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Glass fibre reinforced polymer (GFRP) bars have now been increasingly used as longitudinal reinforcement in concrete columns. In column design and analysis, the contribution of GFRP bars to compression is often ignored or is estimated as a fraction of its tensile strength due to the limited understanding on their compressive behaviour. Moreover, there exists no standard test method to characterise the properties of GFRP bars in compression. This study implemented a novel test method to determine and characterise the compressive properties of high modulus GFRP bars. During the preparation of test specimens, hollow steel caps filled with cementitious grout were used to confine the top and bottom ends of the GFRP bars. The effects of the bar diameter (9.5, 15.9, and 19.1 mm) and the unbraced length-to-bar diameter ratio, L u / d b (2, 4, 8, and 16) were investigated on the compressive strength of the bars. The results showed that the increase in bar diameter increases the micro-fibre buckling and decreases the compressive-to-tensile strength ratio. Similarly, the failure mode changed from crushing to fibre buckling with the increase of L u / d b ratio. Simplified theoretical equations were proposed to reliably describe the compressive behaviour of GFRP bars with different bar diameters and L u / d b ratios.

An interface equivalent modeling method is proposed in this study to describe the bond behavior between multi-strand tendons and surrounding grout. The interface equivalent principle is firstly proposed to determine the effective bond interface between tendons and grout considering the effects of the quantity, the arrangement and the space of strands. Then, the maximum bond stress of the multi-strand tendons provided by the interface is derived and incorporated into the existing bond stress-slip relationship to characterize the bond of multi-strand tendons. Subsequently, a pull-out numerical model incorporating the considered effects is developed to predict pullout forces-slip response for tendons. Finally, a direct pull-out test on three strands tendons is designed to verify the interface equivalent modeling method by comparing with the numerical and experimental results. The proposed method is also validated against previous experiment on seven strand tendons. Results indicate that the proposed interface equivalent modeling method can reasonably predict the bond behavior between multi-strand tendons and surrounding grout. The applicability and feasibility of the proposed equivalent modeling method is also investigated.

To explore solutions for water plugging and reinforcement problems of water-rich and broken rock mass in underground engineering, it is necessary to study the performance of cement-based grout and its reinforcement effect. In this study, Portland cement-based grouts with high amounts (70%) of granulated blast-furnace slag (GBFS) (30%) and Class C fly ash (FA) (40%) were prepared. The superplasticizer (SP) and anti-washout agent (AWA) were formulated to improve flowability and stability of single slurries. A new self-developed experimental device was designed for the grouting simulation. The fresh-state properties of cementitious single slurry i.e., flowability, mini-slump, stability, effective W/S and initial/final setting time; flexural and compressive strengths of grout stone bodies were studied. Meanwhile, the grouting reinforcement effect; mechanical performance of reinforcement sample i.e., unconfined compressive strength (UCS), failure mode, process and key parameters were evaluated. The results show that the performance and grouting effects of cement-based grouts with high amounts of GBFS and FA were generally acceptable. The addition of SP + AWA enhanced the stability and was beneficial to the grouting effectiveness especially at higher (0.8–1.2) water-solid (W/S) ratios. The diffusion or setting time of this type grout should be shortened appropriately in practice. The rupture interface and tensile fracture of grout were two main failure modes of reinforcement samples. The variations of key parameters corresponding to different failure modes were analyzed.

Failures of fully grouted bolts due to the combination of tensile and shear loads are commonly observed, but the bolting mechanism is not clearly revealed. Direct shear tests were conducted on three groups of specimens with different bolting angles or grout strengths, and shear loads, shear displacements and bolt strains were measured. The deflecting shape, the bending angle and the failure characteristic of the bolts were described in detail. The relationship between the shear load and the shear displacement was analyzed, and the internal forces were determined according to the bolt strains or the shear displacement of the joint. The test results show that the bolting angle and grout strength play significant roles in influencing the bolt contribution. With increasing the bolting angle, the bolt contribution rises first and then reduces, and they obey a parabola relationship. Particularly, the contribution of the bolt is less than its ultimate tensile load by a large margin when the bolt steeply intersects the rock joint. A higher shear contribution will be mobilized in a weaker grout. It is also observed that the failure of the bolt occurs at the bolt-joint intersection rather than at the two plastic hinges.

Within the British nuclear inventory, waste is classified into three main categories, including Intermediate Level Waste (ILW). ILW mainly consists of fuel casing metallic swarf, where parts of uranium metal are also expected to have been agglomerated. ILW treatment route includes the material storage in stainless steel drums and subsequent grout encapsulation. The solidified matrix is believed to maintain the radioactive waste fully confined and immobile. Recent inspections revealed mechanical distortion around the steel liner in a proportion of the inspected drums. The distortion has been ascribed to the corrosion of the encapsulated metallic parts. The generated corrosion products occupy greater volume than the parent metal, resulting in an internal volume expansion which imposes stress/strain on the encapsulants. This study attempts to correlate the level of internal corrosion with the magnitude of package degradation in ILW drum–simulant systems by favouring the use of powerful synchrotron X-rays.

Preplaced casting scheme is applicable for manufacturing the minimum unit weight lightweight aggregate concrete with a higher content of lightweight aggregates. High-volume of aggregate can be achieved by fully packing aggregates in the empty formwork and filling the interstitial voids with grout mixtures. This unique manufacturing process of preplaced lightweight aggregate concrete forms extensively interconnected aggregate network with the grout-coated aggregate grains, influencing the mechanical characteristics of concrete. Thus, these complex homogeneities are considered in a micromechanical four-phase model, from which we predict the elastic properties of preplaced lightweight aggregate concrete. The inverse homogenization is used for the identification of equivalent homogeneous parameters of concrete composites referring the microstructural images of intermediate zone. The compressive strength and drying shrinkage of preplaced lightweight aggregate concrete are also investigated by proposing the corresponding micromechanics-based models using the elastic moduli of grout and equivalent aggregate network. Finally, the predicted strength and drying shrinkage well agree with the measurements on preplaced lightweight aggregates concrete.

To date, controlled low-strength material (CLSM) has been used widely as fill material in flowable fills, structural fills, and void fills. However, owing to its good flowability and low shrinkage, CLSM can be considered a heat transfer medium as long as it has sufficiently high thermal conductivity. In this study, a newly developed CLSM, a blend of natural sand, marine dredged soil (MDS), and binders, was investigated and evaluated for the feasibility of it being used in geothermal systems. In addition to its general properties (flowability, fresh density, and unconfined compressive strength), thermal conductivity (i.e., heat transfer capacity), bleeding rate (i.e., involving volume compensation for boreholes), and environmental impacts (i.e., involving the potential risk of water pollution) were broadly investigated in this study. A bleeding-rate-based volume compensation concept is described for an actual large-scale geothermal system to evaluate total cost. All of the prepared CLSM mixtures performed well in terms of general and environmental characteristics. Moreover, the thermal conductivity of the developed CLSM-based grout was much higher than that of conventional grouts (i.e., bentonite and silicate sand). More importantly, an outstandingly positive effect of MDS was discovered: a sufficient addition of MDS to CLSM-based grout can lead to a considerable decrease in bleeding rate; hence, to only a small volume compensation of required boreholes. Ultimately, the total cost for geothermal construction can be reduced.

Constructing a soilcrete column by injecting grout into the soil is a common method of stabilizing loose soil in coastal areas. Although tap water usually is used in the grout mixture for soil improvement projects, before the cement in grout mixture has completely set, tap water will mix with in situ saline seawater. Researchers have not previously considered the behavior of clay-cement under marine conditions, especially the effect of water salinity, on the performance of soilcrete. The goals of this study were to investigate the effect of the use of naturally saline seawater in grout preparation on the mechanical, physical and microstructural behavior of cement-stabilized marine clay. Marine clay and seawater samples were prepared along the northern shore of the Persian Gulf. Tap water as low salinity water, brackish water as medium salinity water (50% tap water and 50% seawater) and natural seawater as high salinity water were used. Specimens were prepared using the deep mixing method recommendations for laboratory soilcrete tests. Macroscopic evaluation was performed by unconfined compressive strength and indirect Brazilian tension test. The physical aspects of the plasticity of the soilcrete specimens with regard to the Atterberg limits and changes in the particle size distribution caused by cement bonding were evaluated by hydrometer testing. For the micromechanical study, SEM images were prepared from selected specimens. The results show that the use of natural seawater does not reduce the strength in comparison with tap water. Specimens containing brackish water (50% seawater and 50% tap water) showed maximum strength due to flocculation in the structure of the clayey cluster in comparison with tap water. The compressive strength ranged from 1.5 to 5 MPa for clay-cement specimens made of natural soil and seawater. The ratio of tensile strength to compressive strength of these specimens was 0.15–0.25. The results show that the unconfined compressive strength of soilcrete specimens constructed under field conditions was 30% that of specimens constructed under laboratory conditions.

This paper investigates the effectiveness of Steel-Reinforced Grout (SRG) jackets to strengthen shear critical reinforced concrete (RC) beams. Eleven RC beams were tested in three-point bending. Key parameters of investigation were the strengthening configuration (U- and fully-wrapped jackets), the density of the fabric (1.57 and 4.72 cords/cm) and the number of the strengthening layers (one and two). The test results demonstrated the efficiency of SRG jacketing in increasing both strength (up to 160%) and deformation capacity (up to 450%) of the shear critical beams. Expressions are proposed for estimating the effective strain of the SRG jacket.

With widespread usage of grouted connection in offshore wind turbines, large-diameter grouted connections became popular. Due to the overestimation of the capacity of the cylindrical specimens, segment specimens were designed to investigate the mechanical behavior of large-diameter grouted connections. A test program involving 10 specimens was executed to explore the behavior of grouted connection when subjected to lateral pressure and vertical loads. The test parameters include grout thickness, lateral pressure, and shear key spacing. The number of shear keys were also considered. The failure modes, bearing capacity and longitudinal strain distribution of grouted connections are studied. Test results showed that all tested specimens failed in a ductile way and diagonal cracks between shear keys were observed in the final failure modes. In addition, the nonlinear finite element analysis (FEA) models were established to predict the behavior of grouted connections. The concrete damaged plasticity model available in ABAQUS was adopted, and the FEA models were verified using the test results. An extensive parametric study was conducted to identify the effect of steel yield strength, grout compressive strength, lateral pressure, grout thickness, shear key spacing, and the thickness of steel plates on the bearing capacity of grouted connections. Results indicated that the bearing capacity increased with the lateral pressure or grout compressive strength but decreased with the grout thickness.

This study investigates the feasibility of using a cement-based capillary crystalline material, Penetron Admix (PA), to enhance the performance of a cement grout for sealing tunnel leakage. A series of experiments were carried out to investigate the effects of PA on the viscosity, setting time, concretion rate, permeability and compressive strength of the cement grout. The experimental results show that inclusion of PA into cement grout has no effect on its viscosity and setting time, but can markedly increase the concretion rate, and the compressive strength of the grout concrete and reduce its permeability. Micro structure characterizations by CT scanning indicate that cement-gravel grout concrete samples with additional PA show a compact and smooth structure compared to those without PA; SEM images show that the dendritic crystals are observable under high magnification in the cement grout concrete samples with PA, and the number of crystals increases as the amount of PA increases. Based on the experimental results and the micro structure characterizations, it can be concluded that PA can be used as an additive to improve the rate of concretion, compressive strength, and impermeability of cement grout. To achieve an optimum leakage-sealing effect, the weight ratio of PA to cement of 1.4–1.6% is recommended.

To ensure desirable fluidity, less leaching and mechanical properties of grouts in geotechnical engineering, a microfine-cement-based grout mixed with microfine fly ash (MFA), colloidal nanosilica (NS) and superplasticizer (SP) was designed. In this paper, the rheological and mechanical properties of grouts with different additives were investigated. The results show that all microfine-cement-based grouts have satisfactory apparent viscosity, behave as Bingham fluids, are stable for water/solid (W/S) ratio = 1.2. The incorporation of MFA and SP each improve the fluidity and spreading ability of fresh grouts, while prolonging the setting time. The addition of NS has negative effects on fluidity and shrinkage property of fresh grouts, nevertheless, it has positive effects on shortening setting time, enhancing stability and mechanical properties.

This paper reports the effect of mix composition of grout on the fluidity, rheological behaviour and hydro-mechanical behaviour (permeability and compressibility). Factorial design was used in this investigation to assess the combined effects of the four mix composition parameters on fluidity, rheological properties, permeability and compressibility: water/binder ratio (W/B), percentage of limestone filler as replacement of cement (LF), dosage of viscosity modifying admixture (VMA), and dosage of superplasticiser (SP). To evaluate both the rheology of the cement grout and its hydro-mechanical behaviour, mini-slump test, Lombardi plate test, and forced bleeding test, coaxial rotating cylinder viscometer were used. A two-level fractional factorial model was used to model the effect of key variables on the fluidity, the cohesion, permeability and compressibility. The predicted models are valid for mixtures made with W/B ranged from 0.35 to 0.42, LF from 12% to 45% as replacement of cement, VMA (percentage of binder) from 0.02 to 0.7%, and SP from 0.3 to 1.2%. The effects of W/B, LF, VMA and SP were analysed using polynomial regression which can identify the primary factors and their interactions on the measured properties. Prediction models were developed for mini-slump, plate cohesion meter, permeability and compressibility as function of W/B, LF, VMA, and SP. The factorial statistical approach used highlighted the effect of W/B, the dosages of SP and VMA on the various rheological properties, permeability and compressibility.

We present below an analytical solution to model the radial transient flow of polymer grout with variable density in a planar fracture. The flow of polymer grout mainly depends on the secondary pressurization caused by its own expansion, which is different from the diffusion mechanism of the grout with constant density driven by constant pressure. The diffusion process of polymer grout in the fracture can be divided into two stages: static-pressure injection phase and self-expansion phase. In the self-expansion phase where the external grouting pressure has been removed, the polymer grout is idealized as a self-expanding Newtonian fluid whose density decreases over time with the negative exponential law. Base on the theory of viscous fluid mechanics, the analytical expressions of the diffusion radius, radial velocity and pressure distribution over time between the fracture walls in this phase were derived. Furthermore, two typical cases were numerically simulated by commercial CFD code Fluent to validate the analytical solution. Then, the diffusion characteristics of the expansible grout were briefly analyzed and summarized. The aim of the present study is to provide a theoretical method for studying the diffusion mechanism of the polymer grout with a feature of self-expansion in the rock fracture.

Grouting is a widely used intervention technique for the consolidation and strengthening of historic masonries. During the recent decades, lime-based grouts have been developed, tested and applied, taking into account parameters, such as their compatibility with the historic structures and their performance both in terms of fresh and hardened state properties. The exploitation of perlite by-products on the other hand (named as ‘waste perlite’), is a field that should be further envisaged, due to the gradually increasing demand of expanded perlite production, as well as the need of minimizing the environmental burden from its industrial process. To this direction, a series of grout mixtures based on two types of perlite by-products (D1S and D1C) and lime (air and hydraulic) were manufactured and tested. According to the experimental results, waste perlite-based grouts presented effaceable fresh and hardened state properties, while their performance was enhanced when superplasticizer and a short proportion of white cement or metakaolin was added in the air lime mixtures. In the hydraulic lime mixtures, the addition of waste perlite enhanced their properties and significantly increased their strength. Therefore, it was concluded that according to specific requirements, both perlite by-products studied could be used in combination with lime, for the manufacture of light-weight, low cost and environmental friendly grouts. Future oriented research should be therefore made in order to further investigate the parameters influencing the performance of grouts based on other waste perlite types.

The rigid polyurethane grout materials with different densities show elastoplastic or atypical brittle characteristic, which will significantly affect their performance. To clarify these mechanical characteristics of polyurethane foams with different densities, uniaxial compression tests and SEM experiments were carried out. To further describe these different mechanical characteristics quantitatively, two integral models based on superposition and segmentation methods were proposed, respectively. Moreover, two simplified integral models were developed to make models easy to be applied. Through error analysis, it is found that the average errors of integral models are less than 0.02 MPa and the average errors of simplified integral models are less than 0.035 MPa. The integral models are accurate while the parameters of simplified integral models are less.

The aim of this investigation was the development of a geopolymer grout. To achieve this goal, it is necessary to control the characteristics of the reactive mixture (i.e., between the dissolution of the mineral source and the consolidation of the binder) and its setting time. The targeted application (geological radioactive waste disposal) requires a grout with a setting time greater than 24 h, a viscosity in the range from 1 to 5 Pa·s and a moderate pH value between 10 and 11. To reach these values, a metakaolin-based geopolymer was used with the addition of mineral additives. The viscosity measurements reveal that a focused viscosity is reached and that the setting time can be easily controlled and extended above 24 h with the addition of 2.8%weight of acids (boric and phosphoric) or 10%weight of borax. The acids reduce the reactivity of the mixtures by decreasing the alkalinity and inducing slow silica/alumina dissolution. The borax extends the setting time by increasing the water content and by modifying the polycondensation reactions to form huge structural entities. The decrease in the pH value to the target (10–11) can only be reached using 10%weight of borax or 7.5%weight of lithium tetraborate due to the insertion of B[IV] in the geopolymer network.

The recent need to develop infrastructure, driven by global population growth is forcing societies to construct on any soil type available within their vicinity including weak soils. However, due to the poor physical and engineering properties of weak soils, they are not suitable for construction purposes. Given many ground improvement techniques that are presently employed to improve the properties of weak soils and to reduce the potential damages caused by them, this paper addresses this issue by conducting a literature review and collecting information on the application of polyurethane chemical grout for improving the properties of weak soils. While, many researchers have investigated the application of polyurethane, its application and the methods of improving the properties of weak soils, including detailed information on the application of polyurethane on weak soils for improving its properties is limited. Accordingly, this paper has examined the chemistry of each component of polyurethane and its application and explored the methods of grouting, grouting materials, the advantages and disadvantages as well as the applications of grout both in the field and in the laboratory. The review also discussed the possible means of improving polyurethane by incorporating reinforcing fillers, surfactant, catalyst and other additives. The review concluded that improved polyurethane has the potential to improve weak soil types for infrastructure development.

Grouting is an important method to reinforce fractured rock mass in underground engineering. To improve the grouting reinforcement effect of fractured rock mass, the theory of self-stress grouting reinforcement was put forward for the first time, and the self-stress grouting material was developed. The swelling stress of self-stress grouting material was tested by self-developed testing device to analyze the relationship between swelling stress and expansive agent content. Then, with cement, bentonite, silica fume, FZ expansive agent, accelerator, water reducer and water as raw materials, the effects of bentonite-cement ratio, silica fume content, accelerator content and water reducer content on the fluidity, initial setting time, uniaxial compressive strength at 3 days and 28 days of grouts were investigated by orthogonal test. Finally, the optimum proportion of the cement-based self-stress composite grouting material was applied to reinforce crushed coal blocks and the surrounding rocks of mine roadway, respectively. The results shown the optimum expansive agent content of the grout was 10%, corresponding swelling stress of 0.82 MPa. The proportion of the cement-based self-stress composite grouting material was bentonite-cement ratio of 1, FZ expansive agent content of 10%, silica fume content of 6%, accelerator content of 2.9%, and retarder content of 2.5%. The uniaxial compressive strength of the crushed coal blocks after reinforcement was 12.1 MPa, which was greater than the strength of the original coal. The cement-based self-stress composite grouting material had significant effect on the reinforcement of the surrounding rocks of mine roadway.

To plug dynamic water effectively during underground constructions, it is important and urgent to determine the performance of quick-setting cementitious grouts. In this study, the Ordinary Portland cement (OPC) and sulphate aluminium cement (SAC) were selected as two typical cements, and the double slurry were prepared with cement suspension and sodium silicate slurry. The fresh-state properties of cement single slurry i.e., mini-slump, flowability and bleeding; basic work performance of double slurry i.e., flowability losing time, anti-washout and initial or final setting time; flexural and compressive strengths; failure mode; brittleness evaluation and microstructure of the double slurry grout were studied. The water/cement (W/C) ratio was selected as 0.6:1–1.2:1. The volume ratios of cement slurry and sodium silicate were 1:1, 2:1, 3:1 and 5:1. The results show that the sodium silicate slurry disturbed and accelerated the normal hydration process of cementitious minerals, and the SAC was not suitable for preparing double slurry compared with OPC. The flowability losing times of SAC double slurry were higher than those of OPC double slurry. The anti-washout, failure modes of OPC double slurry have more advantages. Considering the flowability losing time, controllability, pumpability, diffusibility, mechanical strength, failure mode and microstructure, the volume ratios should not be over 5:1 and not be less than 2:1.

A friendly novel material called geopolymer has recently presented some promising uses for enhancement of weak ground through grouting alternative to Portland cement especially for avoiding from large CO2 emissions during cement production. However, research using the geopolymer technology is still insufficient for grouting specifically concerning with rheology. This paper investigates the rheological properties (shear stress, apparent viscosity, shear rate, yield stress, plastic viscosity) of geopolymer grout in comparison with the cement-based grouts included fly ash and cold bonded fly ash (i.e., geopolymer aggregate) at various dosage rates (0%–100%) and water/binder ratios (0.75–1.5). Some alkaline activator solutions (sodium hydroxide, sodium silicate) and some precursor of aluminosilicate sources (fly ash, silica fume) are used for obtaining the geopolymer grout. Rheometer tests are performed for the grout rheology. It is found from the experimental work that most of the grout mixtures lead to dilatant behavior similar to the one of native cement, while some geopolymer grouts result in the pseudoplastic and Bingham behaviors. All rheological responses of grouts decrease with increased water/binder ratios. While the inclusions of fly ash and geopolymer aggregate bring about minor changes in the rheological properties, the geopolymer grouts mostly result in the magnitudes more pronounced. The grout rheology becomes more close to the ones of native cement by the proportions 30%–40% of fly ash and geopolymer aggregate, and using the geopolymer grout in the combinations with 30%–60% silica fume. The plastic viscosity versus yield stress produces moderate correlations for the grouts with fly ash, but strong correlations for the geopolymer grouts and the grouts with geopolymer aggregate. The study indicates that the geopolymer comparatively attempted with fly ash and geopolymer aggregate could offer many choices for experimenters in practice for feasible grouting compared to native cement.

Dry-stacked interlocking masonry (DSIM) systems were developed worldwide to minimize the disadvantages of traditional masonry systems such as shrinkage, weak joints, and the need of skilled labors. Nevertheless, dry-stacked walls are recommended to be designed as reinforced and fully grouted. In this paper an experimental study conducted to evaluate the in-plane behavior of full-scale DSIM shear walls under cyclic in-plane loading and to explore the effectiveness of using post-tensioning (PT) instead of grout and reinforcement. A sliding control system to enhance the ductility of the DSIM system was developed. The test program consists of nine masonry shear walls constructed with three different types of locally available concrete masonry blocks (Conventional, Azar and Sparlock). The specimens were tested under reversed cyclic lateral load up to failure. The test results, including load displacement response, failure mode, modes of deformation, residual drift ratio, displacement ductility, wall stiffness, stiffness degradation, and energy dissipation are presented and discussed. The results showed that a similar behavior of Azar and conventional masonry systems in both reinforced and PT specimens. The utilization of PT with excluding the grout in DSIM shear walls improved the displacement ductility, effective stiffness and energy dissipation. Finally, the developed sliding control system in DSIM PT specimens increased the sliding contribution to 35% of total deformation, hence improved the displacement ductility.

Sonic pulse velocity is a non-destructive method used for diagnosing existing masonry and evaluating the effectiveness of interventions. A new comparative study is presented here, aimed at checking the reliability of the method in detecting inhomogeneities in order to qualify various masonry conditions, according to common practice and up-to-date tools, for both on-site testing and data handling. Four research groups applied direct and tomographic sonic velocity tests on three full-size wall specimens representing existing masonry types. The surface wave method was also applied to one of the specimens, to compare various outputs of elastic wave transmission. The panels incorporated various flaws and inclusions and were consolidated by grout injections. Each research unit applied its own acquisition systems and processing methods before and after panel consolidation. The results confirmed the ability of sonic pulse velocity tests in detecting large inclusions and significant variations in compactness, and provided quantitative reference values for materials and conditions. The research provided directions for further optimization of sonic waves transmission test application in already existing masonry constructions.

Recently, ultra-high-performance concrete (UHPC) material has been adopted as a grout material to fill connections between adjacent girders. Research to date has showed that using UHPC in the shear key connections of bridges improves the bridge superstructure performance. However, shear key configuration used in the most bridges are custom-designed and do not follow any specific design code. In a previous study by the authors, an optimized shape of the UHPC shear key (OPT-UHPC) was introduced in attempt to enhance load transfer and increase ultimate strength capacity. The optimization was conducted using three 3D finite element models simulating direct shear, flexural, and direct tension tests. The objective of the present study is to experimentally measure the performance and ultimate load capacity of the OPT-UHPC shear key by placing it between two high strength concrete (HSC) components and subjecting to direct shear, direct tension, and flexural tests. These results are then compared to the modeling predictions from the previous study. Two 45°-rectangular rosette strain gauges were placed on the surface of UHPC shear key and HSC components under direct shear load to obtain the strain in the shear key and the adjacent HSC components. The test results showed the OPT-UHPC design has an ultimate load capacity 32% larger than the FHWA-UHPC shear key, even though the cross-sectional areas are approximately equal, 19677 mm2 for FHWA-UHPC and 20161 mm2 for OPT-UHPC, a difference of about 2.5%. Also, the experimental results indicate the OPT-UHPC shear key enhanced the strain distribution between the concrete components and as result improved the load transfer. Thus, the load transfer mechanism is substantially influenced by the shear key configuration.

Grouting is one of most important techniques for underwater tunnelling in karst ground which is actually difficult to be resolved due to the presence of underground water flow. This paper proposed a new grouting material to fill karst caverns when there is flowing underground water prior to shield tunnel construction. The grout uses bentonite and cement as the base material, and a curing agent were added to form excellent fluidity, stability and scour resistance. The effects of the composition and formulation on the performance of the grouting material, and the optimal formulations were determined through a series of laboratory experiments. The recommended parameters for the grout are a specific gravity for the bentonite slurry from 1.30 to 1.35, a cement content of 30%, a meta-aluminate content of 1.25% and a lignin content of 0.20%. The effectiveness of the hardened cement-bentonite grouting material (HCBGM) was checked by a field grouting application for a underwater shield tunneling in karst area, and the results illustrated that the proposed grouting material not only can fulfill the engineering requirements but also turns out cost effective and eco-friendly.

Natural hydraulic lime (NHL) based grout has been widely used in construction project related to ancient architecture in recent decades. In order to improve grouting performance of NHL based grout, silica fume (SF) and silicon-acrylic latex (SAL) were incorporated in the preparation of grout. For the grout in fresh state, compared with control grout, bleeding rate of modified grout with SF and SAL incorporation decreased. Wettability, interfacial bond and simulated grouting properties of grout were improved. For the grout in hardened state, water absorption of grout decreased. Compactness, mechanical strength and salt resistance were improved. SAL played a more important role in improving both grout’s flexural strength and interfacial bond property between grout and consolidated matrix. Generally, combined use of SF and SAL made the grout with the most beneficial grouting performance.

Investigation on the degradation of improved ground is crucial for predicting its life span and performance under unfavorable conditions. In this study, effects of magnesium chloride (MgCl2) and magnesium sulfate (MgSO4) attacks on gravel-sand-cement-inorganic binder mixtures were investigated. Electrical resistivity, free-free resonant column (FFRC) and uniaxial compression tests were performed at different exposure periods, and results showed that saline solutions exert considerable effects on the geophysical parameters of the mixture. As the samples were exposed to chemical attacks, the electrical resistivity and damping ratio increased, while the longitudinal wave velocity and UCS decreased. Especially, the results at 28 days showed that mixtures without inorganic binder lost approximately 40% of its initial strength in MgCl2 and 12% in MgSO4, while samples with inorganic binder (IBS) only lost about 30% and 8% in MgCl2 and MgSO4 respectively. Thus, it is expected that increasing the inorganic binder content in the mixture can enhance the performance of the grout and reduce strength degradation induced by chemical attacks.

Pre-stressed Concrete (PSC) has various engineering advantages like reduction of dead load, enhancement of shear strength, and reducing crack, however tendon corrosion in grout caused by deficient grout and intrusion of chlorides causes a tendon break and the related structural problems. It is important to understand the corrosion pattern varying with grout properties and placement conditions. In the work, TG (Tendon-Grout) systems are prepared considering grout quality, bleeding, tendon location, and crack width. In order to evaluate corrosion pattern in TG systems in a short period, ICM (Impressed Current Method) is adopted for corrosion acceleration for 2 and 4 days of duration. For two types of grout (conventional one and improved grout with reduced water to cement ratio and silica fume), corrosion current and its amounts are evaluated for various conditions. In the TG system with crack, corrosion greatly increases with extension of test duration for both types of grout since crack width on grout is a main channel for ion intrusion. In spite of crack effect, improved grout has better resistance to corrosion considering crack and bleeding condition. When TG system has eccentricity of tendon with small cover depth, no significant differences between conventional and improved grout are measured since cover depth is too small to protect chlorides from outside. Various effects like bleeding, crack, tendon location, and grout quality are discussed in the work. The improved properties in IG like porosity, strength, absorption ratio, and expansion rate are also investigated.

In shield tunneling construction, grout of precast concrete segments is widely applied to various geological conditions. However, the connection performance between the grout and segments after the grout cannot be determined by destructive means, such as coring. The impact-echo method is used extensively in nondestructive testing of civil engineering structures. Nevertheless, there are inadequate researches on determining defects in segment-grout structure. In this paper, the segment-grout structure was simulated experimentally and artificial defects were introduced in the grout. The Short-time Fourier Transform (STFT) and Wavelet Transform (WT) of signals obtained by the impact-echo method were carried out to analyze the time-frequency domain features of the impact-echo signals with and without defects in the grout. On this basis, defects in the grout layer were determined. Finally, energies of wavelet packet were calculated and characteristic relative energy indexes of wavelet packet at different positions were detained. It’s found that the values at positions without defects are relatively low. It’s demonstrated that the signal analysis of impact-echo method has to combine time-frequency domain information and energy distribution for detection of defects in the grout layer. Wavelet transform and energy analysis methods are effective means to detect defects in the grout layer.

Grouted dowel connections are widely used to resist tension induced by in-plane straining actions and to provide ductility to precast concrete load bearing wall structures. Yet, such connections have not yet been duly investigated. Current design code and standard provisions treat it similar to a simple bar-in-concrete detail. The present study reports the findings of 22 full-scale tests undertaken to examine the bond behaviour of grouted connections under monotonic tensile loading. The examined test parameters included the bar embedment length, bar material and corrugated duct. Results indicate that grouted connections behave quite differently from the bar-in-concrete model assumed in design codes, primarily due to the confinement mechanism of the duct, which provides restraint to lateral expansion of the grout. Varying the embedment length seemed to affect both the bond stress and slip, but did not influence the failure mechanism of the connections. The experimental results were used to calibrate two well-known bond-slip analytical treatments, predictions of which appear to be in good agreement with experimental results. The experimental and analytical findings provide an enhanced understanding on the behaviour of such connections, highlighting the need for revisions in future relevant design code provisions.

This paper aims to evaluate the influence of concrete blocks and grout’s properties on the masonry’s compressive strength and stiffness. Prisms were produced with blocks and grouts with different strength levels, and mortars with strength of 70% of the blocks’ net area strength. It was possible to understand the effects of using low strength and high strength blocks, check the effectiveness of using grout or increasing its strength, and develop response surfaces, contour graphs, and empirical equations. Predictions about the masonry failure mechanisms are proposed for different block and grout combinations. It helps the designer to associate strength and failure mechanisms, prevent or mitigate their undesirable consequences, and eliminate brittle rupture modes. Results complement the existing database and can be used to properly select blocks and grout for masonry structures.

The greatest difficulty of grouting fractures under flowing condition was that the slurry was easily washed out by the flowing. To raise the sealing efficiency (SE) and dynamic flowing resistance of slurry, carbon fiber was added into the grout and a new grout for flowing water environmental was provided. Contrast tests and SEM tests were conducted to investigate the effect of carbon fiber. The result showed that the solidification velocity and dynamic flowing resistance increased with an increase of carbon fiber content due to the stochastic distribution and great surface friction of carbon fiber. In addition, a series of orthogonal tests were conducted to investigate the effect of some factors on the SE. The result showed that the SE decreased with the increase of initial flow speed and aperture width, and it increased with the increase of cement water ratio and additive content. Finally a fitting equation was acquired to provide reference to the practical engineering.

Two-graded roller compacted concrete (RCC) containing high volumes of fly ash has been widely used in anti-seepage structures of RCC dams in China. The crystalline additive as a self-healing addition is added to the grout enriched two-graded RCC to increase crack resistance. The effects of fly ash and crystalline additive on mechanical properties of two-graded RCC were investigated in this research. Tests were performed to measure plastic and hardened RCC properties. The results indicate that the vibrating compacted values and air contents of plastic RCC containing fly ash of up to 58% conform to the engineering requirements. As the fly ash content in RCC increases, the air content increases and the unit weight decreases. Adding crystalline additive to the concrete mixture has no apparent effect on the slumps of grout enriched two-graded RCC, but may increase the air content and reduce the unit weight. The cube compressive strength, splitting tensile strength, axial tensile strength, ultimate tensile strain, modulus of elasticity, and axial compressive strength of two-graded RCC all decrease with increasing amounts of fly ash content. At 90 days, the relations between these properties and two variables, fly ash to cementitious material ratio (F/CF) and water to cementitious material ratio (W/CF), between splitting tensile and cube compressive strengths, between axial tensile and cube compressive strengths, and between axial and splitting tensile strengths were analyzed. The values for these properties of two-graded RCC were lower than those of grout enriched two-graded RCC at the same age, F/CF and W/CF, and adding crystalline additive to the grout enriched two-graded RCC may produce higher values for these properties than that without crystalline additive in most cases. The results confirm the feasibility of using crystalline additive in two-graded RCC of high RCC arch dams.

The evolution of technical and environmental requirements fosters the development of geopolymer based grouts for soil reinforcement. Geopolymer based materials actually have several advantages but the improvement of their rheological performances remains a challenging task, as the raw materials, especially sodium silicate and metakaolin, do not have favorable properties and the main chemical admixtures used to optimize cement-based materials have not been found compatible. As mix-design takes into account the performances in both fresh and hardened states, a comprehensive study is necessary to develop geopolymer grouts based on metakaolin-fly ash-stabilizer mixtures. Fly ash allowed reducing the viscosity and increasing the setting time and the stabilizer provided the fresh mixes with better homogeneity and stability. At constant liquid to solid ratio, the packing density of the powders actually increases with fly ash proportion. Fly ash affected the mechanical properties, especially at replacement rates of 40% and higher, due to combined effects of reduced reactivity and higher packing density of the powders. This could be shown by a new methodology combining the monitoring the elastic properties with isothermal calorimetry for understanding the early-age behavior and the distinction between the geopolymerization stages. The addition of xanthan gum had a beneficial effect on the stability of grouts, by acting on the activation solution without having any significant effect on the geopolymerization reaction.

This paper introduces the detection of grouting quality in plastic ducts in prestressed concrete structures based on impact-echo (IE) testing with an HHT-based method. This method takes steps to suppress unrelated signals. At first, the thickness frequency of the intact concrete whose thickness is equal to the detected concrete is calculated, then a band pass filter is conducted to filtering uncorrelated frequency component. Secondly, complementary ensemble empirical mode decomposition (CEEMD) is used to decompose the signal to intrinsic mode functions (IMFs). Thirdly, an IMF screening process is conducted on the IMFs to extract the main patterns of vibrations related to grouting. At last, the Hilbert marginal cumulative spectra are set up. This method has been verified by both simulated and laboratory models. The cumulative Hilbert marginal spectra showed that the thickness frequencies decreased gradually with the decreasing of grouting compactness. On-site IE tests verified the feasibility and practicability of the proposed method.

In grouted post-tensioned (PT) systems, cementitious grouts are supposed to completely fill the interstitial spaces between the strands and act as the ‘last line defence system’ against corrosion. However, use of poor quality grout materials and grouting practices result in voided grout systems, ultimately leading to premature failure of tendons in many bridges around the world. To ensure an intact system, the grout must have excellent fresh properties, in particular the flow properties. Such high-performance grouts are not available in many developing countries, where grouting for post-tensioned structures is still a nascent technology. In this research, a two-stage test program was carried out to evaluate the fresh and hardened properties of seven commercial grouts, which includes three Pre-Packaged Grout mixes (PPG); three Site-Batched Grout mixes (SBG) and one standard Ordinary Portland Cement grout mix (PCG). Further, one PPG mix and SBG mix were chosen and their properties were evaluated for three levels of mixing speed and two ambient temperature conditions. Fresh properties such as wet density, efflux time and its retention, standard bleed, wick-induced bleed and pressure bleed, as well as set/hardened properties such as setting time, compressive strength and volume change were evaluated. Three batches of grout were tested for each grout material, to ensure reliability of results. The influence of binder fineness on the performance of grouts was also evaluated. The study serves as a strong evidence in substantiating that the most commonly used grout materials for PT system in developing countries, fail to meet the standard requirements and even the manufacturer’s own specifications. It is also found that the performance of the grout is influenced by mixing speed, ambient temperature, and fineness. The study emphasises that the evaluation of the grout behaviour under simulated field conditions is essential to ensure void free and durable PT systems.

Numerous research has been conducted on the axial performance of cement-based grouts. However, much less work has been focused on the shear behavior of cement-based grouts. In this study, the shear behavior of a Portland cement grout was investigated with the triaxial test. Cylindrical samples with two different water-to-cement (w/c) ratios: 0.42 and 0.35 were cast and prepared. In the test process, a series of confining pressures was applied on the samples and the confining pressure was ranged from 1 MPa to 35 MPa. The results show that there is a bi-linear relationship between the maximum vertical stress and the confining pressure independent of the w/c ratio. Low w/c ratio can effectively increase the maximum vertical stress of grouts. Mohr-Coulomb models were used to fit the shear strength envelopes of grouts. The results show that the shear strength of grout with a w/c ratio of 0.35 is much higher than that with a w/c ratio of 0.42. When a w/c ratio of 0.42 was used, the grout has a cohesive strength of 31.4 MPa and an internal friction angle of 15.1° while when the w/c ratio was decreased to 0.35, the cohesive strength of grout increases to 34.2 MPa and the internal friction angle rises to 24.3°.

Recent laboratory experiments have demonstrated the superior performance (high stiffness, load-carrying capacity and ductility) of bolt shear connectors embedded in the pockets of cementitious grout compared to conventional fasteners (e.g. screws) for developing composite action between steel beams and timber slabs. Accordingly, this paper investigates the structural behaviour of steel-timber composite (STC) joints with bolt connectors embedded in grout pockets (BCGP) using 3-D continuum-based finite element (FE) models. Following validation of the FE models against available push-out test data, they are used to conduct a parametric study that elucidates the influences of the compressive strength of the grout, the yield strength and size of the bolt shear connectors, the size of the grout pockets and the thickness of the steel profile flange on the load-slip behaviour, service stiffness, peak load-carrying capacity and failure modes of STC joints with BCGP. Simple formulae for the stiffness and load-carrying capacity of the STC joints with BCGP are derived from linear regression of the results of the parametric study.

Half grouted sleeve connection is widely used in joining rebars in precast concrete structures. However, its mechanical behaviors at elevated temperatures remain to be a topic with little research. This paper presents experimental results of 12 half grouted specimens and 12 single rebars under static tension at different temperatures. The tensile properties of half grouted sleeve connection were found to be directly affected by the temperature, and some characteristics are different from that of the rebar. The results showed that the half grout sleeves exhibited two types of failure, namely rebar fracture and rebar pullout due to bonding failure. The mechanical properties of specimens were similar to that of single rebars. When the temperature elevated, the failure mode and rebar breakpoint location may change. The bonding length that would be sufficient at room or low temperature, becomes insufficient at 600 °C. Suggestions about the bond length are given to avoid rebar pull out from the grout due to bond failure at elevated temperature.

Grouted splice sleeve connection is a crucial component in modular/prefabricated building structures. However, the reliability (e.g., crack-induced durability issues) of the grouting materials in the splice sleeve connection during their service life is hardly assessed. The external maintenance strategy is usually unimplemented. A capsule-based grouting material was considered in this paper to prolong the service life of the connection through self-healing micro-cracks induced by mechanical force (e.g., seismic and wind load). The influences of capsules on the grouting material in terms of flowing property, compressive strength and porosity were investigated in this paper. The morphological features of the capsule, as well as its status in uncracked and cracked (i.e., failed and triggered) grout matrix, were characterized by scanning electron microscope (SEM). The experimental results revealed that adding no more than 3% capsules into the grouting material can meet the engineering requirements of flowing property (i.e., more than 300 mm in the initial time and more than 260 mm at 30 min) and compressive strength (i.e., over 35, 60 and 85 MPa at 1-day, 3-day and 28-day, respectively). Excessive dosage of capsules added to the grouting materials increased the porosity of the matrix. The pores ranging from 100 nm to 500 nm were significantly influenced due to poor hydration (free water absorbed by the capsule), whereas the relatively large pores (>200 μm) formed weak zones in the matrix. The self-healing effect of the capsule on the splice sleeve connection was assessed by a preliminary pull-out test. It was found that the overall ductility of the connection system could be improved after self-healing for the crack-induced damage of the grouting materials.

This paper investigates the properties of injection grouts with different amounts of natural hydraulic lime (NHL) replacement by metakaolin MK1 or MK2. The focus is dedicated to the fresh properties of the NHL-based grouts, as well as to a parallel study of the evolution of compressive strength and phase composition of hardened grouts, through tests at 28, 56, 90 and 900 days. Additionally, at 90 days, the influence of the MK1 and MK2 incorporation on the porosity characteristics of hardened grouts was determined. Tensile bond strength, being one of the key hardened properties of the injection grouts, was for the time being determined only at an early age of 28 days. The results showed that by adding metakaolin at constant fluidity, the water demand of the fresh mixture increases with the increase of the metakaolin content. At the same time the water retention capacity of the grout is enhanced. In a hardened state the addition of metakaolin increases early age and long term compressive strength of the grout. Also, its bond strength can be considerably increased, by applying MK1. Mixtures with metakaolin resulted in the formation of hydration products such as ettringite, hemicarboaluminate and monocarboaluminate, whereas stellerite was present only in the case of higher proportions of metakaolin with a higher BET surface area and Al2O3 content.

Prefabricated fibre-reinforced polymer (FRP) composite jacket is now becoming an effective repair system for deteriorating piles and columns exposed to marine environment. This system works by providing grout infills between the annulus of the existing structure and the composite jacket. Few studies are however available on the optimal grouting materials that can effectively transfer the stresses between the existing structure and the FRP jacket. This study is investigating the effect of cementitious, concrete and epoxy-based grout infills on the structural behaviour of pre-fabricated glass-FRP (GFRP) tubes. The considered grouts have compressive strength and modulus of elasticity ranging from 10 MPa to 70 MPa and from 10 GPa to 35 GPa, respectively. The experimental results showed that the behaviour of the composite repair system is highly dependent on the modulus of elasticity and the compressive strength of the grout infill. The brittle failure behaviour of the cementitious and epoxy grouts led to localised failure in the FRP repair system while the progressive cracking and crushing of the concrete infill resulted in effective utilisation of the high strength properties of the composite materials. Theoretical analysis of the overall compressive behaviour has also been conducted and showed very good agreement with the experimental results. Refereed/Peer-reviewed

This paper deals with theoretical, numerical and experimental investigations of guided wave propagation in multilayered cylindrical bars with pre-existing debonding. The research focuses on a complex description of the nature of the wave phenomena occurring in a debonded specimen with a special emphasis on the influence of the location of damage on the wave conversion and diffraction. Experimental non-destructive and destructive tests are conducted on the laboratory models of ground anchors with a variable debonding length and location. Debonding is simulated by wrapping the bar in the cellophane film with very small thickness, providing indirect contact between steel and grout but reducing grout adhesion to steel. Guided waves are excited and measured at the free end of the bar with the use of piezo actuators. Characteristic reflections are identified in signals registered for anchors with three locations of debonding and five debonding lengths. The obtained results show that despite of such small thickness of debonding (60 µm), guided waves may be used as an effective method for detection of adhesive debonding at an early stage of its development.

To create composite behaviour in precast concrete panel construction, grouted dowel connections are widely used owing to their simplicity and ability to divert damage from panels during excessive deformation. Yet, current design codes treat this connection as a bar-in-concrete idealization, disregarding the sleeve confinement and composite behaviour of the assembly. Moreover, the performance of this connection under cyclic excitation is yet to be explored. In this study, full-scale grouted dowel connection specimens mimicking actual field conditions were tested to failure under quasi-static loading. Experimental findings revealed that, regardless of the strain level, grouted connections consistently failed in a pull-through mode by shearing of grout between the lugs of the bar. For all dowel embedment lengths, the load capacity of connections depended primarily on the connection seams of the sleeve, and not on the hoop strain level developed in it. Measurement of the hoop strain values allowed calibrating the Frictional Model, which yielded satisfactory predictions of the experimental results. An empirical model was developed using the experimental results to capture the grout damage due to cyclic excitation, thus providing a rational and accurate design tool for grouted dowel connections in composite panel precast concrete wall construction.

Aiming at the utilization of regional mining wastes including iron tailings sand and coal gangue (CG), a novel coal gangue-filled backfill (CGFB) is proposed in this paper, which is achieved by casting the self-consolidating cement-tailings grout (CTG) into pre-placed CGs skeleton. The mixture proportions of self-consolidating CTGs were first designed based on the rheological properties by adding viscosity enhancing agents (i.e. hydroxypropyl methylcellulose and polyacrylamide) and polycarboxylate superplasticizer (PCE). As a consequence, the static stabilities and filling abilities of fresh CTGs were also strengthened. The filling ability of fresh CTGs is a flowability-related parameter and can be reflected by the surface bugholes of hardened CGFBs. The results indicate that the use of CTG with flow diameter > 25 cm and flow time

Alkali-activated materials (AAM) have attracted extension attention as a promising alternative to ordinary Portland cement (OPC) in many applications. Back-fill grouting is a key procedure in shield tunnel construction. In view of the deficiency of traditional OPC-based grout in consuming natural resources and polluting the environment, it is of great significance to develop low carbon and environmentally friendly alkali-activated grouts (AAG). In this study, AAG used for back-fill grouting in shield tunnels were prepared with fly ash, ground granulated blast-furnace slag and steel slag as the main cementitious materials, supplemented by fine sand and additive. Through laboratory tests, the effects of factors including the concentration of the alkaline activator solution and liquid-to-solid ratio on the performance of AAG were studied systematically. Moreover, the performance of AAG was analyzed and evaluated in terms of basic physical properties, working properties, hardening properties and pore structure properties, and two representative groups of AAG (AAG-Ⅰ and AAG-Ⅱ) were recommended by comparing with a typical OPC-based grout. The results show that the setting time, fluidity and its loss rate over time of AAG can be adjusted in a wide range, and AAG can be flexibly selected for use according to the requirements of grout performance for specific construction cases. By adjusting the ratio parameters of AAG, the 28-day underwater/in-air strength ratio and impermeability pressure of AAG can reach over 0.80 and 0.8 MPa, respectively, showing excellent water dispersion resistance and impermeable performance, while AAG have excellent working properties. Compared with the typical OPC-based grout, AAG-Ⅰ shows better engineering performance.