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Article

Influence of Composite C-S-H Seed Prepared by Wet Grinding on High-Volume Fly Ash Concrete

by
Shiheng Wang
1,
Jianan Liu
2,*,
Yaogang Tian
1 and
Peng Zhao
1,*
1
School of Materials Science and Engineering, Chang’an University, Xi’an 710061, China
2
School of Mines, China University of Mining & Technology, Xuzhou 221116, China
*
Authors to whom correspondence should be addressed.
Buildings 2025, 15(2), 270; https://doi.org/10.3390/buildings15020270
Submission received: 30 December 2024 / Revised: 11 January 2025 / Accepted: 14 January 2025 / Published: 18 January 2025
(This article belongs to the Section Building Materials, and Repair & Renovation)
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Versions Notes

Abstract

:
In order to reduce the production cost of preparing C-S-H seeds (C-seeds) by wet grinding cement, this paper prepares a composite C-seed by mixing cement and silica fume (SF) in six proportions. Adding the C-seed to high-volume fly ash (FA) concrete would improve the insufficient early strength of this type of concrete. The properties of different C-seeds, as well as their effects on the mechanical properties, hydration characteristics and microstructure of concrete, were assayed by XRD, SEM and TG. As the results show, silica fume can contribute to the formation of the C-seed by promoting the hydration of cement. As the ratio of cement to silica fume (C/S) decreases, the particle size of the C-seed gradually decreases, the volume of CH decreases and the volume of C-S-H increases first, but when the C/S is less than 4/6, it decreases significantly. After the composite C-seed was added, the compressive strength (CS) of concrete at 1 d and 28 d was significantly improved. The CS at 1 d decreased following the decrease in the C/S ratio; however, it increased at 28 d. As the C/S ratio decreased, the porosity of the concrete with added C-seed decreased at 28 d, making the structure denser. The XRD, NMR and TG results show that C-seeds with C/S values greater than 4:6 have a more pronounced effect on promoting the hydration of cement.

1. Introduction

Green buildings usually use fly ash in place of cement in order to reduce resource waste and environmental pollution, but an insufficient early strength is one of the main factors affecting its dosage in concrete. To improve the early strength of concrete, researchers have tried to use early strength agents, both inorganic and organic, conducting a series of studies. In further research, a nanomaterial was proposed as a nucleation point for cement hydration that could induce the formation and accumulation of C-S-H gel and assist in the hydration of cement. This method can shorten the induction period when increasing the strength of cement, which would contribute to improving the early strength of concrete, yielding high-volume fly ash concrete by eliminating the adverse effects of fly ash. The numerous nano-crystalline seed materials include nano-TiO2 [1,2], nano-Fe2O3 [3], nano-ZrO2 [4], carbon nanoparticles [5], nano-SiO2 [6], nano-Ca(OH)2 [7], and nano-CaCO3 [8]. Artificially synthesized nano-C-S-H seeds (C-seeds) have similar chemical compositions to C-S-H gel, the main hydration product of cement. The chemical composition of C-seeds does not change when they are used in cement slurry, making them valuable early strength agents that can be used as nucleating substrates [9,10,11].
The effectiveness of using C-seed technologies as early strength agents in concrete materials has been widely recognized [12,13,14]. However, C-seeds prepared by chemical synthesis, such as via the hydrothermal method or the chemical precipitation method, are expensive, and the process is complicated [15,16,17], which restricts the promotion and application of C-seed technology. To reduce the manufacturing costs associated with C-seeds, Li [18] prepared micro-hydrated cement with a high reactivity, nucleation induction effects and filling effects by wet grinding cement. Although the prepared product showed a certain effect on early strength, the degree of hydration of the raw materials was not high, and the particle sizes in the micro-hydrated cement were large, resulting in a lot of waste. Tan [19] further ground wet-ground C3S and cement to the nanometer level so as to fully hydrate them and ultimately prepare C-seeds, but the process and equipment requirements for this method are high, and this process is difficult to complete in industrial production. In addition, in order to further reduce costs, researchers have used solid mineral wastes such as Ground Granulated Blast Furnace Slag (GGBS) [20], metakaolin (mK) [21,22,23] and FS [24,25,26] to obtain solid waste slurry via wet grinding. This product can show high volcanic ash activity, and after use, it can substantially improve the early compressive strength (CS) of concrete materials; further, the more the grinding time is increased, the more significant this effect is. This is because such solid waste has a certain hydration activity, and through the wet grinding process, its structure is destroyed and its reaction activity increases. At the same time, a small amount of C-seed is generated during the hydration process; however, the composition of such solid waste fluctuates greatly, and is difficult to control, which affects the production results and hinders quality. Further, in order to achieve a better wet grinding effect, chemical agents are required to assist in grinding or increasing the grinding time, which increases the production cost and energy consumed. In summary, C-seeds are a new type of early strength agent applicable in cement concrete that, based on the seed effect, can improve the insufficient early strength of concrete, which can induce the infiltration of Ca2+ in a directional manner during the cement hydration process and provide nucleation bases for the growth of C-S-H gels or other crystals, thereby accelerating the rate of C-S-H gel production and improving the extent of cement hydration [27]. The method of preparation for C-seeds is complicated, the process conditions are strict, and the process parameters are difficult to control, which makes them difficult to industrialize and apply [28].
In order to raise the degree of hydration of wet-ground cement and decrease production costs, this paper prepared composite C-seeds according to cement/silica fume (C/S) ratios of 10:0, 8:2, 6:4, 4:6, 2:8 and 0:10, and these were applied to high-volume fly ash concrete. The physical and chemical properties of C-seeds with such different proportions were analyzed by XRD, SEM, TG and NMR, and the influences on the mechanical properties, hydration characteristics and microstructures of high-volume fly ash concrete were studied.

2. Materials and Methods

2.1. Raw Materials

The Portland cement (P.O. 42.5), fly ash (FA) and silica fume (SF) used in this paper were tested by X-ray fluorescence (XRF-1800ASF, SHIMADZU, Kyoto, Japan), and their chemical compositions are shown in Table 1.

2.2. Sample Preparation

2.2.1. Preparation of C-Seed

To prepare the composite C-seed, cement and SF were mixed in ratios of 10:0, 8:2, 6:4, 4:6, 2:8 and 0:10, and water was added to the mixture at ratio of 3:1. The mixture was stirred for 24 h, and wet grinding was applied for 120 min at 3000 r/min to obtain the composite C-seed suspension. The ratio of the composite C-seed suspension is shown in Table 2.

2.2.2. Preparation of Concrete

The content of the composite C-seed is 3% of the mass of cementitious materials in concrete, and the concrete mix proportion is shown in Table 3. Concrete specimens measuring 100 mm × 100 mm × 100 mm were prepared and cured according to the Chinese national standard GB/T 31387-2015 [29], and their compressive strength (CS) was tested. Each specimen was crushed into small pieces, immersed in anhydrous ethanol for approximately 3 h to terminate the hydration reaction, and dried for 24 h at 100 °C.

2.3. Test Methods

2.3.1. Composite C-S-H Seed Particle Size

A Malvern laser particle size analyzer (Zetasizer Nano ZSE, Malvern, Worcestershire, UK) was used to measure the particle distribution of C-seed samples with different C/S ratios. The samples were ultrasonically dispersed for 5 min in deionized water at 0.1 g/L of solution.

2.3.2. Compressive Strength (CS) Test

According to the GB/T 31387-2015 standard [29], a press machine (TYE-2000, Wuxi Jianyi, Wuxi, China) was used to test the 1 d and 28 d CS of concrete containing the C-seed agent. Three samples were measured in each group, and the results were averaged.

2.3.3. X-Ray Powder Diffraction (XRD) Analysis

Phase analysis of the C-seed samples and concrete samples was conducted via XRD (XRD-6100, SHIMADZU, Kyoto, Japan). Hydrates in composite seed sample powders with different C/S ratios and concrete powders containing the composite seed were analyzed; the angles of the patterns were selected in a range from 15° to 90°, with a scanning rate of 4°/min.

2.3.4. Scanning Electron Microscope (SEM) Analysis

The microscopic morphology of the samples was observed via SEM (SIGMA HD, Carl Zeiss, Oberkochen, Germany). Small amounts of composite seed sample powder with different C/S ratios and concrete samples mixed with a composite nucleation agent were fixed on conductive glue and sprayed with platinum; the operating voltage was 5 kV.

2.3.5. Thermal Gravimetric (TG) Analysis

A comprehensive thermal analyzer (STA449, NETZSCH, Selb, Germany) was used to obtain thermogravimetric diagrams, which were used to analyze concrete sample powders containing the C-seed agent with different C/S ratios. The heating rate was 10 °C/min, and the angles of the patterns were selected in a range from 50 °C to 800 °C.

2.3.6. Pore Structure Analysis BET (Brunauer–Emmett–Teller)

The pore structure of the samples was evaluated using an automated surface area and porosity analyzer (Autosorb-iQ, Quantachrome, Boynton Beach, FL, USA), adopting the BET method.

2.3.7. Nuclear Magnetic Resonance Spectroscopy (NMR) Analysis

Structural changes in the silicon–oxygen chains within the samples were analyzed using solid-state NMR (AVANCE III 400 WB, BRUKER, Billerica, MA, USA).

3. Results and Discussion

3.1. Composite C-Seed Particle Size Distribution

Figure 1 shows the grain size distribution of C-seed samples with different C/S ratios. The results show that the C-seed particle size ranges from 0.1 μm to 200 μm. When the average cement particle size is 16.5 μm, a C-seed particle size of less than 3.95 μm can be achieved after wet grinding, demonstrating that wet grinding can effectively improve the fineness of C-seed. The C-seed grain sizes gradually decrease as the C/S ratio decreases. This is because the D50 particle size of a C-seed prepared using cement is 3.95 μm, while the D50 particle size of SF is usually less than 1 μm. Adding SF can significantly increase the specific surface area of the C-seed, which helps the nuclei adsorb Ca2+, thereby improving its efficacy in promoting cement hydration.
SEM and TEM (Transmission Electron Microscope) images of the morphology of the composite C-seed are shown in Figure 2. A reduction in particle size can be observed in the figure. In addition, the wet-ground cement and SF underwent hydration reactions to varying degrees, generating a large quantity of C-seed particles. When the C/S ratio decreased and the SF ratio increased, the hydration capacity of the SF itself was poor, resulting in a decrease in the C-S-H generated via the hydration of the C-seed and a decrease in the degree of hydration.

3.2. XRD of Composite C-Seed

Figure 3 shows the XRD phase characteristic spectrum of the composite C-seed. After wet grinding, the cement and SF underwent hydration reactions to varying degrees, generating a large volume of C-seed and CH particles. The peaks of CH appeared at 18.3° and 34.3° at 2θ, and the peak of the C-S-H gel appeared at 28.6° at 2θ. In the XRD spectrum of the composite C-seed, as the C/S ratio decreases, the peak of C-S-H first increases and then decreases; however, the peak in CH decreases significantly. This shows that C-S-H and CH are produced as the cement undergoes wet grinding [18,30]. As the SF content increases, SF reacts with CH to produce C-S-H; however, as the C/S ratio decreases, the C-S-H generated begins to decrease, and unhydrated SF appears. This is consistent with the C-seed morphology observed in the SEM and TEM images.

3.3. Compressive Strength (CS)

Figure 4 shows the effect of a 3% composite C-seed on the 1 d and 28 d CS of concrete at different proportions. Compared with the Control, the 1 d CS of the test group is significantly improved, though it gradually decreases with a decrease in the C/S ratio of C-seed. The 1 d CS of the CS-1 sample increased from 9.0 MPa to 11.3 MPa, an increase of 25% compared with the Control. The CS of the CS-4 sample was the same as that of the Control, and the CSs of the other samples were all lower than the CS of the Control. The 28 d CS of the test group increased substantially with a decrease in the C/S ratio; the 28 d CS of the CS-6 sample increased from 35.2 MPa to 42.7 MPa, an increase of 21%. In the composite C-seed CS-6, the cement content is 0, and the composite C-seed is wet-ground silica fume. Related studies have reported that wet-ground silica fume, which is a nanomaterial, can be used as a nano-seed in concrete to induce cement hydration [31,32,33]. Although wet-ground silica fume has the advantage of a smaller particle size, its ability to promote the 1 d CS of concrete is weaker than that of the composite C-seed CS-1, indicating that the induction effect of the C-seed is better than that of wet-ground silica fume. The CS of concrete containing the composite C-seed is higher than that of the Control, which indicates that the composite C-seed has a good early promotion effect on CS [34]. Generally speaking, short-term strength agents usually decrease the long-term strength of concrete [35,36,37], but the long-term strength of concrete containing the composite C-seed is improved. The CS of concrete containing the composite C-seed is higher than that of the Control in both the early and late stages: the 1 d CS gradually decreases when the SF content in the composite C-seed increases, while the 28 d CS increases as the SF content in the composite C-seed increases. This is because, when the cement content in the composite C-seed is high, more C-seed particles are produced, and these help accelerate cement hydration [34]. With an increase in the SF content, the C-S-H in the composite C-seed decreases, and the induction of concrete hydration is decreased. However, at the same time, the grain size of the composite C-seed decreases, allowing it to better fill the pores of the concrete and improve the CS, thus improving the overall strength of the concrete. Wet-ground SF is also able to induce hydration and reacts with the CH in concrete to produce C-S-H gel [31,32,33], which improves the long-term strength of concrete. Therefore, the composite C-seed comprehensively affects the 1 d and 28 d CS of concrete through the hydration-inducing effect of the C-seed and the filling effect and secondary hydration effect of SF.

3.4. XRD of Concrete

Figure 5 shows the XRD spectra of concrete containing the composite C-seed at 1 d and 28 d. C-S-H gel and CH are usually considered the main hydration products of cement [38,39]. The stronger peaks for the C-S-H gel and CH indicate that more C-S-H gel and CH were produced during the hydration process. In this study, CH was mainly affected by (1) the hydration of the cement and (2) the secondary reaction between the fly ash and CH. As shown in the figure, after adding the 3% composite C-seed to the cement, the peak intensity of CH at 1 d is significantly enhanced, which indicates that the composite C-seed accelerated the hydration process [27]. The peak intensity of CH at 28 d was significantly weakened with the decrease in the C/S ratio, indicating that CH was consumed in the secondary reaction with FA. These results show that the composite C-seed promotes the short-term strength of high-volume fly ash concrete. The C-seed induces cement hydration, which can result in a large amount of CH being produced, and then reacts with the FA for secondary hydration, thereby improving the strength of the concrete in the short term [12,24]. Therefore, in the composite C-seed samples with different proportions, as the C/S ratio in the composite C-seed decreases, the content of C-seed in the composite C-seed decreases. This gradually decreases the hydration of the concrete at 1 d as the C-seed CS-6 prevents the CH from reacting with the FA by adsorbing CH, decreasing the amount of C-S-H produced and affecting the secondary hydration of FA [25], which subsequently affects the strength of the concrete. This result is consistent with the results of the mechanical properties test.
It can be seen from the SEM spectrum (Figure 6) that the hydration product of the Control at 1 d is mainly CH, which is an early feature of cement hydration. At this time, less C-S-H gel is generated by hydration. After adding composite C-seed, the C-S-H gel content begins to increase, indicating that the cement has undergone a hydration reaction with the composite C-seed. The morphology of the C-S-H gel is typically inferred from the Ca2+/Si4+ ratio. As the Ca2+/Si4+ ratio increases, the degree of polymerization of the silicon chains in the C-S-H molecules decreases, transforming the C-S-H gel’s morphology from sheet-like to networked and fibrous [38,39]. The Ca2+/Si4+ ratio of the Control at 1 d is 2.70 when the CS-2 is 1.85, indicating that the C-S-H gel is in a weakened stacking state. Meanwhile, CS-6’s Ca2+/Si4+ ratio of 0.31 signifies that the molecular structure of the C-S-H cannot maintain stability, suggesting that there are fewer hydration products in the concrete. The degree of hydration of cement is reflected in changes in its C-S-H gel and CH contents; the stronger the peaks of the C-S-H gel and CH, the greater the quantity of hydration products produced [40,41], which is consistent with the XRD test results.

3.5. TG Analysis of Concrete

Figure 7 clearly shows that the TG curve of cement can be divided into three stages [27]: mass loss at 50–200 °C, which is due to the loss of free water and water from the C-S-H gel and ettringite; mass loss at 400–500 °C, which is due to the decomposition of CH; and mass loss at 600–800 °C, which is due to the decomposition of CaCO3. As the main components of cement concrete are C-S-H, ettringite and CH, the mass loss of concrete at 50–200 °C and 400–500 °C was analyzed in detail. Due to the low hydration activity of fly ash, when fly ash replaces 14.2% of the cement, the hydration product in the concrete at 1 d is provided by the cement. Therefore, compared with the Control, the 1 d mass loss of concrete containing the composite C-seed agent is less than that of the Control. The 1 d loss of the sample after adding the composite C-seed increases with the decrease in C/S. It can be seen that the mass loss of CH is the largest in sample CS-1, and the mass loss of CH in sample CS-6 is the smallest. This shows that the nucleating agent CS-1 has the most obvious effect on promoting cement hydration and generates more CH in 1 d than the other C-seed agents. This indicates that the composite C-seed promotes the formation of C-S-H gel and CH in concrete, and the CS-1 sample produces more C-S-H gel and CH. The 28 d loss of the sample first increases with the decrease in C/S. Compared with the Control, the C-S-H content of the cement containing the composite C-seed increases, and the CH is greatly reduced. The above results are consistent with the XRD results shown in Figure 5 because the CH in the concrete is consumed by the secondary hydration reaction with the FA. The results show that the composite C-seed induces cement hydration, produces a large amount of CH and promotes the secondary hydration of FA, thus improving the CS of concrete with a large volume of FA [13,14]. In composite C-seed samples with different proportions, as the SF content in the composite C-seed increases, the C-seed content in the composite C-seed decreases, causing the concrete’s degree of hydration to gradually decrease at 1 d. At 28 d, the cement and FA are fully hydrated, the CH is consumed in large quantities and a large amount of C-S-H gel is produced.

3.6. Analysis of Concrete Pore Structure

The evolution of the pore distribution of the concrete samples is shown in Figure 8. It is generally believed that the pore structure of concrete is closely related to CS [42]. Generally, the pores in concrete include gel pores (<10 nm) and fine (10–50 nm), medium (50–100 nm) and large capillary pores (>100 nm) [43,44,45], among which pores with a diameter of less than 20 nm are considered harmless and pores with a diameter between 20 and 50 nm are considered less harmful. Pores larger than these are considered harmful [46]. As can be seen in Figure 8, after adding the composite C-seed, the pore structure of the concrete at 28 d is optimized, and the number of harmful pores larger than 50 nm is significantly reduced. Compared with the Control, the D50 of concrete containing the composite C-seed is reduced at 28 d; the range is gradually narrowed and its peak value is significantly increased. This is because the FA plays a filling and balling role in concrete, improving the ratio of harmless pores and transforming connected pores into closed pores [24,25,26]. At the same time, the small grain size of the composite C-seed allows it to fill the pores of the concrete, further reducing its porosity. The nucleation effect of the composite C-seed can accelerate cement hydration and produce large amounts of C-S-H gel and CH. CH further stimulates fly ash hydration to produce C-S-H gel, which fills the concrete and increases its density [27]. This shows that the composite C-seed improves the pore structure of concrete. After the addition of the composite C-seed, the D50 of the sample at 28 d decreases with the decrease in C/S. This shows that the composite C-seed promotes the formation of hydration products in cement, and the CS-1 sample forms more C-S-H gel and CH. Compared with the Control, the C-S-H content of cement containing the composite C-seed increases and the CH is greatly reduced, which is consistent with the results of the mechanical property test. The above results prove that the composite C-seed can change the pore structure of concrete, transforming harmful pores into harmless pores; reduce the size of the pores by filling them; and accelerate cement hydration via nucleation, generating C-S-H and making the concrete’s structure denser.
According to Figure 7b, the concrete sample with the composite C-seed agent loses less mass than the Control in the range of 600–800 °C at 28 d. This shows that there is less CaCO3 in the concrete containing the composite C-seed agent than in the Control. CO2 is the main cause of concrete carbonization, which generates CaCO3. The decrease in CaCO3 content shows that concrete can resist CO2 erosion. The above results show that the addition of the composite C-seed agent makes the concrete’s inner structure dense and contributes to its durability.

3.7. NMR Analysis of Concrete

The NMR spectra of composite C-seed concrete with different dosages of the C-seed agent were studied via 29Si NMR to analyze the effect of the C-Seed agent on cement hydration, and the results are shown in Figure 9. Qn represents local Si-O chemical bonding, where n represents the degree of aggregation with SiO4 tetrahedra. As shown in Figure 9, the Q0 is mostly concentrated at less than −85 ppm, indicating unhydrated cement. The Q2 and Q1 groups from −75 ppm to −85 ppm represent the C-S-H gel generated from the cement, and the occupied area in the fitted curve represents its proportion in the concrete, and thereby its degree of hydration. Q3 and Q4 are the main distribution peaks in the FA [11,47]. As shown in Figure 9,the Q0 peak of the C-seed concrete is lower than that of the Control, the area of which is reduced from 38.6% to 9.9%, indicating that the amount of unhydrated cement is reduced compared to the Control. The sum of the integrated areas of Q1 and Q2 for the 28 d sample is 64.2%, which is 12.2% higher than that of the Control. Meanwhile, it can be observed that the Q3 and Q4 peaks of the C-seed concrete are higher than that of the Control, indicating that the FA underwent the hydration reaction. The main chain length (MCL) of the C-S-H gel can be calculated based on 2(Q2 + Q1)/Q0. The longer the MCL, the greater the degree of C-S-H gel [11] polymerization; the MCL of the CS-6 sample is longer than that of the Control. These results show that the wet grinding approach is more conducive to the growth of C-S-H gel than the control method, a conclusion consistent with the results for compressive strength, XRD and TG.

4. Conclusions

The effect of wet-ground C-Seed with different C/S ratios on high-volume FA concrete was studied, with the aim of reducing the demand for cement and increasing the FA content in concrete without any adverse effects. Based on the above analysis, the main conclusions of this study are as follows:
  • The wet grinding process can be used to prepare composite nucleating agents from a mixture of cement and silica fume. The particle size of the composite C-seed agent can be decreased to less than 3.9 μm, indicating that wet grinding can effectively improve the fineness of the C-seed. With an increase in SF content, the particle size of the C-seed agent decreases to 0.66 μm. During wet grinding, C-S-H and CH are produced. As the SF content increases, SF reacts with CH to produce C-S-H, but as the C/S ratio decreases further, the content of C-S-H produced begins to decrease, and unhydrated SF appears. As there are few studies on wet grinding C-S-H seed and its key parameters, such as grain size and hydration degree, further research on this subject is necessary.
  • Adding a composite C-seed can improve the compressive strength of concrete in both the early (1 d) and late (28 d) stages; in this study, the resulting compressive strength was higher than that of the Control. However, the difference is that the short-term compressive strength at 1 d gradually decreases with the increase in SF content in the composite C-seed, while the compressive strength at 28 d increases with the increase in SF content in the composite C-seed.
  • The addition of a composite C-seed reduces the number of harmful pores in concrete, and the nucleation effect of the composite nucleating agents can accelerate cement hydration, producing large amounts of C-S-H and CH. CH further stimulates the hydration of fly ash to produce C-S-H, which fills the concrete and makes its structure denser. With this improvement in pore structure, the degree of carbonation in the concrete diminishes, showing that concrete can resist corrosion due to carbon dioxide. Therefore, conducting durability-related research on concrete containing C-seed with different C/S ratios is imperative.
  • XRD, NMR and TG test results show that the addition of a composite C-seed agent promotes the short-term strength of high-volume fly ash concrete. As the C-seed agent induces cement hydration, a large amount of CH is produced, which then undergoes a secondary hydration reaction with the fly ash, improving the short-term strength of the concrete. Therefore, as the C/S ratio in the composite C-seed decreases, the C-seed content in the composite C-seed decreases, resulting in a gradual decrease in the hydration of the concrete at 1 d and a reduction in CH production, which affects the secondary hydration of fly ash.

Author Contributions

Conceptualization, P.Z.; software, S.W.; investigation, S.W.; data curation, S.W. and J.L.; writing—original draft preparation, S.W.; writing—review and editing, P.Z. and J.L.; supervision, Y.T.; funding acquisition, P.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by the Fundamental Research Funds for The Central Universities, CHD (300102312405).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Buildings 15 00270 g001
Figure 1. Particle size distribution of composite seed.
Figure 1. Particle size distribution of composite seed.
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Figure 2. SEM and TEM images showing morphology of composite C-seed.
Figure 2. SEM and TEM images showing morphology of composite C-seed.
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Figure 3. XRD pattern of composite C-seed.
Figure 3. XRD pattern of composite C-seed.
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Figure 4. Compressive strength test results.
Figure 4. Compressive strength test results.
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Figure 5. XRD analysis of composite C-seed concrete.
Figure 5. XRD analysis of composite C-seed concrete.
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Figure 6. SEM and EDX images of composite C-seed concrete.
Figure 6. SEM and EDX images of composite C-seed concrete.
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Figure 7. TG of composite C-seed concrete.
Figure 7. TG of composite C-seed concrete.
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Figure 8. Pore diagram of composite C-seed concrete.
Figure 8. Pore diagram of composite C-seed concrete.
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Figure 9. NMR spectra of composite C-seed concrete.
Figure 9. NMR spectra of composite C-seed concrete.
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Table 1. XRF results (%).
Table 1. XRF results (%).
SampleSiO2Al2O3CaOFe2O3SO3MgOLoss
Cement22.814.5261.963.432.842.621.81
FA52.5225.329.534.591.531.390.51
SF90.301.113.075.010.110.730.04
Table 2. Composite C-S-H seed ratio (wt%).
Table 2. Composite C-S-H seed ratio (wt%).
SampleCS-1CS-2CS-3CS-4CS-5CS-6
Cement100806040200
SF020406080100
Table 3. Concrete mix ratio (kg/m3).
Table 3. Concrete mix ratio (kg/m3).
SampleCementFASandStoneWater
Control280908201020160
CS-12401308201020160
CS-22401308201020160
CS-32401308201020160
CS-42401308201020160
CS-52401308201020160
CS-62401308201020160
Note: It is important to maintain a consistent total water consumption while mixing the concrete as the C-seed agent contains water.
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MDPI and ACS Style

Wang, S.; Liu, J.; Tian, Y.; Zhao, P. Influence of Composite C-S-H Seed Prepared by Wet Grinding on High-Volume Fly Ash Concrete. Buildings 2025, 15, 270. https://doi.org/10.3390/buildings15020270

AMA Style

Wang S, Liu J, Tian Y, Zhao P. Influence of Composite C-S-H Seed Prepared by Wet Grinding on High-Volume Fly Ash Concrete. Buildings. 2025; 15(2):270. https://doi.org/10.3390/buildings15020270

Chicago/Turabian Style

Wang, Shiheng, Jianan Liu, Yaogang Tian, and Peng Zhao. 2025. "Influence of Composite C-S-H Seed Prepared by Wet Grinding on High-Volume Fly Ash Concrete" Buildings 15, no. 2: 270. https://doi.org/10.3390/buildings15020270

APA Style

Wang, S., Liu, J., Tian, Y., & Zhao, P. (2025). Influence of Composite C-S-H Seed Prepared by Wet Grinding on High-Volume Fly Ash Concrete. Buildings, 15(2), 270. https://doi.org/10.3390/buildings15020270

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