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Article

Performance and Microstructural Characteristics of Cement-Based Grouting Materials Modified with Fly Ash and Corrosion-Control Admixtures

by
Rui Xu
1,2,
Jingjia Xue
1,
Tianlei Wang
1,2,
Ben Peng
3,
Wen Lv
3,
Yuedong Wu
3,* and
Lei Zhang
1,2,*
1
School of Materials Science and Engineering, Tianjin Chengjian University, Tianjin 300384, China
2
Tianjin Key Laboratory of Building Green Functional Materials, Tianjin Chengjian University, Tianjin 300384, China
3
State Key Laboratory of Iron and Steel Industry Environmental Protection, Central Research Institute of Building and Construction Co., Ltd., Beijing 102629, China
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2026, 16(17), 8532; https://doi.org/10.3390/app16178532
Submission received: 6 August 2026 / Revised: 20 August 2026 / Accepted: 23 August 2026 / Published: 27 August 2026
(This article belongs to the Section Materials Science and Engineering)
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Versions Notes

Abstract

Grouting materials used in water-rich and chloride-exposed environments require adequate workability, mechanical performance, and durability. To optimize the formulation, a series of orthogonal tests was conducted to assess how fly ash (10–30%), rust inhibitor (1–3%), and anti-corrosion agent (2–6%) affect the fresh and hardened properties of cement grouts at a constant water-to-binder ratio of 0.5. Setting behaviour, mechanical properties, chloride ion penetration resistance, pore structure, and hydration products were investigated. Fly ash and the anti-corrosion admixture prolonged the setting time. The highest 28-day compressive and flexural strengths were obtained at 20% fly ash. At 30%, the dilution effect outweighed the later-age pozzolanic contribution and slowed strength development. Within the investigated range, 6% anti-corrosion admixture provided the greatest improvement in strength and chloride ion penetration resistance, whereas the rust inhibitor had a smaller effect on the charge passed. Mixtures containing 20% fly ash and 4–6% anti-corrosion admixture exhibited lower porosity and a refined pore-size distribution. By contrast, 30% fly ash resulted in a less favourable pore structure. SEM and XRD results indicated a denser matrix at 28 days, consistent with continued cement hydration and the later-age pozzolanic reaction of fly ash. Previous studies have mainly focused on individual mineral or chemical admixtures, whereas the combined effects of fly ash, rust inhibitors, and anti-corrosion admixtures under fixed workability conditions remain insufficiently understood. This study reveals their distinct and complementary roles, providing a basis for the multi-objective optimisation of grouting materials in chloride-rich and water-saturated environments. Overall, 20% fly ash, 4–6% anti-corrosion admixture, and 1–2% rust inhibitor provided the best performance balance under the investigated conditions.

1. Introduction

Grouting technology is widely used in underground engineering, tunnel construction, geotechnical reinforcement, mine rehabilitation, and the repair of existing structures. By filling voids and fissures, grouting improves ground integrity, increases structural load-bearing capacity, and enhances impermeability [1]. Grouting materials are the core component of grouting reinforcement and waterproofing systems. Their setting and hardening behavior, strength development, and long-term durability directly influence the effectiveness of structural reinforcement and operational safety. Under complex service conditions, including water-saturated soft ground and chloride-bearing environments, conventional cement grouts may not simultaneously meet the requirements for injectability, early-stage performance, volume stability, and long-term durability. Grouting materials must provide controllable setting times, low bleeding rates, and volume stability. After hardening, they should also exhibit sufficient strength, a limited interconnected pore network, and high resistance to chloride ion permeation. Therefore, achieving balanced fresh, mechanical, transport, and microstructure properties remains an important challenge in the design of grouting materials for complex service environments.
Cement-based grouting materials are widely used for backfilling behind tunnel linings, reinforcing rock fractures, sealing groundwater pathways, and repairing structures. Their widespread application is attributed to the availability of raw materials, relatively low cost, mature construction techniques, and good compatibility with rock, soil, and concrete matrices [2,3]. Despite their widespread use, conventional cement-based grouts suffer from several limitations in field applications. First, the setting and hardening behaviour of cement-based grout is strongly affected by the water-to-binder ratio, mineral composition, and admixture type. Excessively rapid setting reduces the available time for injection and placement, whereas excessively slow setting delays early strength development and reduces the efficiency of reinforcement operations. Second, a coarse and highly interconnected pore structure facilitates the transport of moisture and aggressive ions through the hardened matrix. This process may restrict strength development and reduce long-term durability. In water-saturated or chloride-corrosive environments, the transport of pore water and chloride ions can further impair the integrity and long-term stability of the hardened grout [4]. Therefore, the optimisation of cement-based grouting materials should not focus on a single performance indicator. Setting behaviour, bleeding resistance, mechanical properties, volume stability, chloride ion penetration resistance, and microstructural evolution should instead be considered together.
Fly ash, an industrial by-product and widely used supplementary cementitious material, has been extensively incorporated into cement-based materials. It primarily consists of oxides such as SiO2, Al2O3, and CaO, and exhibits potential pozzolanic activity [5]. In cement-based grouting systems, fly ash affects fresh and hardened properties through age-dependent physical and chemical mechanisms. At early ages, it primarily acts through dilution, particle filling, and morphological effects. These effects influence the setting behaviour, bleeding resistance, and early strength development of the grout. At later ages, reactive siliceous and aluminous phases in fly ash can react with Ca(OH)2 produced by cement hydration. The additional C-S-H gel and aluminosilicate hydrates formed through these pozzolanic reactions contribute to pore refinement and densification of the hardened paste [6,7,8]. Furthermore, partially replacing cement with fly ash reduces clinker consumption and may therefore lower carbon emissions and resource consumption, providing both environmental and economic benefits [9,10,11]. Recent studies have further demonstrated that fly ash can be processed into lightweight aggregates for internal curing applications, where its porous structure enables water storage and release to promote sustained hydration and refine the pore structure of cementitious materials [12]. This indicates that the beneficial effects of fly ash in cementitious systems can arise from both chemical (pozzolanic) and physical (moisture regulation) pathways. However, a higher fly ash content is not always advantageous. An appropriate amount of fly ash can optimise particle packing and promote later-age microstructural development. Excessive fly ash replacement lowers the clinker fraction in the cementitious system, thereby hindering the generation of early-age hydrates. When the amount of Ca(OH)2 available in the system is insufficient, the later-age pozzolanic reaction of fly ash may also be restricted. This can result in delayed strength development and limited refinement of the pore structure. It is therefore necessary to determine an appropriate fly ash content for cement-based grouting materials by jointly considering setting time, mechanical properties, and pore structure.
In addition to mineral admixtures, functional chemical admixtures provide another means of regulating the performance of cement-based materials. Rust inhibitors are commonly incorporated into cementitious systems to mitigate chloride-induced corrosion of embedded steel [13]. Depending on their chemical composition, these admixtures may adsorb onto cement particles or hydration products, alter the chemistry of the pore solution, and affect hydration kinetics [14,15]. In cement-based grouting materials, rust inhibitors may therefore influence not only corrosion protection but also early hydration and the pore structure of the hardened matrix [16,17,18]. Certain hydrophobic or carboxylate-based functional components tend to attach to the surface of cement grains and hydrate phases. This adsorption may delay early hydration and alter setting behaviour [19,20,21,22]. Their reported film-forming and filling effects may also affect pore connectivity and the transport of water and chloride ions through the hardened grout [23,24]. Consequently, rust inhibitors may exert two competing effects in grouting materials. On the one hand, they may delay setting and early hydration. On the other hand, an appropriate dosage may contribute to later-stage strength development and transport resistance by modifying the structure of the hardened matrix. However, these mechanisms cannot be confirmed solely from macroscopic performance tests. Further investigation combining macroscopic measurements with pore-structure and microstructural characterisation is therefore required.
In chloride-bearing environments, chloride ion transport is a key factor affecting the long-term durability of cementitious materials. Rust inhibitors are widely used in reinforced concrete structures to delay or suppress chloride-induced reinforcement corrosion [25,26,27]. Although the grout matrix itself does not undergo reinforcement corrosion, its chloride transport properties can influence the protection provided to adjacent steel components and structures. The incorporation of rust inhibitors may affect chloride transport by altering hydration development, pore-solution chemistry, and resistance to ionic migration. Previous studies have reported that internally added rust inhibitors can, under certain conditions, reduce the chloride ion diffusion coefficient and improve the durability of cementitious materials [28,29]. However, when rust inhibitors are combined with fly ash and anti-corrosion admixtures, their effects on setting time, strength development, pore structure, and chloride ion transport may be complementary, antagonistic, or largely independent. The underlying relationships remain unclear. In particular, the relative contributions of the three components under a fixed water-to-binder ratio and comparable initial workability have not been sufficiently characterised.
Taken together, fly ash, anti-corrosion admixtures, and rust inhibitors may influence cement hydration, pore-structure development, and transport behaviour through different but potentially interacting pathways. However, existing studies have largely focused on individual mineral or chemical admixtures. Limited information is available regarding their combined effects on setting behaviour, bleeding resistance, mechanical properties, shrinkage, chloride penetration resistance, and multiscale microstructure. These relationships are particularly unclear when the water-to-binder ratio is fixed and initial workability is maintained within a comparable range. It also remains uncertain whether changes in macroscopic performance can be consistently related to the evolution of hydration products and the interconnected pore network.
To fill this gap, the novelty of this work is threefold. First, unlike previous studies that typically examine fly ash, rust inhibitors, or anti-corrosion admixtures in isolation, this work systematically investigates their combined effects in cement-based grouting materials using a well-designed L9 orthogonal array under a constant water-to-binder ratio and controlled initial flowability, thereby enabling the relative contribution of each factor to be distinguished and potential interactions to be inferred. Second, rather than relying on a single microscopic technique, this study employs multi-scale correlative characterization to link macroscopic performance (setting, mechanical strength, and chloride transport resistance) with microstructural evolution across different length scales. Third, this work provides a quantitative basis for preliminary mix optimization in chloride-rich and water-saturated environments, yielding specific dosage ranges for the ternary system that have not been previously reported for this particular combination of admixtures.
To obtain grouting materials with balanced fresh and hardened properties for water-rich and chloride-laden environments, the present work employed an L9(34) orthogonal array at a fixed water-to-binder ratio of 0.5. The performance parameters examined included setting time, bleeding rate, mechanical strengths, drying shrinkage, and chloride penetration resistance, with fly ash (10–30%), rust inhibitor (1–3%), and anti-corrosion admixture (2–6%) as the main variables. To reduce the influence of workability variations on the hardened properties, the superplasticizer dosage was adjusted to maintain comparable initial flowability among the mixtures. This procedure minimised potential confounding effects associated with differences in initial flowability. Low-field nuclear magnetic resonance (LF-NMR), X-ray computed tomography (X-CT), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to characterise porosity, pore-size distribution, hydration product morphology, and phase composition. The study aimed to evaluate the main effects of the three investigated components, establish relationships between macroscopic properties and microstructural characteristics, and identify a mixture with balanced fresh and hardened performance. The findings provide an experimental basis for designing cement-based grouting materials with controllable setting behaviour, sufficient early-age strength, low shrinkage, a limited interconnected pore network, and improved resistance to chloride ion penetration in complex service environments.

2. Test Materials and Methods

2.1. Raw Materials

P·O 42.5 ordinary Portland cement, supplied by Qingdao Shanshui Innovation Cement Co., Ltd. (Qingdao, China), was used as the cementitious binder. It had an initial setting time of 193 min, a final setting time of 281 min, and a specific surface area of 372 m2/kg. The fly ash was Class F, Grade I fly ash supplied by Laizhou Huadian Power Generation Co., Ltd. (Yantai, China), with a loss on ignition of 0.84%, a water demand ratio of 96.8%, a specific surface area of 343 m2/kg, and a 28-day reactivity index of 80%. The cementitious material is a blend of cement and fly ash; its chemical composition is shown in Table 1. Both the rust inhibitor and the anti-corrosion admixture were supplied by Jiangsu Subote New Materials Co., Ltd. (Nanjing, China) and were functional liquid admixtures. The hydrophobic anti-corrosion admixture, designated SBT®-TIA, consists primarily of organic carboxylate polymers and nanomaterials, and its performance complies with the requirements of JC/T 2553-2019 [30], Concrete Erosion Inhibitors. The polycarboxylate superplasticizer (PCA®-I) was supplied by Jiangsu Subote New Materials Co., Ltd. (Nanjing, China) Its solid content is 20%, and its water-reducing rate is approximately 28%.

2.2. Design of Grouting Material Mix Proportions

An L9(34) orthogonal array based on the Taguchi method was adopted to design the mix proportions, with the water-to-binder ratio fixed at 0.5. The effects of three factors—fly ash (A), rust inhibitor (B) and anti-corrosion admixture (C)—at three levels on grouting material performance were systematically investigated. The fly ash content (by mass of cementitious materials) was set at 10%, 20%, and 30%. The rust inhibitor content was set at 1%, 2%, and 3%, and the anti-corrosion admixture content was set at 2%, 4%, and 6%, both by mass of cementitious materials. The performance indicators evaluated in this orthogonal experiment included setting time, bleeding rate, mechanical strength, drying shrinkage, chloride ion penetration resistance, and pore structure parameters. To eliminate the interference of differences in grout workability on the evaluation of hardened properties, the dosage of water-reducing agent was dynamically adjusted to control the initial flow of each group within (210 ± 10) mm. The exact dosage of polycarboxylate superplasticizer for each mixture, as well as the full mix proportions, are listed in Table 2.
In the L9(34) orthogonal array, the fourth column (Column D) is designated as a blank column and is used to estimate the experimental error. This column does not correspond to any actual factor and serves as a basis for evaluating the relative importance of the three investigated factors through range analysis.

2.3. Preparation and Curing of Test Specimens

The raw materials were weighed according to the design mix proportion. The cementitious materials (cement and fly ash) were mixed with water in a paste mixer at low speed for 30 s. The mixing regime complied with the requirements of GB/T 1346-2024 [31]. The rust inhibitor, anti-corrosion admixture and water-reducing agent were then added. The speed was then increased to high for 120 s of mixing. The mixer was then paused and the mixture was left to rest for 90 s, followed by high-speed mixing for an additional 60 s. Workability tests were performed promptly on the fresh mixture, and the corresponding test specimens were moulded. Depending on the specific test requirements, the test specimens were moulded to the appropriate dimensions. After being compacted on a vibrating table, they were covered with plastic film to prevent moisture evaporation and left to stand at room temperature (20 ± 5) °C for 24 h before demoulding. They were then transferred to a standard curing chamber (temperature (20 ± 2) °C, relative humidity ≥ 95%) for curing until the specified age. The dimensions of test specimens for compressive and flexural strength testing were 40 mm × 40 mm × 160 mm, in accordance with GB/T 17671-2021 [32]. The same dimensions were used for drying shrinkage testing. Specimens for chloride ion penetration testing (charge passed) were cylindrical, with a diameter of 100 mm and a height of 50 mm.
For each mixture, three parallel specimens were prepared for each testing parameter (setting time, bleeding rate, compressive/flexural strength, drying shrinkage, and electrical flux) to ensure result reliability, unless otherwise specified in the corresponding characterisation method. All reported values for these tests are expressed as mean ± standard deviation.

2.4. Characterisation

The initial flowability of the freshly mixed grouting material was determined in accordance with GB/T 8077-2023 [33]. Per GB/T 1346-2024, the initial and final setting times of the grouting materials were recorded. The 24 h free bleeding rate was determined in accordance with TB/T 3192-2008 [34], Technical specifications for grouting of post-tensioned prestressed concrete beams in railway applications. Compressive and flexural strengths were measured per GB/T 17671-2021 on specimens subjected to standard curing for 3, 7, and 28 days. The drying shrinkage rate over the period from demoulding to 28 days was determined in accordance with GB/T 29417-2012 [35], Test method for drying shrinkage and cracking properties of cement mortar and concrete.
Resistance to chloride ion penetration was assessed following GB/T 50082-2009 [36]. Cylindrical specimens with a diameter of 100 mm and a height of 50 mm were cured under standard conditions for 28 days. A direct-current voltage of 60 V was then applied for 6 h, and the total charge passed through each specimen was measured.
Low-field nuclear magnetic resonance (LF-NMR) was used to characterise the pore-size distribution and pore structure of specimens cured for 7 and 28 days. Prior to testing, the specimens were machined into cylinders 20 mm in diameter and 20 mm in height and were subsequently vacuum-saturated. The transverse relaxation time (T2) spectral were then acquired. The test parameters were a resonance frequency of 7.158 MHz, 6000 echoes, and a repeat delay of 1200 ms.
An industrial X-ray computed tomography system (X-CT, nanoVoxel-3000, Tianjin Sanying Precision Instruments Co., Ltd., Tianjin, China) was used to scan the specimens after 7 and 28 days of standard curing. Three-dimensional images were obtained with a voxel size of 25.25 µm. Three-dimensional reconstruction and image processing were subsequently performed to quantify the pore structure characteristics.
A scanning electron microscope (SEM, JSM-7800F, Rigaku Corporation, Tokyo, Japan) was used to observe the microstructure of the hydration products at 7 and 28 days. An accelerating voltage of 5 kV was used. Prior to observation, the samples were sputter-coated with gold.
The phase composition of the hydration products was analysed by X-ray diffraction (XRD, Ultima IV, Rigaku Corporation, Tokyo, Japan) with Cu Kα radiation (λ = 1.5406 Å). Patterns were recorded over a 2θ range of 5° to 70° at a step size of 0.02° and a scan speed of 10°/min, with the generator operating at 40 kV and 40 mA.

3. Results and Discussion

3.1. Setting Time and Bleeding Rate

Figure 1 presents the initial and final setting times of nine formulations included in the orthogonal experimental design. The trends shown in Figure 1 suggest that the fly ash content had the greatest influence on setting behaviour among the investigated factors. Raising the fly ash content from 10% to 30% prolonged the initial setting time from 576 to 615 min, corresponding to an increase of 6.77%. At the same fly ash content, the setting time of the grout generally increased with increasing anti-corrosion admixture dosage. By contrast, changes in the rust inhibitor content had a relatively minor effect on setting time. Therefore, within the investigated dosage ranges, the setting behaviour was more sensitive to the fly ash and anti-corrosion admixture contents than to the rust inhibitor content.
The retarding effect of fly ash may be primarily attributed to dilution and physical effects. When fly ash replaces cement on a mass basis, the proportion of clinker phases with high early hydration activity, particularly C3A and C3S is reduced. This dilution decreases the early hydration rate and slows the formation and interconnection of hydration products, thereby delaying the development of a continuous solid network. In addition, the micro-aggregate filling effect of fly ash modifies particle packing and water distribution within the fresh grout. The adsorption of dissolved ions and admixture molecules on fly ash surfaces may also affect the early hydration reactions. These combined effects can extend the induction period and delay setting.
The retarding effect of the anti-corrosion admixture may be related to its molecular structural characteristics. This type of admixture has an amphiphilic structure, with hydrophilic groups and hydrophobic segments linked to the same molecular backbone via covalent bonds. The hydrophilic groups tend to attach preferentially to the interface of clinker grains and the nuclei of hydrated phases at early ages. This adsorption may be particularly pronounced on C3A because of its high early reactivity and surface activity. The hydrophobic segments then extend towards the pore solution, forming an adsorption layer around cement particles and hydration products. This adsorbed film may impede the migration of aqueous and ionic species towards the interface of unhydrated clinker grains. It may also retard the formation of hydrate phases via nucleation and crystal growth at early ages, which in turn prolongs the induction period and delays the start and completion of setting. As the dosage of the anti-corrosion admixture increases, its surface coverage may increase, strengthening the barrier effect and producing a more pronounced retardation of setting.
It should be noted that the initial setting times of the investigated mixtures range from approximately 576 to 615 min, which are considerably longer than those of typical neat cement grouts. This extended setting behaviour is primarily associated with the retarding effects of fly ash and the anti-corrosion admixture, as discussed above. For grouting operations that require extended pumping and injectability times, such as long-distance transport, large-volume backfilling, or grouting in highly fractured formations, this prolonged setting window is advantageous by reducing the risk of premature blockage and ensuring sufficient time for complete void filling. For applications that demand rapid strength development, such as emergency repairs, water-sealing of active inflows, or early load-bearing support, the setting times observed in this study can be tailored to field requirements by incorporating accelerators or reducing the dosages of the retarding components. The present results thus provide a baseline understanding of the setting characteristics of this ternary system, while formulation adjustments should be made according to specific project needs.
The 24 h free bleeding rate of all nine grout formulations were 0%. This result satisfied the requirements specified in GB/T 50448-2015 [37]. The absence of bleeding indicates that the prepared grouts exhibited good water-retention capacity and resistance to segregation under the test conditions. The observed bleeding resistance may be associated with the combined effects of fly ash and the anti-corrosion admixture. The micro-aggregate and filling effects of fly ash improve the particle-packing characteristics of the cementitious system. The effect may increase the packing density and plastic viscosity of the grout, thereby restricting the migration of free water. The anti-corrosion admixture may also modify particle–water interactions and the rheological behaviour of the fresh grout, promoting a more uniform distribution of water throughout the mixture. Together, these effects reduce particle settlement and water segregation, thereby maintaining the homogeneity and stability of the fresh grout. The absence of bleeding also provides favourable conditions for the uniform development of mechanical properties and resistance to fluid penetration after hardening.

3.2. Analysis of Mechanical Properties

Figure 2 shows the flexural and compressive strengths of the nine grout formulations at different ages. As shown in Figure 2, the effect of fly ash content on strength development exhibits marked age-dependent behaviour. For the 28-day compressive strength, the groups containing 20% fly ash (Groups S4–S6) achieved higher values than those containing 10% or 30% fly ash. The test groups with the highest fly ash content (Groups S7–S9, 30%) showed lower strength values at all ages. At 7 days, the differences in flexural strength between the groups were relatively small. By 28 days, however, the groups containing 20% fly ash generally exhibited higher flexural strength, whereas the strength development of the groups containing 30% fly ash remained limited. These results suggest that the effect of fly ash content on mechanical properties became more pronounced with increasing curing age. The aforementioned patterns of strength development can be explained by the physical effects of fly ash and the temporal evolution of the pozzolanic reaction. At early ages, particularly within the first 7 days, the effects of particle-packing fly ash are mainly associated with particle filling and cement dilution. The former can improve particle packing and contribute to the development of a denser matrix. By contrast, the latter reduces the formation of early-age hydration products by lowering the relative content of cement clinker, particularly C3S and C3A, in the system. Under the combined influence of these two effects, early-age strength generally decreases as the fly ash content increases [6].
Between 7 and 28 days, the reactive SiO2 and Al2O3 in fly ash react pozzolanically with Ca(OH)2 liberated during cement hydration, yielding additional C-S-H gel with a relatively low calcium-to-silica ratio, together with aluminosilicate hydration products [38,39]. The resulting hydration products gradually fill the pores and refine the pore structure, thereby increasing the density of the hardened paste. This process may partly compensate for the loss of early-age strength and contribute to the continued development of both compressive and flexural strengths. However, when the fly ash content reached 30%, the cement clinker content was substantially reduced. This diminished the generation of hydrates during the initial stage, which was in line with the extended setting time and the decreased early-age strength. At later stages, the reduced amount of cement also limited the production of Ca(OH)2 available for the pozzolanic reaction. Consequently, the contribution of the pozzolanic reaction may have been insufficient to compensate fully for the dilution effect by 28 days. Therefore, under the conditions of this experiment, a fly ash content of 20% provided the most favorable balance between the dilution, filling, and later-age pozzolanic effects among the three investigated contents.
In addition to fly ash, the results suggest that the dosage of the anti-corrosion admixture may also affect later-stage strength. At the same fly ash content, Group S4, which contained 6% anti-corrosion admixture, exhibited the highest 28-day compressive strength, with a mean value of 41.6 MPa. This result indicates that an appropriate dosage of the anti-corrosion admixture may contribute to strength development. The observed improvement may be associated with changes in the pore structure and the formation of hydration products. First, the film-forming and filling actions of the hydrophobic components in the admixture may reduce capillary-pore connectivity in the hardened paste. This effect could restrict crack initiation and propagation along interconnected pores under loading. Second, the admixture may affect the nucleation and crystallisation of hydration products, promoting a more compact matrix architecture and thus improving the overall mechanical performance [20]. These interpretations are further evaluated in conjunction with the pore-structure and microstructural results presented in the following sections.
The 28-day drying shrinkage values of all nine test groups remained close to zero and complied with the requirements of GB/T 50448-2015. These results indicate that the prepared grouting materials exhibited limited drying shrinkage and satisfactory volumetric stability. The low shrinkage may be associated with the combined influence of fly ash and the anti-corrosion admixture through physical restraint and possible chemical compensation. At the physical level, the microfiller effect of fly ash may improve particle packing and reduce the capillary stress generated by moisture loss. Unreacted fly ash particle may also act as relatively rigid inclusions and provide limited restraint against shrinkage deformation. At the chemical level, the anti-corrosion admixture may contribute to the formation of small amounts of expansive hydration products, including ettringite-type crystals. These products could partially compensate for the shrinkage associated with cement hydration and moisture loss. The rust inhibitors may have affected shrinkage indirectly by influencing early hydration and matrix development. For mixtures that developed higher early-age strength, the resulting increase in matrix stiffness may have improved resistance to shrinkage deformation and limited microcrack development.

3.3. Resistance to Chloride Ion Permeation

The charge-passed results from the electrical flux conducted at 28 days for the nine grout mixtures are shown in Figure 3. Within the framework of this test, a lower charge passed generally indicates greater resistance to chloride ion permeation. It should be noted that the electrical flux primarily reflects the ionic transport resistance of the hardened matrix rather than the electrochemical corrosion rate of embedded steel. However, the electrical flux (RCPT) method has certain limitations, as the results may be influenced by pore solution conductivity and the presence of chemical admixtures. In this study, all specimens were tested under identical conditions (same saturation treatment, same voltage, and same testing duration), so the differences in electrical flux among the nine mixtures predominantly reflect variations in their resistance to ionic transport. Therefore, despite its limitations, the RCPT method remains effective for the relative comparison of chloride penetration resistance within the orthogonal design. As shown in Figure 3, the groups containing 6% anti-corrosion admixture (Groups S2, S4 and S9) exhibited comparatively low charge-passed values. Among them, Group S9, containing 30% fly ash, 3% rust inhibitor, and 6% anti-corrosion admixture, recorded the lowest charge passed, with a value of 2783 C. The reduction in charge passed may be associated with both chemical interactions and physical changes in the hardened matrix. Previous studies suggest that the active components of the anti-corrosion admixture may interact with free chloride ions or calcium-bearing phases, thereby reducing the mobility of ions within the pore solution [23]. The admixture may also modify pore connectivity and tortuosity during hydration, thereby increasing resistance to ionic transport. Carboxylate-containing components may interact with calcium ions and affect the development of the hardened matrix [40]. Although these improvements in chloride penetration resistance do not constitute direct electrochemical protection of embedded steel, they directly reduce the flux of chloride ions migrating towards the steel surface. Since chloride accumulation at the steel surface is a prerequisite for corrosion initiation, the enhanced matrix barrier property provides an indirect but important contribution to corrosion protection. Therefore, the chloride penetration resistance evaluated in this study represents a meaningful matrix-level indicator of the anticorrosion potential of grouting materials. The rust inhibitors also affect the measured charge passed by altering the pore-solution chemistry and surface interactions within the pore network. Its active components adsorb onto solid surfaces and modify the local charge environment, thereby influencing ionic migration [29]. Under the investigated conditions, the effect of the rust inhibitor on the charge passed appeared less pronounced than that of the anti-corrosion admixture. Fly ash contributes to resistance to chloride ion penetration through particle filling and subsequent pozzolanic reactions. Its reactive siliceous and aluminous phases can react with Ca(OH)2 produced by cement hydration to form additional C-S-H gel and aluminosilicate hydration products. These products may refine the pore structure, reduce pore connectivity, and increase the tortuosity of ion transport pathway. However, the contribution of the pozzolanic reaction may not have fully developed by 28 days.

3.4. Analysis of the Pore Structure of Grouting Materials

Figure 4 shows three-dimensional X-CT reconstructions of the grouting materials with different mix proportions at 28 days. Compared with the other groups, Groups S4 and S5 exhibited fewer visually identifiable large pores and a more homogeneous spatial distribution of the segmented pores. The spatial distribution of large pores in the X-CT reconstructions correlates well with both mechanical properties and chloride penetration resistance. Mixtures with fewer and more uniformly distributed large pores, such as Groups S4 and S5, exhibited higher strengths and lower chloride permeability (Figure 2 and Figure 3). Conversely, the presence of a large pore near the centre of the specimen in Group S6 (Figure 4f) was associated with reduced mechanical performance, as such pores act as stress concentration sites under loading. These observations are consistent with the quantitative pore structure data in Figure 5 and Figure 6, confirming that pore refinement, particularly the reduction in large capillary pores, is key to improving both the mechanical strength and durability of the grouting materials. Figure 5 and Figure 6 show the porosity and pore-size distribution, respectively, of grouting materials with different mix proportions.
As shown in Figure 5 and Figure 6, the porosity of all groups decreased with curing age. Groups S4, S5, and S6 generally exhibited lower porosity than the other groups. The three groups containing 6% anti-corrosion admixture (Groups S2, S4 and S9) also exhibited relatively low porosity, although the effects of the other mixture variables should also be considered. The pore-size distribution results further indicate that Groups S4, S5, and S6 contained relatively small proportions of large pores and showed more concentrated pore-size distributions.
These patterns of pore-structure evolution may be attributed to the particle-filling and subsequent pozzolanic reaction of fly ash. At an appropriate content of 20%, fly ash particles fill voids between cement particles and improve particle packing through the microfiller effect. At later ages, the reactive components of fly ash can react with Ca(OH)2 generated by cement hydration to form additional C-S-H gel. These products may progressively fill larger pores and refine the pore structure, resulting in a more homogeneous pore network.
By contrast, when the fly ash content reached 30%, the higher replacement level substantially reduced the proportion of cement clinker and limited the formation of early hydration products. At later ages, the lower production of Ca(OH)2 may also have restricted the extent of the pozzolanic reaction by 28 days. Consequently, the formation of additional hydration products may have been insufficient to compensate fully for the dilution effect, resulting in less effective pore refinement and a greater proportion of large pores.

3.5. Microscopic Morphology and Composition of Hydration Products of Grouting Materials

Figure 7 and Figure 8 show the SEM morphologies of the grouting materials with different mix proportions at 7 and 28 days, respectively. At 7 days, the matrices were at an early stage of hydration, and clear differences in the morphology and distribution of hydration products were observed among the mixtures. Needle-like and short rod-like crystals were widely distributed within the matrix. Based on their morphology and the corresponding XRD patterns, these crystals were assigned to ettringite (AFt). They formed a relatively loose framework around the unreacted particles. As the fly ash content increased, the amount of needle-like AFt appeared to decrease. This trend may be related to the dilution of cement clinker and the limited early-age reactivity of fly ash. The C-S-H gel exhibited a fibrous or reticulated morphology and contributed to bonding among the solid particles and early matrix development. A high fly ash replacement level reduced the amount of early hydration products and resulted in a less compact matrix. By comparison, the mixtures containing more anti-corrosion admixture showed more continuous gel-like products and fewer visible voids. This observation suggests that the admixture affected early hydration and microstructural development. Spherical particles were also observed in some regions. Overall, the 7-day microstructure was governed mainly by early cement hydration, the dilution and filling effects of fly ash, and the influence of the anti-corrosion admixture on matrix development. At this age, the contribution of fly ash was primarily associated with particle filling and cement dilution because its pozzolanic reaction had not yet developed fully.
At 28 days, the matrices became denser, and the gel-like hydration products formed a more continuous network. These changes were consistent with continued cement hydration and the progressive pozzolanic reaction of fly ash. Fine needle-like products remained visible around some fly ash particles. Plate-like products were observed in some mixtures with a relatively low fly ash content. Based on their morphology and the corresponding XRD patterns, these products were tentatively identified as Ca(OH)2. The C-S-H gel became more continuous and filled the spaces between hydration products and around the fly ash particles. The additional gel products formed through the pozzolanic reaction may have merged with those produced by primary cement hydration, thereby refining the local interfacial regions and densifying the matrix. The microstructural refinement was particularly evident in mixtures containing an appropriate fly ash content and anti-corrosion admixture dosage. This observation is consistent with their improved later-age strength, pore structure, and resistance to chloride ion penetration. The amount of spherical particles tentatively associated with CaCO3 appeared to decrease at 28 days, particularly in the mixtures with a high fly ash content. This trend may be related to the lower availability of Ca(OH)2 and the reduced accessibility of CO2 within the refined pore network.
The SEM observations were further evaluated using the XRD patterns shown in Figure 9. At 7 days, the intensity of the characteristic Ca(OH)2 peak was lower in the mixtures with a high fly ash content than in those with a low fly ash content. This result is consistent with the lower cement clinker content and, consequently, the lower amount of Ca(OH)2 generated by cement hydration. Early pozzolanic consumption of Ca(OH)2 may also have contributed to this difference. A higher anti-corrosion admixture content was also associated with a lower Ca(OH)2 peak intensity. This result suggests that the admixture may have altered the hydration process or interacted with calcium-bearing phases. Residual C2S and C3S peaks were detected in the XRD patterns. Their relative peak intensities varied among the mixtures. AFt was detected in all groups, which is consistent with the needle-like crystals observed in the SEM images. The CaCO3 peak intensity was generally lower in mixtures with a high fly ash content. This result may be associated with the lower amount of Ca(OH)2 available for carbonation.
At 28 days, the XRD results were generally consistent with the denser microstructures observed by SEM. The Ca(OH)2 peak intensities generally increased compared with those at 7 days, indicating the continued hydration of the cement clinker. However, the Ca(OH)2 peak intensity remained relatively low in the mixtures with a high fly ash content, and the increase from 7 to 28 days was limited. This trend is consistent with both the lower cement clinker content and the progressive consumption of Ca(OH)2 during the pozzolanic reaction. The intensity of the AFt diffraction peaks generally decreased between 7 and 28 days. This decrease may reflect changes in the amount, crystallinity, or phase assemblage of AFt-containing products. The CaCO3 peak intensity remained lower in the mixtures with a high fly ash content. This result may be explained by two related mechanisms. First, the pozzolanic reaction reduced the amount of Ca(OH)2 available for carbonation. Second, the refined hydration-product network may have reduced pore connectivity and restricted CO2 transport through the matrix.
Taken together, the SEM and XRD results indicate that an appropriate fly ash content, combined with the anti-corrosion admixture, promoted the development of a denser microstructure at 28 days. The observed refinement was associated with continued cement hydration, the later-age pozzolanic reaction of fly ash, and changes in the distribution of hydration products. These microstructural changes are consistent with the improvements in pore structure, mechanical performance, and chloride ion penetration resistance discussed in the preceding sections.

3.6. Orthogonal Statistical Analysis of Factor Effects

To quantitatively evaluate the relative importance of fly ash (A), rust inhibitor (B), and anti-corrosion admixture (C) on the multiple performance indicators, both range analysis and analysis of variance (ANOVA) were performed based on the L9(34) orthogonal experimental data. The results are summarised in Table 3 and Table 4, respectively.
The range analysis results indicate that the dominant factor varied across different performance indicators. For setting time and mechanical strength, fly ash exhibited the largest range R (R = 127.89 for initial setting, R = 10.23 for compressive strength), indicating that fly ash was the dominant factor for these two properties. For porosity, the rust inhibitor showed the largest range (R = 0.0466). For electrical flux, the anti-corrosion admixture exhibited the largest range (R = 862.08), with a contribution rate of 62.05%. These results suggest that the three components play distinct roles in the grouting materials: fly ash primarily regulates setting behaviour and mechanical strength, the rust inhibitor mainly affects final setting, flexural strength and pore structure, while the anti-corrosion admixture primarily improves resistance to chloride ion penetration.
The ANOVA results show that initial setting time was significantly influenced by both fly ash and rust inhibitor (p < 0.05), and flexural strength was highly significantly influenced by all three factors (p < 0.01). For the remaining indicators, none of the factors reached statistical significance. This is primarily attributed to the limited error degrees of freedom (df = 2) inherent to the L9(34) orthogonal design, where the critical F-value is as high as 19.0, resulting in limited statistical sensitivity. Nevertheless, the ranking order from the range analysis is fully consistent with the contribution rates from ANOVA, and is further corroborated by the pore structure and microstructural observations presented in the previous sections, providing a reliable basis for identifying the optimal factor levels.
Nevertheless, the ranking order from the range analysis is fully consistent with the contribution rates from ANOVA, and is further corroborated by the pore structure and microstructural observations presented in the previous sections, providing a reliable basis for identifying the optimal factor levels.

3.7. Proposed Combined Mechanism of Fly Ash and Functional Components in the Grouting Materials

Based on the mechanical properties, chloride ion penetration resistance, pore structure, SEM observations, and XRD results, the combined effects of fly ash, the anti-corrosion admixture, and the rust inhibitor can be interpreted in terms of particle packing, hydration development, and ionic transport. These effects occur at different stages of curing and collectively influence the macroscopic performance of the grouting materials.
Regarding particle packing and pore-structure development, fly ash particles fill some of the spaces between cement grains and improve the packing of the solid particles. At an appropriate replacement level, this microfiller effect reduces the initial void space and provides a more favourable microstructure for subsequent hydration. As curing progresses, the pozzolanic reaction of fly ash consumes part of the Ca(OH)2 and produces additional C-S-H gel. These products fill larger pores, reduce pore connectivity, and increase the tortuosity of transport pathways. The anti-corrosion admixture may further influence pore refinement and the surface properties of the pore network.
The three components also affect hydration development at different curing ages. At an early age, fly ash mainly produces dilution and particle-filling effects because its pozzolanic activity is still limited. A high fly ash replacement level therefore reduces the amount of cement clinker available for early hydration and may delay matrix densification. The anti-corrosion admixture and rust inhibitor may modify the early hydration environment through their interactions with cement particles, dissolved ions, and hydration products. At later ages, the progressive pozzolanic reaction of fly ash generates additional gel products and contributes to the development of a more continuous hydration-product network. This interpretation is consistent with the reduced porosity and denser microstructure observed in mixtures containing appropriate dosages of fly ash and functional components.
The improvement in chloride ion penetration resistance may result from the combined effects of pore-structure refinement and changes in ionic mobility within the pore solution. The refined pore network produced by cement hydration and the pozzolanic reaction reduces pore connectivity and lengthens the transport pathways for chloride ions. The active components of the anti-corrosion admixture may interact with chloride ions or calcium-bearing phases and thereby reduce chloride mobility. The rust inhibitor may also modify the pore-solution chemistry and solid-surface charge, which can affect ionic migration through the hardened matrix.
Overall, the experimental results indicate that an appropriate combination of fly ash, anti-corrosion admixture, and rust inhibitor promotes the formation of a denser pore structure and improves resistance to chloride ion penetration. The proposed mechanism, as illustrated in Figure 10, involves the complementary contributions of particle filling, later-age pozzolanic reactions, hydration-product development, and changes in ionic transport.

4. Conclusions

The influences of fly ash (10–30%), rust inhibitor (1–3%), and anti-corrosion admixture (2–6%) on the workability, mechanical properties, chloride ion penetration resistance, and microstructure of grouting materials (w/b = 0.5) were systematically evaluated via an L9(34) orthogonal array. The main conclusions are as follows:
(1)
Among the investigated factors, fly ash exhibited the most significant influence on setting behaviour and compressive strength, as evidenced by the range analysis (R = 127.89 for initial setting) and the contribution rate of 67.23% to compressive strength. The retarding effect of fly ash is primarily attributed to the dilution of cement clinker, which reduces the availability of early-age hydration reactants. A fly ash content of 20% provided the optimal balance between the early-age dilution effect and the later-age pozzolanic reaction, yielding the highest 28-day compressive and flexural strengths. Increasing the fly ash content to 30% resulted in a dilution effect that outweighed the pozzolanic contribution, thereby limiting further strength development. The anti-corrosion admixture positively contributed to later-age strength, with the most pronounced improvement observed at a dosage of 6%.
(2)
The anti-corrosion admixture was the dominant factor governing chloride ion penetration resistance, with the largest range (R = 862.08) and the highest contribution rate (62.05%). Its mechanism involves reducing ionic mobility within the pore solution and increasing pore tortuosity, thereby enhancing the barrier performance of the hardened matrix. The lowest electrical flux (2783 C) was achieved at 6% anti-corrosion admixture dosage (Group S9). The rust inhibitor also contributed to reducing chloride migration, albeit to a lesser extent (contribution rate of 22.13%). Fly ash, through particle packing and pozzolanic reaction, refined the pore structure, but its contribution to chloride penetration resistance was relatively limited (0.70%). All nine mixtures met the specified requirements for bleeding rate and 28-day drying shrinkage.
(3)
The pore structure evolution was strongly governed by the fly ash content. The 20% fly ash mixtures exhibited the lowest porosity, the smallest proportion of large pores, and the most refined pore size distribution, attributed to the micro-filler effect of fly ash particles and the formation of additional C-S-H gel through the pozzolanic reaction, which progressively filled and refined the pores. At 30% fly ash content, the reduced clinker fraction led to fewer early-age hydration products and limited Ca(OH)2 availability for the pozzolanic reaction, resulting in less effective pore refinement. The anti-corrosion admixture further reduced pore connectivity through its film-forming and filling effects. The pore structure evolution mechanisms were consistently corroborated by X-CT, SEM, and XRD analyses.
(4)
Based on the integrated assessment of fresh-state performance, strength development, chloride resistance, and microstructure, the optimal formulation in this study is defined as the combination of factor levels that achieves the highest compressive strength, the lowest chloride ion permeability, and a refined pore structure, without causing excessive retardation of setting. Among the nine mixtures tested, Groups S4 and S5 consistently exhibited the best overall performance across these criteria. In contrast, the mixtures with 3% rust inhibitor (Groups S3, S6, and S9) showed no systematic improvement over their 1% or 2% rust inhibitor counterparts across the evaluated properties. Therefore, the rust inhibitor dosage can be limited to 1–2% for practical optimisation. Within the tested ranges, mixtures with 20% fly ash, 4–6% anti-corrosion admixture, and 1–2% rust inhibitor, particularly Groups S4 and S5, exhibited the best overall performance. These proportions can provide a reference for the mix design of high-performance grouting materials under conditions comparable to those investigated in this study. The relatively long setting times of these mixtures (approximately 10 h initial set) should be considered in field applications. The proposed formulations are best suited for grouting operations that require extended pumping and injectability times. For rapid-strength applications, adjustment through accelerator incorporation or dosage modification of retarding components is recommended. Further experiments involving single-component control groups, interaction analysis, long-term durability tests, and field validation are required to confirm the proposed combined effects and determine the optimum mixture for engineering applications.

Author Contributions

Conceptualization, R.X. and J.X.; Methodology, J.X. and T.W.; Validation, B.P. and W.L.; Investigation, R.X. and J.X.; Resources, B.P.; Writing—original draft, R.X. and J.X.; Writing—review and editing, R.X. and Y.W.; Supervision, Y.W. and L.Z.; Project administration, R.X. and L.Z. All authors have read and agreed to the published version of the manuscript.

Funding

The authors would like to acknowledge financial support provided by the National Natural Science Foundation of China (Grant Nos. 52408311, 52322806) and the Youth Science Fund Program of China Minmetals Corporation (Grant No. 2024QNJJB18).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding authors. The data are not publicly available due to on going research.

Conflicts of Interest

Authors Ben Peng, Wen Lv and Yuedong Wu were employed by Central Research Institute of Building and Construction Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from the Youth Science Fund Program of China Minmetals Corporation. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.

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Figure 1. Effect of different mix ratios on the setting time of grouting materials.
Figure 1. Effect of different mix ratios on the setting time of grouting materials.
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Figure 2. Effect of different mix ratios on the mechanical properties of grouting materials: (a) compressive strength; (b) flexural strength.
Figure 2. Effect of different mix ratios on the mechanical properties of grouting materials: (a) compressive strength; (b) flexural strength.
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Figure 3. Effect of different mix ratios on the chloride ion permeability resistance of grouting materials.
Figure 3. Effect of different mix ratios on the chloride ion permeability resistance of grouting materials.
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Figure 4. Three-dimensional pore distribution of grouting materials at 28 days for different mix proportions (a–i): Groups (1–9).
Figure 4. Three-dimensional pore distribution of grouting materials at 28 days for different mix proportions (a–i): Groups (1–9).
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Figure 5. Effect of different mix ratios on the porosity of grouting materials.
Figure 5. Effect of different mix ratios on the porosity of grouting materials.
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Figure 6. Effect of different mixing ratios on the particle size distribution of grouting materials: (a–i) Groups S1–S9.
Figure 6. Effect of different mixing ratios on the particle size distribution of grouting materials: (a–i) Groups S1–S9.
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Figure 7. SEM images of grouting materials at 7 d for different mix ratios: (a–i) Groups 1–9.
Figure 7. SEM images of grouting materials at 7 d for different mix ratios: (a–i) Groups 1–9.
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Figure 8. SEM images of grouting materials at 28 d for different mix ratios: (a–i) Groups 1–9.
Figure 8. SEM images of grouting materials at 28 d for different mix ratios: (a–i) Groups 1–9.
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Figure 9. XRD patterns of grouting materials from different age groups: (a) 7 d; (b) 28 d.
Figure 9. XRD patterns of grouting materials from different age groups: (a) 7 d; (b) 28 d.
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Figure 10. Combined Mechanism of Fly Ash and Functional Components in the Grouting Materials.
Figure 10. Combined Mechanism of Fly Ash and Functional Components in the Grouting Materials.
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Table 1. Chemical composition of cementitious materials (%).
Table 1. Chemical composition of cementitious materials (%).
OxideAl2O3CaOFe2O3K2OMgONa2OSO3SiO2TiO2
P·O 42.58.4751.904.040.553.020.361.8421.290.48
Fly ash41.564.164.930.670.420.0120.7843.451.85
Table 2. Mix proportions designed by L9(34) orthogonal array.
Table 2. Mix proportions designed by L9(34) orthogonal array.
Test No.A Fly AshB Rust InhibitorC Anti-Corrosion AdmixtureD Blank ColumnPolycarboxylate Superplasticizer
S110%1.0%2%10.3%
S210%2.0%6%20.5%
S310%3.0%4%30.3%
S420%1.0%6%30.5%
S520%2.0%4%10.2%
S620%3.0%2%20.2%
S730%1.0%4%20.3%
S830%2.0%2%30.1%
S930%3.0%6%10.3%
Table 3. Range analysis of orthogonal experimental results.
Table 3. Range analysis of orthogonal experimental results.
Performance IndicatorA Fly AshB Rust InhibitorC Anti-Corrosion Admixture
Initial setting time (min)127.89110.7844.33
Final setting time (min)110.56168.5637.89
28 d flexural strength (MPa)0.170.600.21
28 d compressive strength (MPa)10.232.655.22
Electrical flux (C)96.16566.69862.08
28 d porosity (%)0.040.050.03
Table 4. Analysis of variance (ANOVA) of orthogonal experimental results.
Table 4. Analysis of variance (ANOVA) of orthogonal experimental results.
Performance IndicatorStatisticA Fly AshB Rust InhibitorC Anti-Corrosion Admixture
Initial setting time (min)F-value33.6828.496.3
p-value0.030.030.14
Contribution48.48%41.01%9.07%
Final setting time (min)F-value4.652.100.34
p-value0.180.320.75
Contribution57.54%25.90%4.19%
28 d flexural strength (MPa)F-value3281.00771.00878.00
p-value0.00030.00130.0011
Contribution67.25%15.81%17.99%
28 d compressive strength (MPa)F-value4.290.210.88
p-value0.190.820.53
Contribution67.23%3.31%13.77%
Electrical flux (C)F-value0.051.474.11
p-value0.950.410.20
Contribution0.70%22.13%62.05%
28 d porosity (%)F-value0.640.990.32
p-value0.610.500.76
Contribution21.54%33.59%10.97%
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MDPI and ACS Style

Xu, R.; Xue, J.; Wang, T.; Peng, B.; Lv, W.; Wu, Y.; Zhang, L. Performance and Microstructural Characteristics of Cement-Based Grouting Materials Modified with Fly Ash and Corrosion-Control Admixtures. Appl. Sci. 2026, 16, 8532. https://doi.org/10.3390/app16178532

AMA Style

Xu R, Xue J, Wang T, Peng B, Lv W, Wu Y, Zhang L. Performance and Microstructural Characteristics of Cement-Based Grouting Materials Modified with Fly Ash and Corrosion-Control Admixtures. Applied Sciences. 2026; 16(17):8532. https://doi.org/10.3390/app16178532

Chicago/Turabian Style

Xu, Rui, Jingjia Xue, Tianlei Wang, Ben Peng, Wen Lv, Yuedong Wu, and Lei Zhang. 2026. "Performance and Microstructural Characteristics of Cement-Based Grouting Materials Modified with Fly Ash and Corrosion-Control Admixtures" Applied Sciences 16, no. 17: 8532. https://doi.org/10.3390/app16178532

APA Style

Xu, R., Xue, J., Wang, T., Peng, B., Lv, W., Wu, Y., & Zhang, L. (2026). Performance and Microstructural Characteristics of Cement-Based Grouting Materials Modified with Fly Ash and Corrosion-Control Admixtures. Applied Sciences, 16(17), 8532. https://doi.org/10.3390/app16178532

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