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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]

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]

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]

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]

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]

With the increased use of cable bolts in mining and civil projects worldwide, it is important to understanding the performance of these support structures in different scenarios. The axial load transfer mechanisms of six cable bolts were investigated experimentally in this research study. A large-scale pull-out testing apparatus with a capacity of 1000 kN was designed and manufactured as part of the investigation. A common commercial cementitious grout with a uniaxial compressive strength of 60 MPa was used to encapsulate 300 mm length samples. Passive confinement encapsulated each sample to ensure the concrete's integrity during the testing. The encapsulated cable bolts were then subjected to axial loads using a hydraulic ram, with the axial load and displacement measured using a load cell and LVDTs. Two scenarios were investigated: free rotation and restricted rotation. The results demonstrated that the apparatus effectively recorded the behaviour of the cable during pull-out and identified that the radial stiffness of the samples had a significant impact on the overall load of the system. The results also indicated that rotation had a limited influence on the load behaviour of the samples tested. Highlights: Design and manufacturing of a high-capacity 1000 kN pull-out apparatus for newer cables, Rotation investigation showed less adverse effect than previously reported. It was concluded that a zero-rotation test is not feasible as the rotation of the cable inside the annulus is not uniform, Cable modifications such as surface indentation and bulbing significantly change the failure mode from strain hardening or perfectly plastic to strain softening, Interaction of cable strands with grout ridges inside the grout annulus creates relative movements and oscillations in the post-peak loading zone, and Failure is not uniformly distributed in the grout annulus, with higher damage observed at the cable's exit point and minor damage toward the entry point. [ABSTRACT FROM AUTHOR]

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]

Rock salt stratums are likely to be encountered during the injection process in tunnel construction, anchorage and similar in situ applications. In such stratums, the effects of rock salts on the unconfined compressive strength of the grout have not been clearly stated in the literature. For this purpose, cylindrical samples (38 mm x 76 mm) were produced with grout prepared at different water/cement ratios (0.8-1.0-1.2 and 1.4). In addition, granular rock salt was placed in cylindrical transparent molds (100mm x 200mm) with a relative density of Dr = 65% in order to determine the effect of this stratum on the strength of the grout in injection applications made in rock salt stratums. Then, grouts prepared for each water/cement ratio were injected into these samples with a special mechanism. The unconfined compressive strengths of the produced samples were determined after they were cured in appropriate air and water conditions (28 days). According to the test results in laboratory, while no strength could be obtained in the water cure in injected rock salt samples, the highest unconfined compressive strength was obtained as 12.52 MPa at water/cement ratio of 0.8 in air cure. [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]

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]

• Reactive transport model is applied to spatially varied initial conditions after aging. • Mineralogy evolution concerning major constituents after carbonation is investigated. • Carbonate co-precipitates with calcite control the solubilities of Li, Sr, and Ba. • Effective diffusivity is significantly increased after carbonation under 2% CO 2. • Carbonation reduces the solubility and the release of Cr from Cast Stone. Carbonation can be a major aging process during disposal of alkaline cementitious waste forms and can impact constituent leaching by changes in material alkalinity, pore structure, and controlling mineral phases. The effect of carbonation on the leaching of major and trace constituents from Cast Stone, a cementitious waste form developed to treat high salt content low activity waste, was studied through a combination of leaching experiments and reactive transport simulations. Diffusive transport of constituents in the waste form was evaluated using reactive transport modeling of diffusion-controlled leaching test results and a geochemical speciation model derived from pH-dependent leaching. Comparisons between Cast Stone materials aged under nitrogen, air, and 2% carbon dioxide in nitrogen showed that carbonation impacts solubility, physical retention and observed diffusivity of major and trace constituents. Carbonation under 2% CO 2 decreased the diffusion-controlled leaching of chromium by two orders of magnitude. Modeling results suggest that carbonation may also decrease solubility of technetium while changes to microstructure by carbonation increases effective diffusivity of constituents in Cast Stone. [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]

This study investigated the influence of fluorogypsum and KH 2 PO 4 on the mechanical properties and hydration mechanisms of aluminate cement based grouting materials. Physical properties including setting time, pH value and the compressive strength of aluminate cement based grouting materials with different mix design were investigated. The influencing factors and hydration mechanisms were quantified and discussed through XRD, TG, SEM and NMR. The water-cement ratio was fixed at 0.40, and the fluorogypsum content accounted for 10 wt% of the cement mass. With increasing KH 2 PO 4 content, the setting time initially decreased and then prolonged, while the compressive strength at 3d and 28d first increased and then decreased. Among these variations, a content of 0.2 wt% KH 2 PO 4 exhibited the optimal performance with initial and final setting times of 264 min and 308 min, respectively. The compressive strengths at 3 days and 28 days were recorded as 26.4 MPa and 60.5 MPa, respectively, exhibiting an increase of 76% and a remarkable enhancement of 228.80% compared to that of pure aluminate cement. The addition of fluorogypsum facilitated the formation of AFt, while KH 2 PO 4 regulated the slurry's pH, concurrently enhancing AFt production, and the morphology of AFt transformed from acicular to a more slender fiber shape, which exhibited improved interlacing and overlapped properties, thereby promoting strength development. The hydration process was analyzed in conjunction with low-field nuclear magnetic resonator analysis. The findings revealed that the samples containing 10 wt% fluorogypsum and 0.2 wt% KH 2 PO 4 in aluminate cement exhibited the highest levels of chemically bound water at both 3d and 28d, followed by samples with 10 wt% fluorogypsum in aluminate cement, while those composed solely of aluminate cement displayed the lowest content. The T 2 spectra data were also fitted to a function, revealing a positive correlation between pore evolution and the hydration rate of the samples. • Fluorogypsum and KH 2 PO 4 can shorten the setting time and increase the compressive strength of calcium aluminate cement. • Fluorogypsum contributed to AFt formation; KH 2 PO 4 further increased AFt and modified its morphology. • KH 2 PO 4 changed the morphology of AFt to elongated fibers and optimized the pore structure. • Hydration of aluminate cement can be significantly enhanced by combined addition of fluoropgypsum and KH 2 PO 4. • Fluoropgypsum alone could still cause a substantial promotion effect on the hydration rate of aluminate cement. [ABSTRACT FROM AUTHOR]

In situ pull-out tests were performed in claystones at the Andra Underground Research Laboratory of Meuse/Haute-Marne on fully grouted bolts. The bolts were instrumented with strain gauges along their entire length and axial strains were measured from the head to the far end of the bolts, from bolts installation until the end of the pull-out tests. After bolts setting up, one or several neutral points were identified on most of the bolts. The axial strains increased from the head to the far end of the bolts during the pull-out tests. Tests interpretation required numerical modelling to overcome the shortcomings of analytical models, unable to explain the measured axial strain profiles. Numerical modelling was based on a cohesive zone model. The model qualitatively reproduced measured strain distributions and indicated that the bonding between the bolt and the grout is better in the far end of the bolt than at its head. This result is attributed to a more pronounced fracturing during the development of the induced fractured zone at the wall of the gallery, which is typical of these claystones and caused a debonding of the interface at the head of the bolt. [ABSTRACT FROM AUTHOR]

This paper presents the results of field tests performed to investigate the compressive bearing capacity of pre-bored grouted planted (PGP) pile with enlarged grout base focusing on its base bearing capacity. The bi-directional O-cell load test was conducted to evaluate the behavior of full scale PGP piles. The test results show that the pile head displacements needed to fully mobilize the shaft resistance were 5.9% and 6.4% D (D is pile diameter), respectively, of two test piles, owing to the large elastic shortening of pile shaft. Furthermore, the results demonstrated that the PHC nodular pile base and grout body at the enlarged base could act as a unit in the loading process, and the enlarged grout base could effectively promote the base bearing capacity of PGP pile through increasing the base area. The normalized base resistances (unit base resistance/average cone base resistance) of two test piles were 0.17 and 0.19, respectively, when the base displacement reached 5% Db (Db is pile base diameter). The permeation of grout into the silty sand layer under pile base increased the elastic modulus of silty sand, which could help to decrease pile head displacement under working load. [ABSTRACT FROM AUTHOR]

Research on the effects of sulfate ions on steel corrosion has been conducted in response to the observations of premature localized corrosion of steel strands in cementitious grouts in posttensioned bridge construction. Electrochemical noise (EN) was shown to be an effective technique to assess the development of localized corrosion of steel in the alkaline sulfate solution. General statistics of the EN potential and current time signatures revealed the negative effect of elevated sulfate concentrations and the development of pitting events. Spectral analysis indicated an increase in the characteristic charge and decrease in characteristic frequency with sulfate ion concentration, whereas an increase in the overall corrosion rate was observed, indicating the development of pitting corrosion. Pitting events could be sustained in solutions above 10 g Na2SO4/L H2O and more extensive localized corrosion developed above 20 g Na2SO4/L H2O. [ABSTRACT FROM AUTHOR]

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]

This study aims to study topology Optimized Hammerhead Pier Beam (TOHPB) designed with a density-based technique. TOHPB is made with Preplaced Aggregate Fibrous Concrete (PAFC), which comprises two main preparation processes. First, the fibers and coarse aggregates filled into empty formwork to develop a skeletal system. Second, voids in the skeletal system are filled with cement grout; hence a type of PAFC was obtained. Besides, alleviating the self-weight of the concrete beam is a top priority of design engineering without compromising its strength and durability. The effect of topology optimization in association with the safety of factors and elastic design case is considered in this study. Explicitly, (i) compliance is scaled down to a minimum under a perimeter on the utilized material (ii) the principle Drucker-Prager is employed to impose the stress limitations even though utilization of material is minimized. The problem is designed with imposed stress limitation and generates keys that involve an essential part of post-processing before fabrication. In total, ten TOHPB were prepared with and without the combined shape of crimped-hooked end steel fiber. Two different types of fiber reinforcement schemes were used; first, the fibers were reinforced to full beam cross-section; then, the fibers were reinforced to the top half of the beam cross-section. Results revealed that the TOHPB beam reinforced full cross-section exhibited better ultimate load performance than that of the beam with half reinforced cross-section. [ABSTRACT FROM AUTHOR]

• Porous titanium slag used to modify grout for high radiation attenuation. • LAC improved by 12.8% and 9.8% at 3 days and 2 years, respectively. • LAC and HVL improved with titanium slag content and curing age. • Possible for low-density high-strength radiation shielding cementitious materials. The utilization of industrial waste materials for civil engineering structures has received massive attention in recent decades. In this work, the feasibility of using titanium slag to enhance the radiation attenuation properties of cementitious grout at the ages of 3 days and 2 years was studied. Titanium slag (TS) was incorporated as cement grout replacement at 0%, 10% 20% and 30%. Hardened blocks in dimension of 146 × 146 × 30 m m were fabricated. The porosity of titanium slag was characterized while the phases in the raw materials as well as the fabricated grout were identified. The influence of the titanium slag addition on the grout hydration kinetics, density, compressive strength and porosity of hardened grouts was evaluated. The results show a decrease in density with the increase of titanium slag content as well as a decrease in compressive strength at curing ages of 3, 7 and 28 days. The slag also refined the microstructure, leading to a reduction in average pore diameter. Furthermore, the hardened blocks were subject to gamma-ray sources such as 137Cs (0.662 MeV) and 60Co (1.173 and 1.332 MeV) and the Linear Attenuation Coefficient (LAC) and Half Value Layer (HVL) were evaluated. The results show that increasing curing age improves the shielding performance of the composite. At 30% replacement, the LAC improvement of the samples exposed to Co sources (1.173 and 1.332 MeV) at 3 days was 11.7% and 12.8% respectively while at 2 years, 9.9% and 9.8% improvement was obtained. Reduced HVL is obtained for an increase in replacement percentage and increased curing age. Therefore, this gives an indication of the possibility of developing low-density radiation shielding cement-based materials. [ABSTRACT FROM AUTHOR]

• With microcalorimetry (MC) it was possible to measure thermal events in heterogeneous grout. • The melting and crystallisation in phase change materials was successfully obtained by MC. • Large samples (10 g) could be tested accurately in non-isothermal MC. • Non-isothermal MC were able to properly capture the features of cyclic-temperature tests. • MC is proposed as a standard test for specific/latent heat in heterogeneous (cementitious) systems. • The calibration carried out using standard reference material shows that MC results are only < 2% erroneous. Microencapsulated phase-change-materials (PCMs) incorporated in cementitious grout can be used as a source of energy in an underground thermal energy storage system. Differential scanning calorimetry (DSC) is a widely used technique to measure the latent heat or specific heat of PCM-embedded cementitious materials. However, using milligram sample sizes (as required by DSC) of a cementitious material fails to represent the actual scale of cementitious components. This is the reason why, in the present paper, non-isothermal heat conduction microcalorimetry (MC) was evaluated as a tool for determining the thermal properties of PCM-embedded grout as well as pure PCM (three PCMs were used). An MC experimental protocol (using both single and 5–6 temperature cycles) was developed and used to measure latent heat and melting and crystallization temperatures, which were in good agreement with those reported for pure PCMs by the producers. In addition, the specific heats of the PCM-containing grout also agreed with measurements using the hot disk technique. Overall, the results show that the MC technique can be used as a potential standard method in determining thermal processes in complex systems, such as in PCM-embedded cementitious systems, where a large sample size is needed to represent the material. [ABSTRACT FROM AUTHOR]

This paper presents the results of field tests performed to investigate the behavior of pre-bored grouted planted nodular (PGPN) pile embedded in deep clayey soil. The test piles were all instrumented to measure the shaft and tip resistance and to determine the load transfer along the pile shaft. The test results show that the displacement necessary to fully mobilize the shaft resistance of PGPN pile is in the range of 1.83–3.32% D (D is pile diameter), and that the ultimate skin frictions of grout–soil interface of different soil layers are larger than the conventional proposed ultimate skin frictions for non-displacement piles. Furthermore, the pile tip resistance accounts for about 16% of the total applied pile head load corresponding to a pile head displacement of 0.1 D, and the pile tip resistance continues to increase after tip displacement reaches 5% of pile tip diameter. [ABSTRACT FROM AUTHOR]

Development of a partial safety factor for high strength grouts in offshore applications During the design of grouted connections in offshore applications (wind turbines and platforms), the fundamental material interrelationships are derived primarily on the basis of DIN EN 1992 which is applicable to the design and construction of building of concrete, reinforced concrete and pre‐stressed concrete. In the paper at hand the application of the design value for the compressive strength of concrete fcd to modern, high performance grouts is discussed. Firstly, the components of the design value for the compressive strength of concrete fcd are presented in detail and it is then discussed how in the safety concept within the standards variances are considered in the underlying assumptions and uncertainties are taken into account during their determination. Coefficients of variation were determined based on values of compressive strength from realistic and offshore‐typical grouting experiments, which were applied during the determination of the partial safety factor for grout γG. The applicability of the design value of the compressive strength of concrete fcd under consideration of the derived partial safety factor for grout γG was subsequently tested and compared to the design value of DIN EN 1992. [ABSTRACT FROM AUTHOR]

The design of alkali-activated soil reinforcement grouts faces several challenges regarding the required rheological, mechanical and microstructural properties. In this type of applications, the wide variety of source materials and the necessary addition of water affect the structuration processes and extend to the hardened state properties. A comprehensive characterisation of the specificities of these materials and the relations between the multiple factors is essential. This study aims at linking the physicochemical aspects of alkali-activated materials and their early age as well as long term behaviour. This analysis was carried using conventional evaluation methods as well as innovative approaches to examine the influential parameters for a rational design process. Coupling micromechanics and multiscale homogenisation can offer valuable data and help relate the microstructure to the macroscopic mechanical properties. Finally, the better resistance of alkali-activated materials in acid conditions provides a solution for projects involving chemically aggressive environments. [ABSTRACT FROM AUTHOR]

This study proposes a mathematical approach to obtain the optimal proportion of the grout constituents for a semi-flexible pavement. Grout mixes were prepared using three different water-cement ratio, three sand sizes, one sand-cement ratio, four/five different percentages of super plasticizer, and two different types of super plasticizer. The grout mixes were tested for flowability and strength using Marsh cone test and cube compressive strength test, respectively. The laboratory results were utilized to validate the proposed mathematical programming approach while obtaining the optimal proportion of grout constituents. Experimental results indicated that a minimum of 2% naphthalene super plasticizer and 1% polycarboxylate super plasticizer are required, irrespective of any combination, to achieve the desired flow time of the grout. The flow time and compressive strength were found to be associated with type of super plasticizer used. The proposed approach was found to be statistically satisfactory, with 95% confidence level, for determining the optimum grout constituents. The validation of the grout penetrability, using the proposed approach, has also been provided. Researchers and field engineers may consider to employ this analytical approach for grout constituent proportioning by partial or total replacement of cement with silica fume or fly ash. [ABSTRACT FROM AUTHOR]

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

Abstract Cement-based materials containing carbon nanotubes (CNT) has enhanced electrical and thermal characteristics. This study aimed to detect voids in prestressed concrete (PC) grout using CNT. CNT cement grout specimens were fabricated and tested inside ducts. Test parameters were type of CNTs, concentration of CNTs, and void ratio of grout. Thermal imaging analysis and electrical resistance analysis were performed to detect and identify the void configuration. The field emission scanning electron microscopy (FE-SEM) images were taken to obtain detailed information of microstructure of tested specimen. It was concluded that MWCNT grout was appropriate to detect the void in duct using thermal image analysis. SWCNT grout was more suitable to identify void in duct through electrical resistance analysis. [ABSTRACT FROM AUTHOR]

Highlights • The w/b of cement-sodium silicate grouts is 1.1–2.5, which is higher than previous studies. • The sodium silicate solution is adopted 4.4–7.5 wt% as an accelerator. • The setting time, sulphate resistance, permeability and shrinkage are investigated. • A workable and durable mixture is obtained in marine environments. Abstract This study aims to investigate the durability and microstructure of cement-sodium silicate grouts with high water to binder ratios (w/b) of 1.1–2.5 upon exposure to sea water. Grout specimens were prepared by mixing ordinary Portland cement paste and 4.4–7.5 wt% sodium silicate (water glass solution), which was adopted as an accelerator to prevent dilution and displacement during injection for geological strengthening and water control. The setting time, sulphate attack resistance, permeability and autogenous shrinkage of the grouts were assessed and compared. The microstructures were investigated in terms of the morphology and structure of the pores and cracks. The results reveal that satisfactory properties and durability, such as a setting time of 60–120 s, a flexural strength reduction of −3–6% after sulphate attack by sea water, a permeability of 1.2–1.6 MPa and an autogenous shrinkage of −0.298–1.22 milli, were obtained in cement-sodium silicate grouts with a w/b of 1.1–1.6 and dosages of sodium silicate of 4.4–5.7 wt%. However, hardened grouts suffered serious deterioration due to sulphate attack in 3 wt% sodium sulphate solutions and fatal drying shrinkage when exposed to air with a relative humidity of 60% at 20 °C. The cement-sodium silicate grout with the recommended composition is feasible and durable in marine environments, but special care must be taken when this grout is applied in environments with a high sulphate concentration or wetting-drying cycles. [ABSTRACT FROM AUTHOR]

Highlights • The LTSFC possess high potential to enhance the impact strength. • The LTSFC possess high potential to minimize drawbacks of the conventional FRC. • Innovative LTSFC technology for protection of civilian and military structures under terrorist attack. Abstract This study pioneers the concept of a novel layered two stage fibrous concrete (LTSFC) subjected to falling weight collision. The LTSFC is a newly developed concrete, with unique combination of steel fibres and coarse aggregates that are premixed and preplaced in the formwork in three layers followed by a flowable grout injection in each layer to fill the voids. In this study, some LTSFC slabs were proposed to consider the combined effect of layered and two stage concrete containing different type and combinations of steel fibres. Nine slabs were proposed, casted and tested, for which firstly the LTSFC were prepared and reinforced in three layers of 4%, 2% and 4% with three different fibres viz., crimped fibre (CF), hooked end fibre (HF), combined CF and HF and combined long and short CF. Secondly, the slabs were reinforced with 3.3% of same type of steel fibres over the entire cross section. The average amount of fibre used in LTSFC specimen was 3.3% which is similar to the fibre dosage used in the second series, where the fibres are equally spread in entire cross section. The study parameters viz., number of repeated impacts that induce the first crack and failure, impact ductility ratio, crack resistance (service and ultimate) and impact crack resistance ratio were considered herein. The results indicated that LTSFC specimens exhibited significant increase in the number of repeated impacts for the initial crack and failure to occur, high crack resistance, enhanced ductility and impact crack resistance ratio when related with non-fibrous concrete. Hence, the most significant findings of this research should stimulate innovation and new technology to develop the novel LTSFC in future studies. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

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

• The behavior of the grouted samples up to the yield point (YP) and beyond the YP is different. • The stress–strain curves is separated into two parts, pre- YP and post- YP. • The derived PNN models can effectively predict the stress (q) of the grouted samples. • Up to the YP , the CP is the most important parameter on the injected sand strength. • Beyond the YP , the effect of Z , W/CM and CP on the injected sand strength is almost the same. The process of cement production is costly and one of the main factors in carbon dioxide emission. Hence, part of it should be replaced with eco-friendly pozzolanic materials like zeolite. As the determination of shear behavior of injected sands is time-consuming and laborious, in the present research the polynomial neural network (PNN) model was used to predict stress (q)-strain ( ε ) behavior of zeolite-cement injected sand. For this purpose, a number of consolidated undrained (CU) triaxial tests was performed on sand samples injected with zeolite-cement grout. Due to the difference in the shear behavior of the injected sand before and after the yield point (YP), the stress–strain curves were divided into two parts (up to the YP and beyond the YP), and the curves of each part were predicted with separate relationships. The results revealed that the PNN -based equations can accurately estimate the q - ε curves of sand samples injected with zeolite-cement grout, such that the mean absolute percent error (MAPE) for testing data sets to estimate pre- and post- YP q was 7.79 and 5.38%, respectively. Sensitivity analysis indicated that up to the YP , the confining pressure (CP) was the most important parameter affecting the injected sand strength. The importance of water to cementitious materials ratio (W/CM) and cement replacement with zeolite content (Z) on the pre- YP q predicted by the PNN model was close to each other and less than the CP. Beyond the YP , the effect of W/CM , CP and Z was almost the same. [ABSTRACT FROM AUTHOR]

• Compression behaviour of RMM with changing block types, steel bars and panel heights is presented through experiments and analytical investigation. • Steel bars did not yield and did not contribute significantly to the compression capacity of RMM panels. • Grout played major role in the compression capacity improvement and bonding of mortarless blocks. • Analytical equations for compression capacity prediction and stress–strain behaviour of RMM are proposed. Mortarless masonry can facilitate faster construction of walls over conventional mortared masonry due to the absence of a mortar laying process and availability of interlocking features on the blocks. The structural performance of mortarless masonry can be improved by grouting and providing reinforcement in hollow cores of the interlocking blocks. In this study, axial compression behaviour of the reinforced mortarless masonry (RMM) panels was investigated. The influence of mortarless block types (single and double webbed), grouting and vertical reinforcement ratios were examined to comprehend the axial compression and displacement characteristics of RMM assemblies. In total, 44 RMM panels were constructed and tested under concentric axial compression. Failure patterns, load–displacement responses and compression capacities of the RMM panels were assessed and presented in this paper. The experimental results revealed that grouting significantly improved the axial capacities of RMM panels by bonding the interlocking blocks and reducing the initial settlement in the mortarless block interfaces. The single webbed blocks had higher compressive strength as compared to double webbed blocks, however in RMM panels, early cracking and spalling of face-shells of single webbed blocks resulted in lower compression capacities and stress ratios as compared to double webbed RMM assemblies. Prediction of compression capacities of the tested RMM panels using the current design provisions of Australian Masonry Standards (AS 3700) were found conservative with a safety ratios of 1.1 (for single webbed RMM panels) and 1.4 (for double webbed RMM panels). Subsequently, an analytical stress–strain model was proposed for the RMM under axial compression by calibrating the experimental data obtained through this study. [ABSTRACT FROM AUTHOR]

Evaluation of the long-term retention mechanisms and potential release rates for the primary constituents of potential concern (COPCs) (i.e., Tc, I, Se, and nitrate) is necessary to determine if Cast Stone, a radioactive waste form, can meet performance objectives under near-surface disposal scenarios. Herein, a mineral and parameter set accounting for the solubility of I and Se in Cast Stone was developed based on pH-dependent and monolithic diffusion leaching test results, to extend a geochemical speciation model previously developed. The impact of oxidation and carbonation as environmental aging processes on the retention properties of Cast Stone for primary COPCs was systematically estimated. Physically, the effective diffusion coefficients of 4 COPCs in Cast Stone were increased after carbonation and/or oxidation, reflecting an increase in permeability to diffusion. Chemically, i) pH & pe conditions in the original Cast Stone were favorable for the stabilization of Tc, but not for I, Se, and N; ii) oxidation (with/without carbonation) of Cast Stone changed the pe & pH conditions to be detrimental for Tc stabilization; and iii) carbonation (with/without oxidation) of Cast Stone modified the pH & pe conditions to be beneficial for the stabilization of I (in system with Ag added) and Se. [Display omitted] • Precipitates and parameters accounting for the solubility of I and Se are postulated. • Cast Stone carbonation decreased pH, which was chemically beneficial for Se retention. • Effective diffusivity of ions in Cast Stone was increased by carbonation and/or oxidation. • Ag-based getter was effective to stabilize I under oxic and near neutral conditions. [ABSTRACT FROM AUTHOR]

Geopolymers have gained much interest recently as a promising alternative to cementitious materials in some applications. However, research is still needed to use this technology for soil reinforcement grouts. The specifications of grouts mainly consist in rheological properties, strength and permeability. Grouting actually requires a low viscosity, and thus higher water content. The influence of relatively high water content on the other properties of the material, i.e. strength and microstructure, has been investigated. This effect highly depends on the concentration of the activator (sodium silicate solution) and the precursor (metakaolin, fly ash or blast furnace slag) associated with the activator. This paper deals with the main effects of high water content on the microstructure and mechanical properties of the materials, looking at physical and chemical aspects. Scanning electron microscopy and chemical phase analysis were used to highlight the nuances that are related to the precursors used, especially regarding the microstructure and kinetics of the geopolymerisation process. [ABSTRACT FROM AUTHOR]

This paper presents a study on the valorization of primary lead slag as substituent of aggregate in concrete for gamma radiation shielding and as a component of cementitious binders with application in low level radioactive solid waste encapsulation. The first part of the paper outlines the impact of primary lead slag on the compressive strength and gamma radiation shielding properties of concrete. The presence of the primary lead slag as aggregate substituent in concrete, along with steel shot and barite, enhances the density and shielding efficiency against gamma radiation for Ir 192 , Cs 137 , Co 60 radioactive elements with average gamma energies of 0.37 MeV, 0.662 MeV and 1.25 MeV. The results showed that even the presence of primary lead slag led to a decrease in compressive strength and all the tested concretes exhibited compressive strengths higher than 50 MPa. The utilization of primary lead slag could be recommended as aggregate in heavyweight concrete. The second part of the paper focuses on the experimental investigation of the physic-mechanical properties and low level radioactive solid waste encapsulation capacity of grout based on binders with primary lead slag content. Two binders (30% and 50% lead slag content) were used in cementitious grouts with different binder:sand ratio (1:1, 1:1.5 and 1:2), two types of sand (river sand or crushed concrete sand), different grain size distribution of sand and water/binder ratio of 0.3. It was observed that the grouts exhibit compressive strengths higher than 30 MPa, regardless of the binder:sand ratio. The increase in the binder:sand ratio influenced negatively the flow ability and positively the drying shrinkage. The low level radioactive solid waste encapsulation capacity of studied grout was lower than that of the reference grout with CRT glass waste. [ABSTRACT FROM AUTHOR]

The deep mixing has recently become a popular technique for improvement of weak or problematic soils in order to increase bearing capacity and reduce settlement. Despite various successful applications in construction projects, specifically improvement of marginal sand (i.e., loose poorly graded sand) using new materials in the viewpoint of strength development is still open for the attempt of deep mixing regarding the binder of grout, curing time and clay content. Thus, in this paper, effect of glass powder added to cement-based slurry grout in different proportions (0, 3, 6, 9% by dry weight of binder) has been experimentally investigated for deep mixing of marginal sand with various clay contents (4, 8, 20%). An experimental program has been developed for this purpose conducting the Vicat, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests for the performances of soilcrete samples. From the testing results, it is found that: (i) The glass powder is not able to accelerate the setting times of grout, (ii) the bulk density does not significantly change with the glass powder, clay content and curing time, (iii) the most performed UCS value is obtained due to the addition of 3% glass powder at the 28-day curing for the soilcrete samples of 20% clay content of sand, while all UCS magnitudes obtained for the soilcrete samples are considered acceptable for the construction of soil-cement column, (iv) the elastic modulus correlates well with the UCS values (R≥ 0.83) at the majority of soilcrete samples and (v) the UPV values of soilcrete samples at 28-day curing perform better due to the addition of 3% glass powder similar to the response trend of UCS, while their performances are higher due to 4% clay content in contrast to the trend of UCS. As a consequence, this study demonstrates the use of glass powder added grout to be beneficial for deep mixing of marginal sand, in which 20% clay inclusion contributes more. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted on empty and grouted stainless steel tubular X-joints with circular hollow section (CHS) chord member under axial compression. A total of 25 specimens including empty tubular joints, tubular joints with grouted brace members only, tubular joints with grouted chord member only and tubular joints with both grouted brace and chord members were tested. The joint strengths, failure modes, axial load-vertical displacement curves, axial load-chord deformation curves and strain distribution curves of all specimens were reported. The corresponding finite element analysis (FEA) was also performed and calibrated against the test results. Therefore, an extensive parametric study was carried out to evaluate the effects of main influential factors ( β , τ , grouting and grout strength) on the behaviour of grouted stainless steel tubular X-joints with CHS chord member under axial compression. It is shown from the comparison that the ultimate strengths of empty and grouted stainless steel tubular X-joints generally increased with the increase of the β and τ values. Furthermore, the ultimate strengths of stainless steel tubular X-joints with both grouted brace and chord members generally increased with the increase of the grout strength. Whereas, the grout strength has little influence on the ultimate strengths of stainless steel tubular X-joints with grouted chord member only. On the other hand, the joint strengths obtained from the tests and parametric study were compared with the design strengths calculated using the current design rules. It is shown from the comparison that the current design rules are generally unconservative for empty and grouted stainless steel tubular X-joints with CHS chord member under axial compression. Therefore, the new design equations were proposed in this study, which were verified to be more accurate. [ABSTRACT FROM AUTHOR]

Durability and useful life of the structural concrete are related to the environmental conditions and degrading factors present in the environment. One of most concerning aggressive agents in the civil construction industry is carbon dioxide that penetrates into the pores of the concrete reacting with the interstitial hydrates reducing its pH, promoting depassivation of the steel armours inside the concrete, thus enabling to start the corrosion process. This paper produced grout proof-bodies, concretes with high fluidity used to fill the blocks in structural masonry, with different resistance to compression: 15 MPa, 20 MPa, 25 MPa. The specimens were submitted to a carbonation front in an accelerated chamber under controlled humidity, temperature and carbon dioxide. A numerical model was used aiming to estimate the forecast of the useful life by making a comparison of the values forecasted by the Brazilian and international performance rules. It was observed that the 15 MPa grout has a useful life forecast lower than that recommended by the standard, around 60% lower, while the 20 MPa and 25 MPa grout presented a satisfactory useful life. Hence, it was certified the importance of controlling the grout resistance and coverage in structural masonry works as a form to assure the desired durability to the structure. [ABSTRACT FROM AUTHOR]

This paper evaluates the feasibility of by-product-based controlled low-strength material (CLSM) as a grout for geothermal systems. Quartz-based mine tailings and pond ash were adopted as filler and fine aggregates, respectively. Settlement, compressive strength, and thermal conductivity, required for grout for geothermal systems were investigated and the leaching behavior of toxic elements from the CLSM was evaluated. In addition, a cost analysis for actual construction sites of the geothermal system was conducted using a design program. The high-workable CLSM with tailings and pond ash satisfied the strength specified in the ACI 229R and its thermal conductivity was higher than that of conventional grout, i.e., bentonite-sand mixture. The CLSM made only with tailings satisfied the ‘Treatment Standard for Hazardous Wastes’ in the Code of Federal Regulations of US governments (40 CFR 268.40), whereas that with both tailings and pond ash did not. The total construction costs of the geothermal system reduced up to 20.8% when utilizing the by-product-based CLSM compared with conventional grout. [ABSTRACT FROM AUTHOR]

A long-term disposal of technetium-99 ( 99 Tc) has been considered in a type of cementitious formulation, slag-based grout, at the U.S. Department of Energy, Savannah River Site, Aiken SC, U.S.A. Blast furnace slag, which contains S and Fe electron donors, has been used in a mixture with fly ash, and Portland cement to immobilize 99 Tc(VII)O 4 − (aq) in low level radioactive waste via reductive precipitation reaction. However the long-term stability of Tc(IV) species is not clearly understood as oxygen gradually diffuses into the solid structure. In this study, aging effects of Tc speciation were investigated as a function of depth (<2.5 cm) in slag-based grout using X-ray absorption spectroscopy. All of Fe(II) in solids was oxidized to Fe(III) after 117d. However, elemental S, sulfide, and sulfoxide persists at the 0–8 mm depths even after 485d, suggesting the presence of a reduced zone below the surface few millimeters. Pertechnetate was successfully reduced to Tc(IV) after 29d. Distorted hydrolyzed Tc(IV) octahedral molecules were partially sulfidized and or polymerized at all depths (0–8 mm) and were stable in 485d aged sample. The results of this study suggest that variable S species contribute to stabilize the partially sulfidized Tc(IV) species in aged slag-based grout. [ABSTRACT FROM AUTHOR]

One design for the foundation of an offshore wind turbine consists of partially overlapping cylinders (the monopile and the transition piece) with a layer of grout between the two. Unfortunately, slippage of the transition piece over the monopile has been observed in many foundations, threatening the long-term stability of the structure. Several utilities have arrested the slippage by welding restraints inside the foundation to transfer the axial loads from the tower to the monopile foundation; however, bending moments are still transferred through the grouted section. If the grout degrades in service then the turbine could still be at risk. An inspection technique is therefore necessary so that foundations can be prioritised for repair. A novel solution is required as conventional NDT techniques either cannot find the conditions of concern or deployment in an offshore environment is hazardous. The approach taken has been to use a swept frequency ultrasonic technique operating below 100 kHz, so that resonances characteristic of the structure and its various fault conditions can be mapped. Laboratory trials supported by mathematical modelling have demonstrated the viability of the approach and a method for delivering the sensor to the regions of interest in a foundation has been developed. Offshore trials have been carried out at an operating wind farm, producing excellent results and a practical inspection system. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted on empty and grouted stainless steel square hollow section (SHS) tubular X- and T-joints subjected to axial compression. A total of 24 specimens including empty tubular joints, tubular joints with grouted brace members only, tubular joints with grouted chord member only and tubular joints with both grouted brace and chord members were tested. The joint strengths, failure modes, axial load-vertical displacement curves, axial load-chord deformation curves and strain distribution curves of all specimens were reported. The corresponding finite element analysis (FEA) was also performed and calibrated against the test results. Therefore, an extensive parametric study was carried out to evaluate the effects of main influential factors ( β , τ , grouting and grout strength) on the behaviour of grouted stainless steel SHS tubular X- and T-joints subjected to axial compression. It is shown from the comparison that the ultimate strengths of empty and grouted stainless steel SHS tubular X- and T-joints generally increased with the increase of the β and τ values. The enhancement of joint strengths obtained from grouting both brace and chord members is much greater than that obtained from grouting chord member only. In addition, the ultimate strengths of stainless steel SHS tubular X- and T-joints with both grouted brace and chord members generally increased with the increase of the grout strength. Whereas, the grout strength has little influence on the ultimate strengths of stainless steel SHS tubular X-joints with grouted chord member only. On the other hand, the joint strengths obtained from the tests and parametric study were compared with the design strengths calculated using the current design rules. It is shown from the comparison that the current design rules are generally conservative for the design of empty stainless steel SHS tubular X- and T-joints subjected to axial compression, but unconservative for the design of grouted stainless steel SHS tubular X- and T-joints subjected to axial compression. Therefore, the new design equations were proposed in this study, which were verified to be more accurate. [ABSTRACT FROM AUTHOR]

Chemical stabilization of tank residual waste is part of a Hanford Site tank closure strategy to reduce overall risk levels to human health and the environment. In this study, a set of column leaching experiments using tank C-104 residual waste were conducted to evaluate the leachability of uranium (U) and technetium (Tc) where grout and hydrated lime were applied as chemical stabilizing agents. The experiments were designed to simulate future scenarios where meteoric water infiltrates through the vadose zones into the interior of the tank filled with layers of grout or hydrated lime, and then contacts the residual waste. Effluent concentrations of U and Tc were monitored and compared among three different packing columns (waste only, waste + grout, and waste + grout + hydrated lime). Geochemical modeling of the effluent compositions was conducted to determine saturation indices of uranium solid phases that could control the solubility of uranium. The results indicate that addition of hydrated lime strongly stabilized the uranium through transforming uranium to a highly insoluble calcium uranate (CaUO 4 ) or similar phase, whereas no significant stabilization effect of grout or hydrated lime was observed on Tc leachability. The result implies that hydrated lime could be a great candidate for stabilizing Hanford tank residual wastes where uranium is one of the main concerns. [ABSTRACT FROM AUTHOR]

To accurately predict the initiation and evolution of uranium hydride potentially present in nuclear waste containers, studies of simulated conditions are required. Here, for the first time, the uranium-deuterium reaction was examined in-situ, in real time, whilst within grouted media. A deuterium gas control rig and stainless steel-quartz glass reaction cell were configured on a synchrotron beam line to collect X-ray diffraction and X-ray tomography data. It was found that deuteride formation was limited by the uranium and grout thermal conductivities and deuteride initiation only commenced above a threshold temperature. Strong adherence between uranium oxide and grout was also observed. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to evaluate the compressive behavior of damaged circular hollow section (CHS) steel columns repaired by carbon fiber-reinforced polymer (CFRP) or high-strength grout. A total of 22 specimens, including bare steel specimens, CFRP repaired specimens and grout repaired specimens were tested under axial compression loading. The design parameters are the amount of loss in wall thickness, extent of damage along tube height, and the damage angle around the circumference. Two promising retrofit techniques, external wrapping of CFRP and grouted jacket, were adopted here. The repairing efficiency was assessed in terms of the above-mentioned retrofit techniques and design parameters. A finite element (FE) analysis was also performed and analyzed with test results. The failure modes are presented together with load-shortening and load-strain behavior of specimens. The results indicate that the behavior of damaged CHS steel columns can be effectively rehabilitated by either CFRP or grout jacketing. The local buckling of the internal steel tube was either delayed by fibers or suppressed by the surrounding grout, leading to an improvement both in compressive strength and deformation capacity. It was also found that grouted jacket repair generally shows an overwhelming strength enhancement over the CFRP wrapping method except for specimens with 90° damage around circumference, which shows a delay of the restraining effect. A parametric study was eventually undertaken to fully understand the influences of design parameters on columns' compressive characteristics. [ABSTRACT FROM AUTHOR]