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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 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]

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 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]

"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.

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]

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]

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.

In this study, we report the photocatalytic activity of TiO2 monitored by benzene oxidation in the grout medium. The results of the batch reaction tests indicated that the activity of TiO2 coated on grout was substantially less than TiO2 coated on a glass substrate. CO2 adsorption on these samples monitored by DRIFTS indicated that the loss of activity in the grout medium was due to formation of stable carbonates-bicarbonates in highly alkaline grout media.

There are many factors that may affect the concrete-strand and concrete-duct bond behavior in post-tensioned (PT) concrete slabs and beams. The importance of bond strength is to ensure a proper transfer of stresses from strands and ducts to the surrounding concrete. This research focused on bonded post-tensioned (PT) concrete elements, which includes the use of grout and ducts to provide the link between the strand and the concrete. The strength of the grout, the type and geometry of the ducts, and the embedment length of both strands and ducts were investigated through an experimental testing program to disclose the average interface shear stress within the embedded length of PT elements. This work helped in a better understanding of the bond behavior and the corresponding related parameters involved in the design process.

This article reports a quick-setting agent named AS-G1. In the current offshore oil exploitation, there are usually wastes mixed with the drilling fluid, completion fluid, cement slurry, etc. To protect the marine environment, offshore construction workers need to weakly solidify these wastes so that they can be transported to land for disposal. The accelerating agent can reduce the fluidity of offshore cementing wastes and achieve the effect of solidifying wastes. Compare the time for the three cement slurries to lose fluidity with the addition of accelerating agents. Evaluate the setting time of cement slurry under the action of the accelerating agent after adding two drilling fluids. The solidification effect of this kind of accelerating agent on cementing waste is verified. It can be applied to waste treatment in oil fields.

The utilization of ultra-high-performance concrete (UHPC) permanent formwork could facilitate the construction of hydraulic concrete structures. However, the joints between UHPC formwork are the vulnerable parts of a whole permanent formwork system. This study aimed to develop a High Strength Cementitious Grout (HSCG) for filling these joints, integrating the formwork system, and minimizing the adverse influence on these joints. The aggregate size for the HSCG was optimized, and four kinds of admixtures (i.e., hydrophobic powder (HP), expansive agent (EA), redispersible polymer powder (RPP), and cellulose ether (CE)) and PVA fibers were used to improve the HSCG. The HSCG with different aggregate sizes, admixture dosages, and PVA fiber contents were experimentally investigated. By evaluating the compressive, tensile, flexural, and adhesive strengths of the prepared grout, the aggregate size range was recommended to be 0.15–0.30 ​mm, while the suggested contents of HP, EA, RPP, and CE were 0%, 6%, 2%, and 0.1%, respectively, by weight of binding materials. In addition, the optimal volume content of PVA fibers was 0.45%. In order to avoid the introduced foams, 0.2% of the defoamers were used in combination with the CE. After that, six combinations were tested to consider the coupled effect of different admixtures and PVA fibers on the HSCG. In consideration of the strengths, shrinkage, and abrasion resistance to water impact, the HSCG with the combination of (EA ​+ ​RPP ​+ ​CE), the aggregate size of 0.15–0.30 ​mm showed the optimal overall performance and was regarded as the most suitable HSCG for grouting.

The bore hole is sealed from a sealing hole: the surrounding coal fracture permeability and grout cementation form a new consolidated body and coal material. In this paper, the characteristics of the macroscopic compressive strength, microscopic interface bending, porosity, and fractal dimension of the consolidated body were studied, and the structure strength relationship between loading rates, porosity, fractal dimension, and uniaxial compressive strength (UCS) was established. The results show that the loading rates had a great and consistent effect on the macro- and micro-mechanical properties of the consolidated body. Macroscopically, in the range of 0.1~0.4 mm/min, the UCS and elastic modulus of the solidified body increased with the increase in the loading rate, and there was a critical loading rate (η = 0.4 mm/min). At the microscale, with the increase in loading rates, the interface bending phenomenon, porosity, fractal dimension, and UCS of the grout and coal were consistent, showing a trend of increasing first and then decreasing. The fractal dimension was linearly correlated with the UCS and porosity. The loading rates, porosity, fractal dimension, and UCS had a multivariate nonlinear regression distribution. [ABSTRACT FROM AUTHOR]

An acceptable viscosity and an easy penetrability of cement - limestone filler grout in the granular matrix of self compacting concrete are an important factors that affecting both its rheological and its hardened properties. This experimental and theoretical work consists to study the effect of limestone filler fineness on the rheological behavior of cement - limestone filler grout. In the first part, five different grouts were prepared by varying the Blaine Specific Surface (BSS) of the limestone filler, 3060, 4750, 6320, 7680 and 9440 cm2/g, respectively. A large number of properties relating to the rheology and the stability are carried out on the five grouts such as grain dispersion, density, volume concentration of solid, dynamic viscosity and Marsh funnel flow. The second part consists to develop a theoretical model to predict the different rheological properties of the grout as function of limestone filler BSS. The results show that the rheological properties of cement-limestone filler grout such as the dispersion percentage, the intergranular distance and the flow time are strongly affected by the limestone fillers fineness. In addition, the experimental and the predicted results present a good agreement.

The main objective of this work is to highlight experimentally the effect of quarry waste limestone fillers (LF) on the rheological properties of concrete. All mixtures were made with water-to-cement ratio (W/C) of 0.50. The method adopted based on the rheological behavior of concrete incorporating LF as a partial substitute for sand in multi-scale systems (concrete, mortar, grout and LF suspension). The replacement ratio of sand by LF ranged from 0% to 20% (by weight of sand) in concrete and mortar. Whereas, the addition of LF varied from 0% to 60% (by weight of cement) in cement grout. The rheological behavior of concrete and mortar was modeled by the Bingham model with sufficient precision. However, the cement grout shows a nonlinear behavior, which was modeled by the Herschel-Bulkley model. Results indicate that the use of LF has a significant effect on the superplasticizer (Sp) demand of concrete and mortar, for a given slump on one hand. On the other hand, an increase in yield stress, apparent viscosity and flow time of cement grout was obtained when LF is incorporated, which results in a loss of fluidity of the suspensions of LF.

Localized corrosion developed on post-tensioned steel strand in deficient grout, relating to elevated concentrations of sulfate ions. The deficient grout can also have low-level chloride ion concentrations below threshold values originating from the base materials. Open-circuit potential, linear polarization resistance (LPR), and electrochemical noise (EN) measurements were made on steel specimens exposed in saturated calcium hydroxide solution with 0.012 M Cl−, 0.04 M SO42−, or combined. Results showed that the combined presence of sulfates in low-level chloride alkaline solutions elevated the corrosion rate and the extent of corrosion pitting. The EN technique was shown to provide corrosion rate estimates consistent with LPR and was able to identify pitting characteristics. The outcomes of the research provides supporting evidence that analysis of deficient grout for chlorides alone may not capture the risk for corrosion and that corrosion associated with elevated sulfate concentrations can be exacerbated in presence of low-level chlorides.

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.

Axial studies on cable bolts can be conducted using various scale testing apparatuses. Large scale testing, while providing a powerful platform for testing, is expensive and time consuming. This study presents details of a small scale pull out testing campaign on cable bolts and investigates the results achieved. Six popular types of cable bolts were studied using an anti rotation apparatus while encapsulated in cementitious grout and resin. The resin samples were tested under both monotonic and cyclic loading patterns. The results showed that grouted bulbed cables require higher displacement to reach their maximum load capacity which is lost at failure, while plain cables tend to hold lower loads for a longer time. Resin samples provided strain softening behaviour with low capacities, particularly in absence of cable indentation or bulbs. Cyclic loading tended to adversely affect the post peak behaviour of the resin samples, especially in the bulbed cables. Failed samples inspected after the testing suggested a non-uniform damage profile along the cable with extensive damage at the exit point transitioning into almost no damage at the entry point. • Design and manufacturing of a small scall pull out apparatus. • Testing various modern cable bolts comprising multiple cable bolt design trends. • Comparing the performance of cementitious and resin grout in pull out test. • Comparing cable bolts in monotonic and cyclic loading scenarios. [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. [ABSTRACT FROM AUTHOR]

The usability of two environmentally important waste materials in cementitous fine grout production was investigated as partial replacement materials for cement and aggregate. The influence of replacement materials on flowability and strength of was investigated by rheological and compressive strength tests. The strength of 28 and 90 days grouts was determined. It was found that the flowability and strength of the mixes were heavily dependent on W/C ratio and affected by type and amount of replacement materials. Increasing W/C ratio and fly ash amount increased flowability, but inversely affected the strength of grouts. On the other hand, marble powder was found to increase the strength of grout to a large extent, but decreased the flowability. It was interestingly found that the strength of all grout mixes increased at different levels with aging and the lowest and the highest increase were observed with marble powder and fly ash replaced mixes, respectively.

The reduction of CO2 emissions has become a global concern. In this regard, the EU intends to cut CO2 emissions by 55% by 2030 compared to those of 1990. The utilization of shallow geothermal energy (SGE) in EU countries is considered the most effective measure for decarbonizing heating and cooling. SGE systems utilize heat energy collected from the earth's crust to provide secure, clean, and ubiquitous energy. This paper provides a literature review on the use of SGE for heating and cooling purposes. The latest advances in materials, new innovative structures, and techno-economic optimization approaches have been discussed in detail. Shallow geothermal energy's potential is first introduced, and the innovative borehole structures to improve performance and reduce installation cost is outlined. This is followed by an extensive survey of different types of conventional and thermally enhanced collectors and grouts. Attention is mainly given to the techno-economic analysis and optimization approaches. In published case studies, the least economic break-even point against fossil fuel-based heating systems occurs within 2.5 to 17 years, depending on the local geological conditions, installation efficiency, energy prices, and subsidy. Ground source heat pumps' cost-effectiveness could be improved through market maturity, increased efficiency, cheap electricity, and good subsidy programs. [ABSTRACT FROM AUTHOR]

Preplaced aggregate fibrous concrete (PAFC) is a revolutionary kind of concrete composite that is gaining popularity and attracting the interest of academics from across the world. PAFC is a uniquely designed concrete prepared by stacking and packing premixed fibers and coarse aggregate in a steel mold. The gaps between the fibers and aggregates are subsequently filled by injecting a cement grout with high flowability. This study investigates the impact performance of three different sizes of PAFC beams. Steel and polypropylene fibers were used in a 3% dosage to make three different beam sizes, measuring 550 × 150 × 150 mm, 400 × 100 × 100 mm, and 250 × 50 × 50 mm. According to ACI Committee 544, all beams were subjected to a drop weight flexural impact test. Compressive strength, impact energies at initial crack and failure, ductility index, and failure mode were evaluated. Additionally, analytical modeling was used to compute the failure impact energy for the fibrous beams. The results showed that the addition of fibers increased the capacity of the tested beams to absorb greater flexural impact energy. Compared to polypropylene fibers, steel fibers had better crack propagation and opening resistance because of their higher tensile strength and crimped and hooked end configuration. For all large-size beams, the analysis of the percentage increase in impact energy at the failure stages was found to be 5.3 to 14.6 times higher than the impact energy at cracking. [ABSTRACT FROM AUTHOR]

Post-tensioned (PT) construction incorporating bonded tendons with cementitious grouts has been used for highway bridges. The tendon duct and the encapsulating grout materials provide barrier corrosion protection for the embedded high-strength steel strand. Although generally used in good engineering practice, cases of PT tendon corrosion have been documented relating to inadequate detailing for joints and development of grout bleed water. Recently, in the past several years, unexpected severe localized strand corrosion has related to the segregation of thixotropic grouts. In the latter case, thixotropic grouts (that have been developed to mitigate grout bleeding) formed physical and chemical deficiencies that have been characterized to have high moisture content and elevated sulfate ion concentrations. The early presence of elevated sulfate ion concentrations in the deficient grout hinders stable steel passivation. The corrosion mechanism can be complicated due to the compounding effects of physical grout deficiency, moisture content, pore water pH, and the presence of sulfate ions. There remains interest to reliably assess corrosion of PT tendons with deficient grout. A review of electrochemical techniques and test methods used in earlier research by the authors to identify the role of sulfates on localized steel corrosion in alkaline solutions is presented. It was evident that different testing methods can reveal various aspects of the corrosion of strands in the deficient PT grout. The open-circuit potential and linear polarization method could differentiate corrosion activity between hardened and deficient grout environments but did not reveal the development of localized corrosion. Electrochemical impedance spectroscopy was useful to identify grout deficiencies by the differentiation of its bulk electrical properties. Potentiodynamic polarization and electrochemical noise technique were used to identify metastable and pitting in alkaline sulfate solutions representative of the deficient grout pore water. [ABSTRACT FROM AUTHOR]

In recent years, prepacked aggregate fibrous concrete (PAFC) is a new composite that has earned immense popularity and attracted researchers globally. The preparation procedure consists of two steps: the coarse aggregate is initially piled into a mold to create a natural skeleton and then filled with flowable grout. In this instance, the skeleton was completely filled with grout and bonded into an integrated body due to cement hydration, yielding a solid concrete material. In this research, experimental tests were performed to introduce five simple alterations to the ACI 544 drop weight impact test setup, intending to decrease result dispersion. The first alteration was replacing the steel ball with a steel bar to apply a line impact instead of a single point impact. The second and third introduced line and cross notched specimens at the specimen's top surface and the load applied through a steel plate of cross knife-like or line load types. These modifications distributed impact load over a broader area and decrease dispersion of results. The fourth and fifth were bedding with sand and coarse aggregate as an alternate to the solid base plate. One-hundred-and-eight cylindrical specimens were prepared and tested in 12 groups to evaluate the suggested alteration methods. Steel and polypropylene fibers were utilized with a dosage of 2.4% to produce PAFC. The findings indicated that the line notched specimens and sand bedding significantly decreased the coefficient of variation (COV) of the test results suggesting some alterations. Using a cross-line notched specimen and line of impact with coarse bedding also effectively reduced COV for all mixtures. [ABSTRACT FROM AUTHOR]

This study investigated anchorage behavior of geopolymer-grouted rock bolts. Pull-out tests were conducted on rock bolts grouted by geopolymer mortar (GM), geopolymer paste (GP), and cement mortar (CM), respectively. The effect of grout, type of bolts, spacing of bolts, and anchorage depth on anchorage performance was examined. Experimental results have shown that GM achieves better bond than GP and CM under a constant water binder ratio of 0.4. Deformed bolts grouted by GM and GP exhibit a nominal bond strength 2.4 and 1.6 times higher than the plain round ones, respectively. Bolt spacing of more than 150 mm exerts little influence in the anchorage performance. Increasing anchorage depth contributes to both loading capacity and ductility, while reduces nominal bond strength of deformed bolts. The critical anchorage depth ensuring tensile failure of bolts is 12d for both GM-grouted and GP-grouted bolts. GM-grouted deformed bolts with minimum anchorage depth of 12d and bolt spacing of 150 mm are proposed for practical application. [ABSTRACT FROM AUTHOR]

Colloidal nanosilica hydrosols are electrochemically stabilised polymerised amorphous silica in low viscosity suspensions. They have no known adverse impact on soil health and ecosystem service functions, thereby having a scope for use in groundworks as an alternative low-viscose stabilising material. Six grades of colloidal nanosilica are synthesised through an in-house procedure and introduced to a natural peat soil. The peak and residual compressive strength of compacted and modified soils are measured immediately after treatment and in four strain levels post treatment. Findings suggest that, despite the direct correlation between the nanosilica content and compressive strength, an increase in nanosilica content does not necessarily offer stability at larger strains. This is a major limitation. The particle-level kinematics in modified peat is discussed to gain a new insight into the role played by silica flocs on the build-up of macro-mechanical quantities such as peak and critical state strength. Overall, modification of peat with nanosilica leads to improvements in strength and formation of composites with generally more dilative behaviour. When used as a single stabiliser, a design 15 % to 20 % grade nanosilica solution yields a reasonably high strength although precautions against excessive straining of modified peat soils need to be taken in the first seven days post treatment. At this optimum grade, the loss of strength on further straining is capped to 9 % at plastic strains 1.5 times the peak strain.

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.

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

An acceptable viscosity and an easy penetrability of cement - limestone filler grout in the granular matrix of self compacting concrete are an important factors that affecting both its rheological and its hardened properties. This experimental and theoretical work consists to study the effect of limestone filler fineness on the rheological behavior of cement - limestone filler grout. In the first part, five different grouts were prepared by varying the Blaine Specific Surface (BSS) of the limestone filler, 3060, 4750, 6320, 7680 and 9440 cm2/g, respectively. A large number of properties relating to the rheology and the stability are carried out on the five grouts such as grain dispersion, density, volume concentration of solid, dynamic viscosity and Marsh funnel flow. The second part consists to develop a theoretical model to predict the different rheological properties of the grout as function of limestone filler BSS. The results show that the rheological properties of cement-limestone filler grout such as the dispersion percentage, the intergranular distance and the flow time are strongly affected by the limestone fillers fineness. In addition, the experimental and the predicted results present a good agreement. [ABSTRACT FROM AUTHOR]

Abstract This study aims to evaluate the adherence between clay blocks and grouts. For this purpose, push-out and pull-out tests were performed to assess the adherence presented by different combinations of five types of clay blocks and two types of grouts. The results demonstrated that the geometry of the cells of the clay blocks has a preponderant role in their adherence with grout, as the extent of the contact area between grout and block depends on the geometry of the cell. The shrinkage of the grout can cause the formation of cracks at the interface between block and grout, reducing the adherence between the materials. The shrinkage formed inside each type of block can be estimated based on the testing procedure developed in this research and used in conjunction with the geometric characteristics of the cells of the blocks to estimate the maximum load in the push-out tests. The test procedure developed to estimate the percentage of contact area lost due to grouts shrinkage shows to be promising, since its results were used in the equation to estimate the bond strength between blocks and grouts and shown good correlation. However, more study must be done because there are other variables that can affect the results. These results show that it is possible to use different characteristics of blocks and grouts to increase the adherence between these materials and provide a better behavior for reinforced masonry structures. However, it looks like if block types with a grooved hollow cell are used, a bigger contact surface is produced, and a higher bond strength appears to be assured.

The use of construction and demolition waste is an effective solution to mitigate their environmental impacts and avoid dispose in landfills. This paper aims to evaluate the use of fine recycled-concrete aggregate (FRCA) in grout mixtures used in soil nailing. Compressive strength tests on FRCA grout were carried out at different curing ages and interface shear strength was measured between soil and grout. Properties of a commonly used cement grout are compared with those of sand-cement grout and FRCA-cement grout. Although the FRCA grout shows a lower compressive strength compared to commonly used grout and sand-cement grout, its measured properties still meet the minimum standards requirements. The interface friction angle and adhesion of the FRCA exhibit higher values compared to those measured at the soil–soil interface. The grout mixtures evaluated in this study indicated that it is possible to use 1.126 kg of FRCA for each cubic meter of grout. The consumptions of cement and water were found to be 42% and 24% lower, respectively. This represents approximately 380 kg less of CO2 emissions into the atmosphere per cubic meter. The use of FRCA in soil nail grouting can be a sustainable alternative to reduce environmental impacts, cement consumption, and greenhouse gas emission. [ABSTRACT FROM AUTHOR]

In the present project two series of laboratory tests were performed. The first series aimed at investigating the feasibility of using waste mussel shells as aggregates in the production of concrete. Specimens were prepared by using various types of cements and shells of different size. Their 28-day unconfined compressive strength and stress-strain response was evaluated and compared with the one of specimens composed with compatible calcareous sand or gravel. The second series was carried out on specimens of cement grouted soils with different particle sizes to assess how the size of specimens used for strength testing influences the measured strength and stress-strain response. The model that was utilized to relate the size effect on the compressive strength is the one proposed by Carpinteri.