Search Results (94)

As a key connection technology in prefabricated buildings, offshore wind power, and bridge engineering, the performance and environmental sustainability of grouted sleeve connections are essential for the long-term development of civil infrastructure. To address the environmental burden of conventional high-strength cement-based grouts, an eco-friendly sleeve grouting material incorporating industrial solid waste was developed. In this study, silica fume (15%) and fly ash (5%) were employed as supplementary cementitious materials, while nanosilica (NS) was introduced to enhance the material properties. Mechanical testing, microstructural characterization, and half-grouted sleeve uniaxial tensile tests were conducted to systematically evaluate the effect of NS content on grout performance. Results indicate that the incorporation of NS significantly accelerates the hydration of silica fume and fly ash. At an optimal dosage of 0.4%, the 28-day compressive strength reached 105.5 MPa, representing a 37.9% increase compared with the control group without NS. In sleeve tensile tests, specimens with NS exhibited reinforcement necking failure, and the load–displacement response closely aligned with the stress–strain behavior of the reinforcement. A linear relationship was observed between sleeve wall strain and reinforcement stress, confirming the cooperative load-bearing behavior between the grout and the sleeve. These findings provide theoretical guidance and technical support for developing high-strength, low-impact grouting materials suitable for sustainable engineering applications. Full article

Polyurethane grouting materials are polymer materials formed through the reaction of polyisocyanates and polyols. They play important roles in underground engineering, tunnel construction, and mining due to their fast reaction rate, high bonding strength, and excellent impermeability. However, traditional polyurethane grouting materials have shortcomings such as high reaction heat release, high brittleness, and poor flame retardancy, which limit their applications in high-demand engineering projects. This paper systematically reviews the research progress on modified polyurethane grouting materials. Four major modification technologies are summarized: temperature reduction modification, flame retardant modification, mechanical enhancement, and environmental adaptability improvement. A multi-dimensional performance characterization system is established, covering slurry properties, solidified body performance, microstructure characteristics, thermal properties and flame retardancy, diffusion grouting performance, and environmental adaptability. The application effects of modified polyurethane grouting materials in grouting reinforcement, grouting water plugging, and grouting lifting are analyzed. Future development directions are projected. This review is particularly valuable for researchers and engineers working in tunneling, mining, geotechnical engineering, and infrastructure rehabilitation. Full article

Coral sand grouting materials can effectively meet the new development requirements of remote island and reef engineering projects, demonstrating significant application value. However, its early-age shrinkage deformation may compromise structural stability. To effectively regulate this early shrinkage behavior, this study investigated the influence of varying dosages of early strength agent (ES), plastic expansive agent (PEA), and post-hardening expansive agent (HP-CSA) on the complete vertical expansion rate curve of coral sand grouting materials during 0–48 h, while comparatively examining the combined effects of composite expansive agents on early autogenous shrinkage and drying shrinkage characteristics. The results show that during 0–48 h, ES and composite expansive agents can precisely control the activation window of PEA, enabling controllable development of ultra-early vertical expansion in the grouting material, with increased HP-CSA dosage accelerating the progression of the complete vertical expansion rate curve. From 2 to 28 days, the coral sand grouting materials exhibit continuous shrinkage development. An appropriate combination of PEA and HP-CSA effectively synergizes to regulate shrinkage deformation. The drying shrinkage significantly correlates with the water loss rate. Within the scope of this study, when the dosages of ES, PEA, and HP-CSA are 1%, 0.06%, and 4%, respectively, the performance of coral sand grouting materials is relatively good. Full article

Grouting is an effective method for enhancing the stability of poor strata such as sand layers. The performance of the grouting materials directly influences the effect of stratum reinforcement. To meet the urgent demand for efficient grouting materials, this study selected a high-permeability, flexible polymer (PFP) as the grouting material. The influences of the PFP content, curing time, and dry density on the mechanical and impermeable properties of PFP-improved sand were systematically analyzed via unconfined compressive tests, split tensile tests, and variable head permeability tests. Moreover, the section morphology and pore characteristics of the PFP-improved sand were qualitatively described and quantitatively analyzed by scanning electron microscopy (SEM) and image processing software. The results indicated that the mechanical properties and impermeability of the test sand were significantly improved by adding the PFP, and the improvement effect continued to increase with increasing PFP content, curing time, and dry density. The compressive strength and splitting tensile strength of PFP30 (PFP content of 30%, curing time of 28 d, dry density of 1.5 g/cm³) reached 8.3 MPa and 1.4 MPa, respectively. The permeability coefficient reduced to 5.41 × 10⁻⁶ cm/s. The microscopic results revealed that the PFP effectively cemented the isolated sand particles through bridging, filling, and encapsulation as well as substantially filled the internal pores of the test sand. The percentage of the pore area, the total number of pores, and the maximum pore diameter of the test sand were significantly reduced. The pore area percentage, the total number of pores, and the maximum pore diameter of PFP30 were reduced to 0.124, 30, and 213.84 μm, respectively. This study reveals that PFP has potential for application in the grouting construction of poor strata, such as sand layers. Full article

Cracking in semi-rigid cement-stabilized macadam bases constitutes a prevalent distress in asphalt pavements. While extensive research exists on grouting materials for crack rehabilitation, quantitative assessment methodologies for treatment efficacy remain underdeveloped. This study proposes a novel evaluation framework integrating fiber Bragg grating (FBG) technology to monitor pavement mechanical responses under traffic loads. Conducted on the South China Expressway project, the methodology encompassed (1) a method for back-calculating the modulus of the asphalt layer based on Hooke’s Law; (2) a sensor layout plan with FBG sensors buried at the top of the pavement base in seven sections; (3) statistical analysis of the asphalt modulus based on the mechanical response when a large number of vehicles passed; and (4) comparative analysis of modulus variations to establish quantitative performance metrics. The results demonstrate that high-strength geopolymer materials significantly enhanced the elastic modulus of the asphalt concrete layer, achieving 34% improvement without a waterproofing agent versus 19% with a waterproofing agent. Polymer-treated sections exhibited a mean elastic modulus of 676.15 MPa, substantially exceeding untreated pavement performance. Low-strength geopolymers showed marginal improvements. The modulus hierarchy was as follows: high-strength geopolymer (without waterproofing agent) > polymer > high-strength geopolymer (with waterproofing agent) > low-strength geopolymer (without waterproofing agent) > low-strength geopolymer (with waterproofing agent) > intact pavement > untreated pavement. These findings demonstrate that a high-strength geopolymer without a waterproofing agent and high-polymer materials constitute optimal grouting materials for this project. The developed methodology provides critical insights for grout material selection, construction process optimization, and post-treatment maintenance strategies, advancing quality control protocols in pavement rehabilitation engineering. Full article

To investigate the anchorage performance of an innovative assembled joint with large-diameter steel bar grout lapping in a concrete reserved hole, the effects of anchorage length and high-strength grouting material types on the failure mode, load–displacement curve, ultimate bond strength and strain variation were analyzed through the pull-out tests of 15 specimens. On this basis, the calculation formulae of critical and ultimate anchorage length were established and the applicability was verified, and then the recommended value of minimum anchorage length was provided. The results showed that the failure modes included splitting-steel bar pull-out failure and UHPC-concrete interface failure. With the increase in anchorage length, the bond strength showed a trend of increasing first and then decreasing. Increasing the grouting material strength can effectively improve the bond performance. When the anchored steel bar is HRB400 with a diameter not less than 20 mm, the recommended minimum anchorage length is 15.0d~18.3d. When the grouting material strength is larger than or equal to 100 MPa, the anchorage length should not be less than 15.0d. Full article

The mechanical properties of grouting materials and their cured grouts significantly impact the reinforcement effectiveness in deep coal mine roadways. This study employed shear rheology tests of slurry, structural tests, NMR (nuclear magnetic resonance), and uniaxial compression tests to comparatively analyze the mechanical characteristics of a composite cement-based grouting material (HGC), ordinary Portland cement (OPC), and sulfated aluminum cement (SAC) slurry and their cured grouts. The HGC (High-performance Grouting Composite) slurry is formulated with 15.75% sulfated aluminum cement (SAC), 54.25% ordinary Portland cement (OPC), 10% fly ash, and 20% mineral powder, achieving a water/cement ratio of 0.26. The results indicate that HGC slurry more closely follows power-law flow characteristics, while OPC and SAC slurries fit better with the Bingham model. The structural recovery time for HGC slurry after high-strain disturbances is 52 s, significantly lower than the 312 s for OPC and 121 s for SAC, indicating that HGC can quickly produce hydration products that re-bond the flocculated structure. NMR T2 spectra show that HGC cured grouts have the lowest porosity, predominantly featuring inter-nanopores, whereas OPC and SAC have more super-nanopores. Uniaxial compression tests show that the uniaxial compressive strength of HGC, SAC, and OPC samples at various curing ages gradually decreases. Compared to traditional cementitious materials, HGC exhibits a rapid increase in uniaxial compressive strength within the first seven days, with an increase rate of approximately 77.97%. Finally, the relationship between micropore distribution and strength is analyzed, and the micro-mechanisms underlying the strength differences of different grouting materials are discussed. This study aids in developing a comparative analysis system of mechanical properties for deep surrounding rock grouting materials, providing a reference for selecting grouting materials for various engineering fractured rock masses. Full article

The monolithic composite action of structures relies on the interface bond strength between concrete and the repair material. This study uses explainable deep learning techniques to evaluate the ultimate strength capacity (Us) of U-shaped normal concrete (NC) strengthened with polyurethane grouting (PUG) materials. Machine learning algorithms (ML) such as Long Short-Term Memory (LSTM), Random Forest (RF), and Wide Neural Network (WNN) models were developed to estimate Us by considering five input parameters: the initial crack strength (Cs), thickness of the grouting materials (T), mid-span deflection (λ), and peak applied load (P). The results indicated that LSTM models, particularly LSTM-M2 and LSTM-M3, demonstrated superior predictive accuracy and consistency in both the calibration and verification phases, as evidenced by high Pearson’s correlation coefficients (PCC = 0.9156 for LSTM-M2) and Willmott indices (WI = 0.7713 for LSTM-M2), and low error metrics (MSE = 0.0017, RMSE = 0.0418). The SHAP (SHapley Additive exPlanations) analysis showed that the thickness of the grouting materials and maximum load were the most significant parameters affecting the ultimate capacity of the composite U-shaped specimen. The RF model showed moderate improvements, with RF-M3 performing better than RF-M1 and RF-M2. The WNN models displayed varied performance, with WNN-M2 performing poorly due to significant scatter and deviation. The findings highlight the potential of LSTM models for the accurate and reliable prediction of the ultimate strength of composite U-shaped specimens. Full article

Interface debonding between high-strength grouting materials and the inner surfaces of steel tubes in grouting jacket connections (GJCs), which have been widely employed in offshore wind turbine support structures, negatively affects their mechanical behavior. In this study, an interface debonding defect detection and localization approach for scaled underwater GJC specimens using surface wave measurements with piezoelectric lead zirconate titanate (PZT) actuation and sensing technology was validated experimentally. Firstly, GJC specimens with artificially mimicked interface debonding defects of varying dimensions were designed and fabricated in the lab, and the specimens were immersed in water to replicate the actual underwater working environment of GJCs in offshore wind turbine structures. Secondly, to verify the feasibility of the proposed interface debonding detection approach using surface wave measurements, the influence of the height and circumferential dimension of the debonding defects on the output voltage signal of PZT sensors was systematically studied experimentally using a one pitch and one catch (OPOC) configuration. Thirdly, a one pitch and multiple catch (OPMC) configuration was further employed to localize and visualize the debonding defect regions. An abnormal value analysis was carried out on the amplitude of the output voltage signals from PZT sensors with identical wave traveling paths, and the corresponding abnormal surface wave propagation paths were identified. Finally, based on the influence of interface debonding on the surface wave measurements mentioned above, the mimicked interface debonding defect was detected successfully and the region of debonding was determined with the intersection of the identified abnormal wave travelling paths. The results showed that the mimicked debonding defect can be visualized. The feasibility of this method for interface debonding defect detection in underwater GJCs was confirmed experimentally. The proposed approach provides a novel non-destructive debonding defect detection approach for the GJCs in offshore wind turbine structures. Full article

As one type of critical load-bearing element in precast concrete structures, grouted sleeve (GS) connections enable efficient force transmission between reinforcing bars while maintaining structural integrity. Despite their growing global adoption, significant variations exist in design philosophies, construction specifications, and performance requirements among regional standards. Through bibliometric analysis, the most active countries and regions in GS application and research worldwide were identified, and the relevant technical standards established by these countries and regions were systematically reviewed. By comparing standards from Asia, the Americas, Europe, and Oceania, the main differences in design philosophy, construction quality control, material specifications, and performance requirements among these standards were analyzed and identified. The results show that different standards have a conceptual difference at the materials and quality control level, with one approach focusing on stricter management of sleeve materials and more detailed on-site construction requirements, and another approach emphasizing testing-based methods and third-party verification. These standards can be divided into the following two categories for the design limits of GS tensile performance: one category takes multiples of the yield strength of the connected reinforcing bars as the limit, and the other category takes multiples of the tensile strength of the connected reinforcing bars as the limit. Regarding mechanical performance requirements, standards using the ultimate tensile strength of the connected reinforcing bars as the control parameter differ from those using multiples of yield strength in their performance requirements for connections of low-strength and high-strength reinforcing bars. The variation in yield-to-tensile strength ratios among steel grades across different countries is a key factor leading to these different requirements. When using the uniform steel bar material properties specified in the standard for quantification, as the bar strength increases from approximately 240 MPa to 600 MPa, the minimum required ratio of the limits for standards based on multiples of yield strength and multiples of tensile strength increases from 0.79 to 1.07. When applying GS connections to reinforcing bars of varying strength levels, using fixed strength multiplier requirements may result in uneconomical designs or create technical challenges in achieving the required strength. Full article

The application and promotion of grouted sleeve connectors in prefabricated structures are closely related to their high efficiency and intensive advantages. Numerous scholars have conducted experimental studies on the performance of sleeves, but there has been no systematic consolidation of these efforts. In this study, the latest developments in grouted sleeve connection technology are systematically reviewed and analysed, focusing on its applications and characteristics, performance testing, influencing factors, load-transfer mechanisms, and performance evaluation. First, the differences in sleeve code formulation across various countries are compared, the advantages and disadvantages of different sleeve types and grouting techniques are reviewed, and the application scenarios of sleeves are summarized. Second, an overview of the performance of grouted sleeves in tensile, fatigue, and seismic tests is provided, highlighting key factors affecting structural performance and experimental results. Furthermore, the effects of various factors (the anchorage length, diameter and strength of reinforcing bars; types and defects of grout materials; sleeve tube design; and temperature) on the performance of sleeves are investigated, and some beneficial conclusions are drawn. The load-transfer mechanisms of different sleeve types are subsequently compared, and the common features of the sleeves that meet the performance evaluation criteria are analysed. Finally, potential future research directions and innovations in sleeve technology are suggested to provide researchers and scholars with innovative ideas and research perspectives for developing new sleeves and advancing the application of grouted sleeve connectors. Full article

Deep grouting rock engineering is faced with the dual influence of high temperature and dynamic load, which has become a hot issue in geotechnical engineering. This study analyzes the mechanical responses and failure properties of deep-grouted fractured rock under real-time coupling of temperature and dynamic loads through the high-temperature-split Hopkinson pressure bar (HT-SHPB), high-speed imaging, and scanning electron microscopy (SEM) tests. Key findings reveal that (1) the dynamic compressive strength of grouted fractured rock exhibits significant temperature dependency, where the strength increases with the increase of temperature, which has been verified by relevant references. From indoor temperature to 100 °C, the dynamic strength increases moderately, while a pronounced increase is observed between 100 °C and 300 °C. (2) In contrast, the dynamic peak strain demonstrates a two-stage evolution, which sharply rises from indoor temperature to 100 °C, followed by a slowly rise from 100 °C to 300 °C. (3) Macroscopically, impact fractures preferentially initiate as parallel lines at the extremities of pre-existing grouted fractures, consistent with stress concentration patterns under dynamic loading. Microscopic analysis reveals that grouting materials effectively suppress micro-crack generation and propagation at 300 °C, attributed to thermally enhanced cementation and pore-filling effects, explaining the variation of the macroscopic dynamic strength with temperature from the microscopic point of view. Full article

This study investigates the mechanical behavior of fractured sandstone under various factors, including freeze–thaw cycles, fracture dip angle, roughness, grouting material, and confining pressure. Freeze–thaw and triaxial compression tests were conducted to analyze the effects of individual factors and their interactions on the mechanical properties of sandstone. The results indicate the following: (1) Under independent factor conditions, freeze–thaw cycles generate frost heave forces through the water–ice phase transition, leading to the expansion of microcracks and deterioration of the pore structure, which results in a weakening effect. Grouting material enhances the bonding strength and supporting capacity of the rock sample, roughness improves the anchoring effect of the grout, fracture dip angle improves stress transmission efficiency, and confining pressure increases rock sample density and restricts deformation, all of which exhibit strengthening effects. (2) Interaction analysis revealed three types of interaction mechanisms for the peak stress and elastic modulus of the rock samples: interaction enhancement mechanism, where peak stress or elastic modulus significantly increases when the related factors are at high levels, demonstrating a synergistic strengthening effect; interaction inhibition mechanism, where factors at high levels suppress each other’s strengthening or weakening effects; and interaction reversal mechanism, where the influence trend of certain factors reverses under different conditions. Specifically, the interaction enhancement mechanism for peak stress is observed in the interactions between grouting material and roughness, grouting material and confining pressure, and fracture dip angle and roughness. The interaction inhibition mechanism occurs between grouting material and freeze–thaw cycles and confining pressure and freeze–thaw cycles. For elastic modulus, the interaction enhancement mechanism is observed in the interactions between fracture dip angle and confining pressure, grouting material and roughness, and confining pressure and roughness; the interaction reversal mechanism appears in the interaction between freeze–thaw cycles and fracture dip angle. Full article

Traditional acrylate grouting materials often suffer from mechanical performance degradation and interfacial bonding failure under long-term water immersion, significantly limiting their application in pressurized water environments. This study proposes a composite crosslinking synergistic strategy to address these challenges. By constructing a dual-network structure through polyethylene glycol diacrylate (PEG500DA) and a monofunctional crosslinker (PEG-MA), and systematically optimizing the material formulation by regulating the triethanolamine content to control gelation time, the mechanical and hydraulic stability of the material was significantly enhanced. Increasing the acrylate concentration to 35% achieved an optimal balance between a slurry viscosity (8.3 mPa·s) and mechanical performance, with tensile strength reaching 76 kPa and the compressive strength of the sand-solidified body measuring 440 kPa. At a PEG500DA/PEG-MA ratio of 2:3, the material exhibited both high tensile strength (78 kPa) and exceptional ductility (elongation at break > 407%), with a compressive strength of 336 kPa for the sand-solidified body. When the total crosslinker content exceeded 5%, the 28-day water absorption and volume expansion rates were effectively reduced to 12% and 11%, respectively. Under simulated pressurized water conditions, the modified material demonstrated a water-pressure resistance of 300 kPa after 1 day, stabilizing at 350 kPa after 56 days—a 75% improvement over commercial products. This study provides an innovative solution for long-term anti-seepage applications in complex hydrogeological environments, offering significant advancements in material design and engineering reliability. Full article

With the increasing number of anti-seepage reinforcement projects and the continuous improvement of quality requirements, high-performance and green requirements have also been put forward for grouting materials. Traditional karst cave grouting mainly uses cement-based grouting materials, which not only have high carbon emissions but also do not comply with the sustainable development strategy with regard to being green, low-carbon, and environmentally friendly. A green grouting material made by mixing a slurry A and slurry B is proposed in this paper. The solid phase of slurry A is composed of stone powder and bentonite, for which an anti-washout admixture is necessary. Slurry B is a suspension of thickener (CMC or HPMC) and anhydrous ethanol. By mixing the two slurries evenly, the grouting material is obtained. Experiments were used to investigate the ideal ratios of stone powder, bentonite, and water in slurry A, and the ratio of thickener to anhydrous ethanol in slurry B, and to analyze the development and evolution of the apparent viscosity of slurry A and slurry B after mixing. This study revealed that the optimum ratio of stone powder and bentonite was 4:1, and the most reasonable water–solid ratio was 0.8:1.0. The optimum ratio of anhydrous ethanol to CMC or HPMC in slurry B was 5:1. Slurry B was added to slurry A at a rate of 5~10% to obtain the best grouting material properties. The proposed mixed grouting material would not disperse even in flowing water and could harden and consolidate quickly. The strength of the consolidation grouting body was close to that of wet soil, which can meet requirements for tunnel construction. Full article