Strength Of Grout Research Articles

Manuscript title: Experimental investigations of concrete-filled double skin steel tube column-column grouted connection under axial compression

This paper presents a novel grouted connection joint for prefabricated CFDST columns. In order to ascertain the reliability of this grouted connection, axial compression tests were conducted on 24 CFDST columns with grouted connections and 3 CFDST columns without grouted connections. The test parameters were grout strength, casing tube length, and length-to-diameter ratio. The results showed that the stub columns failed due to local buckling and the slender columns failed due to global buckling with significant lateral flexural deformation. CFDST columns with grouted connections exhibited a similar or even higher ultimate bearing capacity and much higher later bearing capacity than conventional CFDST columns. The ultimate bearing capacity of CFDST columns with grouted connections is influenced by the casing tube length and the length-to-diameter ratio. The increase in casing tube length leads to an increase in bearing capacity, while an increase in length-to-diameter ratio results in a decrease. Enhancing the grout strength does not significantly improve the ultimate bearing capacity. Furthermore, the effects of each test parameter on the stiffness, strength and ductility of the CFDST column-column grouted connections were evaluated. Finally, by considering the interaction between components and the impact of casing tube length on bearing capacity, a prediction equation for the ultimate bearing capacity of CFDST column-column grouting connections was developed. This equation can offer accurate predictions with an average error of less than 1% to provide a reference for the joint design.

Seismic Behavior of Concrete Beam-Column Joints Reinforced with Steel-Jacketed Grouting

Joints in frame structures often fail before beams and columns in an earthquake and are a key part of reinforcement. In this study, to enhance the seismic performance of concrete frame structures, a steel-jacketed grouting composite reinforcement method is proposed by combining reinforcement technology, steel cladding technology, and eco-efficient materials from grouting technology. This method effectively utilizes the advantages of various materials, avoids major demolition and construction, and reduces waste and resource consumption. In order to verify the feasibility and effectiveness of the reinforcement method, one of the original joint specimens with a scale of 1:3 and one of the reinforced joint specimens were designed and tested. The experiments involved reversed cyclic testing of beam–column to measure its seismic behavior. The seismic performance indexes such as failure characteristics, hysteretic properties, and the energy dissipation capacity of the specimens were analyzed, and the corresponding finite element model was established. The influence of key parameters such as reinforcement range, steel plate thickness, and grout strength on its seismic performance was explored. The research shows that the method can effectively improve the seismic performance of the joints, and seismic performance indexes such as bearing capacity, ductility, and energy consumption of the specimens are significantly improved. The test results of the established finite element model are in good agreement. The variable parameter analysis of the finite element shows that the thickness of the steel plate has little influence on its bearing capacity. With the increase in the reinforcement range of the clad steel and the strength of the grouting material, the bearing capacity of the specimen increases. The research results can provide a reference for the reinforcement of frame structure joints.

Mechanical Properties of Iron Tailing Sand Grout Sleeve Joints and Force Analysis.

In this paper, the mechanical properties and internal stress condition of the reinforcing bar sleeve connectors with ferro-tailed mineral sand cementitious grout as filler material were analyzed as research objects. Firstly, an experimental study was carried out on the reinforcing bar sleeve connectors of iron tailing sand grout with a 40% substitution rate of mechanism sand to analyze the mechanical properties of different grout types, age, and reinforcement diameters under unidirectional tensile, high stress, and large deformation of repeated tensile and compressive stresses. Next, five groups of sleeve joints with different anchorage lengths were set up for unidirectional tensile tests. The results show that, with the decrease of the diameter of the reinforcement, the grip force and bond strength of the iron tailing sand grout on the internal reinforcement gradually increase. Under conditions of large deformation and high stress due to repeated tensile loading, the residual deformation and total elongation of iron tailing sand grout sleeve joints are satisfactory. Additionally, the restraining anchorage effect of iron tailing sand grout in the end section is small. The utilization rate and integrity of iron tailing sand grout in the initial anchorage section are better.

Study on the working performance and microscopic mechanism of high-performance grouting material (HPGM) reinforced dense fine sand layer

To address the challenges of small diffusion radius, low early strength and long setting time of traditional cement grout in dense fine sand layer, based on the synergistic mechanism, a novel high-performance grouting material (HPGM) was developed using ground granulated blast-furnace slag (GGBS), ultra-fine fly ash (UFFA), and ultra-fine Portland cement (UFPC) as raw materials. Firstly, Laboratory experiments were conducted to investigate the working performance of HPGM under varying proportions. Secondly, based on the self-designed advanced small pipe grouting full-scale test device, the diffusion performance and reinforcement characteristics of HPGM under varying proportions were analyzed. Finally, the XRD and SEM testing methods were employed to elucidated the hydration mechanism of the HPGM. The test results indicate that as the mass ratio of GGBS to UFFA decreases, there is a gradual increase in hardening rate, fluidity and setting time of HPGM. Additionally, the unconfined compressive strength (UCS) initially increase before decreasing. Furthermore, with the decreased mass ratio of GGBS to UFFA, the HPGM diffused in dense fine sand layer through compaction-splitting, permeation-splitting, and splitting grouting processes. The hydration products of the HPGM primarily consist of C(-A)-S-H, AFt, and Ca(OH)2, when the mass ratio of GGBS to UFFA falls within the range of 4:2–3:3, the UFFA facilitates the AFt hydration products in significant quantities. Its cementation and filling effect lead to the formation of a dense microstructure in the soil, resulting in a substantial reduction in permeability coefficient and a marked increase in UCS. The research findings can offer high-performance grouting material for underground engineering construction while also presenting innovative ideas for resource utilization from solid wastes like GGBS and UFFA.

Effects of Polymer-Curing Agent Ratio on Rheological, Mechanical Properties and Chemical Characterization of Epoxy-Modified Cement Composite Grouting Materials.

This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA and analyze the modification mechanism by means of chemical characterization to explore the feasibility of WBER as a high-performance modifier for tunnel construction. The composite grouting is prepared by mixing cement paste with polymer emulsion. A series of experiments was carried out to investigate the effects of WBER and CA, including the slump test, viscosity, rheological curve, setting time, bleeding rate, grain size distribution, zeta potential, compressive and splitting tensile strength, X-ray diffraction(XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), on the composite grout. The results show that WBER improves grout fluidity, which decreases in combination with CA, while also reducing the average particle size of the composite grout for a more rational size distribution. Optimal uniaxial (38.9%) and splitting tensile strength (48.7%) of the grout are achieved with a WBER to CA mass ratio of 2:1. WBER accelerates cement hydration, with the modification centered on the reaction between free Ca2+ and polymer-OH, significantly enhancing the strength, fluidity, and stability of the polymer-modified composite grout compared to traditional cement-based grouting.

Robust prediction models for flow and compressive strength of sustainable cement grouts for grouted macadam pavement using RSM

This study investigates the utilization of pumice stone ash in cementitious grouts for grouted macadam pavement, aiming to enhance flowability and compressive strength. Partial replacement of ordinary Portland cement (OPC) with varying percentages (5–20 %) of powdered pumice stone (PPS) ash was explored, alongside adjustments in water-to-cement (w/c) ratios. Experimental assessments, including flowability tests and compressive strength evaluations, were conducted on fresh and hardened grouts. Response surface methodology (RSM) and ANOVA analysis were employed to analyze the relationship between pumice stone ash content, w/c ratio, flow, and compressive strength. The results show that increasing the PPS content from 0 % to 20 % led to an increase in flow time from 23.6 to 34 seconds at a 0.3 w/c ratio, from 9 to 19 seconds at a 0.35 w/c ratio, and from 7 to 14 seconds at a 0.40 w/c ratio: indicating reduced flowability of the grouts. The 7-day compressive strength increased by approximately 2–17 % when 5–15 % of the cement was replaced with PPS, but a reduction occurred at 20 % PPS. Similarly, the 28-day compressive strength increased by about 4–23 % with 5–15 % PPS, while 20 % PPS led to a decrease in strength. The results highlight specific combinations of pumice stone ash content and w/c ratios, particularly 10 % PPS at 0.35 w/c and 15 % PPS at both 0.35 and 0.40 w/c, that meet grouted macadam standards, balancing flowability and strength. Fit statistics demonstrate the reliability of the predictive model. Optimization aims to maximize pumice stone ash content and w/c ratio, with graphical representation indicating an optimal composition at 17.25 % PPS and 0.35 w/c ratio for efficient grouted macadam construction. Additionally, Significant contribution towards sustainability can be achieved by replacing cement with pumice stone ash in pavement construction.

Revamp of the eco-friendly grouting materials by mixing basalt fiber for earthen sites conservation: Compressive performance and constitutive models

Reinforcement techniques, including anchorage and sealing with grout, are frequently employed to protect earthen sites and minimize the impact of fissures, the effectiveness of these approaches relies heavily on the mechanical properties of grout. To enhance the strength and ductility of the conventional grout, an eco-friendly composite grouting material mixture basalt fibers of varying lengths and contents is prepared. The DIC-based UCS tests were conducted to evaluate its compressive performance. Constitutive models of the basalt fiber-reinforced grout, including elastic perfectly-plastic (EPP) and median nonlinear (MNL) constitutive models, were established respectively based on the equal energy rule and cross-sectional data analysis for simplification application and precision evaluation purposes. The results show that the mixture of basalt fibers resulted in a distinct semi-brittle failure mode for the grout, with a significant increase in its compressive strength, ductility, compressive fracture energy, and residual bearing capacity. However, the elastic modulus will be lower when the fibers are relatively longer. Considering the differences in the relations between performance parameters and fiber content, and length, the highest compressive strength was reached at the fiber length of 6 mm and the content of 0.2 wt%, while maximum ductility was achieved at 18 mm and 0.4 wt%. The fracture energy exhibits an approximate positive correlation with fiber content. In addition, the EPP and MNL constitutive models can effectively characterize the compressive mechanical behavior of semi-brittle materials to satisfy different requirements on the precision of engineering analysis. This study contributes valuable insights into the development of high-ductility grouting materials of earthen sites, and the establishment of constitutive models for semi-brittle materials.

Performance and Microstructure of Grouting Materials Made from Shield Muck.

In response to the environmental pollution caused by transportation and accumulation of large-scale shield muck, the on-site reutilization of shield muck is an effective approach. This study explored the feasibility of silty clay muck to prepare muck grout. Through orthogonal experiments, the effects of cement, fly ash, shield muck, admixture, and the water-solid ratio on the fresh properties and mechanical properties of muck grout were studied. The performance prediction model was established Additionally, the intrinsic relationships between the compressive strength and microstructure of shield muck grouting materials were explored through multi-technology microstructural characterization. The results indicate that the content of muck and the water-solid ratio have a greater significant influence on the bleeding ratio, flowability, setting time, and volume shrinkage rate of muck grout compared to other factors. Cement has a greater significant influence on the compressive strength of muck grout than other factors. An optimal mix proportion (12% for cement, 18% for fly ash, 50% for muck, 0.465 for water-solid ratio, 19.5% for river sand, and 0.5% for bentonite) can produce grouting materials that meet performance requirements. The filling effect of cementitious substances and the particle agglomeration effect reduce the internal pores of grouting materials, improving their internal structure and significantly enhancing their compressive strength. Utilizing shield muck as a raw material for shield synchronous grouting is feasible.

Predicting grout’s uniaxial compressive strength (UCS) for fully grouted rock bolting system by applying ensemble machine learning techniques

This study proposes a novel system for accurately predicting grout’s uniaxial compressive strength (UCS) in fully grouted rock bolting systems. To achieve this, a database comprising 73 UCS values with varying water-to-grout (W/G) ratios ranging from 22 to 42%, curing times from 1 to 28 days, the admixture of fly ash contents ranging from 0 to 30%, and two Australian commercial grouts, Stratabinder HS, and BU-100, was built after conducting comprehensive series of experimental tests. After building the dataset, a metaheuristic technique, the jellyfish search (JS) algorithm was employed to determine the weight of base models in the ensemble system. This system combined various data and modelling techniques to enhance the accuracy of the UCS predictions. What sets this technique apart is the comprehensive database and the innovative use of the JS algorithm to create a weighted averaging ensemble model, going beyond traditional methods for predicting grout strength. The proposed ensemble model was called the weighted averaging ensemble model (WAE-JS), in which the obtained results of several soft computing models such as multi-layer perceptron (MLP), Bayesian regularized (BR) neural networks, generalized feed-forward (GFF) neural networks, classification and regression tree (CART), and random forest (RF) were weighted based on JS and the new results were then generated. Eventually, the result of WAE-JS was compared to other models, including MLP, BR, GFF, CART, and RF, based on some statistical parameters, such as R-squared coefficients, RMSE, and VAF as indices for evaluating the performance and capability of the proposed model. The results suggested the superiority of the ensemble WAE-JS system over the base models. In addition, the proposed WAE-JS model effectively improved the predicting accuracy achieved from the MLP, BR, GFF, CART, and RF. Furthermore, the sensitivity analysis revealed that the W/G had the most significant impact on the grout’s UCS values.

Optimization of pre-grouting construction and evaluation of grouting effect in a deeply buried silt-filled shield tunnel

Controlling strata deformation during shield tunneling beneath unconsolidated soil layers poses a significant challenge in engineering construction. Limited research exists on optimizing pre-grouting mechanisms for shield tunnels in unconsolidated soil layers and controlling strata deformation. Therefore, conducting on-site optimization experiments for pre-grouting is crucial for controlling strata deformation. The paper employs crushed stone aggregate as a basis for modifying the shield jacket material. The primary method of verifying grout strength involves direct detection of foundation bearing capacity using a heavy-duty probe inside the tunnel. The feasibility of the comprehensive evaluation scheme is further confirmed through a combination of multi-point core sampling, five-point water pressure tests, and on-site shield monitoring data. The research results indicate that this technology effectively enhances the stability of deep-buried weak strata. By improving the physical and mechanical properties of backfill soil through a combination of crushed stone-cement slurry-soil skeleton, the self-stabilizing ability of surrounding rock is enhanced, and strata deformation is controlled. Additionally, a set of pre-grouting reinforcement and evaluation techniques suitable for deep-buried weak strata is proposed, providing valuable references for similar projects.

Optimum embedment depths for CFST column-to-foundation connections: Analytical and reliability-based approach

In the present study, the pullout capacity models were developed to derive analytical expressions for the minimum required depths of embedment for conventional and two recently published schemes of connection for circular and square concrete-filled steel tubular (CFST) columns. The models were developed by equating the pullout strength of the tube with the pullout capacity of the reinforced concrete (RC) footing. The pullout capacity of the RC footing was a function of the strength of cement grout, footing concrete, and RC footing reinforcement. The analytical expressions derived for the minimum required depths of embedment were utilized to deduce limit state functions. These limit state functions were then employed for the reliability calculations by means of the Monte Carlo Simulation (MCS) technique. The reliability calculations provide optimum embedment depths for CFST columns for the given reliability level. It was shown for the required reliability index of 3.0, the requirements of nominal embedment depth for the second column-to-foundation connecting scheme for circular and square CFST columns are 37.3% and 45.2% less than their corresponding first schemes of connection. This outcome proves the superiority of the second scheme (as a result of mechanical interlocking) over the first scheme. A few parametric studies were also conducted to obtain results of practical value.

Grout sleeve splicing of steel-fiber reinforced polymer composite bars: Tensile behavior and bond mechanism

In reinforced concrete structures exposed to harsh environments, steel corrosion poses a significant problem. Ductile and durable steel-fiber reinforced polymer composite bars (SFCBs), which can effectively address this issue, are a perfect alternative to conventional steel bars. However, the lack of suitable connection methods for SFCB has hindered their widespread adoption in civil engineering. To address this limitation, this paper proposes the use of grout-filled steel sleeves as a solution for connecting SFCB. The study designed 120 specimens of grout sleeve splices for SFCB to investigate their performance under unidirectional tensile forces. The experimental variables included the ratio of grout thickness to SFCB diameter, SFCB diameter, anchorage length, and grout strength. The results revealed various failure modes and found that specimens with a smaller ratio of grout thickness to SFCB diameter and greater grout strength demonstrated higher peak stress. The peak stress first increases and then slowly declines with an increase in anchorage length. Additionally, the peak stress decreased with increasing SFCB diameter, and the peak slip remained constant. Meanwhile, the bond mechanism between SFCB and grout was revealed. Finally, the study derived a theoretical bond-slip curve between SFCB and grout, as well as the development anchorage length.

Uniaxial tensile behavior of half-grouted sleeve connections with concrete cover after exposure to elevated temperatures

This study presents the tensile behavior of a half-grouted sleeve connection (HGSC). A total of 15 prism samples of grout are subjected to a series of tests before and after exposure to various temperatures. A total of 75 eccentric HGSC specimens with a 40 mm concrete cover and 15 central HGSC specimens without a concrete cover were fabricated for uniaxial tensile loading tests. A pseudo-transient heating regimen was applied to HGSC specimens with concrete covers; the specimens were heated to the desired temperature and left there for a duration of 0 min. This study systematically investigates the tensile properties of post-fire HGSC specimens to assess the combined effects of peak environmental temperature (20 °C, 200 °C, 400 °C, 600 °C, 800 °C), concrete cover depth (0 mm, 40 mm), concrete strength grade (C30, C35, C40, C45, C50), and concrete spalling (burst or unburst). The failure mode, load–displacement curves, sleeve strain distribution, and heat transfer are employed to characterize the response of the HGSC specimens, which is subsequently discussed. It is discovered that, although concrete compressive strength plays a minor role, temperature, concrete cover, and explosive spalling significantly influence certain post-fire tensile parameters of the HGSC. Based on the results, there is considerable potential for determining the ultimate tensile force in HGSC specimens with concrete covers and the remaining compressive strength of grout using ultrasonic pulse velocity detection. Furthermore, a comparative accuracy analytical model, incorporating the influence of tangential strain derived from the experimental results, is established based on confinement stress.

Formulation of a cement-based grout characterizing controllable gelation time and its modification mechanism

Achieving a coordinated balance between pumpability, setting time, and compressive strength is essential for the effective implementation of grouting tasks. This facet also poses a significant challenge in the formulation of cement-based rapid-setting grout. Therefore, precise control over gelation time, while concurrently preserving the pumpability and mechanical strength of cement grout, unquestionably enhances its engineering feasibility. In pursuit of this objective, the current study executed a factorial experiment, assigning alkanolamine, fluoride, aluminum sulfate, and citric acid as experimental factors. Subsequently, through an experiment involving changes to the experimental setup, mathematical predictive models for diverse performance parameters were established to determine the optimal formula. Moreover, to elucidate the hydration process of the proposed grout, a comprehensive investigation was conducted using factor effect analysis, isothermal calorimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Finally, by drawing on the results of the above-mentioned experiments and theoretical analyses, the modification mechanisms of the admixtures on the performance of the matrix were deduced. This paper introduces a novel approach to optimize the overall performance of rapid-setting grout, providing a new material solution for grouting jobs.

Numerical analysis and design methods of grout-filled GFRP tube repaired corroded CHS T-joints

This study explores the compressive behavior of Grout-Filled GFRP Tube (GFGT) repaired corroded circular hollow section (CHS) T-joints. Finite element models of GFGT repaired corroded joints were developed, validated, and utilized to examine the influence of the joint geometric, material, and chord end stress parameters on the compressive strength and repairing efficiency of the joints. The findings reveal that the ultimate strength of the GFGT repaired joint increases with a thicker GFRP tube, a lower repaired chord section hollow ratio, a higher grout strength, and a longer repaired range. By optimizing the repairing parameters of the grout-filled GFRP tube, the compressive strength of GFGT repaired corroded joints with 16% and 32% corrosion rates can be up to increase to 164% and 147% of the uncorroded counterparts, respectively. The chord end stress exerts a similar but weaker effect on the repaired joints than on the unrepaired joints. A series of suggestions were proposed for repairing joints with different corrosion degrees to achieve a 20% ultimate strength enhancement compared to uncorroded joints. The compressive strength degradation rate of corroded joints was accurately predicted by the design method in the CIDECT and prEN guidelines. The feasibility of the guideline formulae to evaluate the strength reduction rate caused by the chord end preload was verified. A design method to predict the compressive strength of GFGT repaired corroded joints was proposed.

Reinforced concrete block masonry walls under eccentric compression: Assessment using experimental and numerical data

This paper presents the outcome of a research study carried out to assess the eccentric compression behaviour of reinforced concrete block masonry (RM) walls. The design provisions pertaining to axial compression capacity of RM walls are overly conservative, especially where slender walls are to be designed. To verify the relevancy of the design provisions outlined in the Australian masonry standards (AS 3700), an experimental database of RM walls tested under eccentric compression was created by gathering data from the past studies. In total, 76 partially grouted (PG) and 18 fully grouted (FG) RM wall test data were gathered. The established database revealed that the performance of fully grouted (FG-RM) walls are generally overlooked. To fill this gap, a finite element (FE) based numerical modelling procedure was established to understand the performance of FG-RM walls under eccentric compression. The established FE modelling procedure was validated with a set of experimental results and the validated modelling procedure was then used to parametrically analyse the eccentric compression behaviour of FG-RM walls. In total, 72 FG-RM wall cases were numerically simulated under eccentric compression, varying slenderness ratios (15, 21, 26, 32, 37, and 42), grout strengths (20 MPa, 30 MPa and 40 MPa) and boundary conditions (pinned-pinned and fixed-fixed). The analysed numerical data along with the experimental database were then used to verify the design provisions outlined in previous version of AS 3700 (2011) and current version of AS 3700 (2018). It was found that the provisions specified in AS 3700 (2011) were overly conservative than the AS 3700 (2018), justifying the need of deliberate revisions in terms of the treatment of slenderness, eccentricity and grout strength for designing the RM walls under compression.

Temperature effect on density, strength, and microstructure of sustainable coal char-cement grout

Coal char, a coal pyrolysis product, is a lightweight carbon-rich material, which exhibits significant potential as an innovative and sustainable construction material. Recent research has indicated that the coal char addition enhances the engineering performance of conventional cement grout at ambient temperature. This experimental study evaluates the performance of coal char-cement grouts under varying curing temperatures (−25, 5, 25, and 35 °C) and conditions (sealed and water-soaked), focusing on the impacts of char contents (≤30 %) and temperatures on the bulk density, unconfined compressive strength, mineralogical, and microstructural properties of grouts. Findings reveal that grouts cured at 5, 25, and 35 °C possess 7.0–7.9 %, 5.3–5.4 %, and 5.1–6.4 % higher bulk density than those cured at −25 °C, primarily attributable to water absorption in water-soaked curing conditions. Furthermore, at −25 °C, the increasing compressive strength is obtained in low w/c ratio (0.8) grouts as char content increases. Compared to curing temperatures of 5 and 35 °C, char-cement grout at an ambient temperature of 25 °C demonstrates better strength performance because of more hydration products formed, higher calcite content, the predominance of amorphous calcium silicate hydrate, and the reduction in the crystalline phase of portlandite.

Improving the Anti-washout Property of Acrylate Grouting Material by Bentonite: Its Characterization, Improving Mechanism, and Practical Application.

Acrylate is a popular polymer grouting material that has been widely used to control groundwater seepage. However, the vulnerability of acrylate slurry to dynamic water washout restricts its application in groundwater environments characterized by high flow velocity and water pressures. In this paper, lithium bentonite (Li-B) was used to modify the traditional magnesium acrylate (AC) grouting material. The influence of Li-B to AC ratios on the modified materials' washout resistance was explored, and the modification mechanism was analyzed using X-ray diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM). Finally, the anti-washout ability of the modified slurry was verified through engineering applications. Results revealed that LiB-AC grout had adjustable setting times (10.5 to 395.6 s), minimal bleeding (0.1%), higher viscosity (65 mPa·s) and expansibility (350%), stronger anti-water dispersibility (24 times that of pure AC slurry), higher mechanical strength (compressive strength is 0.386 MPa, tensile strength is 0.088 MPa), and better impermeability (2.23 × 10-8 m/s). The lithium bentonite was beneficial to the setting time, bleeding, viscosity, slurry retention rate, impermeability, and mechanical strength of the acrylate grout. However, it diminished the expansibility of the acrylate grout. At the optimal acrylate content (20%), the mechanical strength and impermeability of the LiB-AC grout were the highest. The better performance of LiB-AC grout was attributed to the formation of a more stable and dense interlaced spatial network structure after the modification by Li-B. The LiB-AC grout was used in the dynamic water grouting project of a metro shield tunnel segment and achieved better anti-washout performance than cement-water glass and pure AC slurry.

Experimental Study on Bonding Performance between Prestressed Concrete Pipe Piles and Core Grout

To make the bearing capacity tests safer and more affordable for prestressed high-strength concrete (PHC) piles, this paper proposes a reaction device for anchor piles filled with core grout based on the geometric and mechanical characteristics of PHC piles. The proposed reaction device has the advantages of convenient construction, strong controllability of the connection quality and low cost. In addition, the pile will not experience prestress unloading or tensile stress under the effect of the upward pulling load. To promote the application of the reaction device developed for PHC pile bearing capacity tests, experimental studies are conducted on the bonding performance between the core grout and the inner wall of the PHC pile. The influence of various factors such as the strength of the core grout, the grouting length, the curing time, and the inner diameter of the PHC pile on the bond strength between the core grout and the inner wall of the PHC pile are investigated. Results show that as the inner diameter of the PHC pile increases, the bond strength between the core grout and the inner wall of the PHC pile decreases with a maximum difference of 5%. The bond strength decreases as the grouting length increases, and gradually stabilizes, with a difference of no more than 10% between the maximum and minimum bond strength values. The higher the strength of the grout is, the greater the bond strength between the core grout and the inner wall of the PHC pile is. The bond strength between the core grout and the inner wall of the PHC pile increases with the increase of the curing time within 28 days of curing, and the bond strength at 3 days meets the requirements of the PHC pile bearing capacity test.

Mechanical properties of an improved grout for cementitious precast beam-column joints

This study proposed a new formulation for an improved grout with superior early strength and ultra-high cured strength; it was designed on the basis of the theory of closest packing. Orthogonal experiments were conducted to analyse the effects of four factors, silica powder content, water reducer content, steel fibre content, and water-cement ratio, on the flowability, compressive strength, and compactness of grout. The criteria for determining whether the grout met the requirements for Code included initial flowability greater than 300 mm, flowability more than 260 mm after 30 min, and compressive strength more than 60 MPa after 12 h of standard curing. The results showed that the performance of the grout satisfied specified requirements for Code with small internal voids and acceptable durability. After the ratio of raw materials was optimized, The grout sleeve test showed that the failure occurred in the steel bars outside the sleeve, and no grout pulling, slipping, splitting, or other behaviour occurred within the sleeve, which meant that the specimens met the design requirements. The development of this grout will greatly reduce construction time for Code and improve the quality of connections in prefabricated components. The results of this study will provide a reference for the design and development of new grouts in the future.