Search

Insight into the seepage patterns of fluid flow within fractured rocks can lead to a better understanding of many challenging issues, such as oil or gas exploitation, heat extraction from hot dry rock (HDR), and controlling water inflow through cement grouting. However, these can only be assessed via some macroscopic phenomena like inlet or outlet flow properties or numeral simulation with synthetic rock fractures. This situation is because the real-time seepage diffusion features within rock fractures cannot be directly observed via conventional techniques, including the CT scanning technique, even if the colored solution is used as a developer. Therefore, we remove the obstacles that prevent fluid flow visualization within rock fractures by developing a transparent rock replica, and introducing Particle Image Velocity (PIV) technology. In addition to overcoming the opacity of rock, this method can help analyze the distribution patterns of velocity and vorticity fields, as well as the main seepage path by capturing the migration of particles and the fluid flow. The results show that the fluid transports along the low part of the rough fractures. Meanwhile, the flow direction is less affected by the fracture geometry if the flow rate exceeds a certain value. When the number of vortices on the fractures increases, they are mainly distributed in areas with large surface fluctuations. Interestingly, the maximum vorticity first grows slowly and then increases rapidly with increasing pumping rates. This study contributes to a more comprehensive understanding of the seepage patterns of fluid flow within rock fractures and their related engineering applications. Highlights: Based on PIV technology, a set of visual test equipment for seepage in rock fractures is developed. The distribution information of velocity vector, flow field and vorticity field on rock fractures can be obtained in real time. The digital extraction of fracture surface of rock samples is realized. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The dynamic modulus of asphalt mixture is an important factor in the design of asphalt pavement, and many scholars have proposed different models for estimating the dynamic modulus of asphalt mixture, but there are almost no studies on the prediction of the dynamic modulus of semi-flexible materials. In order to analyze and estimate the dynamic modulus of semi-flexible materials, we set up a high-performance cementitious paste (HPCP) semi-flexible material and a reference group Stone Mastic Asphalt (SMA-16) under multiple conditions, first measured its dynamic modulus in the laboratory, and analyzed the dynamic modulus characteristics of the material, and then used the equation the estimation equation proposed by Witczak et al. (Witczak1-37A) as a benchmark to introduce a new parameter, grouting mass ratio (Pb) to develop a Witczak- G prediction model to compare and validate the predicted dynamic modulus with the measured values. The results show that compared with SMA-16, HPCP semi-flexible material exhibits higher dynamic modulus and lower phase angle, and its temperature sensitivity and deformation resistance are significantly better than those of SMA-16. Under the influence of porosity and Pb factor, the dynamic modulus is positively correlated with both factors, and the phase angle increases first and then decreases, showing strong elastic properties. In this paper, we propose a dynamic modulus prediction model based on viscosity and Pb, Witczak-G, which predicts the highest coefficient of determination (R2) of the predicted dynamic modulus as high as 0.99 after initial fitting and validation, which indicates that the Witczak-G model is suitable for predicting the dynamic modulus of semi-flexible materials injected with HPCP. [ABSTRACT FROM AUTHOR]

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

Grouting engineering is extensively employed in highway maintenance, tunnel excavation, mining, and other domains. As application scenarios become more complex, the demands for injectivity and toughness of grouting materials escalate. This research presents the fabrication of a dual-network cementitious material through acrylamide (AM) monomers in-situ polymerization and ultra-fine portland cement for grouting. The in-situ polymerization of AM increases the fluidity of cement paste, forms a hydrogel three-dimensional network structure, and significantly reduces the initial setting time from 345 to 35 min at a 5% AM content. The early-stage compressive strength (0–7 days) is inhibited by the in-situ polymerization, the flexural strength is notably increased, with an overall toughness improvement of 174.4% at a 7% AM content. The in-situ polymerization influences the early hydration behavior of ultra-fine portland cement by delaying the hydration induction period and affecting calcium hydroxide content and the bound water in calcium silicate hydrate. The complexation between metal ions (Ca2+, Al3+) in ultra-fine portland cement and carboxyl groups in the polymer enhances organic–inorganic interaction. The three-dimensional network structure of the cement hydration products and the polymer will form a dual-network structure, further enhancing the performance of the ultra-fine portland cement. In this research, the potential application of AM in-situ polymerization in the enhancement of ultra-fine portland cement grouting is proposed. [ABSTRACT FROM AUTHOR]

Cement grout is widely used in underground excavations and constructions. Recent research reveals that coal char, a sustainable coal-derived material, can enhance the engineering properties of traditional cement grouts, such as higher compressive strength and lower bleeding at room temperature. However, the effect of coal char addition on the heat of hydration and rheological behaviors of char-cement grouts at lower or higher temperatures remains unclear. In this study, considering different w/c ratios (0.8–1.2) and char contents (10%–30%), the heat of hydration of char-cement is investigated to understand the hydration mechanism of cement with adding char. The rheological behaviors of new char-cement grouts at two different temperatures of 5 and 35°C are studied. It is found that the addition of char at the same w/c ratio leads to a higher first heat flow peak in the initial reaction period and facilitates hydration reaction in cement grouts based on cumulative heat evolution over a longer period (typically >14 h). The effect of 5 and 35°C on rheological behaviors of char-cement grouts is consistent with the respective pure cement grouts. A simple model based on cumulative flow resistance is proposed for describing the rheological behavior and can well fit all pure cement and char-cement grouts with a relatively high average R2 value of 99.7%. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Portland cement products are extensively used as parent materials in construction projects. However, the production and consumption of these products result in various environmental pollutants, including the emission of carbon dioxide gas and excessive water usage. Geopolymer products have emerged as a promising alternative to Portland cement and its products due to their diverse mechanical and chemical properties. Therefore, in this study, we aim to investigate the potential of geopolymer products as a replacement for Portland cement. To this end, the optimal mixing design was obtained by performing uniaxial compressive strength and flow table tests. Nailing is a commonly used method for stabilizing soil excavations and slopes, often involving the use of Portland cement as grout. Geopolymer is used as a potential replacement for cement grout in this system. Pullout tests were conducted to investigate the interaction between the soil and grout, considering the effect of curing conditions and environmental factors such as temperature, humidity, and overburden pressure for both the geopolymer and cement grouts. The results indicate that, in general, the pullout force of geopolymer samples is lower than that of cement samples. However, raising the temperature in geopolymer samples results in an increase in the pullout force, whereas an increase in temperature in cement samples leads to a decrease in pullout force. It can be concluded that geopolymer samples need to be modified by using an additive, such as sodium silicate, to achieve proper pullout force and suitable interlocking with soil grains. [ABSTRACT FROM AUTHOR]

The Church of Panaghia Krena is a very important Byzantine monument situated in the island of Chios, well-known due to the high aesthetic value of the ceramic tile decoration on its facades and of its frescoes. The church suffered severe damage especially due to the 1881 devastating Chios earthquake and different interventions were implemented soon after (1884), consisting mainly of the reconstruction of collapsed areas and the addition of ties. Nevertheless, deterioration of old damages and appearance of new ones was observed. Thus, a restoration program was carried out between 2000 and 2007. This paper presents the basic characteristics of all types of historic materials examined, the main results of the in situ and laboratory experimental program carried out for the selection of the raw materials, and the design of optimum compositions of mortars and grouts to be used for the restoration works. The importance of in situ pilot applications is underlined, as well as of the production of site-specific aggregates for the repointing mortars by crushing a local rock, in order to succeed the adequate reddish color to match with the original mortars and bricks still preserved and achieve an aesthetic harmony with the color hue and texture of the original materials. [ABSTRACT FROM AUTHOR]

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

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Shallow geothermal energy systems (SGES) are a promising technology for contributing to the decarbonization of the energy sector. Soil thermal conductivity (λ) governs the heat transfer process in ground under a steady state; thereby, it is a key parameter for SGES performance. Soil mixing technology has been successful in enhancing the shear strength of soils, but is adopted in this paper for the first time to improve soils as a geothermal energy conductive medium for SGES applications. First, the thermal conductivity of six types of soils was systematically investigated and the key parameters analyzed. Next, graphite-based conductive cement grout was developed and mixed with the six soils in a controlled laboratory setting to demonstrate the significant increase in soil thermal conductivity. For example, the thermal conductivity of a very silty dry sand increased from 0.19 to 2.62 W/m·K (a remarkable 14-fold increase) when mixed with the conductive grout at a soil-to-grout ratio of 6∶1. In addition, the mechanical properties of the cement grouts and cement-mixed soils were examined along with the microstructural analysis, revealing the mechanism behind the thermal conductivity improvement. [ABSTRACT FROM AUTHOR]

In internally post‐tensioned (PT) prestressed concrete (PC) structures, the prestressing system is usually made of high‐strength steel tendons embedded within concrete through either metallic or plastic ducts filled with cement grout or grease. Construction defects or degradation phenomena may lead to insufficient covering, exposing the prestressing steel to a harmful environment, potentially compromising the durability and load‐bearing capacity of the structure. Based on experimental tests on six 1:5 scaled PT specimens, this study presents accurate numerical simulations of four‐point bending tests on girders with unbonded and partially bonded tendons having different levels of initial prestress. Nonlinear finite element analyses (FEAs) were developed to reflect the friction‐type interaction mechanism between unbonded tendons and external ducts under increasing external load up to failure. Both global and local response parameters of the girders were studied validating numerical results against experimental findings. The numerical simulations provide insights on the stress pattern of unbonded and partially bonded strands, shedding light on the lower bearing capacity of defective girders compared to those with bonded tendons. Such findings contribute to a multi‐scale assessment and decision‐making framework for existing PT girders with defective grouting and low residual prestress levels, enhancing the understanding of their structural behavior and informing maintenance or retrofitting decisions. [ABSTRACT FROM AUTHOR]

Thickening the foundation slab and improving the subgrade soil using geo-techniques are effective measures for controlling unwanted vibrations at high-tech facilities. In this study, the vibration-reduction performance of 1-m-thick concrete slabs with natural and cement-improved subgrades was investigated based on in situ frequency sweep tests. One 1-m-thick concrete slab rested on 1-m-thick compacted sandy gravel backfill atop an undisturbed subgrade was constructed on the north side of the experimental site, and another identical concrete slab rested on 1-m-thick compacted sandy gravel backfill atop a cement-improved subgrade was constructed on the south side. The vibration-reduction effect was evaluated by comparing the free-field ground vibrations and surface vibrations of the two slabs at three pairs of evaluation locations. In terms of peak velocity, the 1-m-thick concrete slab with the natural subgrade exhibited a slight vibration amplification effect at low frequencies and a significant reduction effect at middle and high frequencies; the 1-m-thick concrete slab with the cement-improved subgrade exhibited a continuous vibration reduction action at all frequencies. In terms of RMS velocity, the vibration-reduction performance of the 1-m-thick concrete slab with the cement-improved subgrade was better than that with the natural subgrade. The results demonstrated that the vibration-reduction effect of the thick concrete slab was significant and could be increased by improving the subgrade using the cement grouting method. [ABSTRACT FROM AUTHOR]

Cement grout is traditionally used for treating water leakage distress in tunnels. However, traditional cement grout has the disadvantages of a poor anti-seepage performance, long setting time, and slow strength gain. To this end, a high-performance cement-based capillary crystalline waterproofing (CCCW) grouting material was synthesized using cement, capillary crystalline material, and several admixtures. The influences of the material proportions on the viscosity, bleeding rate, and setting time of the fresh grout, as well as the permeability coefficient of the grouted aggregate and the unconfined compression strength of the hardened grout material, were systematically studied. The mineralogy and microstructure of the CCCW grouting material were examined using X-ray diffraction, industrial computed tomography, and scanning electron microscopy. The results indicated that the capillary crystalline material PNC803 was not suitable for mixing with bentonite, sodium chloride, and triethanolamine in cementitious slurries, but it can produce excellent synergistic effects with sulfate, calcium chloride, and triisopropanolamine. An analysis of the microstructure of the CCCW grouting material showed that the PNC803 and additives can promote the hydration of cement, which yields more hydration products, sealing water passage and filling micro voids and therefore leading to enhanced waterproofing and strengthening effects. These research results could improve the applicability of CCCW material in tunnel engineering. [ABSTRACT FROM AUTHOR]

Ultrafine hydraulic binder grout injection is a technique utilised for repairing masonry, either to connect sections, seal joints, or fill voids due to its great capacity for penetration and higher mechanical strength than lime grout. In this research, the mechanical properties of ultrafine hydraulic cement grout are analysed considering the influence of the mould material for preparing the specimens and their geometry characteristics in the context of the specifications set out in several international standards. The test campaign to ascertain compressive and flexural strength in different circumstances is supplemented with a physical and chemical characterisation of both binder and fresh and hardened grout. Significant differences in mechanical properties between specimens prepared with absorbent or non-absorbent-water material are found due to the influence of drying shrinkage and decanting binder during the curing process. Furthermore, the slenderness of specimens is presented as an important factor in determining the compressive strength of mixtures. [ABSTRACT FROM AUTHOR]

Solving the challenges facing the mining industry is crucial for shaping the global attitude towards clean energy technologies associated with critical minerals extracted from depth. One of these challenges is the well-known explosion-like fractures (rockbursts) or spalling failures associated with the initiation of internal cracks. To prevent such catastrophic failure, shotcrete, as a cement grout, is widely used in tunnel support applications. In areas where the tunnels are constructed within the limestone strata using tunnel boring machines (TBM), drilling, and/or blasting, millions of cubic meters of crushed limestone (CL) in powder form are extracted and landfilled as waste. Given the fact that natural sand consumption as a raw material in the construction industry exceeds previous records, recycling of such excavation material is now becoming increasingly needed. From this perspective, this study aims to utilize crushed limestone as a potentially sustainable alternative to natural sand in shotcrete applications in deep tunnels. Accordingly, several strength characterization and crack initiation determinations through various stress–strain-based models were carried out on cylindrical samples containing different proportions of crushed limestone. By increasing the crushed limestone content in the shotcrete mix, the crack initiation stress (as a measure of the in situ spalling strength) increased as well. The results suggest that the crushed limestone has good potential to replace the natural sand in the shotcrete mixture used in tunnel support applications. [ABSTRACT FROM AUTHOR]

Hydrophilic polymer grouting with a particular water-to-binder ratio could block soil pores in a short time to prevent the loss of cement slurries in sandy strata in water-rich areas. Meanwhile, when combined with cement, the setting time and permeability of sandy soils could be minimized significantly. In this study, a series of indoor permeability tests, unconfined compression tests, and field grouting tests were conducted to investigate the influence of the ratio of polymer to water, the ratio of water to cement, polymer and cement content on the solidification time, setting time, impermeability effect, and compression resistance of silty sands and summarize the recommended grouting parameters of cement and polymer for the water-rich sandy stratum. The results illustrated that the recommended ratio of the primary and auxiliary agents in the polymer was 2:1. If the solidification time was required to be earlier than the initial hydration time of cement as the standard, the ratio of polymer to water should be higher than 1:3. The setting time of cement- and polymer-stabilized silty sands decreased with curing temperature and polymer content. The permeability coefficient of cement- and polymer-stabilized silty sands decreased nonlinearly with the increase in polymer and cement contents. Their permeability coefficients were basically within the range of 10−6 cm/s. The compressive strength of cement- and polymer-stabilized silty sands decreased with polymer dosage but increased linearly with cement content. The compressive strength and permeability coefficient of the field grouted samples showed that the cement and polymer grouted silty sand had better impermeability than that grouted with the mixture of cement and metakaolin and the mixture of cement, red mud, and phosphogypsum. The permeability coefficient of cement and polymer grouted silty sand after 28 days could reach 0.89 × 10−7 cm/s, while the improvement of their compressive strength was relatively low, with an average value of 2.46 MPa. The failure of cement- and polymer-stabilized silty sands showed typical plastic shear characteristics rather than brittle and splitting characteristics that appeared in the failure of silty sand grouted by cement and metakaolin, or the mixture of cement, red mud, and phosphogypsum. The results of this study can provide a reference for the construction of low-permeability barriers at sandy strata in water-rich areas. [ABSTRACT FROM AUTHOR]

To enhance the cracking resistance of semiflexible pavement, short polypropylene fibers with lengths of 3 mm and 6 mm were incorporated into cement grouting material, and their effect on fluidity, mechanical properties, drying shrinkage, and pore structures was systematically investigated. When polypropylene fiber dosage is less than 0.9 vol%, the reduction in fluidity is relatively minor. Polypropylene fiber can not only improve toughness, but also inhibit water loss and reduce drying shrinkage, which is related to the distribution of polypropylene fiber and the bonding performance between fiber and matrix. However, excessive polypropylene fiber can lead to uneven distribution of the porosity along vertical direction. With a 0.9 vol% of 3 mm polypropylene fiber, the 28d flexural strength of the grouting material increased by 38%, and the drying shrinkage decreased by 22%. This article provides some guidance for enhancing the overall performance of cement grouting material using polypropylene fiber. [ABSTRACT FROM AUTHOR]

This study undertakes a comprehensive experimental and numerical analysis of the structural integrity of buried RC sewerage pipes, focusing on the performance of two distinct jointing materials: cement mortar and non-shrinkage grout. Through joint shear tests on full-scale sewer pipes under single point loading conditions, notable effects on the crown and invert of the joint were observed, highlighting the critical vulnerability of these structures to internal and external pressures. Two materials—cement–sand mortar and non-shrinkage grout—were used in RC pipe joints to experimentally evaluate the joint strength of the sewerage pipes. Among the materials tested, cement–sand mortar emerged as the superior choice, demonstrating the ability to sustain higher loads up to 25.60 kN, proving its cost-effectiveness and versatility for use in various locations within RC pipe joints. Conversely, non-shrinkage grout exhibited the lowest ultimate failure load, i.e., 21.50 kN, emphasizing the importance of material selection in enhancing the resilience and durability of urban infrastructure. A 3D finite element (FE) analysis was also employed to assess the effect of various factors on stress distribution and joint deformation. The findings revealed a 10% divergence between the experimental and numerical data regarding the ultimate load capacity of pipe joints, with experimental tests indicating a 25.60 kN ultimate load and numerical simulations showing a 23.27 kN ultimate load. Despite this discrepancy, the close concordance between the two sets of data underscores the utility of numerical simulations in predicting the behavior of pipe joints accurately. This study provides valuable insights into the selection and application of jointing materials in sewerage systems, aiming to improve the structural integrity and longevity of such critical infrastructure. [ABSTRACT FROM AUTHOR]

The hydrogeological conditions of Huainan Coalfield are complex. The Taiyuan formation limestone water (Taihui water) in this area is a direct threat to the water source of the 1# coal mining floor. In order to prevent and control water disasters, Gubei Coal Mine adopted ground high-pressure grouting with fly ash cement to block the hydraulic connection between the Taiyuan formation limestone aquifer and the Ordovician limestone aquifer. However, the injected slurry will destroy the original hydrochemical balance of Taihui water and change its hydrochemical characteristics. Taking the influence area of the 2# karst collapse column in the Beiyi 1# coal mining area of Gubei Coal Mine as an example, a total of 25 Taihui water samples were collected. The hydrochemical characteristics and evolution law of Taihui water before and after grouting are studied via the multivariate statistical method. The research methods include constant index statistics, Piper diagram, correlation analysis, ion combination ratio, and saturation index analysis. The results show that after grouting, the concentrations of Na+ + K+, Ca2+, Mg2+, and Cl− in Taihui water decrease, while the concentrations of SO42− and HCO3− increase. The average values of PH and TDS become larger. The hydrochemical types of Taihui water are more concentrated, mainly HCO3-Na and Cl-Na. The correlations between conventional indicators decrease. According to the analysis of ion combination ratio, dissolution, cation exchange, and pyrite oxidation mainly occur in Taihui water, and these effects are enhanced after grouting. The saturation index results show that after grouting, the saturation index of dolomite, calcite, and gypsum is significantly reduced, and the saturation index of rock salt is slightly increased. The conclusion of this study is that the hydrochemical characteristics of Taihui water are greatly affected by fly ash cement. Moreover, because fly ash cement contains a lower calcium oxide content than ordinary Portland cement, the effect of fly ash cement on the ion concentration of Taihui water and the resulting hydrogeochemical effect are significantly different. Therefore, in the treatment of mine water disasters, the hydrogeochemical evolution law affected by fly ash cement grouting should be identified. [ABSTRACT FROM AUTHOR]

Grouting is a method or technique that is carried out to improve underground conditions by injecting material that is still in a liquid state, through pressure (it can inject semi-viscous materials) so that the material will fill in all the existing cracks and holes. The main purpose of grouting in this study is to strengthen the soil and increase soil strength. The injection material will enter the soil pores, react with the soil, and harden to form a strong and sturdy bond. The grouting material in this study was applied to filling boreholes in pile foundations when a load is applied, will be held by the frictional resistance between the piles, cement, epoxy paste, and soil. The filling materials for this grouting are soil paste, cement, and epoxy resin which were observed in a laboratory with a tensile test system to see the behavior of increasing soil strength at 7 days, 14 days, and 28 days. Based on the results of laboratory tests carried out, the use of epoxy resin, cement, soil, and water as grouting materials for foundations increases the soil stiffness value expressed in the modulus of elasticity value and increases the soil shear parameter values, namely the values c and f. The increase in value occurs at the ratio ER/W = 80/180 where with a longer curing time, namely 28 days, the value of shear stress, c and f and the modulus of elasticity are each 2.3kg/cm2; 39,520; 12.08 MPa. [ABSTRACT FROM AUTHOR]

This study investigated the application of electrical resistance tomography (ERT) in characterizing the slurry spatial distribution in cemented granular materials (CGMs). For CGM formed by self-flow grouting, the voids in the accumulation are only partially filled and the bond strength is often limited, which results in difficulty in obtaining in situ samples for quality evaluation. Therefore, it is usually infeasible to evaluate the grouting effect or monitor the slurry spatial distribution by a mechanical method. In this research, the process of grouting cement paste into high alumina ceramic beads (HACB) accumulation is reliably monitored with ERT. It shows that ERT results can be used to calculate the cement paste volume in the HACB accumulation, based on calibrating the saturation exponent n in Archie's law. The results support the feasibility of ERT as an imaging tool in CGM characterization and may provide guidance for engineering applications in the future. [ABSTRACT FROM AUTHOR]

Grouting cable is one of the most critical technologies in mine support. However, there are few studies on the effect of post-peak residual strength of cement grout under direct shear testing, which is of great significance for evaluating the bearing capacity of grouting cables in the whole life cycle. Hence, in this study, we carried out a systematic direct shear test to reveal the shear characteristics of cement grout under both constant normal loading (CNL) and constant normal stiffness (CNS) boundary conditions. The test results show that, under the same initial normal stress, the peak shear strength of the cement grout obtained under the CNS boundary conditions is greater than that under the CNL boundary conditions. The high initial normal force reduces the effect of boundary conditions on the post-peak mechanical shear properties of the cement specimens. Moreover, under CNS boundary conditions, the acoustic emission activity of the sample has an obvious signal before the peak shear strength, accompanied by multiple large ringing counts, indicating that the internal damage of the cement grout starts before the peak intensity. This work enhances the understanding of cement grouting fracture characteristics in mining support engineering. [ABSTRACT FROM AUTHOR]

To study the effect of sulfate ion erosion on grouted reinforced coal bodies, downhole grouting reinforcement was simulated by artificially prefabricating regular serrated structural surfaces and grouting them with cement. In addition, sulfate erosion tests were carried out at three erosion ion concentrations (3%, 5%, and 10%) and four erosion times (7d, 14d, 28d, and 40d) at a pressure of 0.2 MPa using self-developed constant pressure accelerated erosion equipment, and then, mechanical property tests were conducted using an MTS816 rock mechanics shear tester, which is the most effective way to test the mechanical properties of coal. The test results are as follows: (1) the shear stress–displacement curves of the specimens were of slip type at lower normal stresses and of peak shear type at higher normal stresses, (2) the shear strength of the specimen was linearly negatively correlated with the erosion time and erosion ion concentration, (3) the effect of erosion time was greater than the effect of erosion concentration on the specimen shear strength parameters, (4) sulfate erosion can only affect the degree of shear shrinkage and shear rise and cannot change the damage behavior, and (5) with an increase in erosion ion concentration and the prolongation of the erosion time, the damage morphology of the specimen was shown as the "coal body destruction–nipping fracture–climbing nipping fracture" (coal–pulp interfacial separation) damage form. [ABSTRACT FROM AUTHOR]

The two main parameters of grouting volume and grouting pressure are the keys to ensuring the quality of postgrouting. However, there is no equation for predicting the main grouting parameters of long and large-diameter postgrouting drilled shafts. In this paper, field data of 708 shafts in 128 projects were systematically investigated utilizing mathematical statistics, and equations for predicting the grouting volume and grouting termination pressure of long and large-diameter drilled shafts suitable for various soil layers were proposed. The range of coefficients of the grouting volume classified by soil types was defined. When establishing the equation for predicting the grouting termination pressure for a long drilled shaft, the influences of the cement grout weight in the grout pipe and the height difference between the pressure sensor and the grout valve on the grouting pressure were considered. Taking the grouting pressure and grouting volume as the control conditions of postgrouting operation, the criteria conditions for terminating postgrouting were proposed.The proposed equations for predicting the grouting volume and grouting termination pressure were verified based on a project case study. The factors affecting the grouting termination pressure were analyzed in detail. These research results were of great significance to the design of postgrouting drilled shafts. [ABSTRACT FROM AUTHOR]

Microbial cement, known for its superior fluidity, stable crystal formation, and strong bond with concrete, is an effective solution in fixing defects such as voids that appear due to insufficient grouting in the joints of precast concrete components. To evaluate the mechanical properties of rebar anchored with microbial cement grout, three pull-out tests were designed, taking into account parameters such as calcium source concentration, the filler in borehole voids, and the shape of the rebar. The results indicate that specimens with a higher concentration of calcium source require fewer grouting cycles, but the pull-out bearing capacity of the anchored rebar is lower. However, the introduction of quartz sand as a filler in the borehole voids results in a significant increase in the pull-out bearing capacity of the rebar compared to specimens without filler. Among these, the specimens with a medium particle size of 0.5 ~ 1 mm (1/4δ ~ 1/2δ, the gap of δ = 2 mm between the steel bars and hole wall) have the highest pull-out bearing capacity. In comparing rebar shapes, ribbed rebar slightly outperforms smooth round rebar in terms of pull-out bearing capacity. Based on the experimental results analysis, the anchoring mechanism of microbial cement grouting on reinforcement has been elucidated. [ABSTRACT FROM AUTHOR]

To study the applicability of the new geopolymer grouting material for super-long and large-diameter post-grouting bored piles in silty fine sand geology, this paper compares the bearing capacity of two grouting materials, geopolymer and normal Portland cement, and different grouting volume pile side-distributed grouting piles in silty fine sand based on field model tests are analyzed through the diffusion forms of the two materials in silty fine sand through the morphology of the grouted body after excavation. The results show that the ultimate bearing capacities of P0 (ungrouted pile), P1 (8 kg cement grouted pile), P2 (6 kg geopolymer-grouted pile), P3 (8 kg geopolymer-grouted pile) and P4 (10 kg geopolymer-grouted pile) are 5400 N, 8820 N, 9450 N, 11,700 N and 12,600 N, respectively, and that the ultimate bearing capacity of the grouted pile is improved compared with that of the ungrouted pile since, under the same grouting amount, the maximum bearing capacity of the pile using geopolymer grouting is increased by 133% compared with that of the pile with cement grouting. This further verifies the applicability of the geopolymer grouting material for the post-grouting of the pile foundation in silty fine sand. Under the action of the ultimate load, the pile side friction resistance of P1, P2, P3 and P4 is increased by 200%, 218%, 284% and 319% compared with that of P0. In addition, the excavation results show that the geopolymer post-grouting pile forms the ellipsoidal consolidation body at the pile side grouting location, which mainly comprises extrusion diffusion with a small amount of infiltration diffusion, and the cement grouting pile forms a sheet-like consolidation body at the lower grouting location, which primarily comprises split diffusion. This study can provide a reference basis for the theoretical and engineering application of post-grouting piles using geopolymers. [ABSTRACT FROM AUTHOR]

Rocks containing flaws around rock structures are often subjected to complex temperatures and geological conditions. This study investigates the mechanical behavior of heat-treated rock samples with a flaw under ungrouted and grouted conditions subjected to dynamic loading. Rock samples were prepared from two different types of rocks, model rock and natural marble, with an existing flaw at a fixed orientation under three different infill conditions, i.e., ungrouted, cement grouted, and epoxy grouted. Samples were initially heat treated to a temperature between 30 and 650 °C for 0–15 h and then subjected to dynamic loading using Split Hopkinson Pressure Bar (SHPB). A high-speed camera was coupled with SHPB to record the progressive failure process of these samples, and Digital Image Correlation (DIC) captured the strain evolution. It was observed that the strength and stiffness of samples remained constant up to a certain temperature, namely transition temperature (i.e., 100–150 °C and 500–650 °C for model rock and marble, respectively) and then reduced significantly. The presence of grouts improved the mechanical behavior of samples significantly. However, their efficiency was dependent on the degree and duration of heating. Epoxy grout was observed to have superior efficiency compared to cement grout at lower degrees and lesser durations of heating which reverses for their higher magnitudes. Except for the epoxy-grouted samples at low temperatures, fracture initiation took place from the flaw tips in all other samples. Fracturing was dominated by tensile cracks at lower degrees and lesser duration of heating which changes to shear cracks-dominated mechanism, especially for porous model rock with the increasing degree and duration of heating. Highlights: Grouts were efficient in improving the dynamic response of jointed rocks with efficiency dependent upon the heat treatment of samples. Crack initiation and progression for grouted samples depend on grout strength, degree and duration of heating. Crack initiation and progression for ungrouted samples depend on the degree and duration of heating. Epoxy grout was more efficient for lower degree and duration of heating while cement grout was for higher ones. The transition from tensile-dominated fracturing to shear-dominated fracturing with increasing duration and degree of heating with more dominant effect on porous model rocks as compared to crystalline marble. [ABSTRACT FROM AUTHOR]

Reinforced concrete beams must meet strength and durability standards, but aggressive environmental factors are the main cause of corrosion, which can affect the strength and durability of building structures. Maintenance, retrofitting, and reinforcement of structures are important to ensure safety. It is necessary to take appropriate measures to address corrosion problems in building structures early on. One way to achieve this is by repairing damaged structures using more modern and effective technologies and materials. This study aims to determine the flexural behavior of reinforced concrete (RC) beams repaired with Sikagrout-215 material and reinforced with GFRP sheets with different layer configurations. The study used three RC beams as the control group, three RC beams coated with Sikagrout-215 mortar, and six RC beams reinforced with GFRP. All beams were subjected to 4-point bending tests to determine their load capacity, crack response, ductility, and energy absorption capacity. The results showed that repair with grouting decreased the load capacity, while reinforcement with a combination of mortar grouting and GFRP increased the maximum load. Reinforcement of the support region could restore the function of the beam by 9.3%. Among the three types of reinforcement, BGRST significantly improved the first crack response, yield response, and ultimate performance of the RC beams. Beam fracture occurred more frequently with Sikagrout-215 mortar reinforcement, while reinforcement with GFRP composites partially protected the load capacity after fracture. [ABSTRACT FROM AUTHOR]

This study introduces a Multi-Depth Deflectometer (MDD) combined with a Global Navigation Satellite System (GNSS) which was developed for measuring the deformation of railway slab track layers. We newly designed the MDD with the addition of laser sensor modules for increasing precision in which the MDD head is fixed at the top of the track slab. The MDD/GNSS system can measure the relative deflection between each track layer as well as the total deflection at the top of the track slab, which makes it possible to evade the fixed condition problem of classical MDD. The new MDD/GNSS system was installed at the transition zone between a tunnel entrance and its embankment, which experienced high settlement levels prior to repair. The system was used to monitor whether the repaired concrete track foundation with pressurized cement grouting was stabilized effectively and what track layer position was most unstable so that it had the most influence. The GNSS system was designed and built for computing net settlement at each track layer even when the MDD could not be fixed firmly at the end point, which is a major drawback of classical MDD. The results obtained from MDD and GNSS measurements indicated significant potential in aiding railway track settlement measurements. [ABSTRACT FROM AUTHOR]

Top-down cracking (TDC) as a severe type of cracking has been widely reported in pavements with heavy traffic loads and mixtures sensitive to rutting damages. Since the likelihood of TDC increases as a result of weak mastic, semi-flexible pavements (SFPs) grouted with cement asphalt emulsion pastes (CAEPs) were introduced in this study to evaluate its performance in prevalence or mitigation of this problem. Using laboratory tests, the material properties and rutting resistance of SFP with CAEPs were compared to the conventional asphalt mixture. Then comprehensive finite element (FE) models were employed to investigate the influence of rutting damage severity on non-uniform contact stresses and critical TDC responses. Considering various degrees of rutted surface, the critical locations of TDC were predicted based on maximum transverse and shear strain responses. The results demonstrated that the presence of a rutted surface induced the near-surface responses significantly, and the more severe rutting, the higher propensity for TDC. Besides, the location of TDC initiation was greatly influenced by the severity of the rutted surface. Finally, based on SFP performance in the surface layer, CAEP40 was recommended as the best grouting material to reduce the likelihood of TDC and rutting damage development. [ABSTRACT FROM AUTHOR]

The poor cracking resistance of Semi-Flexible Pavement (SFP) mixture has limited its wider application. Particularly, the dual skeletal interlocking structure makes its damage process complicated. Its fracture process is expected to change with aggregate gradation and temperature, but the relevant knowledge is very limited. Thus, this study aims to investigate the effects of the two factors on the fracture characteristics of SFP using the acoustic emission (AE) technique and X-ray computed tomography (CT) approach. SFP specimens with three gradations (the target cement grout volume is 22%, 25% and 30%, respectively) were fabricated and subjected to the split tensile tests at three different temperatures (−10°C, 10°C and 25°C). Machine learning-based techniques were applied to analyze the AE signals to improve the understanding of the mesoscale damage process. Although the analysis of macro mechanical parameters showed the diminishing effect of temperature dependency on the fracture process with an increase in cement grout volume, the effect was found to be still significant based on the mesoscale analysis. Besides, it was found that the damage process transferred from the main crack going through cement to distributed meso-cracks in asphalt and cement with the temperature increase. [ABSTRACT FROM AUTHOR]

Cement Grouted Bituminous Macadam (CGBM) is a composite pavement that can offer sustainability in the pavement construction sector. The main objective of this study emphasises designing and evaluating the CGBM mixes prepared with different cementitious grouts and aggregate gradations. Compressive strength (7 and 28 days), Flexural strength (28 days), Marsh cone flow, and Initial and final setting time were considered for optimising the cementitious grouts. The details of several investigations on CGBM that include Marshall stability, Compressive strength, Indirect Tensile Strength (ITS), Resilient Modulus (Mr), Fracture energy, and Cantabro abrasion test were reported. The experimental results showed that sand and micro silica influence the mobility of grout to a greater extent. Percolation of grouts into Open Graded Friction Course (OGFC) mixes was a critical concern for grouts with flow time longer than 35 s. A reduction in the pore volume and reduced interconnected links in finer gradation resulted in improper full-depth penetration (FDP) characteristics. Mixture level tests for CGBM revealed that Mr of CGBM improved by about 6 times compared to the bituminous mix. In addition, CGBM showed high tensile strength with rapid crack propagation behaviour. Further, pavement design demonstrated a 35% of thickness reduction and cost reduction due to CGBM implementation. [ABSTRACT FROM AUTHOR]

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

Semi-flexible material (SFM) is produced by pouring cement grouting material into the asphalt concrete skeleton. It exhibits both characteristics of cement and asphalt, increasing structural stiffness and reducing rutting. Extensive studies have shown that the temperature load coupling effect is one of the leading causes of road rutting. However, few researchers focused on the anti-rutting impact and structural layer applicability of SFM under this effect. Thus, a coupled temperature-mechanical approach was developed based on the finite element (FE) method to simulate the rutting of SFM at different pavement layers and times of the day. During simulation, both standard load and overload were applied to the FE model of pavement. Asphalt mixture and SFM specimens were prepared for essential road performance and dynamic modulus testing. The mechanical properties of SFM and asphalt mixtures at different temperatures were obtained based on the measured data. The structural layer applicability of SFM was revealed by simulating the response of the pavement structure under the combined action of temperature and load. An accelerated pavement test (APT) based validation indicated that the simulation results were accurate. The results show that traditional asphalt pavement and pavement with SFM at the surface and bottom layers tend to exhibit dilative heave adjacent to the wheel load. Using SFM at the middle layer shows a compacted rutting mode, and the pavement has a minimum rise of 51% in rutting depth under the double overloading compared with the pavements with SFM in other layers. It implies that using SFM in the middle layer gives optimal resistance to overload. Considering the depth, form, and resistance of rutting, the SFM in the middle layer of pavement can functionally exert its anti-rutting characteristic. [ABSTRACT FROM AUTHOR]

In order to study the reinforcing effect of the different grouting materials applied in fissure rock engineering, ultra-fine cement slurry, cement–silicate slurry, and MARITHAN® were used to carry out grouting tests on specimens of fissure-containing rocks. With the help of a uniaxial compression acoustic emission test system, the mechanical characteristics of the grouted specimens were obtained, and the damage process of the specimens was revealed by using the acoustic emission signals. The tested results showed the following: the residual strength of the grouted specimens using the three grouting materials increased by 16.931%, 13.075%, and 39.998%, respectively; the ultra-fine cement grouting and cement–silicate grouting specimens showed damage patterns of shear-slip damage along the original rupture surface; the specimens of MARITHAN® grouting cracked from a position near the end of the specimen with no damage to the grouted body portion; the cumulative acoustic emission energy curves of the grouted specimens showed obvious stage characteristics; and the acoustic emission energy distribution characteristics of the grouted specimens differed depending on the grouting materials. [ABSTRACT FROM AUTHOR]

Increasing the water–cement ratio and water-reducer dosage of cement slurry enhances its fluidity. However, a high water–cement ratio diminishes the beneficial effects of water reducers on fluidity. The stone content of the slurry decreases as the water-reducer dosage increases. Additionally, the water–cement ratio significantly affects stone content. However, when the water–cement ratio exceeds a threshold value, stone content decreases. Furthermore, the threshold value of the water–cement ratio decreases with increasing water-reducer dosage. Without the addition of the water reducer, as the water–cement ratio increases the overall integrity of the grout stone decreases. The addition of the water reducer alters the surface pore distribution, wherein "uniform small pores" change to "localized large pores." Based on the multi-objective optimization of Matlab, the recommended optimal mix composition for a slow-setting cement slurry is a water–cement ratio of 0.25 and water-reducer dosage of 1.5%. With the use of this optimized mix composition, the stone content and compressive strength increase by 7.8% and 145.6%, respectively, compared to those obtained using the recommended mix ratio in the specifications. Additionally, all relevant performance parameters meet the requirements specified by previous standards. [ABSTRACT FROM AUTHOR]

In soft soil areas, to compare the load-bearing characteristics of bag grouting piles and cement mixing piles and study the load-bearing mechanism of bag grouting piles, field tests are conducted in this study, including the comparative compressive test of bag grouting piles and cement mixing piles, and the analysis of pile axial force, pile side friction resistance, and pile end resistance. Moreover, a numerical simulation is developed using ABAQUS 2020 (finite element analysis software) for three-dimensional modeling. The numerical simulation results are compared with the field test results to verify the reliability of the numerical simulation. Furthermore, the influences of five factors are studied; namely, pile length, pile diameter, pile spacing, the thickness of the bedding layer, and grouting pressure are studied for their effects on the compressive bearing characteristics of the bag grouting pile. The results show the following: (1) For composite foundations, bag grouting piles are more effective than cement mixing piles in soft soil areas, and the former provide an 8.8% increase in the bearing characteristics. (2) With an increase in the load, the bag grouting pile experiences greater compression in the middle of the pile body, and the pile side friction resistance is increased; therefore, the pile side friction resistance can be fully developed, and the bag grouting piles have the ability to transfer the load from the top of the pile to the soil at the bottom of the pile. (3) When the external load is maximized, the sharing ratio of pile side friction resistance reaches 96.3%, which shows the excellent frictional performance of bag grouting piles. (4) Among the five factors mentioned above, the most important one is the pile diameter, followed by the pile length and pile spacing, the thickness of the bedding layer, and finally the grouting pressure. The optimal combination in this paper is a pile length of 18 m, pile diameter of 0.4 m, pile spacing of 1.0 m, bedding thickness of 0.3 m, and grouting pressure of 0.6 MPa. Therefore, changing the pile diameter can be given priority during the construction design. The findings in this paper can provide valuable insights and practical experience for the design of similar engineering projects. [ABSTRACT FROM AUTHOR]

In this paper, an experimental and numerical study was achieved to investigate the behavior of masonry beams internally reinforced using carbon fiber-reinforced polymer (CFRP) and hybrid steel/CFRP reinforcements. Three beams were built using concrete bricks and grout mortar. The brick was designed with two holes that were filled with grout before placing the rebar inside. One beam was built without shear reinforcement, and the other two were with shear reinforcement. Material characterization tests were performed to evaluate the compressive strength of the brick and the masonry cube and the flexural strength of the masonry prism. The masonry cubes were prepared and tested to evaluate their equivalent mechanical properties. The beams were tested in three-point bending with an effective simply supported span of 840 mm where the load deformations and failure loads were monitored. Finite element models were built using ANSYS and validated with experimental results. Additional beam models were analyzed to study the effect of shear reinforcement spacing from 0.78d to 0.39d and more hybrid reinforcement configurations. Results showed that using equivalent material properties in numerical modeling instead of modeling bricks and mortar was acceptable. In addition, using shear reinforcement with a spacing of 0.78 d didn't enhance the shear behavior of the spacing. Finally, the hybrid steel/CFRP-reinforced beam with shear reinforcement achieved the highest capacity compared to the two other beams. [ABSTRACT FROM AUTHOR]

The air voids in the bituminous mix are filled with a cementitious grout to create cement grouted bituminous (CGB) mix, which is a semi-flexible material. The material has a high resistance to permanent deformation at high temperatures and under heavy loads because of the cementitious grout used in the mixture. Despite their increased brittleness, CGB layers are more prone to cracking when used as thin (40–60 mm) surface or base layers. Increase in binder content in mix decreases air void content and grout content, which leads to reduction in rutting resistance and expected to improve the fatigue cracking resistance. The results of an investigation into the impact of aggregate gradation and binder content on the fatigue performance of CGB mixes are presented in this paper. In a four-point bending test mode at 25 °C, beam specimens of CGB Mixes made with four different aggregate gradations and four different binder contents were tested at four strain levels. The fatigue life measured at higher strain levels of 225 and 250 µε and various mechanical properties like indirect tensile strength and modulus of rupture showed good correlation. By analysing pavements with CGB layers used as the base or surface layer, the fatigue cracking susceptibility of the CGB layer in a typical highway pavement has been determined. It has been found that using the CGB mix as the surface layer is a good choice because the mix also provides a very strong rut as well as an oil and chemical-resistant layer. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

External prestressing tendons are a major structural element for the durability of concrete bridges. In France several cases of sudden breaks in external pre‐stressing tendon made of HDPE duct injected by cement grout directly in contact with strands have been recorded in the past decade [2]. In order to prevent this sudden breaks Cerema has experimented the magnetic rope testing technology from ropeways to develop a non‐destructive inspection technic of the free length and junction of prestressing. The method is based on magnetic leakage field detection and allows to detect defaults of the strands inside the tendon such as corrosion and wire breaks. The article first focuses on the magnetic rope testing technic. Then tests previously performed on laboratory tendons with reference wire breaks will be analyzed for defaults characterization. Finally, the particular methodology adapted to the nondestructive magnetic inspection of prestressing tendons on site will be detailed. A general feedback including handling issues and analysis of non‐destructive magnetic controls completed with visual controls by removing the high‐density polyethylene (HDPE) sheath will be given. [ABSTRACT FROM AUTHOR]

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

Combined with a strategic policy for the recycling of construction waste, this paper puts forward a programme for treating a goaf foundation with waste concrete powder, waste brick powder, and cement grout (BCP cement grout). The BCP cement grout is prepared by replacing part of the waste concrete powder with waste brick powder, and the changeable rule of the setting time, water separation rate, stone rate, and viscosity of the grout with different rates for replacement are studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out. The mineral composition is analyzed and the microscopic mechanism is studied. The results show that the ratio of BCP cement grout developed by the experiment is reasonable; the unit cost is less than 160 yuan/t, which is 40% lower than that of pure cement grout; and both a good economic effect and good environmental effect are obtained. It has the advantages of low water separation rate, high stone rate, and low viscosity. When the ratio of cement powder: waste concrete powder: waste brick powder is 3:5:2 or 3:6:1, the 28 d compressive strength of the stone body is more than 2 MPa, meeting the filling requirements for a goaf foundation. It is not only technically feasible but also economically reasonable to apply construction waste powder to fill the goaf foundation. Recycling and utilizing construction waste can also achieve the ecological restoration of mined-out areas, highlighting the ecological benefits. [ABSTRACT FROM AUTHOR]

Lime mortars have played an important role in constructing ancient Chinese masonry structures, including city walls, buildings, and tombs. A tomb built with lime mortars and stones belonging a Ming high‐ranking official, Xu Jie, was discovered in Huzhou City of China. Eight different samples from Xu Jie's tomb, representing four types of lime‐mortar‐based materials: joint mortar between stone bricks, bedding mortar, grouting mortar, and plaster mortars were collected for analysis and comparison. The characterization of the construction materials has therefore become of primary importance. The function of each mortar was reported and studies into the micro‐textural features and mineralogical compositions of those mortars were performed via a multi‐analytical approach. The joint mortars were all found to be aerial lime mortars with predominately lime. The bedding mortar was found to consist of lime, soil and sand, typical of a tabia mortar. The grouting mortar was found to consist of lime and ground contact metamorphosed limestone. Analysis of plaster sample taken from the roof of the main tomb identified the presence of calcium stearate/palmitate, indicating the usage of plant‐based tung oil as an additive. The analytical results will promote our understanding of Ming architectural technology and craftsmanship, and provide critical information for the conservation of Xu Jie's tomb. [ABSTRACT FROM AUTHOR]

Postgrouting at the pile tip can improve the behavior of pile shaft resistance through the grout returned along the pile shaft. The soil radial unloading effect that existed in the bored pile shaft soil and the cement viscosity with time-dependent behavior affect the grout diffusion. A grout returned height model for postgrouting at the bored pile tip considering the soil unloading effect and time-dependent behavior of cement viscosity was proposed to analyze the grout returned diffusion behaviors. The reliability of the grout returned height model was compared and verified with a series of model bored pile tests and the measured results of the field case. The analysis results showed that considering the influence of pile shaft soil unloading for bored piles and the time-dependent behavior of cement viscosity in the grout returned height model is essential for analyzing the grout returned diffusions. A parametric study with the proposed model was performed, and the effects of soil unloading degree, the grout flow rate, the grouting pressure, and the pile scaling effect on the grout returned height were analyzed. [ABSTRACT FROM AUTHOR]

Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As greener and carbon-friendly material, geopolymer grouting material has a broad application potential in the field of road grouting and is expected to replace cement grouting material in the future. In order to explore the effects of the kinds and dosages of each composition on the performance of geopolymer grouting materials, three kinds of silica-aluminum sources (fly ash, slag powder and coal gangue powder) were used to prepare road geopolymer grouting materials by different alkali activators. The mix proportion range of road geopolymer grouting materials was optimized by single factor test. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy ( FTIR) were used to analyze the phase composition, micro morphology, energy spectrum and chemical bond composition of road geopolymer grouting materials. The results show that road geopolymer grouting material with the best performance is prepared with fly ash and slag powder as raw materials, KOH and sodium silicate solution as composite alkali activator. The recommended mix proportion range of road geopolymer grouting material is: fly ash and slag powder mass ratio is 4 : 6, sodium silicate dosage is 10% ~ 15% (mass fraction), KOH dosage is 5% ~ 11% (mass fraction), water-cement ratio is 0. 50 ~ 0. 65. The fly ash and slag powder are dissolved and regenerated by alkali activation to form amorphous gel products such as C-(A)-S-H, and finally formed SiO4 and AlO4 tetrahedron network structure, accompanied by zeolite like phase, carbonate, calcium hydroxide and other substances. These substances can make geopolymer paste compact and promote its strength growth. [ABSTRACT FROM AUTHOR]

Of the digital concrete-additive-manufacturing techniques, extrusion-based systems are probably the most widespread and studied. Despite the significant potential offered by 3D printing, several challenges must still be overcome. For instance, although several solutions have already been explored, the automated reinforcement of the layer-wise printed structures represents a challenge. The inline quality control of the fresh-state properties of 3D-printed materials is also an open question that needs to be addressed to find an efficient shared practice. This study proposes a new device designed to simultaneously reinforce 3D-printed structures along and through the layers and to be used as an inline quality-control device. This device consists in a sewing system, which is composed of a rotating system, and a hollow needle, which drives a reinforcing cable or yarn and can be used to inject cement grout to fill holes and improve bonding with reinforcement. The rotation is induced by a stepper motor, which measures the torque that is required to make the needle penetrate. This measurement can be used as a quality-control index to ensure material homogeneity. This paper aims to present an original reinforcement system that can be fully automated and simultaneously create reinforcement patterns in different directions of the printed structure while controlling the material's fresh properties. [ABSTRACT FROM AUTHOR]