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Cement grouting material is one of the most important materials in civil construction at present, for seepage prevention, rapid repair, and reinforcement. To achieve the ever-increasing functional requirements of civil infrastructures, cement grouting materials must have the specific performance of high fluidization, early strength, and low shrinka...
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... cement grouting material developed in this paper involves the following five types of raw materials: Shanlv P. O. 42.5R cement, polycarboxylate water-reducing agent, accelerating agent, UEA expansion agent, and nano-SiO2, as illustrated in Figures 1 and 2. The technical characteristics of the five types of raw materials are shown in Tables 1-5, respectively. ...
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... microstructures of the HCGAs with different nano-SiO2 contents, at the curing age of 1 day, are shown in Figure 10. Figure 10. ...
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... microstructures of the HCGAs with different nano-SiO2 contents, at the curing age of 1 day, are shown in Figure 10. Figure 10. Microstructure of HCGA with different contents of nano-SiO2 at 1 d curing age. ...
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... shown in Figure 10, the following observations can be made. The CSH (calcium silicate hydrate) gels and AFt crystals (ettringite) can be observed in each HCGA, whether the nano-SiO2 is added or not. ...
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... microstructures of the HCGA with different nano-SiO2 contents, at the curing age of 3 days, are shown in Figure 11. Microstructure of HCGA with different contents of nano-SiO2 at 3 d curing age. ...
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... shown in Figure 11, compared to the microstructure at the curing age of 1 day, the number of voids and the amount of layered CH crystals in the HCGA at the curing age of 3 days significantly decreases in the field of the microscope, and the amount of CSH gel accordingly increases. This indicates that the hydration degree of the HCGA is further strengthened. ...
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... microstructure of cement grouting materials with different nano-SiO2 contents at 7 days is shown in Figure 12. As shown in Figure 12, the hydration products are closely connected to form a relatively dense and stable microstructure. ...
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... microstructure of cement grouting materials with different nano-SiO2 contents at 7 days is shown in Figure 12. As shown in Figure 12, the hydration products are closely connected to form a relatively dense and stable microstructure. This shows that the hydration of the HCGA has tended to be completed at the curing age of 7 days. ...
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... effect of nano-SiO2 on the strength will occur ahead, as the hydration rate quickens. Figure 13 shows the XRD results of the HCGA in the case of different contents of nano-SiO2 at the curing age of 1 day, 3 days, and 7 days. In Figure 13, C2S and C3S represent dicalcium silicate and tricalcium silicate, respectively. ...
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... 13 shows the XRD results of the HCGA in the case of different contents of nano-SiO2 at the curing age of 1 day, 3 days, and 7 days. In Figure 13, C2S and C3S represent dicalcium silicate and tricalcium silicate, respectively. As shown in Figure 13, the constituents of the HCGA in the case of different contents of nano-SiO2 are similar in the XRD images. ...
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... Figure 13, C2S and C3S represent dicalcium silicate and tricalcium silicate, respectively. As shown in Figure 13, the constituents of the HCGA in the case of different contents of nano-SiO2 are similar in the XRD images. At the curing age of 1 day, the intensity of the diffraction peak of C3S decreases as the content of nano-SiO2 increases, showing that nanoSiO2 accelerates the consumption of C3S to generate CH crystals and CSH gels, to realize the early strength. ...
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... mass loss curve (TG curve, red) and heat flow curve (DSC curve, black) of the HCGA are shown in Figure 14. In the curves, there are two obvious segments for the weight loss and enthalpy change. ...
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... second thermal decomposition peak and the corresponding weight loss that appeared at 350-600 °C represent the decomposition of CH crystals [39], abbreviated as II-stage. Moreover, the enthalpy change and weight loss in the DSC curves are extracted to further analyze the effects of nano-SiO2 content and curing age, as shown in Figure 15. Figure 14. ...
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... the enthalpy change and weight loss in the DSC curves are extracted to further analyze the effects of nano-SiO2 content and curing age, as shown in Figure 15. Figure 14. DSC-TG curve. ...
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... 1 day, 0% SiO2; (b) 1 day, 1% SiO2; (c) 1 day, 2% SiO2; (d) 1 day, 3% SiO2; (e) 3 days, 0% SiO2; (f) 3 days, 1% SiO2; (g) 3 days, 2% SiO2; (h) 3 days, 3% SiO2; (i) 7 days, 0% SiO2; (j) 7 days, 1% SiO2; (k) 7 days, 2% SiO2; (l) 7 days, 3% SiO2. As shown in Figures 14 and 15, at the curing age of 1 day and 3 days, the weight loss and enthalpy change in the I-stage decrease by 3.34% and 0.97%, on average, for every 1% increase in the content of nano-SiO2, respectively, while, in the II-stage, they accordingly increase by 12.04% and 0.51%. The less free water there is, the more bound water there is, and the more complete the hydration reaction is. ...
Citations
... Crushed specimens were kept in anhydrous ethanol for 7 days to stop the hydration reaction after the flexural and compressive strength tests [42,43]. Then, the specimens were removed from the anhydrous ethanol and dried to a dehydrated state. ...
The use of titanium gypsum instead of gypsum as a raw material for the preparation of gypsum-slag cementitious materials (GSCM) can reduce the cost and improve the utilization of solid waste. However, titanium gypsum contains impurities such as Fe2O3, MgO, and TiO2, which make its effect on the performance of GSCM uncertain. To investigate this issue, GSCM doped with different ratios of Fe2O3, MgO, and TiO2 were prepared in this study, the setting time and the strength of GSCM at 3, 7, and 28 days were tested. The effects of different oxides on the performance of GSCM were also investigated by scanning electron microscopy, energy spectrum analysis, X-ray diffraction analysis, and thermogravimetric analysis. The experimental results showed that Fe2O3, MgO, and TiO2 all had a certain procoagulant effect on GSCM and a slight effect on the strength. Through micro-analysis, it was found that the main hydration products of GSCM were AFt phase and calcium–alumina–silicate–hydrate (C–(A)–S–H) gels. Fe-rich C–(A)–S–H gels were observed with the addition of Fe2O3, and Mg(OH)2 and M–S–H gels were observed with the addition of MgO. The addition of TiO2 did not result in new hydration products from GSCM.
... The rapid development of infrastructure construction creates an ever-increasing demand for river sand, gravel stone, cement and other engineering materials, resulting in the depletion of natural resources and causing serious threats to the eco-system [1][2][3]. To alleviate the environmental burden and realize the sustainable development of society, the utilization of resource-saving and environment-friendly engineering materials is required [4][5][6]. ...
Discharged slag not only occupies a large amount of land for disposal, but also causes serious environmental pollution. The use of alkali-activated slag (AAS) instead of cement as a soil-stabilization agent is beneficial for industrial waste disposal and energy conservation, which complies with the concept of green and low-carbon sustainable development in the construction industry. In this study, the compressive strength, water permeability coefficient, chloride migration coefficient and sulfate resistance of alkali-activated slag-stabilized soil (AASS) were evaluated, and compared with those of cement-stabilized soil (CSS). The hydrated crystalline phases and microscopic pore structures were analyzed by X-ray diffraction, electrochemical impedance spectroscopy (EIS) and mercury intrusion porosimetry (MIP) tests, respectively. The results indicate that, compared with CSS, AASS exhibits a higher compressive strength, lower water permeability, chloride migration coefficient and better resistance to sulfate attack, with the optimum dosage higher than 10 wt.%. The results of the MIP analysis show that the addition of AAS reduces the porosity by 6.47%. The combined use of soil and AAS proves to be a viable and sustainable method of waste utilization and carbon emission reduction in the construction industry, which provides a practical path towards carbon peaking and carbon neutrality.
... Crushed specimens were kept in anhydrous ethanol for 7 d to stop the hydration reaction after the flexural and compressive strength tests [44,45]. Then, the specimens were removed from the anhydrous ethanol and dried to an absolutely dry state. ...
High mud content in the sand has a negative impact on cement mortar but there is little research on Alkali-activated slag (AAS) mortar. In order to explore the impacts of mud content in the sand on the performance of AAS mortar, this paper used sand that contains silt, clay, and a mixture of silt and clay; tested the setting time of AAS with different mud contents of 0%, 2%, 4%, 6%, 8%, and 10%; and measured the unconfined compressive strength and beam flexural strength of 3 d, 7 d, and 28 d AAS mortar specimens. The microstructure of AAS mortar with different kinds of mud was observed by scanning electron microscope (SEM), the elemental composition of the hydration product was tested by energy dispersive spectroscopy (EDS), and the AAS interaction mechanism with different kinds of mud was analyzed. The main conclusions are: the higher the mud content in the sand, the shorter the initial setting time and the longer the final setting time of AAS, mainly because the mud in the sand affects the hydration process; mud content above 4% causes a rapid decrease in the compressive and flexural strengths of AAS mortar, mainly because the mud affects the hydration process and hinders the bonding of the hydration product with the sand. When there is no mud in the sand, the main hydration product of AAS is dense calcium-alumina-silicate-hydrate (C-A-S-H) gel. When the sand contains silt, the hydration product of AAS is loose C-A-S-H gel. When the sand contains clay, the hydration products of AAS contain C-A-S-H gel and a small amount of sodium-aluminum-silicate-hydrate (N-A-S-H), and needle-like crystals. Loose gel and crystals have a negative effect on the AAS mortar strength.
... It is inevitable to affect the performance of the grouting material. As a result, a frequent case is that there is performance fluctuation of the grouting material, although the raw materials, formula, experimental conditions, and operating personnel are all the same, which will bring unknown risk in engineering application (Ren et al., 2021a(Ren et al., , 2021b(Ren et al., , 2022bZhao, 2022;Zhao et al., 2021aZhao et al., , 2021bZhao et al., , 2021c. The performance fluctuation results from the uncertainty mentioned above during material design (Ren et al., 2020). ...
... The average values of test results are listed in Table 7. Six samples are successfully experimented for each condition, and all the data are used for the uncertainty analysis. It should be explained that the analysis process of formula determination is complex in the orthogonal experimental method, which can be found in our previous study (Ren et al., 2021a(Ren et al., , 2021b and not described in this paper. The formula determined by the orthogonal experimental method is listed in Table 8. ...
... In other words, performance fluctuation will tend to appear in the formula containing the design factor with a low frequency. For instance, water-cement ratio and accelerating agent content are the critical factors for the early strength of the cement grouting material (Ren et al., 2021a(Ren et al., , 2021b. Compared with the O-1 and O-2 (see Table 9), the frequencies when the accelerating agent content and water-cement ratio are equal to 2.5% and 0.56 for the O-2 are higher than the frequencies when the accelerating agent content and water-cement ratio are equal to 2.0% and 0.53 for the O-1, respectively. ...
In pavement engineering, cement grouting material is widely used to pour into large void asphalt concrete to prepare semi-flexible composite mixtures. It plays an essential role in the performance of the semi-flexible composite mixture. To meet specific engineering requirements, various additives are mixed into the grouting material to improve the physical and mechanical properties. As a result, the uncertainty of the grouting material is also more significant as the complexity of material composition increases during the material design. It will bring some unknown risks for the engineering application. Hence, it is necessary to quantize the uncertainty during the material design of the grouting material and evaluate the reliability of the material formula. In this study, a novel framework of material design was developed by combing the Multioutput support vector machine (MSVM), Bayesian inference, and laboratory experiments. The MSVM was used to approximate and characterize the complex and nonlinear relationship between the grouting material formula and its properties based on laboratory experiments. The Bayesian inference was adopted to deal with the uncertainty of material design using the Markov Chain Monte Carlo. An optimized formula of the cement grouting material is obtained based on the developed framework. Experimental results show that the optimized formula improves engineering properties and performance stability, especially early strength. The developed framework provides a helpful, valuable, and promising tool for evaluating the reliability of the material design of the grouting material considering the uncertainty.
... The bonding characteristics of microparticles, the structural characteristics of polymerization products, and the effects of different raw materials on the microstructure were observed under 3000 times magnification. The early compressive strength of specimen L-1 (1 d and 3 d) was clearly insufficient, and the early strength developed slowly, severely affecting the early reinforcement effect of PC grouting materials [28]. Although the compressive strength further increased to 24.3 MPa when curing lasted for 28 d, this still could not compensate for the poor early reinforcement effect of PC grouting materials. ...
In deep coal mining, grouting reinforcement and water blockage are the most effective means for reinforcing the rock mass of extremely broken coal. However, traditional cement grouting materials are not suitable for use in complex strata because of their insufficient early mechanical strength and slow setting time. This study innovatively proposes using alkali-activated grouting material to compensate for the shortcomings of traditional grouting materials and strengthen the reinforcement of extremely unstable broken coal and rock mass. The alkali-activated grouting material was prepared using slag as raw material combined with sodium hydroxide and liquid sodium silicate activation. The compressive strength of specimens cured for 1 d, 3 d, and 28 d was regularly measured and the condensation behavior was analyzed. Using X-ray diffraction and scanning electron microscopy, formation behavior of mineral crystals and microstructure characteristics were further analyzed. The results showed that alkali-activated slag grouting material features prompt and high strength and offers the advantages of rapid setting and adjustable setting time. With an increase in sodium hydroxide content, the compressive strength first increased (maximum increase was 21.1%) and then decreased, while the setting time continued to shorten. With an increase in liquid sodium silicate level, the compressive strength increased significantly (and remained unchanged, maximum increase was 35.9%), while the setting time decreased significantly (and remained unchanged). X-ray diffraction analysis identified the formation of aluminosilicate minerals as the main reason for the excellent mechanical properties and accelerated coagulation rate.
... The grouting is one of the most efficient and common methods for the rapid repairment and reinforcement of the civil engineering structures [2]. High-fluidization and early strength cement mortar (HECM) is one type of grouting material, which has been widely used in repairment and reinforcement engineering [3]. ...
... Their macro morphology is shown in Figure 1. Their properties can be found in our previous study [3]. The technological parameters of the HECM are listed in Table 1, which are measured via laboratory experiments. ...
High-fluidization and early strength cement mortar (HECM) has been widely adopted in various fields of civil engineering. Due to the complexity of the engineering environment, sulfate corrosion cannot be ignored for the HECM. Although the effect of sulfate on the properties of the cement-based materials has been addressed, the degradation mechanisms of the HECM in the case of sulfate corrosion are not clear because of the distinct characteristics of the HECM (e.g., early strength and high fluidization) compared with conventional cement-based materials. Hence, considering the more complex corrosion process of magnesium sulfate, the early flexural and compressive strength of the HECM in the case of different magnesium sulfate concentrations and testing ages are investigated in this study. Moreover, the effects of magnesium sulfate concentrations and corrosion times on the microstructure and hydration products of the HECM are analyzed via a Scanning Electron Microscope (SEM) test, an X-ray diffraction (XRD) test, and a Differential Scanning Calorimeter (DSC) test. Finally, the influence mechanisms of the magnesium sulfate on the early strength formation of the HECM are analyzed to reveal the degradation mechanisms of the HECM.
... According to our studies [27], the formula of the CRTS can be determined as follows: water-cement ratio = 0.56, WA = 1.2%, AA = 2.5%, EA = 5%, and toner = 4%. ...
The reinforced concrete invariably involves some diseases (e.g., crack, void, etc.) due to the complex service conditions. These diseases are usually repaired to extend the service life of reinforced concrete by using cement grouting materials. In order to meet a certain color need of reinforced concrete, toner is mixed into the cement grouting materials. However, the toner has a negative effect on the early strength of cement grouting materials. Unfortunately, the mechanism of the negative effects of toner is still unclear, and no effective and targeted measures have been put forward. Hence, the main work of this paper reveals the mechanisms of the toner and nano-SiO2 (N-S) in the hydration process and the strength generation of the cement grouting materials in the case of different curing ages and nano-SiO2 contents via the scanning electron microscopy test (SEM), X-ray diffraction test (XRD), differential scanning calorimetry test (DSC), and Fourier transform infrared spectroscopy test (FTRI). Results show that: (a) the toner hinders the generation of AFt and CH crystals (especially for 1-day and 3-day), which delays the hydration process and weakens the early performance of cement grouting materials; (b) the N-S promotes the hydration process and the formation of C-S-H gels, so as to effectively increasing the early strength and reducing (but not eliminate) the adverse effect of toner on cement grouting materials; (c) With the increase of every 1% N-S, the flexural strength of 1-day, 3-day, and 7-day average increased by 11.3%, 2.9%, and 0.9%, respectively, and the compressive strength of 1-day, 3-day, and 7-day average increased by 0.8%, 0.3%, and 0.1%.
... As previously mentioned, the semi-flexible composite mixture is composed of the large void asphalt concrete and the cement grouting material [32,33], as illustrated in Fig. 1. The pavement performance of the semi-flexible composite mixture is listed in Table 2 ...
Semi-flexible composite mixture as a new type of pavement materials has been widely adopted in pavement engineering, owing to the advantages in improved rutting resistance, water stability, and mechanical property. However, only one type of fatigue equation using exponential framework based on the stress (or strain) is employed to predict the fatigue life of the semi-flexible composite mixture in existing studies. Considering the importance of the fatigue equation during pavement design, it is necessary to seek an alternative approach to enrich the fatigue prediction equation of semi-flexible composite mixture. Hence, fatigue characteristics of the semi-flexible composite mixture are analyzed in the case of different stress levels and curing times in this study. The damage evolution during the fatigue tests is investigated based on the permanent deformation ratio. Finally, a new framework of fatigue equation via damage stationary value (DSV) is established to predict the fatigue life of the semi-flexible composite mixture. The proposed fatigue equation provides a better prediction effect.
... It should be explained that the analysis process of composition determination is complex in the orthogonal experimental method, which can be found in our previous study [55] and not described in this paper. The detailed material composition of the cement grouting material based on the orthogonal experimental method is listed in Section 3.3 (Table 8) to compare to the composition determined by the developed framework. ...
... The expansion agent has a significant influence on the shrinkage rate. The above influences of the components are similar to the results analyzed through the orthogonal method in our previous study [55]. By contrast, the main influence factor for one property is more obvious and lucid in the AdaBoost-based surrogate method. ...
... Technical characteristics of expansion agent. Test result based on the test scheme[55]. Four types of raw materials including, Shanlv P. O. ...
Cement grouting materials have been widely used in maintenance and reinforcement engineering. Various design methods have been developed to determine the optimal compositions of the cement grouting material. However, it is a challenging task to determine the compositions of the materials due to the complexity of cement grouting. In this study, a novel intelligent optimal method by combing the simplicial homology global optimization method (SHGO), Adaptive Boosting algorithm (AdaBoost), and laboratory experiments were developed to determine the optimal composition of the cement grouting material. The AdaBoost presented the complex interrelations of different material compositions and their properties. The SHGO was adopted to search for a reasonable and optimal composition to improve the performance. Compared to the compositions determined by the traditional method, the optimal composition determined by the developed method provides improved strength, especially for the early strength. The flexural/compressive strengths of the grouting material determined by the proposed method are 3.90/12.12 MPa, 9.71/28.86 MPa, 12.11/38.12 MPa at the curing age of 1-day, 3-day, and 7-day, respectively, which are 1.27/1.12 times, 1.17/1.09 times, and 1.11/1.08 times higher than the grouting material determined the traditional method. The developed intelligent optimal framework provides a helpful, valuable, and promising tool for determining the optimal composition of cement-based materials.
