Search

Compressive strength is a crucial factor in designing masonry walls to withstand various loading conditions, and it is equally significant for the designing of dry-stack masonry walls. Dry-stack masonry uses interlocking blocks, that enable a faster walling construction than the conventional mortared masonry. Widespread use of this walling system is limited due to lack of detailed design provisions in standards, as opposed to conventional mortared masonry. In this study, the compressive strength properties of un-grouted and grouted dry-stack concrete block masonry were experimentally evaluated. In total, 80 dry-stack concrete block masonry wallettes were built and tested with five different types of dry-stack blocks and three different grouts strength (20 MPa, 32 MPa and 40 MPa). The failure patterns, stress-strain curves and compressive strength characteristics obtained through the testing campaign are reported in this paper. The grouted dry-stack concrete block masonry wallettes demonstrated higher compressive capacities (ranging from 11 % to 152 %) than the corresponding un-grouted concrete block masonry wallettes, the increment was dependent on the grout and block types. The experimental data collected in this campaign was then used to assess the available formulae and tabulated values to predict the compressive strength of dry-stack concrete block masonry wallettes. The predictabilities of these formulae and tabulated values are presented and discussed. [Display omitted] • Compression behaviour of grouted dry-stack concrete block masonry was studied. • 80 dry-stack concrete block masonry wallettes have been tested. • The presence of grout had a significant impact on the axial compression capacities. • Compressive strength prediction models were verified, and best models are specified. [ABSTRACT FROM AUTHOR]

Ultrasonic guided wave (UGW) technique has been widely utilized in damage detection of pre-stressed steel strands. However, most of the current UGW-based methods only focus on bare strands, whereas in real projects the strands are usually pre-buried inside the structure and encapsulated by media such as concrete or grout. In this study, the effects of various grouting and tensioning factors on the propagation of UGW in grouted steel strand, as well as the effectiveness of UGW energy leakage ratio (α EL)-based pre-stress evaluation for grouted steel strand, were investigated. Firstly, the theoretical model of UGW propagating in the grouted steel strand was developed. Secondly, a finite element model of grouted strand was established to investigate the dispersion characteristic of UGW as well as the energy distribution and attenuation behavior of UGW in the grout. Thirdly, pre-stressed concrete (PSC) specimens with different grouting diameters, grouting lengths, and tension forces were designed to investigate the effects of grouting thickness, grouting length, and tension force on the group velocity, energy distribution and α EL of UGW. Finally, the α EL -based approach was validated in pre-stress evaluation for grouted steel strand, and the evaluation accuracy was compared with that for bare steel strand. Results show that compared with the helical wire excitation scenario, the UGW signals propagating in steel strands are significantly less affected by variations in grouting thickness and grouting length under core wire excitation scenario. In the grout, the UGW energy tends to decrease exponentially with the increase of the radial propagation distance, and the helical wire excitation scenario leads to more UGW energy leaking into the grout compared with core wire excitation. It is recommended to excite UGW signal in the core wire instead of the helical wire in α EL -based pre-stress evaluation approach for grouted steel strand, in such scenario, the evaluation error is only 4.93 %. • Variations of UGW with various grouting conditions were investigated. • Energy distribution and attenuation of UGW in grout were investigated. • 3. Exciting UGW in core wire instead of helical wire is recommended. [ABSTRACT FROM AUTHOR]

The study on liquefaction mitigation using cement-based materials in soils with liquefaction potential is of great interest. As cement production is a costly and environmentally polluting process, replacing part of it with environmentally friendly and cheaper materials such as natural zeolite is very important and attractive. In the present study, to evaluate the improvement of the liquefaction resistance in loose sand using zeolite-cement injection, a series of triaxial tests was performed. Also, the liquefaction potential of injected specimens was investigated based on the results of bender element, unconfined compressive strength and monotonic triaxial tests. The results of the study indicated that the injection of tested sand with zeolite-cement grout is significantly effective in liquefaction mitigation of the sand. Even under very strong earthquakes, liquefaction did not occur in the injected specimens with water to cementitious materials' ratio (W/CM) of 3 and a cement replacement with zeolite (Z) up to 70 %. The optimum amount of zeolite (Z opt) corresponding to the maximum liquefaction resistance was 30 %. It was shown that, considering the optimization of energy consumption as well as environmental considerations, for earthquakes with a CSR ≤ 0.2, by grout injection with Z 90 and W/CM of 5, the used sand liquefaction resistance is more than double. For more severe earthquakes (CSR ≤ 0.3), injection with a grout containing Z 70 and W/CM of 7 resulted in no liquefaction. To counteract the liquefaction under very strong earthquakes (CSR 0.5), grout injection with Z 50 and W/CM of 5 can be effective. • Zeolite-cement grout injection is significantly effective in liquefaction mitigation of the sand. • The optimum amount of zeolite corresponding to the maximum liquefaction resistance is 30 %. • Injection with grout containing W/CM of 3 and 90 % zeolite significantly increased the liquefaction resistance. • For a CSR ≤ 0.2, by grout injection with W/CM of 5 and 90 % zeolite, the sand liquefaction resistance was more than double. [ABSTRACT FROM AUTHOR]

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]

• 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]

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]

This study investigated the change created in physical properties by irradiating ultrasonic waves in Portland cement grout. In previous research, the grout equipment was scaled-up and a grout circulation system was used for the experiment. The physical properties of ordinary grout materials were compared with those irradiated by ultrasonic waves to observe its effects. This was done by analyzing and comparing the viscosity, strength and granularity. The results indicate that grout irradiated by ultrasonic waves outperformed the non-irradiated grout in all categories of physical properties. [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]

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]

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]

• 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]

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]

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]

This study pioneers the concept of fibre-reinforced preplaced aggregate concrete through premixing and preplacing steel fibres with aggregates in the formwork, then injecting a flowable grout. Unlike in conventional steel-fibre reinforced concrete where the fibre dosage, length and aspect ratio are hampered by workability considerations, the influence of fibres on workability, place-ability and consolidation is eliminated. Hence, fibre dosages beyond those conceivable in conventionally mixed concrete can be considered. The compressive, tensile and flexural strengths, load-deflection curves and toughness were appraised for the new steel fibre-reinforced preplaced aggregate concrete incorporating various dosages of steel fibres having different lengths. It is shown that the ability of using higher fibre dosages allows achieving exceptional engineering properties for preplaced aggregate concrete. Indeed, the material can easily be produced with steel fibre dosages exceeding 6%, making this innovative, yet simple to produce concrete, a strong contender in many construction applications. [ABSTRACT FROM AUTHOR]

This paper represent the results of an experimental study handled with developed grouting materials for fully-cement-grouted ribbed rockbolts. These experimental studies cover the effects of some mineral admixtures (silica fume, blast furnace slag, fly ash etc.) on the bond characteristics between grout and rockbolts. The effect of mineral admixtures on the grout strength of fully-grouted rockbolts and block punch index (BPI) and compressive strength (CS) of the grout on the load bearing capacity (LBC) were investigated. Totally 150 rockbolt pull-out tests were performed using ten different grouts in order to investigate and improve the LBC of grouted rockbolts for five different curing times (1, 3, 7, 28 and 90 days). All grout types were prepared same ratios, and silica sand was used as fine aggregate. Grout mixtures that 15% of mineral admixtures replaced with cement by weight were prepared. The results showed that grouts produced with silica fume (SF) and metakaolin (MK) in all mixtures were yielded the highest CS and bond strength at all ages. The all strength tests of fly ash (FA) grout exhibited low values till 28 days of curing time in accordance with reference grout, but a sharp increase was observed after this period. Grouts with perlite (PRL) and blast furnace slag (BFS) showed the similar strength values according to reference grout. In conclusion, mineral admixtures can be used for high-strength and low cost grout in tunneling applications. In addition, the use of waste materials can contribute to the resolution of environmental problems. [ABSTRACT FROM AUTHOR]

An experimental study was carried out on grout samples prepared from both Stratabinder and BU100 cementitious products. Samples were prepared with various water to grout ratios and tested for uniaxial compressive and shear strength. Triaxial tests were performed on cylindrical samples to determine values for internal friction angle, cohesion and tensile strength. It was found that the water to cement ratio affects the uniaxial compressive and shear strength of grout. The triaxial test indicated that both internal friction angle and cohesion of Stratabinder do not differ significantly from BU100. [ABSTRACT FROM AUTHOR]

The paper presents the assessment of a metakaolin-slag-sodium-silicate GeoPolymer (GP) grout as a matrix for bonding four bidirectional meshes made of basalt, glass, carbon fibres and two unidirectional ultra-high tensile strength steel fabrics to soft mud and strong extruded clay bricks for strengthening purposes. A detailed chemical/physical characterization of the geopolymer is given, evidencing the completion of the geopolymerization reaction and the good stability of the geopolymer to leaching, freeze-thaw cycles and high temperature treatments as well as its adequate mechanical properties. Pull-off tests proved the excellent adhesion strength of the geopolymer grout, also embedding meshes and fabric, to both types of clay bricks. [ABSTRACT FROM AUTHOR]

The axial behaviour and design of hot-finished high strength steel tubular elements with internal prestressing cables, representing the chord members in prestressed trusses, are examined in this paper. A comprehensive programme of experiments and numerical modelling was performed, the results of which were combined to develop resistance expressions for the design of prestressed high strength steel members. A total of 12 tensile and 10 compressive member tests were carried out, with the key variables examined being the steel grade (S460 and S690), the initial prestress level and the presence of grout. Numerical models were developed to replicate the structural response of the compressive member tests and subsequently used to generate parametric results, where the member slenderness, size of prestressing cable, applied prestress level, steel grade (S460 or S690), and grout condition (grouted and non-grouted), were varied. The presence of cables was shown to enhance the tensile capacity of the members, while the addition of prestress resulted in extended elastic range. In compression, the effect of prestress was detrimental, and a modified Perry-Robertson method, developed in [ 1 ], was extended to hot-finished high strength steel members. [ABSTRACT FROM AUTHOR]

During cold weather precast wall construction, in-situ heating of the grout used in grouted dowel connections is usually conducted for short periods of time. Hence, early-age exposure to subfreezing conditions may affect the quality of the grout and subsequently the bond strength of the connection, which can compromise structural integrity. In this study, grout specimens typical of that used in precast wall construction were initially cured at ambient conditions for one day and then placed inside a walk-in environmental chamber at subfreezing temperatures. The hardened grout properties and bond strength of the connection were examined and compared to that of specimens cured at ambient temperature. The compressive strength of the grout was monitored at temperatures of 1°, −10° and −20 °C. The effect of subfreezing exposure on the mechanical properties, hydration process and pore size distribution of the grout were examined. It was found that early-age subfreezing curing temperatures reduced the compressive strength of the grout, leading to increased dowel embedment length to achieve bar fracture. The bond strength of the connection remained proportional to the square root of compressive strength, even subsequent to early-age exposure to subfreezing temperature. [ABSTRACT FROM AUTHOR]

Among the many variables involved in jet grout technology, dealing with the complex phenomena of grout flow, specifically related to the pumping pressure (shear stress), the pumping rate (shear rate) and the viscosity, mostly becomes a difficult task for grouting in practice. Thus, this study presents the capability of a new methodology in soft computing techniques, called gene expression programming (GEP), to predict the rheological behavior (i.e., the shear stress versus the shear rate and the viscosity versus the shear rate) of grout with bottom ash for jet grouting columns, as an alternative approach to traditional methods. For this purpose, shear stress and viscosity formulas, including the main input variables of the shear rate and bottom ash proportion, are derived using GEP modeling through the stages of production and testing. Then, the performances of the GEP formulas are compared with the measured data and the regression and conventional rheological models (De Kee and Robertson-Stiff) for use in practice. The results indicate that the GEP formulas are able to yield estimations with good precision resulting in better predictions ( R ≥ 0.96) compared to the regression model. A successful description of the pseudoplastic response of rheological behavior is given, and a response consistent with conventional rheological models is obtained. Moreover, the measured data (shear stress and viscosity) generally follow the GEP modeling well, but the level of satisfaction is more favorable at high proportions of bottom ash. In conclusion, the study reveals that the derived GEP formulas are relatively promising for estimating the pumping pressure, the viscosity and the pumping rate of grout with bottom ash for jet grouting columns, at least in assisting conventional methods for preliminary designs. [ABSTRACT FROM AUTHOR]

In recent years, the deep mixing technique that utilizes cement-based grout mixtures has become a popular approach, particularly for the enhancement of soft soils. Despite the advantages of deep mixing technique in numerous construction applications, the effort given for this technique still needs to be extended using new material as additive. Thus, this study investigates the use of cement-based grout combined with glass powder to enhance the clay soil via deep mixing technique. An experimental program has been conducted including grout mixtures at different replacements of glass powder (0%, 3%, 6% and 9% by dry weight of binder) mixed with clay having different water contents (36%, 31% and 21%). The Vicat, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests have been carried for analysing performances of mixtures. The results indicate that the setting times of the mixture pastes increase, while the bulk densities of the soilcrete samples do not significantly change with the replacement of glass powder. Moreover, due to the use of glass powder, both the UCS and UPV increase alongside decreasing water content as well as increasing curing time. Test results imply that, owing to the replacement of glass powder, all UCS values of the soilcrete samples are applicable for the purpose of deep mixing. However, the replacement of glass powder by 3% produces a more favorable UCS response. Strong correlations exist for the UCS versus elastic modulus (R ⩾ 0.84) as well as for the UCS versus UPV (R ⩾ 0.82), which practically could be useful for the strength predictions of soil-cement columns. Consequently, the use of cement-based grout with the glass powder replacement could provide a new insight into the deep mixing technique for the treatment of clay. Moreover, the employment of glass powder as a waste material could also benefit the environment and construction costs. [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]

Grout is widely used in bonded post-tensioned bridge construction as an anti-corrosive material for protecting the steel strands. Several occurrences of tendon failures in U.S. bridges, however, have led to an interest in unbonded tendons where a flexible filler, such as wax, grease, or gel, is injected into the tendon duct instead of cement grout. In general, the consistency of these flexible fillers in ambient temperature falls within the realm of semi-solids and, thus, they are not readily injectable without preheating. A major concern with flexible filler injection is, therefore, maintaining an adequately elevated filler temperature to keep the material’s viscosity sufficiently low for complete filling of the duct and to avoid a blockage that might result in a burst pipe or duct. This paper presents a simplified heat transfer model that computes the decrease in temperature of the moving filler front during injection as it cools while interacting with the surrounding strands and duct. The proposed model has been validated by multiple mockup experiments conducted with different filler materials and injection rates. A comprehensive parametric study has been conducted to determine the sensitivity of the filler front temperature to several practical factors, such as effective strand surface area, tendon length, injection rate, ambient temperature, injection temperature, and number of strands in a tendon system. The required minimum injection pressure for different flow velocities and tendon lengths has also been determined. The experimental results confirm the model’s applicability to a wide range of tendon lengths and strand patterns, and its usefulness in determining tendon constructability. [ABSTRACT FROM AUTHOR]

Grouting the fractures encountered when constructing underground facilities is of primary importance for environmental, safety and economic reasons. The success of grouting operation, however, depends upon several parameters governing the grout propagation. Experimental benches replicating fractures have therefore been designed to study processes related to grout propagation. In this paper, we investigate the ultrasonic transport properties of such an idealized fracture whose 100 µm aperture is about 0.02 the wavelength, and filled with various fluids flowing under external forcing. As the artificial fracture is made of two solid and parallel walls separated by a thin fluid layer, we use the thin fluid layer concept to study the compressional (P-) wavefield transmitted across and reflected off the fracture, with no mode-conversion considered. We demonstrate that air and various fluids (water, grouts of varied w/c – water to cement ratio) can be distinguished when injected into the fracture, both at atmospheric pressure or under over-pressure as done in real grouting cases in the field. Then, using an analytical solution, we verify our experimental data and predict the results that can be obtained with a different fracture aperture. Our results illustrate that replicating such ultrasonic measurements both in space and time would allow to monitor successfully the grout propagation within an artificial fracture. The detection of the filtration of the suspended cement-particles of the grout, the formation and erosion of filter-cakes, are also in the scope of the method. [ABSTRACT FROM AUTHOR]

Fresh and hardened properties of steel fiber-reinforced grout (SFRG) containing ground granulated blast-furnace slag (GGBS) were investigated for applications to prestressed concrete substructures of offshore wind turbines. The addition of short smooth steel fibers (6 mm in length, 0.2 mm in diameter) generally decreased the flow, bleeding, and time of setting of SFRG, whereas the addition of GGBS for the replacement of 40% of the cement by weight ratio clearly increased its flow and the time of setting. The effect of adding GGBS on bleeding was different according to the type of cement. Despite these outcomes, it was observed that the addition of GGBS notably enhanced the chloride penetration resistance of SFRGs, while the addition of steel fibers significantly increased their flexural strength. [ABSTRACT FROM AUTHOR]

Natural fractures are commonly infilled by the infilling materials, such as sheared-off or broken rock fragments and clay. Grouting has been widely used to improve the wellbore stability in oil or shale gas reservoirs and reduce the permeability of fractured rocks in tunnel vicinity, and thus rock fractures can also be manually infilled by grout. Although a large number of studies focused on the strength and failure behavior of rock samples with open flaws, the research on the mechanical properties and failure modes of rock specimens with infilled flaws is rather limited. In order to understand the effects of fillings on mechanical properties and crack propagation behavior of pre-flawed rocks, a large number of numerical uniaxial compression tests have been conducted for rock samples with single or double flaws which were open or infilled, using a particle mechanics method. The results showed that infillings play a significant role in improving the mechanical properties of pre-flawed rock samples, especially when the inclination angles of flaws are less than 45°. The infillings mainly play a role in transferring stress and reducing stress concentration at the flaw tip and bridge regions and thus infillings can change the crack initiation position, propagation direction and coalescence pattern in rock samples with infilled flaws. The effects of micro-parameters of infillings on the mechanical properties and behavior of rock samples with single flaws were also studied through sensitivity analysis. [ABSTRACT FROM AUTHOR]

Oil sands drill cuttings waste represents one of the most difficult challenges for the oil sands mining sector. Reducing the amount oil sands drill cutting waste sent to landfill offers one of the best solutions for waste management. The present work offers an innovative solution for the recycle and reuse of treated oil sands drill cuttings waste (TOSW) in grout manufacture. In this study, the physical, chemical and mineralogical characteristics of the treated oil sands drill cuttings waste were investigated. Fresh and hardened properties for grouts incorporating the treated solid drill cuttings waste were evaluated. The results show that incorporating up to 20% of the treated solid drill cuttings waste as a partially replacement of cement will not adversely affect the properties of the grout. Leaching tests evidenced the reduction in the release of heavy metals from the tested mixtures compared to that of the raw waste indicating successful stabilization/solidification of such waste in the grout. [ABSTRACT FROM AUTHOR]

• Commercially available pre-packages grouts tend to form a highly porous layer of grout, that can lead to corrosion of strands. • Prototype scale tendon-grouting tests were conducted assess the resistance against bleeding. • Ability of the fresh grout to retain its properties against variations in the ambient temperature and water content was studied. • A set of stringent and comprehensive specifications were developed for applications in PT systems. • Newly developed grout satisfies all the performance specifications while site batched grouts do not. Grouted, post-tensioned (PT) concrete structures are protected from tendon corrosion by filling the interstitial spaces with cementitious grouts. To achieve complete grouting, the cementitious grout must be sufficiently flowable and bleed resistant. Nowadays, many commercial pre-packaged grouts are available. However, simulated bleed measurements with prototype-scale tendon grouting tests have shown that pre-packaged grouts tend to form a highly porous layer of grout, which poses a severe threat to corrosion protection. This study focuses on evaluating the performance of a novel pre-blended grout produced on an industrial scale using the fluidity and fluidity retention tests, standard, wick-induced, pressure-induced, and inclined tube bleed tests. Also, the ability of the fresh grout to retain its properties against slight variations in the ambient temperature and water content was studied. The performance of the pre-blended grout on a real scale was evaluated and compared with a widely used site-batched grout composition using prototype tendon grouting tests. In addition, a set of stringent and comprehensive specifications were developed for applications in PT systems. It was also observed that the pre-blended grout considered in this study met all the proposed specifications, therefore, can be used for the corrosion protection of tendons in PT structures. [ABSTRACT FROM AUTHOR]

This study investigates the compressive strength of grout and how the filler effect of ground palm oil fuel ash (POFA) contributes to its strength. POFA derived from the palm oil fruit bunches (POFA–FB) and also from the kernels (POFA–K) were ground to two different particle sizes and used to replace Type I Portland cement at 0–40% by weight of binder to cast the grout samples. The compressive strengths of ground POFA grouts were determined at various ages between 7 and 60 days. The results showed that the compressive strength of grout reinforced with POFA–K was much more noticeable as compared to that of POFA–FB. It is also reported that small particles of ground POFA promoted a filler effect that helped to increase the compressive strength of grouts. In contrast, larger particles of ground POFA decrease the value of compressive strength due to the development of more voids in the microstructure. Also, the inclusion of the ground POFA has reduced the charge passed of grout indicating its capacity as chloride resistance agent. [ABSTRACT FROM AUTHOR]

Conservation, repair and strengthening of historic masonry buildings should preserve their significance and ensure their structural stability. The condition of a given structure and the extent of damage determine the type of action needed. Grouting is a well-known remedial technique, which can be durable and mechanically efficient whilst preserving the historic value. Still, the selection of a grout for repair must be based on the physical and chemical properties of the existing materials. Parameters such as rheology, injectability and stability of the mix should be considered to ensure the effectiveness of grout injection. In addition, the bond strength of the grout to the existing material is the most relevant mechanical property. Several commercial lime based grouts are available but it is unclear what are the applicable standards and requirements. This paper evaluates the behavior of commercial grouts under laboratory conditions. First, the properties of the grouts as an independent product are assessed with the objective to perform a comparative analysis of their behavior subjected to different conditions (temperature and working time of grout after mixing). Then, the behavior of the grouts when used in combination with stones used in the construction of masonry buildings is addressed (granite, schist and limestone), again considering different conditions (dry, wet and saturated). It is shown that the performance of the commercial products is rather different and careful selection of injection materials in practical applications is recommended. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide an insight into the effects of a previous cyclic history “triggering” full liquefaction on the subsequent undrained cyclic behaviour of a moderately cemented grouted sand in terms of strength, deformability and pore pressure response. The research was conducted on sand specimens stabilized by a commercial mineral based chemical grout (“Silacsol”), capable of imparting unconfined compression strength (UCS) values ranging between 500 kPa and 700 kPa. Monotonic shear strength parameters of treated specimens were preliminary assessed through a series of isotropically consolidated drained triaxial tests (TX-CID). Afterwards, stress-controlled undrained cyclic simple shear (SS) tests were conducted on both treated and untreated sand specimens in order to evaluate the improvement provided by the grout on the liquefaction resistance of the sand. A significant beneficial effect of the grout was observed, regardless of the initial density of the pure sand. Finally the influence of a cyclic large preshearing on the undrained cyclic behaviour of the grouted sand was investigated by subjecting the specimens to a sequence of two cyclic loadings with the same stress ratio (CSR). After the first loading in which specimens were brought to full liquefaction, they were allowed to reconsolidate in approximately K 0 conditions and then subjected to the second loading. An increase in liquefaction resistance induced by cyclic history was clearly apparent on treated specimens. Excess pore pressures build-up during the first cyclic loading on treated specimens followed a different trend compared to that observed on untreated ones. A significant difference was also observed on the excess pore pressure trends developed in the second loading compared to that developed in the primary loading. A simple model for the prediction of pore water pressure build-up of grouted sands during cyclic loading is proposed. [ABSTRACT FROM AUTHOR]