Cement-based Grouting Materials Research Articles

Experimental and numerical studies of the effects of micro/nano carbon fibers in the dynamic behavior of cement-based grouting materials for reinforcement of sand layers

Geological hazards of sand layers pose a serious threat to engineering safety. Grouting reinforcement technology is widely used in such conditions due to its convenience, economy, and effectiveness. To explore the reinforcement effect of carbon fiber (CF) modified cement-based grouting materials on sand layers, grouting solidified bodies (GSB) with CF contents of 0.0%, 0.5%, 1.0%, and 1.5% are selected for Split Hopkinson Pressure Bar (SHPB) impact tests, scanning electron microscope (SEM) scanning, and numerical simulation experiments. The mechanical properties of specimens under dynamic impact conditions and the reinforcement mechanism of CF are studied. Results show that GSB is a strain-rate-dependent material. With the increase of impact rate, peak stress, incident energy, transmitted energy, and dissipated energy of specimens gradually increase, while the integrity of specimens decreases. The CF content remarkably affects the mechanical properties of specimens. When the impact rate is constant, with the increase of CF content, the peak stress and transmitted energy of specimens show a decreasing–increasing– decreasing trend, and the performance of CF-1.0% specimens is optimal. The cement matrix is the main energy storage and release medium, accounting for 97.66% of the energy. When damaged, the cement matrix is mainly fractured. At the microcrack tip, CF influences the direction of crack propagation, reducing the radius of crack propagation, and the main failure mode of CF is debonding. CF can substantially improve the mechanical properties of specimens and reduce the number of cracks. Compared with CF-0.0%-cementitious material (CM) specimens, the peak stress of CF-1.0%-CM specimens is increased by 19.98%. The magnitude of CF force is related to the angle between crack and CF. As the angle increases from 0° to 90°, the CF force gradually increases, reaching the maximum at 90°, with an increase of 133.82%. At this angle, the anti-cracking effect of CF is most substantial. The research results can provide technical support for sand layer grouting reinforcement technology.

Research on the crack resistance of semi-flexible pavement mixture based on meso-heterogeneous model

Semi-Flexible Pavement (SFP) material, prepared by pouring cement-based grouting material into the voids of a porous asphalt mixture, has good load bearing capacity and excellent resistance to rutting. It is gaining increased applications in areas where permanent deformation of asphalt mixtures is a concern. When applied as the pavement surface course, the major distress observed in SFP is cracking. Currently, there is a lack of comprehensive understanding of the cracking mechanism of SFP. To improve such understanding, this study investigated the effects of fracture parameters of asphalt mortar and asphalt-aggregate interface on the crack resistance of SFP materials through laboratory experiments and numerical simulation using the finite element method. Firstly, a three-point bending test was performed on a beam SFP specimen. A multi-scale mesoscopic heterogeneity model was then established based on the mesoscopic structure of the specimen and calibrated and validated using the load-displacement curves and the cracking process features. With the validated model, the effects of different fracture parameters on the beam cracking process were investigated. It was found that the load-bearing capacity of SFP increased with the increase of the tensile strength of asphalt mortar and asphalt-aggregate interface in a certain range, while the crack propagation rate after crack initiation also increased. An increase in the fracture energy of asphalt mortar and asphalt-aggregate interface delayed the crack propagation rate, but with an attenuative effect with the increase of fracture energy. Based on the actual test conditions, the desirable range of key cracking parameters of SFP materials were recommended.

Study on early hydration and mechanical properties of ferrite-rich calcium sulfoaluminate cement-based grouting materials

Grouting materials play a very important role in the performance of anchor structures. In this study, a new grouting material (FCSA-1) consisting of ferrite-rich calcium sulfoaluminate cement (FCSA) clinker, ordinary Portland cement (OPC), limestone, and anhydrite was prepared. The objective of this study is to examine how the hydration process of the novel grouting material affects its physical and mechanical properties through laboratory tests. This investigation will particularly focus on parameters such as setting time, fluidity, hydration product formation, microstructure, expansion rate, and strength development within a 28-day timeframe. Additionally, 2D numerical simulations of pull-out tests and field pull-out tests were conducted to validate the anchorage performance of FCSA-1. The laboratory tests results showed that the initial setting time was 25 min and final setting time was 40 min. Additionally, the fluidity of the new grouting material measured at 282 mm. The free expansion rate exhibited a non-linear growth trend, with an average growth rate of 4.51‰/d within 14 days. The expansion was attributed to the increased presence of the expansive product ettringite during the early stages, while the expansion was mainly due to the volume growth of ettringite during the later stages. The uniaxial compressive strength reached 40.35 MPa within 1 day and increased to 61.75 MPa within 7 days, remaining stable thereafter. The primary hydration products of the FCSA-1 identified in the quaternary blend were ettringite and hydroxide aluminum (AH3), with a stable phase content after 1 day of curing, indicating rapid hydration reaction. Due to the rapid increase in hydration products and crystal volume growth, the pore structure of the FCSA-1 became more compact. In addition, numerical simulation results showed that using FCSA-1 as a grouting material improved the anchorage performance of the structure compared to OPC. This indicated that the early high-strength properties of the grouting material improve its anchorage performance significantly. Field pull-out tests showed that the combination of resin and FCSA-1 grouting material increased pull-out force by 34.21% compared with that of using resin alone. According to the results, the novel grouting material exhibits early high-strength and slight expansion performance during the early stages of hydration, making it a suitable grouting material for engineering applications.

Feasibility study on superabsorbent polymer (SAP) as internal curing agent for cement-based grouting material

The closed working condition of grouting materials leads to insufficient curing water supply during their strength development. In this work, the superabsorbent polymer (SAP) was used as the internal curing agent for grouting material. The effects of SAP content on the rheological and mechanical properties of grouting material were studied under various water-cement ratios (w/c) and curing environments. The time-dependent variation of fresh slurry's viscosity was measured by Brinell viscometer. The pore structure and micromorphology characteristics were analyzed by Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscope (SEM). The results indicate that the addition of SAP increases the viscosity of fresh slurry and decreases its fluidity, thereby improving the slurry's internal uniformity at a higher w/c. And in its actual working condition, grouting material's strength can be boosted with less than 0.3% SAP dosage. Although SAP will introduce some irregular mesoscopic pores (0.2 − 0.3 mm), the MIP data analysis proves SAP refines the microscopic pore structure of grouting materials. SEM data analysis proves SAP optimizes the microstructure of grouting material, which cured in dry environment. In general, SAP improves the internal uniformity of grouting material by absorbing excess mixing water and gradually releasing it to promote cement hydration, which improves the strength of grouting material. Hence, SAP is a practicable internal curing agent for grouting material and 0.2% is the recommended dosage.

Macrokinetics of the deterioration of cement-based grouting material for predicting its service life under acid rain attack

Cement-based grouting material is widely used to reinforce the unsafe rock and control seepage of rock-carved relics although it is considered inappropriate in protection of ancient sites. As this approach is irreversible, a longer service life is desirable for the grouting material and methods to predict the service life are needed. Here we propose a universal formula based on the dissolved amount of calcium ion to predict the deterioration rate of cement-based grout caused by acid deposition in the laboratory. The experimental results showed that the dissolved amount of calcium ion had a linear relationship with lnT and the pH value, with better accuracy when the pH value was greater than 3.0. This work maybe could provide a facile and quantitative method to help us predict the service life of cement-based grouting material under acid rain attack outdoors.

Study on properties of Portland cement-sulfoaluminate cement-based grouting materials modified by in-situ polymerization of calcium acrylate

To enchance the toughness of ordinary Portland cement-sulfoaluminate cement-based grouting material and minimize the secondary damage of road structure caused by stone body destruction under vehicle load. In this paper, the development laws of setting time, fluidity, and mechanical strength of grouting material, and the characteristics of stone damage under the action of calcium acrylate are systematically analyzed. The mechanism by which in-situ polymerization of improves the toughness improvement of ordinary Portland cement-sulfoaluminate cement-based grouting material is then revealed. In-situ polymerization of calcium acrylate delays the setting time, and an appropriate calcium acrylate content improves the flowability. The addition of calcium acrylate largely enhances the mechanical strength of the stone body, improving the 1-day compressive strength and flexural strength by 279.18% and 301.64%, respectively. Calcium acrylate also increases the flexural compression ratio of the stone body. The highest flexural compression ratio at 28d is 0.5592. The microscopic analysis reveals that calcium acrylate promotes hydration, and forms stable calcium polyacrylate in the stone body, which connects the hydration products into a more densely cement-calcium polyacrylate composite structure. Consequently, the toughness of the stone body improves. By analyzing the stress–strain curve, the stone body still exhibits a capacity to resist damage after the peak stress under the action of calcium acrylate. Finally, a damage constitutive equation of the stone body with different damage factors is established, which has excellent agreement with the test curve and can predict the mechanical properties of cement-based grouting material modified by in-situ polymerization of calcium acrylate. The findings provide a theoretical framework for designing the strength of grouting materials and evaluating road stability.

Investigation on hydration behavior and microscopic pore structure of early-age cement-based grouting material

The present paper reports an experimental investigation into the hydration behavior and microscopic pore structure evolution of early-age cement-based grouting material (CGM) with the same compressive strength as concrete (C60) at various ages (18 h, 1 d, 3 d, 7 d, and 28 d). The hydration process, hydration products, microstructure, and pore structure changes of early-age CGM were analyzed using isothermal calorimetry, thermogravimetry (TG), X-ray diffraction (XRD), backscattered electron imaging (BSEI), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results show that the hydration process of early-age CGM can be classified into five stages: pre-induction, induction, acceleration, deceleration, and stabilization. Compared to C60, early-age CGM displays a higher initial heat flow but lower subsequent heat flow, with a cumulative heat release (72 h) only 38 % of that of C60, effectively avoiding temperature shrinkage and ettringite decomposition. During the hydration process, CGM continuously generates portlandite along with substantial quantities of ettringite and calcite. The addition of calcium sulphoaluminate expansive admixture (CSA) is advantageous in facilitating CGM's hydration process, effectively promoting the formation of ettringite and C–S–H gel, thus leading to an enhancement in the microstructure of CGM. At 28 d, the microstructure of CGM displays a relatively compact morphology. The porosity of CGM at 28 d was 13.74 %, with a higher proportion of harmless and less-harmful pores. These research findings contribute to a better understanding of the hydration process and microscopic pore structure evolution of early-age CGM, providing a reliable theoretical basis for the rational application of CGM in engineering and guidance for the improvement and optimization of CGM.

Enhancing cementitious grouting performance through carbon nanotube-coated fly ash incorporation

Cementitious composites reinforced with carbon nanotubes (CNTs) offer notable benefits compared to conventional cement-based materials in terms of durability and strength. Despite these advantages, the widespread implementation of CNTs in cement-based grouting engineering has not been carried out due to the limitations of dispersion issues. In order to facilitate the progression of carbon nanotubes (CNTs) from laboratory experiments to engineering applications, we proposed a method of using amino-functionalised functional groups to coat CNTs on the fly ash (FA) particles’ surfaces to assist the dispersion and prepare cost-effective, low-carbon emission, energy consumption-saving and high-performance cementitious slurry. The experimental results exhibit that compared with plain cement-based grouting materials, incorporating 0.023 wt% CNTs and 14.3 wt% FA can reinforce the compressive and tensile strength by 14.2–25.8% and improve the workability by about 21.0%. The application of coated CNTs induces nucleation and pore-infilling effects within the interfacial transition zone (ITZ) of the cementitious composites. This action leads to a reduction in ITZ width and a decrease in crack occurrence within the ITZ. Consequently, these effects contribute to an augmentation in the consolidation strength of the slurry. Acoustic emission and fracture surface fractal analysis further reveal that incorporating CNTs enhances the resist-loading ability of the cement matrix by increasing its energy absorption capability. The innovative coating method reported in this work is expected to facilitate the future application of CNTs in practical grouting engineering.

Comparative study of the effects of magnesium aluminum silicate and bentonite clay on the properties of magnesium phosphate cement-based grouting material

In this paper, mineral admixtures of magnesium aluminum silicate (MAS) and bentonite clay (BC) were added to magnesium phosphate cement-based grouting material (MPCG) to improve its poor water resistance and large shrinkage deformation of the matrix, and the effects of MAS and BC on the properties of fresh slurry, compressive strength, volume stability and microstructure of MPCG were comparatively studied. The research results showed that MAS and BC reduced the shrinkage deformation of MPCG, increased MPCG’s density, and decreased porosity. After curing for 28 d, the compressive strength and water resistance of MPCG were improved by adding 2.0 wt% of MAS or BC, and the compressive strength and softening coefficient were 13.9 ± 0.4 MPa and 0.87 (MAS), 12.2 ± 0.7 MPa and 0.84 (BC), respectively, which were all higher than the control group. The hydration heat and phase composition showed that the addition of MAS or BC reduced the cumulative heat of MPCG, but no new crystal phase was formed. The addition of MAS increased the formation of K-struvite (MgKPO4·6H2O), while BC reduced the formation of K-struvite. Therefore, MAS and BC could be used as admixtures of MPCG to improve its workability.

Performance of a New Grouting Material under the Coupling Effects of Freeze-Thaw and Sulfate Erosion.

In order to study the performance of a new cement-based grouting material under the coupling of freeze-thaw cycle and sulfate erosion, tests related to the performance of the new grouting material were designed and carried out to analyze the damage mechanism of the material under the coupling of freezing and thawing and Na2SO4 solution by testing the mass change, relative dynamic elastic modulus, compressive strength loss and mineralogical and microstructural properties of the new grouting material. The test results show that with the increase in the number of freeze-thaw cycles, the mass loss and compressive strength loss of the specimens in 15% Na2SO4 solution gradually increased, and the relative dynamic elastic modulus showed a decreasing trend. When the freeze-thaw cycle number was 30, the mass loss rate, compressive strength loss rate and relative dynamic elastic modulus of the specimens in Na2SO4 solution were 4.17%, 24.59% and 84.3%, respectively, which showed better erosion and frost durability. Mineralogical and microstructural analysis showed that SO42- in solution led to the decomposition of the C-S-H gel and the formation of CaSO4•2H2O inside the specimen, and the internal deterioration was exacerbated by the widening of the crack width being aggravated, suggesting that the rate of material deterioration under the coupling of the two factors increased.

Experimental Investigation on the Mix Proportion of Fiber-Reinforced Ultrahigh-Strength Grouting Material

Concrete tends to develop cracks once damaged, and wide cracks specifically would affect the whole structure negatively. When used for repairing wide cracks, traditional cement-based grouting materials could no longer meet the demand for tensile strength. The paper aims to develop a high-performance grouting material for crack repair and further investigate its fluidity, and compressive strength, flexural strength, and splitting tensile strength after hardening. Based on the design of ultrahigh-performance concrete (UHPC), this grouting material consists of cement, sand, water, superplasticizer, expansion agent, silica fume, fly ash, and flat copper-plated steel fiber. The initial fluidity and 30-min fluidity of the grouting material decreased with the addition of fly ash, silica fume, and flat copper-plated steel fiber, among which the silica fume had the greatest influence on the fluidity, followed by fly ash and steel fiber. The optimal content of flat copper-plated steel fiber, fly ash, and silica fume was 2%, 10%, and 15%, respectively. Furthermore, the prediction model of compressive strength of grouting material was established. It indicated that cement grade, water-cement ratio, curing age, silica fume, fly ash, and flat copper-plated steel fiber and can be used for the mix proportion design of grouting materials.

Study of the Tensile and Bonding Properties between Cement-Based Grout Materials and High-Strength Bolts

This study investigated the tensile and bonding properties between cement-based grouting materials (CBGM) and high-strength bolts. The associated failure mechanism, load-slip curve, ultimate pull-out load and bond stress were also studied. The effects of anchorage length and square steel tube restraint on the bonding properties were explored on the basis of 24 specimens used in central pull-out testing, and a bond stress–slip constitutive relationship model between high-strength bolts and CBGM was proposed. The results indicate that with the increase in the anchorage length of high-strength bolts, the failure modes of specimens can be divided into three types: the fracture failure of high-strength bolt that occurred when the anchorage lengths ranged from 18 d to 31 d, the specimens that experienced splitting failure with the constraint of square steel tube when the anchorage length was less than 15 d and the high-strength bolt that experienced pull-out failure without the constraint of square steel tubes. When the high-strength bolt experiences tensile failure, the ultimate pull-out load remains constant and the bond stress decreases as the anchorage length of high-strength bolts increases. Due to the lateral constrained effect of the square steel tube, the CBGM embodies a three-dimensional stress state, which can delay the generation and development of internal cracks and enhance the bond strength. A calculation formula was proposed to determine the bond strength between high-strength bolt and CBGM, and a constitutive model of the bond stress–slip constitutive relationship was modeled.

Influence of the composite interface on the mechanical properties of semi-flexible pavement materials

Semi-flexible pavement (SFP) materials, composed of porous asphalt mixture (PAM) and cement-based grouting material, are multiphase composites commonly used in roadway construction. However, damage frequently occurs at the composite interface of two-phase materials, and most SFP research has focused on the design of grouting material, with insufficient attention given to the composite interface. This paper aims to investigate the effect of bonding properties between organic PAM and inorganic grout on the mechanical properties of SFP. To investigate the different bonding properties of the SFP asphalt-grout interface, a simple method was employed, in which PAM specimens were immersed in a silane coupling agent solution to form a layer of coupling agent on the PAM surface. A series of SFP specimens were created using PAM with a porosity of 28–30%, and different strength grouting materials (40 MPa, 60 MPa, 70 MPa), and three laboratory tests were conducted to evaluate their mechanical properties. The results demonstrated that the interfacial bonding strength between asphalt and grouting material significantly influences the low-temperature splitting tensile strength, uniaxial penetration strength and uniaxial compression strength of SFP. Compared to specimens formed from high-strength grouting materials, SFP specimens immersed in a silane coupling agent solution exhibited superior low-temperature splitting tensile strength (2.06 MPa > 1.97 MPa, 2.63 MPa > 2.34 MPa) and shear strength (7.28 MPa > 6.46 MPa, 7.97 MPa > 7.26 MPa). As a result, this study highlights the importance of considering the bonding properties of the asphalt-grout interface in the design and preparation of SFP. The results of this study can be useful for enhancing the performance and durability of SFP materials in a more economically efficient way.

Preparation of a carbon-based nanomaterial and its influence on construction engineering

Carbon nanotube cement-based grouting materials currently mostly stay in the pure slurry research stage, and there is little research in the field of rock crack reinforcement combined with the engineering application background. Therefore, on the basis of existing research, it is important to expand the dispersion of carbon nanotubes in cement paste, and to carry out research on the reinforcement of fractured rocks in combination with the engineering background. This paper combines the actual needs of construction engineering to prepare carbon-based nanomaterials, and analyzes its impact on construction engineering in combination with experiments. Moreover, this paper analyzes the influence of carbon nanotubes on the macro-mechanical properties of cement-based materials, and studies the influence of modified carbon nanotubes on the macro-mechanical properties of cement-based materials. In addition, this paper explores the micromechanical properties of carbon nanotube cement materials at the nanometer scale. The research results verify the effectiveness of carbon-based nanomaterials.

Preparation and Performance Improvement Mechanism Investigation of High-Performance Cementitious Grout Material for Semi-Flexible Pavement.

Semi-flexible pavement material (SFPM) combines the advantages and avoids the disadvantages of asphalt concrete flexible pavement and cement concrete rigid pavement. However, due to the problem of interfacial strength of composite materials, SFPM is prone to cracking diseases, which limits the further application of SFPM. Hence, it is necessary to optimize the composition design of SFPM and improve its road performance. In this study, the effects of cationic emulsified asphalt, silane coupling agent and styrene-butadiene latex on the improvement of SFPM performance were compared and analyzed. The influence of modifier dosage and preparation parameters on the road performance of SFPM was investigated by an orthogonal experimental design combined with principal component analysis (PCA). The best modifier and the corresponding preparation process were selected. On this basis, the mechanism of SFPM road performance improvement was further analyzed by scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) spectral analysis. The results show that adding modifiers can significantly enhance the road performance of SFPM. Compared to silane coupling agents and styrene-butadiene latex, cationic emulsified asphalt changes the internal structure of cement-based grouting material and increases the interfacial modulus of SFPM by 242%, allowing cationic emulsified asphalt-SFPM (C-SFPM) to exhibit better road performance. According to the results of the principal component analysis, C-SFPM has the best overall performance compared to other SFPMs. Therefore, cationic emulsified asphalt is the most effective modifier for SFPM. The optimal amount of cationic emulsified asphalt is 5%, and the best preparation process involves vibration at a frequency of 60 Hz for 10 min and 28 days of maintenance. The study provides a method and basis for improving the road performance of SFPM and a reference for designing the material composition of SFPM mixes.

Experimental study on the mix proportion of self-heating grouting materials in alpine regions

The frost heave disease of cement-based grouting materials occurred in the pre-stressed pipeline in alpine regions. This paper proposes a self-heating grouting material and verifies its feasibility by a series of mechanical properties and working properties experiments. Firstly, the water-cement ratio and the dosage of admixture are determined by an orthogonal test at room temperature at 5 °C, and relevant experiments determine the dosage of silica fume to improve its fluidity. Secondly, experiments carried out at −5 °C are used to analyze the influence of calcium oxide and nano-silica on the temperature of the grouting material system. Thirdly, through adiabatic temperature rise test, the exothermic contribution of calcium oxide and nano-silica heating materials in cement-based grouting material is tested, respectively, and the working performance and mechanical properties of grouting material are tested under different negative curing temperatures. Finally, the feasibility of the self-heating grouting material proposed is verified by the confirmatory test of wrapped concrete. The test results show that the self-heating grouting material under the hostile temperature can be stabilized above five degrees, and its expansion stress does not exceed the specification requirements, which can meet the construction requirements in the hostile temperature environment in the Qinghai Tibet Plateau and other Alpine regions.

Reinforcing effects of carbon nanotubes on cement-based grouting materials under dynamic impact loading

Carbon nanotubes (CNTs) are reasonable materials to modify the property of cement-based grouting materials to improve their strength and durability, optimize their pore structure, and reduce their carbon emissions. However, dynamic impact loading frequently occurs in underground engineering, while there is very limited research concerning the reinforcing effects of CNTs on cement-based materials under dynamic impact loading. Hence, in this work, we applied the split Hopkinson pressure bar to investigate the dynamic mechanical behaviors of CNTs cement-based grouting materials. The results exhibited that CNTs cement-based grouting materials presented superior impact resistance, with a maximum peak stress of 59.33 MPa. Compared with plain cement grouting materials, mixing CNTs and fly ash into cementitious composites could reinforce the dynamic compressive properties by 10.25%–31.86%. The impact resistance of CNTs cement-based grouting materials was more significant under high dynamic loading, enhancing the dynamic properties by up to 31.86%, which indicates that CNTs reinforcement is more efficient in impacting engineering. The strain nephogram and fractal dimension further suggested that the excellent capacity of the CNTs in cement-based grouting materials could be achieved after ultrasonic treatment. A mathematical physical model was then established for CNTs reinforcing cement-based materials, revealing the whole process of CNTs extraction from the cement-based and giving a factor that can measure reinforcement performance. The findings of this study not only promote that the CNTs cement-based grouting materials can enhance the dynamic loading properties and reduce cement usage, but also provide a theoretical basis for the subsequent research on the mechanism of the microscopic reinforcement of CNTs.

Experimental analysis of Nano-SiO2 modified waterborne epoxy resin on the properties and microstructure of cement-based grouting materials

Experimental analysis of Nano-SiO2 modified waterborne epoxy resin on the properties and microstructure of cement-based grouting materials

Tensile properties of sulfoaluminate cement-based grouting materials toughened by in-situ polymerization of acrylamide

Polymer-modified cementitious materials with high compression and tensile resistance are considered the most promising materials for fracture grouting in underground projects. In this paper, polyacrylamide was prepared by in-situ polymerization of acrylamide, and its toughening effect on sulfoaluminate cement-based grouting material (SCGM) was investigated. The results show that the toughness index of the acrylamide modified SCGM (PAM-SCGM) was 57.55 times higher than that of the plain one. The PAM-SCGM three-stage failure model and the PAM-AFt-CS dual network structure model were proposed and validated by SEM. A model of PAM inhibition of hydration was proposed and validated using heat of hydration, FT-IR and XRD. BET was used to reveal the evolution of the pore structure and validated the tensile model. An empirical formulation of a three-stage mechanical model was proposed and regressed to validate it. The four models and an empirical formulation showed the great potential for engineering applications.

Effect of Synthetic Ettringite on the Hydration of Sulfoaluminate Cement-Based Grouting Materials

Ultrafine ettringite (UE) can accelerate the hydration of sulfoaluminate cement-based grouting materials (SCGMs). However, the mechanism of UE on the hydration of SCGM is not clear. Many researchers believe that ultrafine materials can serve as crystal nuclei for hydration products. How to prove that UE can supply crystal nuclei for hydrated products remains an open question. It is still unclear for which SCGM hydration products UE can supply a crystal nuclei. In this article, UE was synthesized in different solvent compositions by a separate nucleation and growth step method. Synthetic UE was enclosed in a dialysis bag with a molecular weight cutoff of 7 kDa, which allowed the diffusion of water and ions, and the mechanism of UE’s effect on the hydration of SCGM was investigated. The results indicated that with the increase of the amount of ethanol in the water–alcohol mixed solvent, the particle size of the prepared UE gradually became smaller. UE only provided a nucleation site for ettringite, which was one of hydration products, and thus promoted a cement hydration reaction. The smaller the size of the UE, the higher the cement hydration rate and the greater the amount of hydration products produced.