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Various testing methods have been proposed and conducted on cable bolt pull out in the last century. Large and small scale tests have both provided valuable information about the behaviour of the cable bolts. This study compares large scale and small scale pull out experiments with similar cables, bonding agents (grout and resin), and loading paths (monotonic and cyclic) to juxtapose the unique characteristics of each test. The results suggested that small scale tests in grout tend to have lower repeatability compared to large scale test while large scale test typically provide a stiffer behaviour with higher initial peak loads. In cyclic loading, large scale testing tended to have most of their cycles in the first 5 mm whereas small scale test loading and unloading cycles were more spread. In resin cases, bulbed cables had similar behaviour whereas the unbulbed cables had various load values suggesting the presence of bulbs overshadows other characteristics. [ABSTRACT FROM AUTHOR]

Abstract The utilization of geopolymer as a grouting material has gained significant attention in research and construction applications. Geopolymer grout is a type of binding material that differs from traditional grouts, typically based on Portland cement. Researchers have explored its effectiveness and potential applications in grouting processes, considering its unique properties and characteristics. In this paper, various studies employing and utilizing geopolymer as a grouting material are reviewed. The emphasis is on mixture design of geopolymer grout, physical property, chemical composition of geopolymer grout, rheological behavior of geopolymer grout such as yield stress (in case of Bingham fluid) and viscosity, and engineering properties such as compressive strength, expansion, shrinkage, etc.

The failure of fractured rock masses in slopes due to freeze–thaw processes is a common occurrence in cold regions, leading to significant issues such as soil erosion and landslide disasters, particularly in mining areas. This study utilizes a self-developed true triaxial grouting apparatus to perform full-stress state grouting on freeze–thawed fractured rock. Furthermore, a computational simulation of CT permeability is conducted on the rock mass post-grouting. The primary focus of this research is the quantitative assessment of the waterproofing properties of grout masses utilizing microsilica powder-enhanced cement, along with an analysis of freeze–thaw durability at the grout–rock interface. Experimental findings indicate that microsilica facilitates particle aggregation through nucleation effects and expedites cement hydration via pozzolanic reaction, thereby significantly improving the impermeability and frost resistance of the interface transition zone. Compared to ordinary Portland cement (PC) grouting for waterproofing, the anti-seepage rate is increased by 17% and 20% when microsilica cement is used to grout rock masses that have undergone freeze–thaw cycles of 25 and 45, respectively. The outcomes of this investigation hold substantial importance in enhancing the grouting reinforcement mechanisms of fractured rock masses in cold regions and in implementing targeted preventive and control strategies. Highlights: Grouting in a freeze–thaw rock mass under a true triaxial state. CT reconstruction of the grouting vein and seepage simulation. Microsilica enhancement of the compactness and freeze‒thaw damage resistance of the grout–rock interfacial transition zone. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The utilization of geopolymer as a grouting material has gained significant attention in research and construction applications. Geopolymer grout is a type of binding material that differs from traditional grouts, typically based on Portland cement. Researchers have explored its effectiveness and potential applications in grouting processes, considering its unique properties and characteristics. In this paper, various studies employing and utilizing geopolymer as a grouting material are reviewed. The emphasis is on mixture design of geopolymer grout, physical property, chemical composition of geopolymer grout, rheological behavior of geopolymer grout such as yield stress (in case of Bingham fluid) and viscosity, and engineering properties such as compressive strength, expansion, shrinkage, etc. [ABSTRACT FROM AUTHOR]

The feasibility of using crushed limestone instead of sand in cement grout is examined in this work. This study entails performing several tests, including the Brazilian test, the compressive strength test, and the stress–strain correlation test. The curing times used were 7, 14, and 28 days for mixtures with various proportions of cement to limestone (1:1, 1:2, and 1:4). The conventional sand–cement grout laboratory tests were prepared using a similar methodology to examine the effectiveness of the suggested substitute. The findings show that the limestone-based grout has sufficient strength, but that it is less than that of the typical sand material. The values of the tensile strength and elastic modulus were determined. A focus was made on the tensile strength and stress–strain relationship. A special laboratory set-up was used to look at the progress of failure using strain gauges fitted to the cylindrical samples both vertically and horizontally. The angular shape of the particles' ability to interlock is responsible for the material's increase in strength. According to this study, crushed limestone can be used as a substitute for sand in circumstances where sand supply is constrained. The suggested grout can be used in the shotcrete of tunnels and rock surfaces. [ABSTRACT FROM AUTHOR]

This study focuses on the use of alkali-activated materials and geopolymer grouts in deep soilmixing. Three types of grouts, incorporating metakaolin and/or slag and activated with sodium silicate solution, were characterized at different scales to understand the development of their local structure and macroscopic properties. The performance of the soilmix was assessed by using combinations of the grouts and model soils with different clay contents. Feret's approach was used to understand the development of compressive strength at different water-to-solid ratios ranging from 0.65 to 1. The results suggested that incorporating calcium reduced the water sensitivity of the materials, which is crucial in soilmixing. Adding soils to grouts resulted in improved mechanical properties, due to the influence of the granular skeleton. Based on strength results, binary soilmix mixtures containing 75% of metakaolin and 25% of slag, with H2O/Na2O ratios ranging from 28 to 42 demonstrated potential use for soilmixing due to the synergistic reactivity of metakaolin and slag. The optimization of compositions is necessary for achieving the desired properties of soil mixtures with higher H2O/Na2O ratios. [ABSTRACT FROM AUTHOR]

As a common defect, the water–cement ratio of grout can currently be monitored only during the maintenance phase, which limits the repair methods and misses the optimal opportunity for repairs. To overcome this limitation, this study integrated ultrasonic parameters previously used to characterise cement-based materials and developed a new Initial Setting Time and Water–Cement Ratio (IST_WCR) risk model to predict the setting time and water–cement ratio grout using machine learning (ML) algorithms. Experiments on grout involved four different water–cement ratios, ranging from 0.11 to 0.18. A data-driven method based on ML was used to extract predictive factors from eight ultrasonic parameters, including the speed, energy, main frequency, and main frequency amplitude of P-waves and S-waves, and to evaluate multiple ML classifiers to establish the IST_WCR risk prediction model. This model underwent internal and external cross-validations and demonstrated very strong performance with a Brier score of under 0.01. The dataset for ML classifiers contained a total of 956 signals and 7648 features. Compared with traditional methods, this method can automatically characterise the setting process of grout and identify defective water–cement ratios at a very early stage of curing. [ABSTRACT FROM AUTHOR]

The study of rough fissure seepage and grouting diffusion, slurry consolidation and filling, as well as the seepage reduction law is of great significance for the detection of grouting effect and water damage prevention and control in fissured rock bodies. To this end, a new technology combining three-dimensional scanning and 3D printing was used to batch prepare a visualization test model based on the morphology of real rock fissures, and carry out visualization tests of seepage in rough single fissure, grouting with different water-cement ratios, and seepage after grouting and consolidation filling of fissures. The test results show that: Rough single fissure seepage in the seepage path and seepage law are non-linear characteristics, for the laminar and turbulent flow of the composite flow form; in the equal flow conditions, the water-cement ratio of small slurry has a pre-diffusion of slow in the middle and late fast, the total time instead of the characteristics of the less; slurries with different water-cement ratios fill and consolidate extremely unevenly in the cracks, and the cross-sectional void ratio gradually decreases from the entrance to the end, while the overall filling rate can be increased by up to 20% in slurries with small water-cement ratios; the seepage coefficient of the fissure before and after slurry filling decreased by a factor of 100–1000, and the seepage flow was along the connected gap network and conformed to the nonlinear characteristics of Forchheimer's equation, and with the decrease of water-cement ratio, the coefficients of the nonlinear term and the coefficients of the linear term increased and decreased, respectively, and the ratio of both of them could reach a maximum value of 102. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effectiveness of grout and the mechanism of force transfer in socket connections. In doing so, it proposes a new transfer mode called integral transfer mode (ITM), as opposed to the conventional separate transfer mode (STM). The proposed ITM suggests that, in a reinforced concrete socket connection, if there is a strong bond between the column, grouting material, and receiving member, the socket connection will function as an integral structure, deforming together as a whole rather than as separate components. Consequently, the grouting material does not need to provide a significant lateral bearing force, and the interface shear stresses become the key focus in designing a socket connection. To explore this concept, quasi-static tests and numerical analyses using solid elements were conducted on three half-scale specimens with varying grout strengths. The results demonstrated that the performance of specimens with normal-strength grout was comparable to that of the specimen with high-strength grout. And the proposed ITM was better than STM at predicting failure modes, force–displacement relationships, the stress states of reinforcements, and grout stresses. [ABSTRACT FROM AUTHOR]

The vast majority of different waste building units have negative environmental impacts around the world. Crushed building units can be recycled and utilized in the concrete industry to solve these problems and maintain natural resources. This study investigated the feasibility of employing crushed autoclaved aerated concrete (CAAC) and crushed clay brick (CCB) as a lightweight aggregate (LWA) to fabricate environmentally friendly recycled lightweight concrete (LWC). In addition, a lightweight expanded clay aggregate (LECA) was also used as an LWA, namely to study how the high porosity of an LWA can adversely affect the properties of LWC. Through the experimental program, all types of LWAs were pre-treated and strengthened with two cementitious grouts, and then the performance of the produced LWC was assessed by determining the slump of fresh concrete, the dry density, the unconfined compressive strength, and the splitting tensile strength at ages of 3, 7, 28, and 56 days. The laboratory results revealed that both CCB and CAAC can be reused as full substitutions for normal-weight coarse aggregate to manufacture LWC with appropriate properties. The obtained data show that the properties of an LECA, CCB, and CAAC were improved, and the porous structure can be strengthened by pre-treatment and coating with grouts. In the same way, the mechanical performance of produced LWC is also enhanced. [ABSTRACT FROM AUTHOR]

The aim of this research was to undertake laboratory testing to investigate the beneficial effects of epoxy resin grouts on the physical and mechanical properties of sands with a wide range of granulometric characteristics. Six sands of different particle size and uniformity coefficients were grouted using epoxy resin solutions with three ratios of epoxy resin to water (3.0, 2.0 and 1.5). A set of unconfined compressive strength tests were conducted on the grouted samples at different curing periods and a set of long-term unconfined compressive creep tests in dry and wet conditions after 180 days of curing were also carried out in order to evaluate the development of the mechanical properties of the sands, as well as the impact of water on them. The findings of the investigation showed that epoxy resin resulted in appreciable strength values in the specimens, especially those of fine sands or well graded sands, grouted with the different epoxy resin grouts. Whilst the higher compressive strength and elastic modulus values at the age of 180 days were obtained for the finer sand, which ranged from 2.6 to 5.6 MPa and 216 to 430 MPa, respectively, the lower compressive strength and elastic modulus values were attained for the coarser sand with low values of the coefficient of uniformity, which varied from 0.68 to 2.2 MPa and 75 to 185 MPa, respectively. Moreover, all grouted sands showed stable long-term creep behaviour, with high values of the creep limit ranging from 67.5 to 80% of compressive strength. The presence of water had a negative marginal effect in the majority of the grouted specimens. In terms of physical properties, the permeability and porosity were estimated. The permeability of fine sands or well graded sands was decreased by two to four orders of magnitude. Using laboratory results and regression analysis, three mathematical equations were developed that relate each of the dependent variables of compressive strength, elastic modulus and coefficient of permeability to particular explanatory variables.

The corrosion of steel in post-tensioned tendons has been associated with deficient grout materials containing high free sulfate ion concentrations. In a Florida bridge in 2011, tendon corrosion failures occurred for a prepackaged thixotropic grout that had developed material segregation. However, the available grout and corrosion testing prescribed in material specifications, such as grout bleed water testing, was not able to identify the propensity or modality for the grout deficiencies and the associated steel corrosion that was observed in the field. It was of interest to identify corrosion testing methods that could prescribe grout resistance to segregation-related deficiencies that can form by aberrations in construction. The objectives of the work presented here included (1) characterizing the development of physical and chemical grout deficiencies due to excess mix water and water volume displacement, (2) developing small scale test methodologies that identify deficient grout, and (3) developing test methodologies to identify steel corrosion in deficient grout. The inverted-tee test (INT) and a modified incline-tube (MIT) test were assessed and both were shown to be useful to identify the robustness of grout materials to adverse mixing conditions (such as overwatering and pre-hydration) by parameters such as sulfate content, moisture content, electrical resistance, and steel corrosion behavior. It was shown that the different grout products have widely different propensities for segregation and accumulation of sulfate ions but adverse grout mixing practices promoted the development of grout deficiencies, including the accumulation of sulfate ions. Corrosion potentials of steel < −300 mVCSE developed in the deficient grout with higher sulfate concentrations. Likewise, the corrosion current density showed generally high values of >0.1 μA/cm2 in the deficient grouts. The values produced from the test program here were consistent with historical data from earlier research that indicated corrosion conditions of steel in deficient grout with >0.7 mg/g sulfate, further verifying the adverse effects of elevated sulfate ion concentrations in the segregated grout.

The mechanical properties of metamorphic rocks are affected by foliation, which induces apparent anisotropy and heterogeneity. In this study, a series of pull-off and direct shear tests were performed to investigate the tensile strength, peak shear strength, and residual shear strength of the foliation in different metamorphic rocks (HY slate, RS schist, and SH schist). In addition, the effect of grout reinforcement on the fractured foliation was evaluated. Finally, a model was proposed to evaluate the shear strength of the cement-grouted foliation. The key findings of this study included the following: (1) The tensile and shear strengths of the schists were higher than those of slate. A nonlinear failure criterion for the foliation was adopted to reasonably describe their failure envelopes. (2) For the long-displacement shear tests, the friction angle of HY slate increased as the number of shearing cycles increased, and the friction angle of schists slightly decreased, which was related to the surface variations of the rocks. (3) Considering the grout reinforcement on the fractured foliation, the low strength of the grouted slate was attributed to the weak interface bonding between the cement and slate. In contrast, the strength of the grouted schists significantly increased. The high roughness strongly contributed to the grout reinforcement on the schist foliation. (4) Our proposed shear strength model for cement-grouted metamorphic rocks, which considered factors such as the joint roughness coefficient, uniaxial compressive strength of cement, residual friction angle, and interface tensile strength, provided reasonable predictions that aligned with the experimental test results. Highlights: A series of pull-off and direct shear tests were performed to investigate the strength of the foliation in metamorphic rocks. The effect of grout reinforcement on the fractured foliation was also evaluated. A model was proposed to evaluate the shear strength of the cement-grouted foliation. The proposed model provided reasonable predictions that aligned with the test results. [ABSTRACT FROM AUTHOR]

The aim of this research was to undertake laboratory testing to investigate the beneficial effects of epoxy resin grouts on the physical and mechanical properties of sands with a wide range of granulometric characteristics. Six sands of different particle size and uniformity coefficients were grouted using epoxy resin solutions with three ratios of epoxy resin to water (3.0, 2.0 and 1.5). A set of unconfined compressive strength tests were conducted on the grouted samples at different curing periods and a set of long-term unconfined compressive creep tests in dry and wet conditions after 180 days of curing were also carried out in order to evaluate the development of the mechanical properties of the sands, as well as the impact of water on them. The findings of the investigation showed that epoxy resin resulted in appreciable strength values in the specimens, especially those of fine sands or well graded sands, grouted with the different epoxy resin grouts. Whilst the higher compressive strength and elastic modulus values at the age of 180 days were obtained for the finer sand, which ranged from 2.6 to 5.6 MPa and 216 to 430 MPa, respectively, the lower compressive strength and elastic modulus values were attained for the coarser sand with low values of the coefficient of uniformity, which varied from 0.68 to 2.2 MPa and 75 to 185 MPa, respectively. Moreover, all grouted sands showed stable long-term creep behaviour, with high values of the creep limit ranging from 67.5 to 80% of compressive strength. The presence of water had a negative marginal effect in the majority of the grouted specimens. In terms of physical properties, the permeability and porosity were estimated. The permeability of fine sands or well graded sands was decreased by two to four orders of magnitude. Using laboratory results and regression analysis, three mathematical equations were developed that relate each of the dependent variables of compressive strength, elastic modulus and coefficient of permeability to particular explanatory variables. [ABSTRACT FROM AUTHOR]

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"In this research, the ultimate bond capacity of post-installed anchors for adhesives (three brands: HITRE10, ROX-GU80 and DUBELLF1331) and grouts (FLO-GROUT2) has been evaluated experimentally and compared with the reference cast-in-place anchors. In addition, a parametric study has been conducted to assess the effects of the anchor diameter (10, 12, 16 mm), anchor embedded length (5db,10db and 15db) and the cleaning method on the adhesive and grouted anchors. Among the used three adhesive brands, the anchor adhesive Brand “HIT-RE10” had the largest bond capacity. Furthermore, apart from the small embedded length (5db), the experimental results showed that the ultimate bond capacity of the post installed anchors was higher than the reference cast-in-place anchors. In the same embedded length range (>5db), the average bond stress decreased with the increase in the embedment length. With respect to the effect of the increase in the embedment length and the diameter parameters, the results showed that there is a corresponding increase in the ultimate bond capacity in both the adhesive and the grout anchors. For the cleaning method parameter in adhesive anchors, the cleaning with air only achieved a higher ultimate bond capacity compared with cleaning using air plus wire brush; however, in grout anchors, the cleaning using air plus wire brush produced the larger capacity. The results also showed that cleaning the holes of the adhesive anchors by washing with water and wire brush produced the highest ultimate bond capacity compared with the other two cleaning method. "

Corrosion of steel strand embedded in deficient grout has been associated with elevated concentrations of sulfate ions stemming from grout segregation and the adverse influences of excess mix water and grout prehydration. There have been discussions about appropriate ways to assess sulfate ion levels in the grout pore water. Various test methodologies can include varying material conditioning procedures, including heating, drying, and chemical reactions that can influence the level of sulfate ion aggregation in the test leachate from the initial bleed water from the bulk material. In this study, the sulfate content was measured by leaching and alternative methods such as XRF and bleed water testing. Six leaching methods were employed to assess the effect of leaching heating, heating time, leaching volume, grout sample mass, and drying temperature. Leaching of larger grout sample mass can yield higher leachate sulfate concentrations, but the concentrations were not commensurate with the larger grout mass. Leaching of a larger grout sample mass with a mass-to-water ratio of 1:10 was not shown to be efficient in the dissolution of sulfate ions. Larger mass-to-water ratio (1:40) yielded higher sulfate concentrations in the leachate and normalized grout mass. Pre-drying of grout samples to 100 °C for 24 h was shown to incur losses in sulfate content. Recommendations of test methods to assess the sulfate ion content from segregated and hardened grout were made.

High‐strength steel pipe joints are proposed for assembled composite columns. The steel pipe extends into the upper and lower prefabricated columns and is anchored by poured concrete or grout to realize the connection of the prefabricated columns. Bonding performance of high‐strength steel pipe and surrounding concrete/grout is critical to the joint reliability. Steel pipe push‐out test was carried out, considering parameters of steel pipe section specification, bonding length, bonding material, and outer wall treatment of the steel pipe. Comparative analysis of measured load–displacement/slip curves and calculated bond strength were conducted. Bonding length of 600 mm could provide sufficient bond strength. Increasing bonding length could delay the slippage, but the bond strength decreased. High‐strength grout significantly increased the peak load size. The slenderness ratio and diameter–thickness ratio of the steel pipe had no obvious influence on the bonding performance. Steel pipe with D114*25 section obtained higher bonding strength with smaller ratio of bonding area to cross‐sectional area. Spiral ribs welded to the outer wall of the steel pipe could effectively improve the bonding strength and delay the interface slip. With easy construction and reliable performance, spiral ribs were recommended to be applied in prRactical projects. [ABSTRACT FROM AUTHOR]

The corrosion of steel in post-tensioned tendons has been associated with deficient grout materials containing high free sulfate ion concentrations. In a Florida bridge in 2011, tendon corrosion failures occurred for a prepackaged thixotropic grout that had developed material segregation. However, the available grout and corrosion testing prescribed in material specifications, such as grout bleed water testing, was not able to identify the propensity or modality for the grout deficiencies and the associated steel corrosion that was observed in the field. It was of interest to identify corrosion testing methods that could prescribe grout resistance to segregation-related deficiencies that can form by aberrations in construction. The objectives of the work presented here included (1) characterizing the development of physical and chemical grout deficiencies due to excess mix water and water volume displacement, (2) developing small scale test methodologies that identify deficient grout, and (3) developing test methodologies to identify steel corrosion in deficient grout. The inverted-tee test (INT) and a modified incline-tube (MIT) test were assessed and both were shown to be useful to identify the robustness of grout materials to adverse mixing conditions (such as overwatering and pre-hydration) by parameters such as sulfate content, moisture content, electrical resistance, and steel corrosion behavior. It was shown that the different grout products have widely different propensities for segregation and accumulation of sulfate ions but adverse grout mixing practices promoted the development of grout deficiencies, including the accumulation of sulfate ions. Corrosion potentials of steel < −300 mVCSE developed in the deficient grout with higher sulfate concentrations. Likewise, the corrosion current density showed generally high values of >0.1 μA/cm2 in the deficient grouts. The values produced from the test program here were consistent with historical data from earlier research that indicated corrosion conditions of steel in deficient grout with >0.7 mg/g sulfate, further verifying the adverse effects of elevated sulfate ion concentrations in the segregated grout. [ABSTRACT FROM AUTHOR]

Cappadocia Region (World Heritage Site registered by UNESCO) carries thousands of rock-cut structures, masonries and fairy chimneys, which have been used in every aspect of daily life. Damages occurred during their working life, and restoration with inappropriate materials are threatened these structures. Moreover, an enormous amount of waste material is excavated throughout the carving process, passing approximately 10 million cubic meters per annum, creating pollution in the region, and not being used efficiently. This study aims to use Cappadocia waste earth (CWE) in the grout for consolidation and strengthening rock-cut structures, masonries and fairy chimneys located in Cappadocia region. The utilization of this waste earth in the grout prevents the destruction of these valuable structures and provides a solution to a critical environmental problem. The experiments were conducted employing by 30%, 40%, and 50 wt% of Cappadocia waste earth with natural hydraulic lime in the existence of chemical admixtures. The influence of ambient temperatures (5°C, 20°C, and 40°C) and time-dependent behavior on the rheological performance of grouts were investigated. The findings revealed that dosages of Cappadocia waste earth, different environmental temperatures, and constant shearing (time-dependent) have critical roles in determining the optimum requirements for injection. [ABSTRACT FROM AUTHOR]

The measurement of the electrical resistivity of cement-based materials, e.g., concrete, is used for quality control and durability assessment. In an existing structure, the electrical resistivity of the concrete can be monitored using either pre- or post-embedded probes. When using post-embedded probes, the contact material (grout) used when installing the probe can affect the measurements. This work investigated the effect on the measurement of two different grouts (in alkaline and carbonated condition) used for the installation of a post-embedded probe in carbonated mortar. The effect of the geometry of the system was also examined. [ABSTRACT FROM AUTHOR]

The article describes recent cases of tendon ruptures by corrosion and investigations carried out on some bridges in France. Several causes related to HDPE ducts have been identified such as damages during handling, threading and tensioning of strands, defective connection of the duct to the anchorage, damage during construction or operation, low quality of HDPE material, etc. These cases of tendon rupture exclusively concern ducts injected with cement grout. To our knowledge, no structure built after the application of the 2001 circular [1] (prohibiting cement grout for the injection of external prestressing) is currently exhibiting major disorders. A warning note on existing structures with external prestressing has been updated by Cerema in November 2018 [2]. It describes the diagnosis methodology based on analysis of documentation, thorough visual inspection, destructive and nondestructive investigations. New non‐destructive techniques such as guided‐wave ultrasonic technique and magnetic leakage field test using permanent magnets and induction coils are presented. Innovative methods of local repair of the ducts are also described. Finally, different protective devices are analysed in terms of worker safety in the event of a sudden failure of tendon. [ABSTRACT FROM AUTHOR]

The grout pressure in the shield tunnel tail void during synchronous grouting is the key to controlling ground settlement and restraining the segment. However, the circumferential, longitudinal, and radial distribution of grout pressure considering the temporal variation in grout viscosity has not been well explored yet. In this study, a theoretical model of grout pressure distribution and dissipation considering the temporal variation in Bingham grout viscosity was established. The simulation results of the pressure model were verified by field-measured data. The results showed that the radial and longitudinal distributions of grout pressure considering the temporal variation in grout viscosity were closer to the field-measured data. The impacts of the main parameters on the pressure distribution and dissipation were analyzed. Compared with the effect of the shield tail void thickness, tunnel radius and yield shear stress have greater effects on grout pressure during the circumferential filling phase. During the longitudinal and radial diffusion phases, the increase in soil porosity and permeability coefficient was conducive to grout diffusion. The increase in the grout viscosity reduces the pressure loss during the grout flow process. The results of this research can provide a theoretical basis for the grout design process in shield tunnels. [ABSTRACT FROM AUTHOR]

High-strength grout is specified to increase the bond between grout and bar in grouted connections and to ensure that the forces in the bars can be transferred to the surrounding material accordingly. Although polymer grout is fast setting and rapid in strength development, the use of polymer mortar in grouted connections is still limited because of the lack of information and familiarity practitioners have regarding the product. The goal of this work is to investigate the mechanical characteristics and performance of polyester grout containing fly ash that can be used as an infill material for grouted connections. This study focused on the composition of polymer grout, which typically consists of a binder, hardener, and filler. In this particular case, the binder was made of unsaturated polyester resin and hardener, while the filler was fine sand. The aim of the research was to investigate the potential benefits of incorporating fly ash as an additional filler in polymer resin grout and examine the mechanical properties of polymer resin grout. To this end, varying amounts of fly ash were added to the mix, ranging from 0% to 32% of the total filler by volume, with a fixed polymer content of 40%. The performance of the resulting grout was evaluated through flowability, compression, and splitting tensile tests. The results of the experiments showed that, at a fly ash volume of 28%, the combination of fine sand and fly ash led to an improvement in grout strength; specifically, at this volume of fly ash, the compressive and tensile strengths increased by 24.7% and 124%, respectively, compared to the control mix. However, beyond a fly ash volume of 28%, the mechanical properties of the grout started to deteriorate. Due its superior properties in terms of compressive and flexural strengths over all examined mixes, the PRG-40-28 mix is ideal for use in the infill material for mechanical connections. [ABSTRACT FROM AUTHOR]

This article discusses a case of occupational allergic contact dermatitis (OACD) in a 49-year-old grout worker due to exposure to Tinuvin 770, a hindered amine light stabilizer (HALS) found in grouting materials. The patient presented with hyperkeratotic fissured eczema and pulpitis on his fingers, which improved after patch testing revealed a positive reaction to Tinuvin 770. This case highlights the allergenic capacity of Tinuvin 770 and emphasizes the importance of identifying occupational allergens in workplace settings. [Extracted from the article]

In post-tensioned systems, grouts act as a last line of defense to prevent the penetration of harmful compounds such as chlorides, moisture and other substances that cause corrosion in the prestressing steel. For this reason, improving grouts results in the enhancement of the overall durability of the structure. In this study, the physical properties of grouts with basalt microfiber additions in the amounts of 0.03, 0.07 and 0.10% with respect to the mix volume were evaluated. The fresh properties included flowability and unit mass. Specimens were fabricated to evaluate drying shrinkage, compressive strength, air permeability and rapid permeability to chloride ions. The incorporation of basalt microfibers showed a beneficial effect on the physical properties of the grout by increasing the drying shrinkage resistance and decreasing the permeability compared to the reference mix and two commercial dry prepackaged grouts. The optimal grout mix was the one with a percentage of basalt microfibers of 0.10%, which decreased drying shrinkage by 15.98% at 14 days compared to the reference mix, and permeability to chloride ions decreased by 10.82% compared to the control mix. [ABSTRACT FROM AUTHOR]

Building foundations are usually retrofitted with directly connected micropiles; however, at the present time, there are different approaches for predicting shear capacity in the micropile–foundation connection. At first, the concrete shear strength was considered. Nowadays, in the EU countries, it is prescribed to use the shear strength of the interface between successive concrete casts at different times. This implies a reduction of the connection capacity by half, and these values are not in consonance with the lab results. This work analyses the economic impact of the previous considerations on retrofit projects with micropiles. To this aim, firstly, seven different formulations were applied to 29 building projects, and the results were compared. Secondly, a Monte Carlo sensitivity analysis was performed using bond stress distribution data obtained from lab tests. Thus, numerical results acquired by comparing European and American regulations show an average difference in cost of around 40%, which may reach up to 50%. Moreover, the Monte Carlo simulation confirms that the connection strength may become a limitation in retrofit projects, also indicating that the application of European codes usually leads to the most expensive designs. Finally, the results show that it is not worth improving the connection to exceed a bond stress of 0.60 MPa, since no relevant savings are produced by achieving higher values. [ABSTRACT FROM AUTHOR]

Lime–pozzolan grouts concern a specific type often applied in the restoration of historic structures. Their water content, a crucial factor of their applicability, has a significant impact on their fresh and hardened state properties. In this study, four grout compositions were manufactured and tested, consisting of hydrated lime and natural pozzolan in a mass proportion 1:1. Their fresh properties were recorded, including fluidity, penetrability, volume stability, viscosity and shear stress, as well as the hardened ones (shrinkage deformations, physical and mechanical characteristics). Results show that water content reduction led to an increase in flow and penetration time, as well as a significant decrease of volume changes. Mechanical properties were significantly enhanced. Generally, the water content played a fundamental role in the behavior of the mixtures, also defining the type and range of their application.