a FLAC-PFC coupling numerical simulation method to conduct shear numerical simulations under different normal stress, rib angle, and rib spacing conditions. The study investigates the impact of rib parameters on the load transfer and microscopic damage evolution of the bolt-grout interface. The results show that: When the rib angle is below 45°, the grout tends to climb along the ribs. As the rib angle increases, the normal stress F n between the grout and ribs gradually increases, leading the grout to adopt a sheared-crush failure mode. When the rib spacing is less than 12 mm, the grout tends to undergo an overall sheared-off failure mode. When the rib spacing is greater than 20 mm, the grout consistently undergoes a sheared-crush failure mode. As the rib spacing increases, the number of ribs gradually decreases, resulting in more intense interactions between each rib and the grout, and a larger damage area around the ribs. With the increase in normal stress, the interactions between the ribs and the grout become more intense, generating more cracks. [ABSTRACT FROM AUTHOR] more...

Researches on synchronous double-liquid plastic grout are limited, particularly for high water-cement (W/C) and volume ratios (V A /V B). To address these gaps, high W/C of 1.0–3.0 and high V A /V B of 7:1–20:1 were applied. Liquid A consisted of cement, bentonite and stabilizer, and liquid B was sodium silicate. Fresh-state performance, rheological properties and thixotropy of cement-bentonite single slurry were studied. Gel time, setting time, time-varying viscosity, strength, water dissolution resistance, drying shrinkage of double-liquid plastic grout were studied systematically. Hydration minerals and microstructural properties were characterized using XRD, SEM-EDS, FTIR, TG-DSC and MIP techniques. The results indicated that the H-B model was more applicable to all cement-bentonite single slurries. Yield stress, plastic viscosity, thixotropy and bleeding were negatively correlated with cement-bentonite ratio. Three periods i.e., low viscosity, rapid increase, and slow increase periods were categorized for the time-varying viscosity. The peak UCS was achieved with the optimal V A /V B of 10 and W/C of 2.75. Shrinkage rate was negatively correlated with V A /V B , the rapid shrinkage process mainly occurred within the first 3 d. Microscopic analyses revealed that sodium silicate significantly promoted the consumption of Ca(OH) 2 and the formation of C-S-H gel. This accelerated the early hydration process and improved microstructure compactness. At the W/C of 1.5, when V A /V B decreased from 18 to 16, small gel pores (< 10 nm) and large gel pores (10–50 nm) were reduced by 28.5 % and 53.5 % respectively. The W/C of 1.5–2.75 and V A /V B of 10–16 are suitable for engineering applications. • Plastic double-liquid grout with high volume ratio and W/C was optimized. • Optimal rheological model for single-liquid grout was evaluated. • Time-varying viscosity characteristics of double-liquid grout were revealed. • Optimum volume ratio and W/C are determined and discussed. • Reaction and microscopic mechanism of double-liquid plastic grout was studied. [ABSTRACT FROM AUTHOR] more...

In the grouting of fractured rock masses, the grout exhibits different flow configurations and nonlinear flow behaviors, which affect the flow characteristics and diffusion distance analysis of the grout within the fractures. The characteristic parameters of grout under unidirectional flow and radial flow were studied through theoretical research, numerical simulation, and experimental analysis. Nonlinear flow models of grout under the two flow configurations were established. The unidirectional and radial flows were simulated under different water-cement ratios. The results indicate that, as fracture roughness increases, both the equivalent hydraulic aperture and the critical Reynolds number decrease, while the non-Darcy coefficient increases. The unidirectional and radial nonlinear flow models were parameterized. The variation of the equivalent hydraulic aperture with fracture roughness is consistent under different flow configurations. The critical Reynolds number for unidirectional flow is larger than that for radial flow, and the velocity distribution of unidirectional flow is more uniform than that of radial flow. The non-Darcy coefficient for unidirectional flow is smaller than that for radial flow, indicating that radial flow is more susceptible to inertia effects. Grout is more susceptible to inertia effects compared to water. [ABSTRACT FROM AUTHOR] more...

Deterministic machine learning methods have been widely utilized for predicting the diameter of jet grout columns. However, these methods often do not account for uncertainties associated with predictions, which are notably variable in practical engineering. To address this limitation, this study presents a framework that utilizes a Bayesian deep neural network to predict the diameter of a jet grout column and quantify the associated uncertainties. A dataset comprising 160 field-measured jet grouting cases was compiled from published case histories. These case histories include details on the ground conditions obtained by Standard Penetration Test (SPT), specific energy utilized during jet grouting, and the resulting jet grout column diameters. The Bayesian deep neural network models were trained, tested, and validated using this dataset, along with uncertainty quantification considering both aleatoric and epistemic sources. The developed model predictions of jet grout column diameters were compared with the diameter predicted using the empirical equation. Design charts were prepared to support optimal jet grouting design, enhancing the accuracy and reliability of jet grout column diameter predictions. [ABSTRACT FROM AUTHOR] more...

The interlaminar shear behavior of bonded prestressing basalt fiber-reinforced polymer (BFRP) tendons in seawater was experimentally studied in this article. The experimental variables mainly consisted of prestressing levels (0, 0.3 and 0.5 f u , where f u represents the original tensile strength of BFRP tendons), environment (grout immersed in seawater, or dry grout), and conditioning duration (240, 480 and 720 days). The effects of the above variables on the interlaminar shear strength (ISS) of the BFRP tendons were analyzed, and the corresponding degradation mechanism of BFRP tendons under a combined effect of prestress, grout and seawater was revealed through scanning electron microscopy (SEM) analysis. The accuracy of the strength degradation model based on Fick's law was also evaluated. The results show the ISS degradation was mainly caused by the fiber-resin interface debonding after conditioning. In a dry grout environment without seawater, the effects of grout and prestress level on the ISS of BFRP tendons could be neglected. In comparison, an 8 % strength decrease occurred in the ISS of BFRP tendons without prestress at the 720th day conditioned in seawater. Furthermore, prestress accelerated the degradation significantly, with a strength retention equaling 83 % at the 720th conditioning day under a sustained stress of 0.3 f u. It is recommended to maintain a long-term prestress level below 0.3 f u in BFRP tendon to ensure a strength retention exceeding 80 %, with seawater conditioning. Finally, it is validated that Fick's law can predict the degradation of ISS of BFRP tendons accurately. The results contribute to the application of BFRP as bonded prestressing tendons in the concrete structures constructed in a marine environment. • A dry grout environment had a negligible effect on the ISS of BFRP tendons. • A significant degradation of tendons occurred after conditioning in seawater. • Prestress accelerated the degradation significantly. • The ISS degradation was mainly caused by fiber-resin interface debonding. • It is recommended to limit the prestress level below 0.3 f u for sufficient ISS. [ABSTRACT FROM AUTHOR] more...

High ambient temperatures during summer exacerbate rutting in asphalt pavements and intensify the urban heat island (UHI) effect. This study introduces a novel light-colored water-retentive semi-flexible pavement (WRSFP) that incorporates recycled glass and ceramic to mitigate these challenges. A comprehensive evaluation of mechanical, optical, and thermal properties for both cement-based grout and semi-flexible concrete specimens was conducted. The results indicate that 15 wt% ceramic powder increased the water absorption of grout by 10.63 % compared to conventional formulations. White grout consistently exhibited significantly higher reflectance across all wavelengths. Within the VIS range, the maximum reflectance for white, gray, and black grout were 76.81 %, 35.97 %, and 17.35 %, respectively. In alignment with previous research, the traditional medium-toned (gray grout) WRSFP achieved a maximum surface temperature reduction of 9.7 °C. In contrast, black grout showed a reduction of only 5.7 °C, while white grout demonstrated a significantly higher temperature reduction of 19.6 °C, highlighting the critical role of grout color in thermal regulation. The incorporation of waste glass aggregates substantially decreased the thermal conductivity of the mixture; a 60 % glass content (volumetric fraction of 4.5–9.5 mm aggregates) resulted in a maximum reduction of 20.05 %, leading to an increased temperature gradient of up to 5.1 °C between the surface and bottom layers of the pavement. Additionally, the WRSFP exhibited excellent skid resistance, high-temperature stability, and water resistance. However, none of the specimens surpassed the flexural strain threshold of 2500 μ ε , suggesting that this pavement structure may be more suitable for application in warm climates, where a glass aggregate content of up to 60 % is acceptable. This research highlights the feasibility and effectiveness of utilizing this eco-friendly pavement to mitigate the UHI effect through enhanced water retention, improved solar reflectivity, and superior thermal insulation. By addressing environmental sustainability and material efficiency, this study contributes to the advancement of urban infrastructure, providing innovative solutions for cooler and more durable roadways. • Developed a light-colored water-retentive semi-flexible pavement that incorporates recycled glass and ceramic. • White grout demonstrated a significantly higher temperature reduction of 19.6 °C. • Up to 60 % recycled glass aggregate was found to be feasible in the mix for warm climates. [ABSTRACT FROM AUTHOR] more...

• A novel Y-S connector embedded in UHPC shear pockets in steel–concrete composite structures was proposed. • Push-out tests were conducted to study the shear behavior of the innovative Y-S connector. • Finite element models were established to investigate the relationship between the shear stiffness and number of perfobond holes. • Analytical models considering the end-bearing effect of UHPC were put forward to estimate the shear stiffness of the Y-S connector. Precast concrete deck panels (PCDPs) with shear pockets offer several advantages to accelerate bridge construction. In this paper, a Y-shaped connector was proposed, which was placed intermittently in the ultra-high-performance concrete (UHPC) shear pockets of PCDPs in composite structures. To assess the shear behavior of the Y-shaped connector, push-out tests were performed by varying plate width and thickness, diameter of the penetrating rebar and perfobond hole, and type of grout. The load-slip curves, failure modes, strain analysis, and shear behaviors were investigated. Then, validated finite element (FE) models were established to investigate the relationship between the shear stiffness and number of perfobond holes. Finally, the shear stiffness model of the Y-shaped connector considering the end-bearing resistance of the UHPC was proposed. The test results show that the Y-shaped connector with UHPC grout has excellent shear performance compared to the specimen with normal concrete (NC) grout. The shear stiffness of the Y-shaped connector is greatly influenced by the effective width of the perfobond plate. The shear stiffness of the Y-shaped connector increases significantly with the number of perfobond holes. The analytical model has a precise prediction for the shear stiffness of the Y-shaped connector. [ABSTRACT FROM AUTHOR] more...

Grouted splice sleeves are widely used in assembly building connections. However, void defects within the sleeve directly affect the load-bearing capacity of the building structure. This paper presents a new method for detecting void defects inside a grouted splice sleeve based on the frequency domain characteristics of mechanical vibration waves. This method analyszes the grouted spliced casing containing void defects as a gas-liquid two-phase flow system. To confirm the validity of the method, this paper builds a test setup for testing. The results showed that the test method can effectively detect the void defects and the volume of the defects inside the grouted splice sleeves when the grout is not solidified. • A new method for detecting cavity defects in grouted splice sleeves is proposed. • Specialized for detecting cavity defects within the sleeve during the grouting process. • Detected defects can be quantified. • The response characteristics of slurry and cavity systems under oscillatory excitation are evidenced. • The feasibility of this detection method was confirmed by the developed equipment. [ABSTRACT FROM AUTHOR] more...

During the course of operation and maintenance, the concrete structure is susceptible to cracking due to external loads, prolonged immersion, and water erosion. The high-flow dynamic water environment presents a significant challenge to the rapid sealing of engineering construction, particularly in steeply dipping cracks where gravitational forces cause the slurry to flow down the cracks and the cracks to fill with low-density material. In this study, a magnetic grouting material whose viscosity can be transiently changed, retained in a fixed area, and capable of automatically discharging gas and water was prepared by the addition of magnetic additives, flocculants, and dispersants using cement and epoxy resin as the base materials. The optimal ratio, which considers the influence of multiple factors, was obtained through the application of the method of range analysis and the comprehensive weighted score optimization model analysis. The specific gravity of epoxy resin to cement was 0.03, the specific gravity of water to cement was 0.4, the incorporation of magnetic powder was 20 %, the incorporation of flocculant was 3 %, and the incorporation of water-reducing agent was 0.2 %. The drilling-grouting integrated self-propelled magnetic anchor was developed, which formed a new grouting technology of self-propelled magnetic anchor with steep inclined fissure, the theoretical model of magnetic powder content and the adsorption radius of self-advancing magnetic bolt anti-gravity grouting was derived. The mechanism of hydration and solidification of MEC slurry was analyzed. The hydration process of MEC slurry was accelerated by magnetic field, the nucleation and surface adsorption of magnetic particles can promote the hydration of cement and increase the number of crystal nuclei. • Under the magnetic field, the viscosity of the CEM can change instantly. • The grouting process can be significantly reduced by means of magnetic anchors. • The magnetic field action accelerates the hydration process of the CEM. [ABSTRACT FROM AUTHOR] more...

This study explored the impact of incorporating fly ash, a coal combustion by-product, and artificial interior stone (AIS) sludge, a waste product from stone manufacturing, into cement grouts. The goal was to improve grout properties by using fly ash as a binder and AIS sludge as a filler. Key parameters such as fluidity, penetration resistance, bleeding, density, compressive strength, and microstructural characteristics were assessed. The findings showed that adding fly ash and AIS sludge improved workability, setting time, and bleeding while significantly enhancing compressive strength. Microstructural analysis revealed reduced porosity, refined pore size, and improved microstructure. • Fly ash and AIS sludge improve grout workability, setting time, and strength. • AIS sludge shortens initial setting time; fly ash delays it by slowing hydration. • Microstructural analysis shows reduced porosity and enhanced matrix densification. [ABSTRACT FROM AUTHOR] more...

• Grout injection produced effects similar to those induced by tunnels excavation. • Protective barrier significantly reduced tunnel-induced ground settlement. • Simulating grout injection ensures agreement between observed and computed settlements. • Simulating side activities as wished-in-place may yield inaccurate predictions. Line C of Rome underground will cross the city from southeast to northwest, with a total length of about 25 km, passing through the historical city centre. This is a difficult environment due to many archaeological finds and pre-existing buildings of great historical value. Along stretch T3 of the line two conventional tunnels connect the TBMs launching pit to the new San Giovanni station. They run for a length of 140 m at a depth of about 25 m and reach the station passing at a short distance from the ancient Aurelian Walls (3rd century CE). Excavation of these tunnels was carried out following a three-stage procedure: (i) excavation of two small diameter tunnels (D = 3 m) using a mini slurry shield machine; (ii) soil improvement via cement grouting using tubes à manchettes installed radially from the mini-tunnels; and (iii) conventional excavation of the two running tunnels in the improved soil. An extensive monitoring system was set to control ground movements induced throughout the excavation process. This paper presents the displacement measured at the ground surface during the construction activities, highlighting the effects induced by grouting. The effectiveness of a protective barrier, made by a line of piles, in reducing the movements induced by tunnelling in the Aurelian Walls is also assessed. A 2D FE back-analysis is finally presented, showing that a satisfactory description of the observed behaviour can only be obtained by simulating the volume changes induced by the cement grouting. [ABSTRACT FROM AUTHOR] more...

This study investigates the effects of grouted extruded-strand (GES) tendon on the web-crushing strength of post-tensioned members. GES tendons, characterized by inserting high-density polyethylene (HDPE)-sheathed prestressing strands into PT duct filled with cement grout, are increasingly utilized in current construction practices with their great merits in low friction loss, superior durability, and ease of regular inspection/maintenance. Despite its growing application, the structural behavior of GES tendons, which differs from traditional bonded and unbonded tendons, requires a thorough understanding on mechanical properties toward better engineering structures. To this end, compression tests on 48 concrete prisms with PT duct oriented orthogonally to the direction of compression were carried out. The primary objective is to discern the crushing mechanism and also to establish the maximum limit of shear strength of prestressed members reinforced by GES tendons. It appears that the reduction coefficients of average effective web width (k) can be taken to be 0.48 and 1.09 for bonded and unbonded tendons, respectively, and it affirms the Eurocode 2 and fib MC2010 provisions. For GES tendons, the presence of flexible HDPE sheath reduced the effective duct stiffness, resulting in coefficient k to be 1.01, comparable to that of unbonded tendons. Those effect of materials was further explained theoretically by introducing the concept of effective stiffness based on a two-phase composite assumption. To ensure conservative design, it is recommended to apply the coefficient, k = 1.2, for GES tendons, consistent with the value suggested for empty ducts in Eurocode 2 and fib MC2010. This study represents the first experimental and theoretical analysis of the impact of GES tendons on web-crushing strength, distinguishing it from the body of data on grouted and empty ducts. The findings provide essential foundational data for the shear design of structural members employing GES tendons. [Display omitted] • Compressive tests were conducted on concrete prisms containing various post-tensioning (PT) tendons. • Previously unreported experimental data on the grouted extruded strand (GES) tendon method is presented. • An effective web width reduction factor (k) is proposed for the web-crushing strength of PT members with GES tendons. • The effect of area ratio of bare or HDPE-sheathed strands within grouted ducts on compressive strength was investigated. • The stress concentration near PT duct was analyzed using digital image correlation (DIC) and a two-phase composite model. [ABSTRACT FROM AUTHOR] more...

To mitigate the cost of utilizing calcium sulfoaluminate (SAC) cement-based grouting materials and alleviate the environmental impact of heavy metals and harmful elements in secondary aluminum ash, this study investigated the effects of different secondary aluminum ash sintered ground powder (AP) dosages on the workability, mechanical properties, volume stability, and environmental compatibility of SAC grouting material. Results indicated that incorporating 15 % yielded the most optimal comprehensive performance. Specifically, the initial setting time and early compressive strength of SAC grouting material exhibited an initial increase followed by a decrease with escalating AP dosage. In contrast, the long-term compressive strength gradually declined with higher AP dosage. Microscopic analyses revealed that AP addition introduced more aluminum phases, facilitating SAC hydration and enhancing the generation of AFt and Al(OH) 3 , thereby improving the pore structure. The SAC grouting material demonstrated effective stabilization of four heavy metals (Pb, Cr, Zn, and Cu) present in AP. Further elemental analysis revealed that fluorine (F) primarily existed in the grouting material containing AP as CaF 2 and AlF 3 , while nitrogen (N) was present as AlN and NH 3. [Display omitted] • Secondary aluminum ash sintered ground powder can promote the hydration of sulfoaluminate cement grouting material. • Sulfoaluminate cement can effectively fix heavy metals such as Pb, Cu, Zn, Cr in secondary aluminum ash. • The N and F elements in the secondary aluminum ash sintered ground powder are mainly composed of CaF 2 and AlN. [ABSTRACT FROM AUTHOR] more...

Adobe construction is a prolific and historically significant building technology, and the rehabilitation of masonry adobe structures is crucial for cultural heritage preservation. The present study proposes novel rehabilitation solutions for masonry construction, aiming to address rising damp and structural damage, two of the most common pathologies in adobe walls. The proposed rehabilitation solutions combine specially developed rehabilitation mortars and grouts with the use of reinforcement meshes. The physical and mechanical properties of the developed materials have been characterized, and adobe walls have been erected to conduct pilot tests and evaluate the effectiveness of the proposed rehabilitation solutions at scale. The results show that natural hydraulic lime mortars can be formulated and used in rehabilitation works to reduce water intake and water front height, while also enhancing the mechanical performance of adobe walls to levels surpassing those of the original walls (prior to damage). The application of reinforcing meshes was shown to further increase the strength of adobe walls, deemed to serve as a complementary reinforcing solution in engineering projects where more demanding structural performances are required. • Novel rehabilitation methods for adobe construction have been investigated. • Natural hydraulic lime mortars and grouting solutions have been developed. • Real-scale adobe walls were built, and rising damp and mechanical strength analyzed. • Rising damp height was significantly reduced, and the structural performance was enhanced. [ABSTRACT FROM AUTHOR] more...

Energy micropiles (EMPs) combine foundation systems with shallow geothermal energy technology, offering the advantages of structural reinforcement alongside enhanced energy efficiency. This research examines the thermo-mechanical behavior of energy micropiles (EMPs) in relation to shallow geothermal systems and retrofitting applications, employing laboratory-scale physical modeling in a controlled environment. Experiments were carried out utilizing a custom-designed sand pluviation system to guarantee uniform soil density in Babolsar sand. EMPs, which include U-shaped copper heat transfer tubes filled with either water or cement grout as the heat transfer medium, were exposed to different thermal loading durations of 6, 12, and 24 h alongside mechanical loads. Essential data were meticulously recorded and analyzed, encompassing micropile head displacement, axial strain, and temperature distribution within the micropile and surrounding soil. The findings indicate that heat dissipation primarily occurs radially, with temperature gradients showing a marked increase at greater distances from the micropile as the duration of heating extends. Mechanical loads mitigated thermal expansion, reducing micropile head displacement by approximately 20%. Compared to water, the higher thermal conductivity of cement grout amplified thermal strains and stresses along the micropile. Thermal stress profiles indicated pronounced strain at the micropile's upper and lower sections, with the neutral axis shifting under mechanical constraints. Furthermore, heat transfer efficiency and mobilized side shear stress were significantly enhanced when cement grout was used, highlighting its superior thermal conductivity. This study advances the understanding of EMP behavior by addressing thermal and mechanical interactions, fluid properties, and heat dissipation patterns. The insights obtained enhance the design and implementation of EMPs for sustainable infrastructure, especially in energy-efficient retrofitting and new building initiatives. These findings highlight the potential of EMPs to improve the integration of structural reinforcing and renewable energy technologies in geotechnical engineering. [ABSTRACT FROM AUTHOR] more...

The grout in water-rich strata is at risk of being washed away. To investigate its retention capacity during the washout process, rheological parameters characterizing the mechanical properties of the grout were tested. Additionally, a comparative analysis was conducted on the prediction accuracy of different rheological models for cement-based grouts, and a recommended prediction model for the rheological parameters was provided. By combining a CFD numerical model, the process of grout being washed out in the stratum was analyzed. The study results indicate that the Bingham model is the most suitable for regression analysis of rheological parameters in cement-based grouts. In the static washout process, reducing Water/Binder and Binder/Sand while increasing Bentonite/Water improves the resistance of grout to washout, with Cement/Fly Ash having a relatively smaller impact. During dynamic washout, Binder/Sand either above or below 0.65 result in higher grout washout resistance. Additionally, grouting increases grout volume in the stratum, with the retention rate being minimally influenced by grouting pressure. The static washout effect showed an excellent correlation with plastic viscosity, while the dynamic washout effect was more significantly related to yield stress. When shear stress exceeds 3.5 and plastic viscosity exceeds 0.6, the influence of rheological parameters on grouting effectiveness and retention capacity becomes negligible. Considering the grouting process, retention rate and diffusion capacity, three reference ratios were proposed for different application needs. [ABSTRACT FROM AUTHOR] more...

Ultrasonic guided wave (UGW) technique has been widely utilized in damage detection of pre-stressed steel strands. However, most of the current UGW-based methods only focus on bare strands, whereas in real projects the strands are usually pre-buried inside the structure and encapsulated by media such as concrete or grout. In this study, the effects of various grouting and tensioning factors on the propagation of UGW in grouted steel strand, as well as the effectiveness of UGW energy leakage ratio (α EL)-based pre-stress evaluation for grouted steel strand, were investigated. Firstly, the theoretical model of UGW propagating in the grouted steel strand was developed. Secondly, a finite element model of grouted strand was established to investigate the dispersion characteristic of UGW as well as the energy distribution and attenuation behavior of UGW in the grout. Thirdly, pre-stressed concrete (PSC) specimens with different grouting diameters, grouting lengths, and tension forces were designed to investigate the effects of grouting thickness, grouting length, and tension force on the group velocity, energy distribution and α EL of UGW. Finally, the α EL -based approach was validated in pre-stress evaluation for grouted steel strand, and the evaluation accuracy was compared with that for bare steel strand. Results show that compared with the helical wire excitation scenario, the UGW signals propagating in steel strands are significantly less affected by variations in grouting thickness and grouting length under core wire excitation scenario. In the grout, the UGW energy tends to decrease exponentially with the increase of the radial propagation distance, and the helical wire excitation scenario leads to more UGW energy leaking into the grout compared with core wire excitation. It is recommended to excite UGW signal in the core wire instead of the helical wire in α EL -based pre-stress evaluation approach for grouted steel strand, in such scenario, the evaluation error is only 4.93 %. • Variations of UGW with various grouting conditions were investigated. • Energy distribution and attenuation of UGW in grout were investigated. • 3. Exciting UGW in core wire instead of helical wire is recommended. [ABSTRACT FROM AUTHOR] more...

The escalating demand for innovative, multifunctional, and advanced composite structures stems from the pressing concerns related to cost efficiency and environmental impact, alongside interest in the prefabrication methods within the construction industry. This paper advances a pioneering approach by proposing the utilization of high-strength bundle-bar-filled circular hollow sections (BBFC) as columns. In this method, a bundle comprising high-strength reinforcing bars with an impressive yield strength of 670 N/mm² is strategically placed within a steel tube, varying in related-slenderness values from 0.86 to 2.44. Subsequent to this arrangement, the bundle undergoes grouting with mortar, resulting in the formation of the BBFCs. The composition of the bundle is a critical aspect, with different configurations featuring 1, 3, 7, and 19 high-strength bars. Given the intricacies involved in the fabrication process, this paper meticulously outlines the unique techniques employed to successfully manufacture the BBFCs. To comprehensively evaluate the performance of these innovative columns, a series of ten real-scale tests were conducted. These tests look at various aspects, including capacity, flexural stiffness, deflection, and strain response. In addition to experimental validation, finite element analysis was applied, not only to corroborate the empirical findings but also to lay the foundation for future parametric studies. These subsequent investigations aim to explore and understand the influence of different geometric and material features on the structural behaviour of this innovative composite column, thereby contributing to the advancement of knowledge in the field. • This study unveils state-of-the-art composite column design and their test results. • Bundle-bar columns offer cost-efficiency and structural robustness. • Bundle-bar columns are recommended for mid- to high-rise buildings. • The study highlights the importance of deflection control measures. • Promising structural and economic advantages pave the way for future design. [ABSTRACT FROM AUTHOR] more...

Compressive strength is a crucial factor in designing masonry walls to withstand various loading conditions, and it is equally significant for the designing of dry-stack masonry walls. Dry-stack masonry uses interlocking blocks, that enable a faster walling construction than the conventional mortared masonry. Widespread use of this walling system is limited due to lack of detailed design provisions in standards, as opposed to conventional mortared masonry. In this study, the compressive strength properties of un-grouted and grouted dry-stack concrete block masonry were experimentally evaluated. In total, 80 dry-stack concrete block masonry wallettes were built and tested with five different types of dry-stack blocks and three different grouts strength (20 MPa, 32 MPa and 40 MPa). The failure patterns, stress-strain curves and compressive strength characteristics obtained through the testing campaign are reported in this paper. The grouted dry-stack concrete block masonry wallettes demonstrated higher compressive capacities (ranging from 11 % to 152 %) than the corresponding un-grouted concrete block masonry wallettes, the increment was dependent on the grout and block types. The experimental data collected in this campaign was then used to assess the available formulae and tabulated values to predict the compressive strength of dry-stack concrete block masonry wallettes. The predictabilities of these formulae and tabulated values are presented and discussed. [Display omitted] • Compression behaviour of grouted dry-stack concrete block masonry was studied. • 80 dry-stack concrete block masonry wallettes have been tested. • The presence of grout had a significant impact on the axial compression capacities. • Compressive strength prediction models were verified, and best models are specified. [ABSTRACT FROM AUTHOR] more...

Contaminants in the deep vadose zone (DVZ) pose a long-term threat to groundwater, human health, and the environment. Polyurethane grouting is a type of chemical grouting that is potentially advantageous in immobilizing contaminants in DVZs. Polyurethane resin has low viscosity that makes it feasible to penetrate and fill the pore space between fine particles. In this study a series of laboratory pressure grouting and leaching tests were conducted to simulate and assess the effectiveness of polyurethane grouting for immobilizing contaminants in DVZs. Soil with fine particles was prepared with 127I (as iodide) that served as a non-radioactive surrogate for radioactive 129I. After grouting and curing, leaching tests were used to measure and compare contaminant diffusivity and leachability index values. Additionally, changes in porosity and saturated hydraulic conductivity of grouted soil were measured. X-Ray Computer Tomography (XCT) results showed that the cured polyurethane was distributed nearly homogeneously and approximately half of the voids were filled with cured polyurethane. Grouting reduced the saturated hydraulic conductivity of soil by 37 %. The effective diffusivity decreased by more than 80 % as compared with the ungrouted soil. The leachability index of the grouted soil was 6.5; meeting the criteria established by the U.S. Nuclear Regulatory Commission (NRC) standard. The results obtained in this study provide a valuable assessment of polyurethane grouting for iodide immobilization in the DVZ and indicate this approach may be a viable method for contaminant remediation in DVZ soils. • The polyurethane grout was distributed homogeneously with half of the voids filled with grout. • The contaminant diffusivity in grouted soil decreased by more than 80 %. • The leachability index of grouted soil exceeds 6 and fulfills the criteria for materials intended for burial with radioisotopes. • The displacement caused by grouting is reduced when the soil water content is low. [ABSTRACT FROM AUTHOR] more...

• Stepwise strategy is integrated with multi-objective optimization methods. • Temperature and temperature derivative are used as a bi-objective example. • The lexicographic method is particularly suitable for stepwise strategies. • The proposed method is robust and reliable for multi-parameter estimation. It is a great challenge to estimate multiple parameters of ground heat exchangers (GHEs) from a thermal response test (TRT) with high reliability. This study proposed a stepwise framework involving the lexicographic multi-objective optimization method to increase the identifiability of multi-parameter estimation of GHEs. Three ideas constitute the foundation of the framework: 1) using a temperature derivative objective-function to complement the temperature objective function, 2) using the lexicographic method for solving the involved multi-objective minimization problem, 3) using an analytical short-time solution for addressing the time-varying features of parameter sensitivity. This framework was illustrated by two variant algorithms for five-parameter estimation (four thermal properties plus borehole thermal resistance). The two variant algorithms were validated by an independent sandbox experiment, and the results show that these algorithms yield estimates for borehole thermal resistance, soil thermal conductivity, grout thermal diffusivity, grout thermal conductivity, and soil thermal diffusivity with relative errors smaller than 2.0 %, 4.0 %, 14 %, 20 %, and 36 %, respectively. [Display omitted] [ABSTRACT FROM AUTHOR] more...

• The NMR technique was used to study grouting diffusion characteristics in real rough rock fracture with flowing water. • The grout flow rate and water flow rate are the main influential factors on grouting effectiveness. • Fracture roughness increases grout resistance to flowing water scouring , which improves the grouting effectiveness. Observation of dynamic water grouting diffusion characteristics presents formidable challenges owing to the concealed and intricate nature of rock formations in underground engineering. Therefore, investigating the grouting diffusion characteristics in rough fracture with flowing water is crucial for preventing water inrush and reinforcing fractured rock masses. This study conducted a series of dynamic water grouting tests encompassing varying grouting parameters, and the grouting diffusion processes were monitored utilizing the nuclear magnetic resonance (NMR) technique. The initial setting time and hydration process of ultrafine cement-sodium silicate (UC-S) grout was first investigated. The effects of water flow rate, grout flow rate, fracture aperture, and fracture roughness on the grouting diffusion process and effectiveness were comprehensively investigated. Then, the effects of varying grouting parameters on the dynamic water grouting effectiveness were evaluated using the global sensitivity analysis method. The results indicated that the fracture roughness notably affects the grouting effectiveness, with a more pronounced effect evident when water flow rate exceeds grout flow rate. In scenarios where water flow rate exceeds grout flow rate, the increase of fracture roughness can extend the total effective grouting time and simultaneously enhance grout diffusion distance under counter-current conditions. Notably, favorable grouting effectiveness can be achieved when the Joint Roughness Coefficient (JRC) exceeds 6. The grout flow rate and water flow rate are the main influential factors on grouting effectiveness, followed by fracture roughness and fracture aperture. The findings of this study can provide valuable reference and guidance for the grouting parameter selection in grouting engineering applications. [ABSTRACT FROM AUTHOR] more...

Over the past few decades, high-capacity post-tensioned anchors have been used in dams for reinforcement and design purposes. The failure mechanisms are divided into four main categories including failure of anchor, anchor-grout interface, grout-rock interface and cone-shaped failure. Cone-shaped failure is dominant when the embedment length is small and/or there is significant overlap in the volume of the influenced rock (group application). The conventional design approaches are based on instantaneous failure at the outer surface of an assumed inverted cone with an apex angle defined based on rock properties. This is contradictory to the results of field tests and a similar failure mechanism in cast-in-place headed anchors in concrete (concrete breakout). Therefore, understanding the quality of failure and the identification of contributing factors to the shape of failure requires further investigation. The aim of the present study is to investigate the spatiotemporal evolution of damage in pullout specimens under a monotonic load. This was realized through an experimental campaign on scaled-down concrete (rock-like) specimens. Acoustic Emission (AE) and Ultrasonic Active Monitoring (UAM) provided insight into crack initiation, propagation and damage evolution in concrete and their contributing factors. The results have shown that fracture propagation is dependent on the strength of the material and the interfaces (grout-concrete). Therefore, mixed failure mechanisms and asymmetric cones are likely to occur due to internal flaws and weaknesses along the interfaces. In the case of active monitoring, the quality of damage evolution was investigated by measuring the strength of similarity between reference and perturbed ultrasonic signal waveforms using correlation coefficients and Power Spectral Density (PSD). The trends of calculated correlation coefficients over the direct section of waveforms could be related to damage progress near the active ultrasonic wave path. A correlation coefficient less than 0.5 for coda was always recorded at the unstable crack growth stage. The results of this study indicated that this approach is efficient and provides sufficient sensitivity for applications in non-destructive evaluation of damage progress in pullout specimens. • Crack propagation is progressive, can be asymmetric, and its orientation depends on internal defects and weak interfaces. • Acoustic emission and ultrasonic active monitoring revealed the complex damage evolution of grouted anchors. • The ultrasonic active monitoring approach based on power spectral density showed potential in damage progress evaluation. [ABSTRACT FROM AUTHOR] more...

• The study investigates geo-grid reinforcement's effect on the mechanical properties of pre-holed concrete grout specimens. • Acoustic emission (AE) methods recorded deformation and fracture behaviors, linking mechanical responses to AE signals. • Results show that the size and arrangement of pre-existing holes significantly influence specimen strength and deformation. • Geo-grid reinforcement changed crack patterns and helped identify failure zones (tensile, shear, or mixed) post-failure. Uniaxial compression tests were performed both physically and using computer simulations (PFC). A study examined the impact of geo-grid reinforcement influences on the mechanical properties and failure behavior of pre-holed concrete grout specimens. These tests utilized concrete grout specimens with pre-existing holes, which were reinforced with horizontal geo-grid, and tested using a servo-hydraulic framework. The geogrid had a tensile strength of 14 MPa. During the experimental tests, the loading rate was set at 0.05 mm/sec, which was deemed too low to meet the static loading criteria. Acoustic emission (AE) methods were applied to monitor and analyze the deformation and fracture behaviors within these reinforced samples. Moreover, the integration of geogrid, does not, as it were, particularly increase the mechanical properties of the pre-drilled tests but moreover supports the structural integrity post-failure. The experimental results clearly illustrate that AE strategies effectively capture the movement of failure within the samples, there is a strong relationship between mechanical responses, strain distribution, and internal AE signals. The results showed that the arrangement and size of the holes significantly influenced the strength and deformation of the samples. Geogrid reinforcement substantially improved the mechanical properties and structural integrity, especially after failure. AE monitoring effectively captured the failure process. The presence of geogrid altered the crack patterns around the holes, affecting stress distribution. After failure, AE detection helps identify different types of failure zones around the holes: tensile, shear, or a combination. [ABSTRACT FROM AUTHOR] more...

• Evaluation of grouting effect combines the non-destructive testing and internal visualization methods. • Grout-soil specimens reveal the notable impact of surrounding soil on grout properties and morphology. • Consolidation process of grouting is divided into three stages by distinct morphological characteristics. Grouting technology is widely used to fill fissures in earthen sites. With numerous earthen sites undergoing restoration, evaluating the effectiveness of grouting in fissures has become an urgent issue. To understand the morphological characteristics of the grout and the mechanism of grouting defects, this study designed a laboratory grout–soil model tests, integrating field non-destructive evaluation methods such as P-wave velocity and infrared thermal imaging with laboratory testing methods and visual analysis. This paper explores the variations in mass, wave velocity, linear shrinkage rate, porosity, and other indexes of grout–soil specimens under different grouting conditions. The characteristics of grout morphology under two grouting modes were summarized, and the curing process of the grout was described in three stages. The experimental results indicate that the mass loss rate and linear shrinkage rate of the grout–soil specimens are significantly higher than those of grout-only specimens. The shrinkage rate of the grout is the primary factor influencing the compressive strength of the grout–soil specimens. Grouts with a high shrinkage rate result in the overall compressive strength of the grout–soil specimens approaching that of grout-only specimens. The porosity of specimens with 5 % and 10 % defect is closely related to the defect degree, but compared to the control group, it increased by approximately 22.6 % and 154.1 %, respectively. Reducing the dosage of CGN (calcined ginger nut, a restoration material) weakens the bonding capacity of the grout concretion, resulting in a decrease in wave velocity by approximately 3.0 % to 8.7 %. Filling site clods reduce the linear shrinkage rate of the specimen by approximately 6 % and increase the wave velocity by 11 % to 21 %, representing the primary method to improve grouting. [ABSTRACT FROM AUTHOR] more...

• Axial behavior of protective sheathed rock bolts was investigated. • Plastic sheath modifies the load transfer mechanism and performance of rock bolts. • Bond stress distribution along the encapsulation length was analyzed. • The failure pattern of protective sheathed rock bolts was examined. • Failure at the grout-sheath interface was found to be the primary failure mode. Understanding the axial load transfer mechanism of rock bolts under diverse conditions is essential for optimizing reinforcement in rock structures, advancing our comprehension of rock support, and facilitating the design of robust engineering solutions. This paper reports the outcomes of an extensive experimental investigation, focusing on the axial behavior of protective sheathed rock bolts employed in corrosive environments, assessed through pullout tests. Three distinct testing setups were designed to evaluate comprehensively the performance of these rock bolts in various scenarios. The results indicated that the failure characteristics and axial behaviors of sheathed rock bolts differ significantly from conventional counterparts. The findings revealed two primary failure modes in sheathed rock bolts: bolt rupture and slip at the grout-sheath interface, based on the testing arrangement and encapsulation length. The lack of adhesion and interlocking at the grout-sheath interface prevents shear stress at the bolt-grout interface from reaching its maximum potential strength, resulting in grout damage manifesting as circumferential cracks. This, in turn, initiates crack formation, reducing the system's bond strength. Additionally, it causes slip at the grout-sheath interface to occur at lower pullout loads. It can be inferred that the inner surface of the plastic sheath lacks the necessary structural integrity to withstand high loads, significantly impacting bond stress distribution and failure modes. The results demonstrate that the protective sheath remains intact up to an axial displacement of 28 mm, irrespective of the testing configuration. Additionally, it was observed that the maximum bond stress at the bolt-grout interface falls within the range of 6–8.7 MPa, which is below the shear strength of the grout. Consequently, achieving failure at the bolt-grout interface is not feasible. [ABSTRACT FROM AUTHOR] more...

• Microencapsulated PCM slurries in water, sand and bentonite backfills are evaluated. • Melting and crystallization behaviours vary with PCM concentration and backfill type. • Transition temperature variations reached 4.8 K for melting and 5.1 K for crystallization. • Sand and bentonite composites showed up to 6 and 7 times higher latent heat. • Sand composites achieved up to 3.5 times higher specific heat capacity. Residential and industrial heating and cooling systems are among the largest consumers of energy. To meet the growing energy demand in this sector, sustainable solutions are being increasingly adopted, with geothermal heat pump systems emerging as a popular choice. The main component of these systems is the ground heat exchanger that comprises a borehole, typically filled with grout, and tubing that carries a heat transfer fluid, transferring thermal energy between the ground and the heat pump. To enhance the thermal performance of the backfilling material, the addition of phase change materials has been presented as a promising solution. This study examines the addition of a microencapsulated organic phase change material slurry into three commonly used geothermal boreholes backfilling materials (water, sand, and bentonite) at various concentrations. The phase change characteristics, including heating–cooling curves from 2 to 10 K·min−1, were analysed by differential scanning calorimetry. Isobaric heat capacities within solid and liquid phases were also measured. Solid-liquid transition temperatures vary up to 4.8 K for melting and 5.1 K for crystallization of bentonite-based samples. Up to 7 times higher latent heat and up to 3.5 times higher isobaric heat capacity were noticed with increasing loading of microencapsulated phase change material. The designed materials show potential characteristics as backfilling materials for geothermal vertical boreholes, particularly those using bentonite and sand backfills. [ABSTRACT FROM AUTHOR] more...

The full scientific utilization of geothermal energy is an indispensable part of realizing the "double carbon" goal, based on its remarkable characteristics of energy saving and environmental protection. The study and utilization of medium-shallow geothermal energy (150–1500 m) has attracted increasing interest. Medium-shallow borehole heat exchanger (MSBHE) can meet the demand of both building cooling and heating, with a greater heat exchange capacity, a lower initial investment, and a greater capacity to withstand imbalance between heat extraction and rejection, which combines the advantages of both shallow borehole heat exchanger (SBHE) and medium-deep borehole heat exchanger (MDBHE). The paper focuses on single U-tube MSBHE. A quasi-three-dimensional heat transfer model of MSBHE is proposed, and then experiments are carried out to verify the rationality and correctness of the heat transfer model. Subsequently, calculations are carried out using the model to study heat extraction in winter and heat rejection in summer for the MSBHE. The variations in the inlet and outlet temperatures of the circulating fluid with operating time are also studied. Moreover, diagrams are presented to show the relationships between the nominal heat exchange capacity (NHEC) and key parameters, such as borehole depth, circulating fluid flow rate, space between the two branches of the U-tube, U-tube size, grout, geothermal heat flux and average annual atmospheric temperature, which are helpful in engineering practice. • The structural characteristics and the heat transfer mechanism of single U-tube middle-shallow borehole heat exchange were described. • A numerical modeling of single U-tube MSBHE was developed and verified by an experiment. • The effect of long-term operation on the geotechnical temperature and the influence of each factor on the heat transfer was studied. [ABSTRACT FROM AUTHOR] more...

• A new method for detecting curtain defects by fiber optic technology is presented. • Defect strain response characteristics were obtained by mechanical analysis. • A UWFBG monitoring system was established in the curtain of Zhuxianzhuang mine. • Curtain defects were successfully recognized and located. The detection of mine curtain grouting defects has become a focal point of attention due to concerns about the quality of the grouting. Detecting defects in curtains is a proactive and efficient approach to identifying potential hazards. However, traditional methods for curtain defect detection are either lagging in results or have detection blind spots. Recognizing the limitations of current monitoring technologies, this paper introduces a curtain defect identification method based on Ultra-weak Fiber Bragg Grating (UWFBG). The defects are classified into three types and the mechanical models are established separately, and then the UWFBG strain curve features caused by the defect deformation are obtained. A UWFBG sensing system is established in Zhuxianzhuang coal mine curtain project in Anhui, China, and the strain data of curtain are collected. The UWFBG technique successfully identified and located the defects and its accuracy is verified by water level monitoring results. These research findings hold considerable significance for the accurate repair of curtain defects. [ABSTRACT FROM AUTHOR] more...

In this study, the effect of grouting defects on the tensile behaviour of half-grouted sleeve connections under sub-zero temperatures was investigated. 26 groups of 78 half-grouted sleeve rebar connections were fabricated with different grouting defects under different curing temperature. The effect of grouting defects on the failure modes, load-bearing capacity, and deformation capacity of half-grouted sleeve connection was analyzed by unidirectional tensile test and numerical modelling. The results showed that the specimens failed due to rebar tension fracture and rebar pull-out attributed to bond failure. The degree of grouting defects significantly impacted the specimen bearing capacity and deformation capacity. With the increase in the length of the grouting defects, the bearing capacity and deformation capacity decreased, the bonding improved, the safety factor decreased, and the ultimate elongation did not meet the specification requirements. Horizontal defects had the most significant impact on the mechanical properties of the specimen. The bearing capacity, deformation capacity and bonding properties were reduced with the increase in the defect chord height, while the ultimate elongation could not meet the specification requirements. The increase in the water-to-cement ratio led to reduced compressive properties of the grout, significantly decreasing the bearing capacity of specimens. When the curing temperature was −15℃, the bearing capacity and deformation capacity decreased significantly. Through finite element analysis, the simulation results were found to be consistent with the experimental results, and the yield load and ultimate load errors were within 5 %. • Tensile behaviour of half-grouted sleeve connection with grouting defects at sub-zero temperature was studied experimentally. • Influence of different grouting defects on the properties of half-grouted sleeve connection was analyzed. • The finite element model was established, and the error between the simulation results and the experimental results was within 5 %. [ABSTRACT FROM AUTHOR] more...

The heterogeneous behaviour of masonry structures arises from the use of materials with different mechanical properties, namely blocks, mortar, grout, and reinforcement. This complexity makes predicting the behaviour of reinforced masonry (RM) challenging. While experimental studies in the literature have focused on the ultimate compression load and strain capacities of masonry prisms, there is still a lack of experimental data on the compressive, shear and tensile behaviours of concrete masonry prisms built with different configurations. A thorough understanding of the complete compressive, shear, and tensile stress-strain curves of fully grouted and ungrouted web and C-shaped boundary element assemblages is vital for assessing the response of reinforced masonry shear walls (RMSWs) under lateral forces. Therefore, this study investigates the mechanical properties of concrete masonry assemblages under axial compression, shear, and tension experimentally and numerically. Eighty-four concrete masonry prisms were constructed either from stretcher or C-shaped masonry units, and were tested under compression, shear or tension loading. The experimental results provide full stress-strain curves, revealing that ungrouted prisms exhibit higher peak compressive stress but lower shear and tensile strengths compared to their grouted counterparts. Stretcher ungrouted prisms showed a reduction of more than 50 % in shear strength compared to their grouted counterparts. Grouted boundary element prisms demonstrated higher tensile strength and fracture energy, with increases of 40 % and 10 %, respectively, compared to the stretcher grouted prisms. Lastly, a numerical investigation was conducted to validate detailed and simplified micro-models against the experimental results, which demonstrated that the numerical results are in good agreement with the experimental outputs of this study. • Masonry behavior varies due to different properties of its constituent materials. • Study investigates axial compression, shear, and tension on masonry assemblages. • Ungrouted prisms show higher peak compressive stress but lower shear/tensile strength. • Grouted boundary element prisms have 40 % higher tensile strength than stretcher prisms. • Numerical models validated with experiments show good agreement with results. [ABSTRACT FROM AUTHOR] more...

Reinforced concrete block masonry walls exhibit complex behaviour under lateral loading due to their composite nature and the interaction between their constituents, including units, mortar, grout, and reinforcement. The shear strength of reinforced masonry walls depends on various factors, including the properties of each constituent material, wall geometry, boundary conditions, and the presence of reinforcement with different configurations. International masonry design standards vary significantly in how they address the parameters influencing the shear capacity of reinforced masonry shear walls. Consequently, the predicted capacities show varying levels of conservatism when compared to experimental values. Given that masonry materials and construction practices are similar in the countries being compared, these discrepancies suggest differing interpretations of the significance of each parameter and possibly different philosophies regarding the balance between conservatism and accuracy in shear design. Therefore, this study investigated the influence of different reinforcement schemes on the shear strength of reinforced concrete block masonry (RM) assemblages with running bond. Forty-one concrete block masonry assemblages were tested under diagonal tension following the ASTM E519 to examine the effect of various parameters, namely, the presence of vertical or horizontal reinforcement, the vertical and horizontal reinforcement ratios, and the spacing and combination of vertical and horizontal reinforcement within the masonry assemblages. The behaviour of the masonry assemblages was evaluated based on the maximum shear stress and the corresponding shear strain, shear modulus, toughness, and pseudo-ductility. Furthermore, the effect of the studied parameters on the stress-strain curves, failure mechanisms, and crack propagation was assessed. The obtained maximum shear stresses of the tested concrete block masonry assemblages were compared with the nominal shear capacity calculated using codified equations of different design standards. The RM assemblages showed an enhancement in the shear behaviour, ductility, and distribution of cracks, especially when combining horizontal and vertical reinforcement. The results showed that adding vertical reinforcement improved the shear capacity of reinforced masonry assemblages by 21%, with an increase in the peak shear strain by 52%. Moreover, combining the vertical and horizontal reinforcement in the reinforced concrete block masonry assemblages increases the shear capacity by 15% with an enhancement in the maximum shear strain by 23%. The CSA S304–14, TMS 402/602–22, and NZS 4230 showed an underestimation of the actual shear capacity of masonry assemblages constructed in running bond and with vertical reinforcement by 177%, 138%, and 79%, respectively. Additionally, the results revealed the need for a re-evaluation of the above mentioned code equations that estimate the shear capacity for different configurations of concrete block masonry assemblages. The analyses aimed to provide insights into the effectiveness of different reinforcement configurations in enhancing the shear resistance of RM walls. The findings of this research contribute to the development of optimized design guidelines for reinforced masonry structures, thereby enhancing their overall seismic performance and safety. • Diagonal tension tested on concrete block masonry assemblages. • Effect of different reinforcement schemes on the shear strength of RM masonry. • Different failure mechanisms and crack patters were investigated. • Shear modulus, modulus of toughness and pseudo ductility were evaluated. • Combining vertical and horizontal reinforcements enhanced the mechanical properties. [ABSTRACT FROM AUTHOR] more...

The utilization of steel-fiber reinforced polymer (FRP) composite bars (SFCBs) reinforcement in precast concrete structures offers numerous benefits, including controllable post-yield stiffness and reduced residual displacement. Employing bundled reinforcement can improve construction efficiency. This study presents direct pull-out tests conducted on SFCBs embedded in grouted corrugated ducts. The results show that bond strength decreases with both the number of bars in a bundle (n b) and the actual embedded length (l a). The bond strength of single bar SF-1b-3d with 3 d embedded length is 24.21 MPa, while that of 2-bar bundled SF-2b-3d and 3-bar bundled SF-3b-3d is 17.41 MPa and 12.61 MPa, respectively. Additionally, the error in predicting the bond strength between bundled SFCBs and grouted corrugated duct using the equivalent diameter method is found to be less than 8.4%. Utilizing the mBPE constitutive model, an analytical hardening-slip model with a linear slip field assumption accurately predicts the full-range behavior, bond stress distribution, and SFCB's axial stress distribution. Furthermore, the effects of different parameters on yield slip s y , ultimate slip s u , and critical anchorage length L tr are investigated by considering different local bond-slip constitutive models (varying peak bond strength τ m and its corresponding slip s m and ascending section coefficient (α) as variables. The yield slip s y varies from 0.1 mm to 1.3 mm, while the ultimate slip s u can reach a maximum of 35.0 mm. Furthermore, the validity of existing models for evaluating the anchorage length of single SFCB and bundled SFCBs grouted in corrugated duct connections is discussed, and a formula to estimate the critical anchorage length of bundled SFCBs and grout considering the number of bars within one bundle (n b) is proposed. • Direct pull-out tests were conducted on the steel-FRP composite bars (SFCBs) embedded in grouted corrugated ducts. • The error in predicting the bond strength between bundled SFCBs and grouted corrugated ducts using the equivalent diameter method is less than 8.4 %. • An analytical hardening-slip model with a linear slip field assumption accurately predicts the full-range behavior. • The effects of different parameters on yield slip s y , ultimate slip s u , and critical anchorage length L tr are investigated. [ABSTRACT FROM AUTHOR] more...