Next Article in Journal
Effects of Crushing and Grinding on the Porosity of Hardened Cement Paste
Next Article in Special Issue
The Influence of Composition Ratio on the Thermal Performance Parameters of Eutectic Phase Change Materials: Experimental Research and Theoretical Prediction
Previous Article in Journal
Research on 3D Visualization of Real Scene in Subway Engineering Based on 3D Model
Previous Article in Special Issue
Impact of Polypropylene Fiber on the Mechanical and Physical Properties of Pervious Concrete: An Experimental Investigation
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Buildings
Volume 13
Issue 9
10.3390/buildings13092318
buildings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Low-Field Nuclear Magnetic Resonance Investigation on Early Hydration Characterization of Cement Paste Mixed with Mineral Admixtures

by
Yu-Juan Tang
1,
Zi-Qi Shan
2,
Guang-Ji Yin
2,*,
Ling Miao
3,
Sai-Sai Wang
2 and
Zhen-Ya Zhang
2
1
School of Civil and Engineering, Yangzhou Polytechnic College, Yangzhou 225009, China
2
School of Civil and Transportation Engineering, Ningbo University of Technology, Ningbo 315211, China
3
College of Art and Design, Nanjing Forestry University, Nanjing 210037, China
*
Author to whom correspondence should be addressed.
Buildings 2023, 13(9), 2318; https://doi.org/10.3390/buildings13092318
Submission received: 23 August 2023 / Revised: 7 September 2023 / Accepted: 11 September 2023 / Published: 12 September 2023
(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)
Browse Figures
Versions Notes

Abstract

:
Mineral admixtures (MA), like fly ash (FA), silica fume (SF), and slag (S), are usually added to cement-based materials to improve their compactness and further enhance their mechanical properties, permeability resistance, and durability. In this study, low-field nuclear magnetic resonance (LF-NMR) is adopted to explore the evolution of the early hydration characterization of cement-based materials with MA by testing the transverse relaxation time T2. Meanwhile, the effect of MA on mechanical properties is analyzed by measuring compressive and flexural strength. The results show that, in the early hydration (0–7 days), the T2 distribution shows a trend of gradually moving to a short relaxation time and changes from a double peak to a single main peak. The decrease in T2i (main peak vertex) means that the evaporated water is gradually distributed in smaller pores with more motion constraints. However, the type and content of MA have little effect on T2i. Porosity gradually decreases in the period of early hydration. The addition of MA causes the porosity to decrease, and the order influence is FA > S > SF, i.e., the porosities of cement paste with 0%MA, 10%FA + 10%SF, 10%FA + 10%S, and 20%FA at 7 days are 48%, 44.5%, 40.7%, and 40.2%, respectively. Additionally, the addition of MA to cement-based materials also decreases the early strength, and the influence order is FA > S > SF, i.e., the compression strength values of cement paste with 0%MA, 10%FA + 10%SF, 10%FA + 10%S, and 20%FA at 7 days are 47.8 MPa, 40.1 MPa, 38.6 MPa, and 37 MPa, respectively.

1. Introduction

Concrete is one of the most widely used building materials in the world today. Its transition from a plastic flow state to a hardened brittle state is mainly attributed to the cement hydration reaction [1]. When the cement is mixed with water, it undergoes vigorous hydration reactions to produce C-S-H gel (semi-crystalline and amorphous hydrated calcium silicate, the detailed description of which can be found in references [2,3]), CH crystals (hexagonal crystal system), and other hydration products. As the hydration products increase, the gel particles agglomerate into a network structure, causing the cement paste to thicken and gradually lose its plasticity, i.e., setting behavior. Subsequently, the hydration products continue to fill the space between cement particles, causing the paste to gradually densify and harden [4], i.e., hardening behavior. At this stage, the mechanical property of cement paste develops rapidly. In summary, during the process of cement hydration, the cement paste undergoes a drastic evolution of microphase, morphology and pore structure, ultimately hardening into a heterogeneous porous material. Therefore, the hydration behavior of cement plays a crucial role in the flowability, mechanical properties, and durability of cement-based materials [5].
For ordinary Portland cement, the main reason for its long-term service performance is the presence of the surface defects of the hardened matrix and its non-dense internal structure. The addition of MAs, such as fly ash (FA) [6], slag (S) [7], and silica fume (SF) [8], to cement-based materials can improve their various performances. Due to the low pozzolanic effect of FA, the reaction rate between FA and CH of cement hydration products is very slow within 7 days of hydration [9]. It reduces the hydration process of the FA-C (cement) system, resulting in low early mechanical properties [10]. With the excitation of the pozzolanic effect, the mechanical properties of the FA-C system are gradually improved. Generally speaking, after 90 days of hydration, the reaction of FA with CH has not yet ended. In addition, FA also has morphological and microaggregate effects, which can improve the workability of the FA-C system [11]. Small particles of FA (with an average particle size of 15–20 mm) can effectively fill the pores between hydration products, improving the structural density of cement-based materials [12]. For the silica fume (SF), the content of active SiO2 is high (>80%). When SF is added to cement, it can react earlier with CH formed by the cement hydration to generate C-S-H gel, i.e., giving better play to the pozzolanic effect [13,14]. Meanwhile, microparticles of SF (with a particle size of about 100 nm) can effectively fill the large pores in the interfacial transition zone between cement paste and aggregate [14]. It improves the structural density of the SF-C system and causes its early compressive strength. Similar to FA, slag (S) also has the pozzolanic and microaggregate effect [5]. So, the influence of its addition to cement on the hydration progress, pore structure, and early strength of the S-C system is also similar to that of FA. In summary, MAs can significantly improve the microstructure of cement-based materials, further increase their later mechanical properties (28 days) and permeability resistance, and significantly inhibit the alkali–aggregate reaction [15,16]. In response to the problems of low early strength and shrinkage cracking, the main method is to mix multiple MAs into cement. At present, the research on the effect of multiple MA addition is very rich, i.e., the synergistic effect of FA and ground granulated blast furnace slag (GGBFS) [17,18], FA and ferrochrome slag [19], F-class FA and nano-SF [20,21], FA, palm oil fuel ash and GBFS [22], SF and metakaolin [23], SF and GGBFS [24], SF and rice husk ash [25,26], SF and glass powder [27], and SF and ferrosilicon [28] on the microstructure and mechanical properties like strength and shrinkage of cement-based materials. By superimposing the regulating effects of MAs on the behavior of cement hydration, the overall performance of cement-based materials can be improved.
The traditional testing methods for cement hydration behavior mainly include the isothermal calorimetry method [29,30], the chemically bound water method [31], and the CH quantitative analysis method [32]. Based on the heat release curve measured by isothermal calorimetry, the process of cement hydration is divided into five stages, i.e., the dissolution, induction, acceleration, deceleration, and stabilization stages. However, Scrivener [33] divided the hydration process into three stages, including the stage before induction end, the main hydration front stage, and the slow reaction stage. According to the measured data of hydration heat, the basic parameters in the model of cement hydration reaction kinetics (such as the Krstulović–Dabić model [34]) can be determined. So, a kinetics equation of hydration degree related to reaction time can be established. However, the isothermal calorimetry is not suitable for analyzing the hydration behavior of cement-based materials with MAs [35,36], because their influence on the cement hydration heat has not been quantified. The chemically bound water method is a method of determining the content of chemically bound water in cement hydration products by the calcination form, to deduce its hydration degree. However, for cement-based composite systems, this method cannot distinguish whether the bound water comes from the hydration of cement or MAs. In summary, traditional testing methods have effectively revealed the process of cement hydration but cannot quantify the impact of MA on the cement hydration. With the development of non-destructive testing technology, methods such as electrodeless resistivity testing [37], dielectric constant testing, and ultrasonic velocity testing [38,39] have been applied to the analysis of the hydration behavior of cement-MA system hydration. Electrical resistivity can reflect the porosity evolution of cement paste in the process of setting and hardening. Li et al. [40] combined electrodeless resistivity and ultrasonic velocity testing to analyze the cement hydration behavior, proving that both methods are effective for continuous monitoring.
The hydration reaction of cement is often accompanied by the transition behavior of the water state in addition to the heat release and the microstructural changes in cement paste. During the hydration process, free water gradually transforms into chemically bound water, physically adsorbed water, and pore water [41], resulting in volume shrinkage, micropore formation, and strength increase in concrete. In recent years, the relaxation method of nuclear magnetic resonance (NMR) has been increasingly developed and applied to analyze the changes in water state caused by cement hydration reactions [42,43]. In the relaxation method, the spin–lattice relaxation time T1 and spin relaxation time T2 are mainly used to describe the response of 1H nucleus spin magnetization to resonance excitation. Compared to T1, the signal value of T2 decreases as the mobility of water molecules decreases (the movement of water molecules is limited by their space) [44], which can better characterize the different states of water [45]. Using the one-dimensional frequency coding technology of low-field (LF) NMR, Zhao et al. [46] analyzed the transport behavior of liquid water in cement-based materials with different mix proportions (water–cement ratio, sand–cement ratio, silica fume content, etc.). Zhang et al. [47] continuously tested the transverse relaxation time T2 in the hydration process of white cement with SiO2 nanoparticles to analyze the influence of SiO2 particle size on the hydration reaction, and then determined the setting time. According to the relaxation time T2, Liu et al. [48] divided the hydration behavior into the heating, thermostatic, and colling processes and established a mathematical model for the relation between T2 and the hydration degree. It should be pointed out that most of the NMR studies [46,47,48,49] used white cement with a low content of Fe2O3 as the material to reduce the impact of iron on the NMR signal. However, recent reports [50,51] have adopted ordinary Portland cement as the research material, and the results in [51] explain well the relationship between pore structure and capillary water in cement-based materials.
In a word, besides the isothermal calorimetry method, the relaxation method of nuclear magnetic resonance (NMR) is also an effective method to analyze the hydration of cement paste. The transverse relaxation time T2 can reflect the motility of water molecules constrained by their space, i.e., the pore structure for cement-based materials. In this paper, LF-NMR is adopted to measure the T2 signal of cement-based materials with FA, SF, and S. According to the relationship between T2 (its value, area, and peak signal) and water motility, the effect of MA type and content on the early hydration characterization (pore structure, water state) can be further analyzed, especially during the first 24 h of hydration. Meanwhile, the compressive and flexural strength of cement paste with different MA is tested at the early hydration stage. On this basis, the collaborative analysis of the evolution of pore structure and the development of mechanical properties can help to better understand the regulatory effect of composite admixtures.

2. Testing Principle

Based on Brownstein–Tarr’s model (BT model) [52], the transverse relaxation time T2 of moisture in cement-based materials can be expressed as
1 T 2 = 1 T 2 S + 1 T 2 D + 1 T 2 B ,   1 T 2 S = ρ 2 S V ,   1 T 2 D = D w 12 γ G T E 2
where T2S is the particle surface relaxation time, T2D is the molecular diffusion relaxation time, T2B is the water-free relaxation time, ρ 2 is the transverse surface relaxation strength, S and V are the specific surface area and volume of pores, Dw is the diffusion coefficient of water molecules, G is the gradient of the external magnetic field, and TE is the echo time.
Due to the value of T2B being approximately 2–3 s, which is much greater than the transverse relaxation time T2 [45], T2B in Equation (1) can be ignored. For a uniform external magnetic field, its gradient G is extremely small and the echo interval is short, and T2D in Equation (1) can also be ignored. Therefore, the T2 is mainly determined by the surface relaxation time of particles [53], which can be simplified as
1 T 2 ≈ 1 T 2 S = ρ 2 S V
in which S/V is equal to 3/r for spherical pores and 2/r for columnar pores, and r is the pore radius.
At present, T2 is mainly measured by using the CPMG (Carr–Purcell–Meiboom–Gill) pulse sequence [54,55], as shown in Figure 1. Firstly, a 90° pulse is applied to deflect the magnetization vector to the x-y plane. Due to the non-uniformity of the applied magnetic field, the transverse components of the magnetization vector undergo phase dispersion. After the TE/2 time, a 180° pulse is applied to reunite the phase-dispersed transverse components, and then an echo can be observed after the TE time (the end of the 180° pulse). So, if a series of 180° pulses are continuously applied at intervals of TE time, an echo string with continuous attenuation of signal amplitude can be obtained, and the envelope curve of this series of signal peaks represents a relaxation signal. By repeating the above testing process m times, the accumulated total relaxation signal can be obtained, and the attenuation law of signal amplitude meets Equation (3). Using InvFit inversion software, the total relaxation signal is processed to obtain the T2 spectrum of moisture in porous cement-based materials.
M t = ∑ m M h 0 exp − t T 2
where TE is the echo time, and m is the repeated times.

3. Experiment

3.1. Materials

The cement used in this study was 42.5-grade P·I cement, whose chemical composition is listed in Table 1, with a density of 3120 kg/m3 and a specific surface area of 358 m2/kg. The initial and final setting times are 115 min and 188 min, respectively, and its normal compression strength and flexural strength for 28 days of curing are 51.2 MPa and 8.8 MPa, respectively. Fly ash and slag are produced by China Longze Materials Co., Ltd., (Yang Zhou City, China) and their basic properties and chemical compositions are shown in Table 2 and Table 3, respectively.
The mixed cement paste with a water–cement ratio of 0.4 was injected into the chromatographic bottles, slightly vibrated to eliminate air, and then sealed to prevent free water from evaporating, as shown in Figure 2. The mix proportion of cement paste is according to the “Specification for mix proportion design of ordinary concrete” (JGJ55-2011), as shown in Table 4. At room temperature, an NMR instrument was used to regularly measure the T2 spectrum in the process of cement hydration.

3.2. Measure Method

In cement-based materials, evaporable water can be divided into free water, physically adsorbed water, and chemically bound water, according to the motility of water molecules [56]. In the process of cement hydration, the original water space is gradually filled with cement-hydrated products, while the unfilled water space forms capillary pores, and the water present in capillary pores is called free water. In the space filled by hydration products, the pores between hydration products are called transition pores, the pores between hydration products C-S-H gel particles are called gel pores, and the water in them is mainly physically adsorbed water. The chemically bound water refers to the water combined with C-S-H gel by hydration reaction, which cannot be evaporated. In summary, during the hydration process, the water changes from a free state to physically adsorbed and chemically bound state, with some remaining in the form of free water.
Based on the correlation between moisture state and hydration kinetics [57], this study analyzes the cement hydration characterization by testing the T2 signals of 1H nuclei in samples of cement-based materials. The LF-NMR experiments were performed using a MesoMR12-060H-1 NMR analysis and imaging system (Suzhou Niumag Analytical Instrument Corporation, Suzhou, China). The permanent magnet magnetic field strength is 0.5 T, the proton resonance frequency is 23 MHz, and the magnet is controlled at a constant temperature of 32 °C. Adjusting the instrument system parameters before the testing, the cement paste samples with different mix proportions were inserted into the instrument probe coil and measured by adopting the CPMG pulse sequence [54]. Its pulse widths of 90° and 180° pulses are 7.40 μs and 14.24 μs, respectively, the echo time is 100 μs, the echo number is 2000, and the accumulative frequency (m) is 32. The specific testing process is shown in Figure 3.

4. Result and Discussion

4.1. Distribution of Relaxation Time

Figure 4 shows the transverse relaxation time (T2) of cement paste with different mix proportions at different curing times. The results show that, at the same curing time, the distribution of T2 is similar for each mix proportion and presents an obvious main peak and a weak peak (or no weak peak). With the increase in curing time, the relaxation peak signal corresponding to large T2 gradually decreases, while the peak signal corresponding to small T2 gradually increases. The distribution of the relaxation peak shows a trend of gradually moving to a short relaxation time and gradually changing from a double peak to a single main peak [48]. In particular, the T2 distribution of JJ-7 becomes a single peak at the curing time of 9 h, while those of other samples are still two peaks.
According to the NMR principle, T2i (T2 corresponding to the main peak vertex) reflects the motion characteristics of water molecules [58]. For the liquid water, the stronger its motion ability and the less its motion constraints, the larger its T2i. Figure 5 presents the change in T2i for different cement paste with curing time. It is obvious that T2i has a rapid decrease at the early hydration age (within 24 h) and then gradually stabilizes. The main reason for the above phenomena is that the relaxation time of confined fluid water in a porous medium is inversely proportional to the specific surface area of its pore [59]. In the curing process, the hydration products continuously generate to fill and refine the larger pores [15,60], causing the unreacted evaporated water to be gradually distributed in smaller pores with more motion constraints. So, the T2i becomes small. In addition, the T2i of JJ-1 (without MA) is larger than that of other samples. For the same curing time, the T2i of cement paste with different MAs are basically the same. It means that the cement content has a slight influence on T2i [61], while the type and content of MAs have little effect.
Besides the decrease in relaxation time, the change in relaxation signal for different samples can also be obtained from Figure 4. Especially at the curing age of 10 min, the relaxation signal of the main peak vertex for JJ-1 is 1370.17, while that for JJ-3 (replacing 40% cement with FA) is 675.53. The signal difference between the two is almost 100%. At the curing age of 24 h, the vertex relaxation signals for JJ-1, JJ-3, and JJ-5 are 778.85, 592.59, and 558.00, respectively, and there is not much difference between them. So, the influence of MAs on the relaxation signal of the specimen is mainly reflected in the early stage of cement hydration.
The relaxation signal area is proportional to the number of 1H protons in the samples, and the larger the signal area, the more water content the specimen contains [62]. Figure 6 presents the effect of MAs on the relaxation signal area of T2 in the hydration time. It can be seen from this figure that the signal area shows a downward trend with the increase in hydration time. The decline rate is fast at the early stage, while the decline rate slows down later. Due to the same type and proportion of water and cement in samples, the smaller the signal area, the more water is consumed in the hydration reaction. It can be known from Figure 6a that the addition of FA accelerates the hydration behavior of cement, and the greater the FA content, the faster the cement hydration. It is because the low-activity FA rarely undergoes hydration reactions during short-term curing, so the addition of FA improves the effective water–cement ratio, accelerating the cement hydration. Certainly, this phenomenon does not contradict the fact that the addition of FA slows down the hydration progress of the FA-C system. Figure 6b,c show that replacing FA with S or SF slows down the hydration rate of the FA-S-C or FA-SF-C system. The reason is that the S and SF have certain activity and undergo hydration reactions in an alkaline environment formed by cement hydration [63,64].

4.2. Evolution of Evaporable Water

As described above, the distribution of T2 reflects the motion constraints of liquid water and its content. Because the motion constraints of water in cement-based materials are related to the pore structure, the distribution of T2 also can be used to describe the pore size and distribution status, as in Equation (2). Li et al. [65] divided the pore formation in hardened cement slurry into four types, including C-S-H interlayer pore, C-S-H gel pore, and small and big capillary pore (between hydration products), and their corresponding values to T2 are 0.08–0.12 ms, 0.2–0.5 ms, 0.8–1.0 ms, and >10 ms, respectively. Similarly, Scrivener et al. [66] divided the pores corresponding to the three peaks of T2 distribution into C-S-H interlayer pore, C-S-H gel pore, and capillary pores, and the T2 times were 0.08–0.12 ms, 0.25–0.5 ms, and >1.0 ms, respectively. Gorce et al. [67] classified pores into gel pores and capillary pores according to T2 distribution and selected T 2 = 1.0 ms as the critical criterion for the two types of pores. In this study, the T2 distribution at the initial hydration stage of 10 m in Figure 4a shows obvious double peaks on both sides of T 2 = 1.0 ms . Combining the above literature research with the results of this study, 1.0 ms is used as the critical T2 to distinguish gel pores and capillary pores [68], and the water in the two types of pores is divided into gel water and capillary water. Therefore, the proportions of the relaxation signal area of T 2 < 1.0 ms and T 2 ≥ 1.0 ms represent the relative content of gel water and capillary water in the sample, respectively.
Figure 7 presents the evolution of the relative content of gel water and capillary water in the samples with different mix proportions in the curing period. With the increase in curing time, the proportion of gel water has an obvious improvement, and it can reach at least 85% for different contents of the mineral mixture. Meanwhile, the proportion of capillary water gradually decreases to below 15%. At the beginning of hydration (10 min), the evaporable water mainly exists in the form of capillary water. The generation of hydration products and their filling in of large pores leads to pore refinement [15]. So, the evaporable water is gradually distributed in the smaller pores and becomes gel water. Comparing JJ-1, JJ-2, and JJ-3, the proportion of gel water decreases with the increase in FA content at the curing time of 7 days, which means that the addition of FA with a low pozzolanic effect slows down the hydration progress of the FA-C system [9]. Comparing JJ-2, JJ-4, and JJ-6 or JJ-3, JJ-5, and JJ-7, the addition of S and SF also improves the content of gel water, and the order of their influence is SF > S > FA. The reason for this phenomenon is that the activity of SF and S is better than that of FA, and the extremely fine-grained SF (the average particle size is smaller than 0.1 mm) has a better effect on refining pores [13,14].

4.3. Distribution of Pore Structures

Pore structures in cement-based materials can be characterized by converting the T2 spectral distribution, and the results are displayed in Figure 8. Based on pore classification, these materials contain four types of pores: gel pores (<10 nm), transition pores (10–100 nm), capillary pores (100–1000 nm), and macropores (>1000 nm). It can be seen from Figure 8a that, at the curing time of 10 min, the main pores in samples are capillary pores, and a few are gel pores. With the increase in curing time, the pore size gradually decreases, leading to the increase in gel pores and transition pores, and the decrease in capillary pores. At the curing time of 7 days, the main pores are gel pores and transition pores, and the proportion of the two types of pores is basically equivalent.
Meanwhile, the average porosity of samples with different MAs can be obtained from the distribution of pore size, as presented in Figure 9. It is obvious that the porosity of cement paste gradually decreases with the increase in curing time, and within 10 min–7 days, the porosity is always high. Comparing JJ-1, JJ-2, and JJ-3, the porosity decreases with the increase in FA content in early hydration. Comparing JJ-2, JJ-4, and JJ-6 or JJ-3, JJ-5, and JJ-7, the addition of S and SF in the FA-C system causes an increase in porosity. The reason for the above phenomenon is that, at the curing time of 10 min, the pores are mainly capillary pores. So, the microaggregate effect of FA is the main reason for low porosity [55]. At the curing time of 7 days, the pores are mainly small pores formed in C-S-H gel and generated between gels. The more C-S-H gel, the greater the porosity [69]. So, the porosity of the SF-FA-C system is larger than that of the S-FA-C system, because SF contains higher SiO2 content to form C-S-H gel. The porosity of the S-FA-C system is larger than that of the FA-C system, because the low-activity FA basically does not produce C-S-H gel at the early hydration [70].

4.4. Evolution of Mechanical Property

Besides the evolution of pore structures, the development of early mechanical properties of cement-based materials is also closely related to their hydration progress. Figure 10 presents the evolution of compression strength and flexural strength of cement-based materials with curing time. Comparing Figure 10a,b, for the different samples, the evolution of their compression strengths with curing time is similar to that of flexural strength. Taking compressive strength as an example, it increases with curing time due to the setting and hardening of cement hydration products. At the curing time of 7 days, the compression strength of JJ-1 without any MAs is 47.8 MPa, while that of JJ-2 (with 20% FA) and JJ-3 (with 40% FA) are 37.5 MPa and 23 MPa, respectively. It is caused by the slow reaction rate of FA with low activity. Comparing JJ-2, JJ-4 (with 10% FA and 10% S), and JJ-6 (with 10% FA and 10% SF), their compression strengths are 36.8 MPa, 38.2 MPa, and 40.1 MPa at the curing time of 7 days, and all of them are smaller than that of JJ-1. That is to say, the addition of MAs leads to a decrease in the mechanical properties of cement-based materials at early hydration. Meanwhile, the ranking of minerals’ contribution to the early strength of cement-based materials is SF > S > FA. The reason for the above phenomenon is that SF has better activity and can generate denser C-S-H gel [13,14] more quickly, which is helpful for early mechanical properties. However, FA with a low pozzolanic effect hardly contributes to the mechanical properties of cement-based materials within 7 days of hydration [9]. Furthermore, the substitution of FA for cement results in the generation of C-S-H gel and CH, causing the reduction of mechanical properties. Comparing the samples with 40% MAs (JJ-3, JJ-5, and JJ-7) and those with 20% MAs (JJ-2, JJ-3, and JJ-6), the evolution of their compression strengths also verified the above viewpoint that the greater the MA content, the lower the early strength. Specifically, the activity of MA is lower than that of cement, so the addition (substitution) of more MA leads to fewer hydration products in a solidified state in the early stage of hydration to contribute to the early strength. In addition, the evolution of the compressive strength of cement-based materials with MA is presented in Figure 11. It is consistent with that of porosity at the early hydration stage, and the two are basically in a linear relationship.

5. Conclusions

(1)
At the beginning of hydration (10 min), T2 distribution presents double peaks (an obvious main peak and a weak peak), and the relaxation time of the main peak is about 1~10 ms. With the curing time, the distribution of the relaxation peak shows a trend of gradually changing to a single main peak. At the curing time of 24 h, the relaxation time of the single main peak is about 0.1~1 ms.
(2)
T2i (relaxation time of the main peak) reflects the motion characteristics of water molecules. At the early hydration stage (within 24 h), T2i has a rapid decrease and then gradually stabilizes. It is because the formation of hydration products refines larger pores, causing the evaporated water to be distributed in smaller pores with more motion constraints. However, the difference in T2i of different mix proportions is not significant, indicating that the type and content of MA have little effect.
(3)
The relaxation signal area reflects the content of unreacted evaporated water in samples, including the gel water and capillary water. So, the results of the relaxation signal area evolution show that the total content of water consumed by the hydration reaction decreases, and the proportion of gel water obviously increases, while that of capillary water gradually decreases. For MAs, the gel water content decreases with the increase in FA content, and the addition of S and SF also improves the gel water content, and the order of their influence is SF > S > FA.
(4)
At a curing time of 10 mins, the main pores are capillary pores. With the curing time, the pore size also gradually decreases, leading to an increase in gel pores and transition pores. At 7 days, the main pores are gel pores. Meanwhile, the porosity also decreases with curing time, i.e., without MA, it decreases from 64.8% at 10 mins to 48% at 7 days. With the effect of MA, the porosity of the FA-C (cement) system decreases with the increase in FA content. The addition of S and SF in the FA-C system causes the porosity to increase, and the order of their porosity is SF-FA-C system > S-FA-C system > FA-C system.
(5)
The ranking of the MA contribution to the early strength is SF > S > FA, but significantly lower than cement itself, i.e., the compression strength at the curing time of 7 days is 47.8 MPa for 0%MA, 40.1 MPa for 10%FA + 10%SF, 38.6 MPa for 10%FA + 10%S, and 37 MPa for 20%FA. It indicates that adding multiple types of MA is an effective method to improve early strength while ensuring other performance.

Author Contributions

Conceptualization, G.-J.Y.; methodology, L.M.; software, Z.-Q.S.; formal analysis, Z.-Y.Z.; investigation, S.-S.W.; resources, Y.-J.T.; writing—original draft preparation, Y.-J.T.; writing—review and editing, G.-J.Y.; funding acquisition, G.-J.Y. and Y.-J.T. All authors have read and agreed to the published version of the manuscript.

Funding

This study is supported by the Natural Science Foundation of China (52308262), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (20KJB430030), the “Chunhui Plan” collaborative research project of the Ministry of Education (HZKY20220199), the Zhejiang Provincial Natural Science Foundation of China (LQ21E080008), the Ningbo Natural Science Foundation (2023J176), the Qing Lan Project, the Yangzhou “Lv-yang-jin-feng” project, and the Scientific Research Start-up Foundation of Ningbo University of Technology in 2020.

Data Availability Statement

We can provide all research data through email as long as the authors required it.

Acknowledgments

Thanks to Cheng Shanshan for her guidance in analyzing the results.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Scrivener, K.L.; Juilland, P.; Monteiro, P.J. Advances in understanding hydration of Portland cement. Cem. Concr. Res. 2015, 78, 38–56. [Google Scholar] [CrossRef]
  2. Izadifar, M.; Natzeck, C.; Emmerich, K.; Weidler, P.G.; Gohari, S.; Burvill, C.; Thissen, P. Unexpected Chemical Activity of a Mineral Surface: The Role of Crystal Water in Tobermorite. J. Phys. Chem. 2022, 126, 12405–12412. [Google Scholar] [CrossRef]
  3. Izadifar, M.; Königer, F.; Gerdes, A.; Woll, C.; Thissen, P. Correlation between composition and mechanical properties of calcium-silicate-hydrates identified by infrared spectroscopy and density functional theory. J. Phys. Chem. 2019, 123, 10868–10873. [Google Scholar] [CrossRef]
  4. Scrivener, K.L.; Nonat, A. Hydration of cementitious materials, present and future. Cem. Concr. Res. 2011, 41, 651–665. [Google Scholar] [CrossRef]
  5. She, A.M.; Ma, K.; Wang, Z.P.; Yao, W. Characterization of hardened cement paste pore structure by low field NMR cryoporometry. J. Build. Mater. 2021, 24, 916–920. [Google Scholar]
  6. Sun, Y.; Wang, Z.H.; Park, D.J.; Kim, W.S.; Kim, H.S.; Yan, S.R.; Lee, H.S. Analysis of the isothermal hydration heat of cement paste containing mechanically activated fly ash. Thermochim. Acta 2022, 715, 179273. [Google Scholar] [CrossRef]
  7. Nedunuri, S.S.S.A.; Sertse, S.G.; Muhammad, S. Microstructural study of Portland cement partially replaced with fly ash, ground granulated blast furnace slag and silica fume as determined by pozzolanic activity. Constr. Build. Mater. 2020, 238, 117561. [Google Scholar] [CrossRef]
  8. Kooshafar, M.; Madani, H. An investigation on the influence of nano silica morphology on the characteristics of cement composites. J. Build. Eng. 2020, 30, 101293. [Google Scholar] [CrossRef]
  9. Zeng, Q.; Li, K. Reaction and microstructure of cement-fly-ash system. Mater. Struct. 2015, 48, 1703–1716. [Google Scholar] [CrossRef]
  10. Sun, Y.; Lee, H.S. Using ensemble model to predict isothermal hydration heat of fly ash cement paste considering fly ash content, water to binder ratio and curing temperature. Case Stud. Constr. Mater. 2023, 18, e01984. [Google Scholar] [CrossRef]
  11. Giergiczny, Z. Fly ash and slag. Cem. Concr. Res. 2019, 124, 105826. [Google Scholar] [CrossRef]
  12. Naik, T.R.; Singh, S.S.; Hossain, M.M. Permeability of concrete containing large amounts of fly ash. Cem. Concr. Res. 1994, 24, 913–922. [Google Scholar] [CrossRef]
  13. Cai, Y.M.; Hou, P.K.; Cheng, X.; Du, P.; Ye, Z.M. The effect of nanoSiO2 on the properties of fresh and hardened cement-based materials through its dispersion with silica fume. Constr. Build. Mater. 2017, 148, 770–780. [Google Scholar] [CrossRef]
  14. Nguyen, V.T.; Lee, S.Y.; Chung, S.Y.; Moon, J.H.; Kim, D.J. Use of multiphase voxels to simulate the effects of nano-silica on cement hydration. Case Stud. Constr. Mater. 2023, 18, e01909. [Google Scholar] [CrossRef]
  15. Qu, L.; Song, W.H.; Wang, Q.; Xu, S.S.; Hou, C. Effects of hydrophobic modified fly ash on resistance of chloride corrosion and water penetration of cement mortar in the early hydration stage. J. Build. Eng. 2023, 64, 105573. [Google Scholar] [CrossRef]
  16. Wang, H.; Wu, D.; Mei, Z. Effect of fly ash and limestone powder on inhibiting alkali aggregate reaction of concrete. Constr. Build. Mater. 2019, 210, 620–626. [Google Scholar] [CrossRef]
  17. He, P.P.; Drissi, S.; Hu, X.; Liu, J.H.; Shi, C.J. Investigation on the influential mechanism of FA and GGBS on the properties of CO2-cured cement paste. Cem. Concr. Compos. 2023, 142, 105186. [Google Scholar] [CrossRef]
  18. Liu, Z.; Takasu, K.; Koyamad, H.; Suyama, H. A study on engineering properties and environmental impact of sustainable concrete with fly ash or GGBS. Constr. Build. Mater. 2022, 316, 125776. [Google Scholar] [CrossRef]
  19. Das, P.; Chakraborty, S.; Dubey, B.; Barai, S.V.; Cheela, V.R.S.; Mistri, A. Performance assessment and life cycle analysis of concrete containing ferrochrome slag and fly ash as replacement materials—A circular approach. Constr. Build. Mater. 2022, 347, 128609. [Google Scholar] [CrossRef]
  20. Nguyen, V.M.; Phung, T.B.; Pham, D.T.; Ho, L.S. Mechanical properties and durability of concrete containing coal mine waste rock, F-class fly ash, and nano-silica for sustainable development. J. Eng. Res. 2023, in press. [Google Scholar] [CrossRef]
  21. Kumar, M.H.; Saikrishnamacharyulu, I.; Mohanta, N.R.; Ashutosh, A.; Mishra, P.; Smantaray, S. Mechanical behaviour of high strength concrete modified with triple blend of fly ash, silica fume and steel fibers. Mater. Today Proc. 2022, 65, 933–942. [Google Scholar] [CrossRef]
  22. Huseien, G.F.; Khamehchi, M.; Kubba, Z.; Benjeddou, O.; Mahmoodi, M.J. Freeze-thaw cycle and abrasion resistance of alkali-activated FA and POFA-based mortars: Role of high volume GBFS incorporation. Heliyon 2023, 9, e17672. [Google Scholar] [CrossRef] [PubMed]
  23. Hasan, M.F.; Hassan, M.A.; Lateef, K.H. Effect of MK and SF on the concrete mechanical properties. Mater. Today Proc. 2021, 42, 2914–2919. [Google Scholar] [CrossRef]
  24. Shamass, R.; Rispoli, O.; Limbachiya, V.; Kovacs, R. Mechanical and GWP assessment of concrete using Blast Furnace Slag, Silica Fume and recycled aggregate. Case Stud. Constr. Mater. 2023, 18, e02164. [Google Scholar] [CrossRef]
  25. Sahoo, S.; Parhi, P.K.; Panda, B.C. Durability properties of concrete with silica fume and rice husk ash. Clean. Eng. Technol. 2021, 2, 100067. [Google Scholar] [CrossRef]
  26. Amin, M.N.; Rehman, K.U.; Shahzada, K.; Khan, K.; Wahab, N.; Alabdullah, A.A. Mechanical and microstructure performance and global warming potential of blended concrete containing rice husk ash and silica fume. Constr. Build. Mater. 2022, 346, 128470. [Google Scholar] [CrossRef]
  27. Paithankar, D.; Sharma, A.; Thenmozhi, S.; Ramteke, P.; Dhanalakshmi, A.; Sivakumar, S. Influence of glass powder silica fume and scrapped ceramic waste on the mechanical properties of concrete. Mater. Today Proc. 2023, in press. [Google Scholar] [CrossRef]
  28. Amin, M.; Zeyad, A.M.; Tayeh, B.A.; Agwa, I.S. Effect of ferrosilicon and silica fume on mechanical, durability, and microstructure characteristics of ultra high-performance concrete. Constr. Build. Mater. 2022, 320, 126233. [Google Scholar] [CrossRef]
  29. Linderoth, O.; Wadsö, L.; Jansen, D. Long-term cement-hydration studies with isothermal calorimetry. Cem. Concr. Res. 2021, 141, 106344. [Google Scholar] [CrossRef]
  30. Han, F.; Zhang, Z.; Wang, D.; Yan, P. Hydration heat evolution and kinetics of blended cement containing steel slag at different temperatures. Thermochim. Acta 2015, 605, 43–51. [Google Scholar] [CrossRef]
  31. Garcia, E. Nonevaporable water from neat OPC and replacement materials in composite cement hydrated at different temperatures. Cem. Concr. Res. 2003, 33, 1883–1888. [Google Scholar] [CrossRef]
  32. Chu, D.C.; Kleib, J.; Amar, M.; Benzerzour, M.; Abriak, N. Determination of the degree of hydration of Portland cement using three different approaches: Scanning electron microscopy (SEM-BSE) and Thermogravimetric analysis (TGA). Case Stud. Constr. Mater. 2021, 15, e00754. [Google Scholar] [CrossRef]
  33. Scrivener, K.; Ouzia, A.; Juilland, P.; Mohamed, A.K. Advances in understanding cement hydration mechanisms. Cem. Concr. Res. 2019, 124, 105823. [Google Scholar] [CrossRef]
  34. Krstulović, R.; Dabić, P.A. Conceptual model of the cement hydration process. Cem. Concr. Res. 2000, 30, 693–698. [Google Scholar] [CrossRef]
  35. Pane, I.; Hansen, W. Investigation of blended cement hydration by isothermal calorimetry and thermal analysis. Cem. Concr. Res. 2005, 35, 1155–1164. [Google Scholar] [CrossRef]
  36. Zhao, K.Y.; Zhang, P.; Kong, X.M.; Li, H.X.; Zhao, H.T. Recent progress on Portland cement hydration kinetic models and experimental methods. J. Chin. Ceram. Soc. 2022, 50, 1728–1761. [Google Scholar]
  37. Li, Z.J.; Wei, X.S.; Li, W.L. Preliminary interpretation of hydration process of Portland cement using resistivity measurement. ACI Mater. J. 2003, 100, 253–257. [Google Scholar]
  38. Yim, H.J.; Bae, Y.H.; Jun, T.B. Hydration and microstructural characterization of early-age cement paste with ultrasonic wave velocity and electrical resistivity measurements. Constr. Build. Mater. 2021, 303, 124508. [Google Scholar] [CrossRef]
  39. Xu, D.Y.; Chen, H.C.; Hu, Y.; Sun, D.D.; Du, P.; Liu, P. Ultrasonic monitoring and property prediction of cement hydration with novel omnidirectional piezoelectric ultrasonic transducer. J. Build. Eng. 2023, 72, 106612. [Google Scholar] [CrossRef]
  40. Zhang, J.; Qin, L.; Li, Z.J. Hydration monitoring of cement-based materials with resistivity and ultrasonic methods. Mater. Struct. 2009, 42, 15–24. [Google Scholar] [CrossRef]
  41. Xu, W.B.; Li, Q.B.; Hu, Y. Water content variations in the process of concrete setting. J. Hydraul Eng. 2017, 36, 92–103. [Google Scholar]
  42. Li, C.J.; Sun, Z.P.; Li, Q.; Luo, Q. Application of low-field nuclear magnetic resonance in cement-based materials. Mater. Rev. 2016, 30, 133–138. [Google Scholar]
  43. Gajewicz, A.M.; Gartiner, E.; Kang, K.; Mcdonald, P.J.; Yermakou, V. A 1H NMR relaxometry investigation of gel–pore drying shrinkage in cement pastes. Cem. Concr. Res. 2016, 86, 12–19. [Google Scholar] [CrossRef]
  44. Cohen, M.H.; Mendelson, K.S. Nuclear magnetic relaxation and the internal geometry of sedimentary rocks. J. Appl. Phys. 1982, 53, 1127–1135. [Google Scholar] [CrossRef]
  45. Valori, A.; McDonald, P.J.; Scrivener, K.L. The morphology of C-S-H lessons from H-1 nuclear magnetic resonance relaxometry. Cem. Concr. Res. 2013, 49, 65–81. [Google Scholar] [CrossRef]
  46. Zhao, H.T.; Wu, X.; Huang, Y.Y.; Zhang, P.; Tian, Q.; Liu, J.P. Investigation of moisture transport in cement-based materials using low-field nuclear magnetic response imaging. Mag. Concr. Res. 2021, 73, 252–270. [Google Scholar] [CrossRef]
  47. Zhang, A.; Ge, Y. 1H Low Field NMR relaxation characteristics of hydration process of while cement modified with silica nanoparticles. J. Chin. Ceram. Soc. 2021, 49, 1662–1669. [Google Scholar]
  48. Liu, H.; Sun, Z.P.; Yang, J.B.; Ji, Y.L. A novel method for semi-quantitative analysis of hydration degree of cement by 1H low-field NMR. Cem. Concr. Res. 2021, 141, 106329. [Google Scholar] [CrossRef]
  49. Ji, Y.L.; Sun, Z.P.; Yang, X.; Li, C.J.; Tang, X.B. Assessment and mechanism study of bleeding process in cement paste by 1H low-field NMR. Constr. Build. Mater. 2015, 100, 255–261. [Google Scholar] [CrossRef]
  50. Zhao, H.T.; Jiang, K.D.; Di, Y.F.; Xu, W.; Li, W.; Tian, Q.; Liu, J.P. Effects of curing temperature and superabsorbent polymers on hydration of early-age cement paste containing a CaO-based expansive additive. Mater. Struct. 2019, 52, 108. [Google Scholar] [CrossRef]
  51. Zhao, H.T.; Ding, J.; Huang, Y.Y.; Tang, Y.M.; Xu, W.; Huang, D.H. Experimental analysis on the relationship between pore structure and capillary water absorption characteristics of cement-based materials. Struct. Concr. 2019, 20, 1750–1762. [Google Scholar] [CrossRef]
  52. Brownstein, K.R.; Tarr, C.E. Importance of classical diffusion in NMR studies of water in biological cells. Phys. Rev. A 1979, 19, 2446–2453. [Google Scholar] [CrossRef]
  53. Song, Y.Q. Magnetic resonance of porous media (MRPM): A perspective. J. Magn. Reson. 2013, 229, 12–24. [Google Scholar] [CrossRef] [PubMed]
  54. Muller, A.C.A.; Scrivener, K.L.; Gajewicz, A.M.; McDonald, P.J. Densification of C-S-H measured by 1H NMR relaxometry. J. Phys. Chem. C 2013, 117, 403–412. [Google Scholar] [CrossRef]
  55. Fu, J.X.; Wang, K.; Wang, J. Internal pore evolution and early hydration characterization of fly ash cement backfill. J. Build. Eng. 2023, 72, 106716. [Google Scholar] [CrossRef]
  56. Juenger, M.C.G.; Jennings, H.M. Examining the relationship between the microstructure of calcium silicate hydrate and drying shrinkage of cement pastes. Cem. Concr. Res. 2002, 32, 289–296. [Google Scholar] [CrossRef]
  57. Poli, T.; Toniolo, L.; Valentini, M.; Bizzaro, G.; Melzi, R.; Tedoldi, F.; Cannazza, G. A portable NMR device for the evaluation of water presence in building materials. J. Cult. Herit. 2007, 8, 134–140. [Google Scholar] [CrossRef]
  58. Bertram, H.C.; Jandersen, H.; Karlsson, A.H. Comparative study of low-field NMR relaxation measurements and two traditional methods in the determination of water holding capacity of pork. Meat Sci. 2001, 57, 125–132. [Google Scholar] [CrossRef]
  59. Liu, L.; He, Z.; Cai, X.; Fu, S.J. Application of low-field NMR to the pore structure of concrete. Appl. Magn. Reson. 2021, 52, 15–31. [Google Scholar] [CrossRef]
  60. Wang, Y.; Burris, L.; Hooton, R.D.; Shearer, C.R.; Suraneni, P. Effects of unconventional fly ashes on cementitious paste properties. Cem. Concr. Compos. 2022, 125, 104291. [Google Scholar] [CrossRef]
  61. Pipikaki, P.; Katsioti, M. Study of the hydration process of quaternary blended cements and durability of the produced mortars and concretes. Constr. Build. Mater. 2009, 23, 2246–2250. [Google Scholar] [CrossRef]
  62. Wen, X.D.; Yin, G.J.; Xia, L.; Zhou, M.; Feng, L.; Wu, J.Y. Spatiotemporal evolution of water and pore structure in cement-based materials containing SRA by LF NMR. Mater. Today Commun. 2023, 35, 106076. [Google Scholar]
  63. Xu, Z.H.; Guo, Z.H.; Zhao, Y.S. Hydration of blended cement with high-volume slag and nano-silica. J. Build. Eng. 2023, 64, 105657. [Google Scholar] [CrossRef]
  64. Whittaker, M.; Zajac, M.; Haha, M.B.; Bullerjahn, F.; Black, L. The role of the alumina content of slag, plus the presence of additional sulfate on the hydration and microstructure of Portland cement-slag blends. Cem. Concr. Res. 2014, 66, 91–101. [Google Scholar] [CrossRef]
  65. Li, W.Y.; Yin, J.H.; Wang, J.; Yang, H.J.; Kong, X.M. Principles and applications of low-field nuclear magnetic resonance in cementitious materials. J. Chin. Ceram. Soc. 2022, 50, 2992–3008. [Google Scholar]
  66. Scrivener, K.; Snellings, R.; Lothenbach, B. A Practical Guide to Microstructural Analysis of Cementitious Materials; Science Press: Beijing, China, 2021. [Google Scholar]
  67. Gorce, J.P.; Milstone, N.B. Probing the microstructure and water in composite cement blends. Cem. Concr. Res. 2007, 37, 310–318. [Google Scholar] [CrossRef]
  68. Faure, P.; Care, S.; Magat, J.; Chaussadent, T. Drying effect on cement paste porosity at early age observed by NMR methods. Constr. Build. Mater. 2012, 29, 496–503. [Google Scholar] [CrossRef]
  69. Wu, F.F.; Shi, K.B.; Dong, S.K.; Chen, S.S.; Ci, J.; Wang, X.; Zhang, K. Influence of admixture and water-cement ratio on hydration products and mechanical properties of cement-based materials. Trans. Chin. Soc. Agric. Eng. 2016, 32, 119–126. [Google Scholar]
  70. Golewski, G.L. The role of pozzolanic activity of siliceous fly ash in the formation of the structure of sustainable cementitious composites. Sustain. Chem. 2022, 3, 520–534. [Google Scholar] [CrossRef]
Buildings 13 02318 g001
Figure 1. CPMG pulse sequence.
Figure 1. CPMG pulse sequence.
Buildings 13 02318 g001
Buildings 13 02318 g002
Figure 2. Chromatographic bottle containing cement paste.
Figure 2. Chromatographic bottle containing cement paste.
Buildings 13 02318 g002
Buildings 13 02318 g003
Figure 3. NMR instrument.
Figure 3. NMR instrument.
Buildings 13 02318 g003
Buildings 13 02318 g004aBuildings 13 02318 g004b
Figure 4. T2 spectra of cement-based materials at different curing ages.
Figure 4. T2 spectra of cement-based materials at different curing ages.
Buildings 13 02318 g004aBuildings 13 02318 g004b
Buildings 13 02318 g005
Figure 5. Change of T2i for different cement paste with curing time.
Figure 5. Change of T2i for different cement paste with curing time.
Buildings 13 02318 g005
Buildings 13 02318 g006
Figure 6. Change of T2 signal area for different cement paste with curing time.
Figure 6. Change of T2 signal area for different cement paste with curing time.
Buildings 13 02318 g006
Buildings 13 02318 g007
Figure 7. Evolution of gel water and capillary water relative content.
Figure 7. Evolution of gel water and capillary water relative content.
Buildings 13 02318 g007
Buildings 13 02318 g008
Figure 8. Distribution of pore size in cement paste samples.
Figure 8. Distribution of pore size in cement paste samples.
Buildings 13 02318 g008
Buildings 13 02318 g009
Figure 9. Evolution of porosity with curing time.
Figure 9. Evolution of porosity with curing time.
Buildings 13 02318 g009
Buildings 13 02318 g010
Figure 10. Evolution of early mechanical properties of cement-based materials with curing time.
Figure 10. Evolution of early mechanical properties of cement-based materials with curing time.
Buildings 13 02318 g010
Buildings 13 02318 g011
Figure 11. Relationship between porosity and compression strength of cement-based materials.
Figure 11. Relationship between porosity and compression strength of cement-based materials.
Buildings 13 02318 g011
Table 1. Chemical composition of cement (%).
Table 1. Chemical composition of cement (%).
SiO2Al2O3Fe2O3CaOMgOSO2Na2Of-CaOCl-Loss
204/403.2763.342.902.420.590.870.021.54
Table 2. Basic properties and chemical composition of fly ash.
Table 2. Basic properties and chemical composition of fly ash.
Physical propertyFineness (45 mm Square Hole Sieve) (%)Water Demand Ratio (%)Strength Activity Index (%)Water Content (%)Density (g/cm3)
2098860.522.25
Chemical compositionSO3 (%)f-CaO (%)SiO2 (%)Al2O3 (%)Fe2O3 (%)
2.160.2650.2631.144.16
Table 3. Basic properties and chemical composition of slag.
Table 3. Basic properties and chemical composition of slag.
Physical propertySpecific Surface Area (m2/kg)Flow Ratio (%)7 Days Activity Index (%)Water Content (%)Density (g/cm3)
4299884.20.453.1
Chemical compositionSO3 (%)MgO (%)CaO (%)SiO2 (%)Al2O3 (%)Fe2O3 (%)
1.646.013434.517.71.03
Table 4. Mix proportions of cement paste (mass proportion).
Table 4. Mix proportions of cement paste (mass proportion).
NumberW/CCementitious Material
Cement (C)Fly ash (FA)Slag (S)Silica Fume (SF)
JJ-10.41000
JJ-20.40.80.200
JJ-30.40.60.400
JJ-40.40.80.10.10
JJ-50.40.60.30.10
JJ-60.40.80.100.1
JJ-70.40.60.300.1
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Tang, Y.-J.; Shan, Z.-Q.; Yin, G.-J.; Miao, L.; Wang, S.-S.; Zhang, Z.-Y. Low-Field Nuclear Magnetic Resonance Investigation on Early Hydration Characterization of Cement Paste Mixed with Mineral Admixtures. Buildings 2023, 13, 2318. https://doi.org/10.3390/buildings13092318

AMA Style

Tang Y-J, Shan Z-Q, Yin G-J, Miao L, Wang S-S, Zhang Z-Y. Low-Field Nuclear Magnetic Resonance Investigation on Early Hydration Characterization of Cement Paste Mixed with Mineral Admixtures. Buildings. 2023; 13(9):2318. https://doi.org/10.3390/buildings13092318

Chicago/Turabian Style

Tang, Yu-Juan, Zi-Qi Shan, Guang-Ji Yin, Ling Miao, Sai-Sai Wang, and Zhen-Ya Zhang. 2023. "Low-Field Nuclear Magnetic Resonance Investigation on Early Hydration Characterization of Cement Paste Mixed with Mineral Admixtures" Buildings 13, no. 9: 2318. https://doi.org/10.3390/buildings13092318

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop