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Article

Effect of Active MgO on Compensated Drying Shrinkage and Mechanical Properties of Alkali-Activated Fly Ash–Slag Materials

by
Hongqiang Ma
1,2,3,*,
Shiru Li
1,
Zelong Lei
1,
Jialong Wu
1,
Xinhua Yuan
1 and
Xiaoyan Niu
1,2,3,*
1
College of Civil Engineering and Architecture, Hebei University, Baoding 071002, China
2
Engineering Research Center of Zero-Carbon Energy Buildings and Measurement Techniques, Ministry of Education, Hebei University, Baoding 071002, China
3
Technology Innovation Center for Testing and Evaluation in Civil Engineering of Hebei Province, Hebei University, Baoding 071002, China
*
Authors to whom correspondence should be addressed.
Buildings 2025, 15(2), 256; https://doi.org/10.3390/buildings15020256
Submission received: 21 December 2024 / Revised: 11 January 2025 / Accepted: 13 January 2025 / Published: 16 January 2025
(This article belongs to the Special Issue Key Technologies and Innovative Applications of 3D Concrete Printing)
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Versions Notes

Abstract

:
The influences of MgO activity and its content on the mechanical properties, drying shrinkage compensation, pore structure, and microstructure of alkali-activated fly ash–slag materials were investigated. Active MgO effectively compensated for the alkali-activated materials’ (AAMs’) drying shrinkage. The drying shrinkage increased rapidly with the increase in curing age and stabilized after 28 d. Within a certain range, the material’s drying shrinkage was inversely proportional to the content of active MgO. The higher the activity of MgO, the lower the drying shrinkage of the AAMs under the same MgO content. The drying shrinkage values of the test groups with 9% R-MgO, M-MgO, and S-MgO at 90 d were 2444 με, 2306 με, and 2156 με, respectively. In the early stage of hydration, the addition of S-MgO reduced the compressive strength. As the content of M-MgO increased, the compressive strength first increased and then decreased, reaching a maximum of 72.28 MPa at an M-MgO content of 9%. The experimental group with 9% M-MgO exhibited higher compressive and flexural strengths than those with 9% S-MgO and R-MgO, demonstrating better mechanical properties. The results of this study provide an important theoretical basis and data support for the optimal application of MgO in AAMs. MgO expansion agents have great application potential in low-carbon buildings and durable materials. Further research on their adaptability in complex environments will promote their development for engineering and provide innovative support for green buildings.

1. Introduction

Portland cement is currently the most widely used cementitious material in the world [1]. The production of cement consumes a significant amount of non-renewable energy and emits large quantities of greenhouse gases such as CO2 and NOx [2], making it one of the major contributors to environmental degradation. In the context of green, low-carbon, and low-emission initiatives, there is a pressing need to develop new eco-friendly cementitious materials. Alkali-activated materials (AAMs), synthesized through the hydration of fly ash and slag catalyzed by alkali activators, are recognized as important components of sustainable construction materials [3,4]. Compared to Portland cement, AAMs offer advantages such as simpler production processes [5], lower energy consumption [6], reduced CO2 emissions [7], and higher utilization rates of industrial solid wastes. They also exhibit outstanding characteristics, including high strength [8,9], low hydration heat [10], corrosion resistance [11], and impermeability [12], making them important for the development of modern construction materials [13,14,15,16,17].
However, one of the major challenges limiting the practical application of AAMs in engineering is their propensity for significant shrinkage and cracking, which occur during the hardening process due to water loss through evaporation [18]. A variety of strategies have been developed with the objective of reducing or compensating for the shrinkage of AAMs. These include the use of shrinkage-reducing admixtures (SRAs) [19], internal curing agents [20], and expansive agents. The addition of expansive agents, particularly MgO, to AAMs has emerged as an effective technical approach to address this issue owing to MgO’s excellent expansive properties. Cao et al. [21] analyzed the microstructure of cement-hardened paste in which varying amounts of MgO expansive agent was incorporated using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). It was found that the MgO-expander-induced swelling originated mainly from the growth in brucite crystals and that the crystals were generated mainly along the subpore walls of the confined regions, while relatively little growth occurred on the surface of the MgO particles. The formation of brucite crystals is controlled by the degree of supersaturation of the Mg2⁺ concentration in the pore solution. Ma et al. [22] investigated the effects of the slag content as well as alkali activator modulus and content on the coagulation behavior, mechanical properties, and drying shrinkage characteristics of AACGS materials. Furthermore, the intrinsic mechanism of drying shrinkage was analyzed in depth using MIP and SEM-EDS techniques. It was found that the drying shrinkage of AACGS materials was significantly higher compared with that of Portland cement materials. Wang et al. [23] found that MgO activity had little effect on the crystallization of C-S-H gel, whereas increasing the MgO activity contributed to the degree of hydration of MgO and AAMs. Crystallinity and hydration analyses revealed that the use of high-activity MgO achieved higher hydration degrees for both MgO and the AAMs. Gu et al. [24] added MgO to cement-based steel tube concrete and found that higher MgO activity resulted in a smaller final restrained expansion ratio and an earlier onset of expansion. An appropriate MgO content, ranging from 9% to 12%, could refine the pore structure and provide good expansive behavior and volume stability. Cui et al. [25] also observed an earlier onset of expansion with higher MgO activity when MgO was added to ultra-high-performance concrete (UHPC) to compensate for shrinkage. Mo et al. [26] investigated the influence of curing temperature on the hydration process and expansion characteristics of expansive MgO agents with varying reactivities in cement paste. The results showed that at 20 °C, high-activity MgO exhibited better expansion within 28 d than low-activity MgO, but the expansion decreased later on. At temperatures ranging from 20 °C to 80 °C or in the later stages, low-activity MgO demonstrated better expansion performance. Sherir et al. [27] explored self-healing cement-based materials by adding MgO expanders to cement-based materials to make ECC-MgO. The results showed that the incorporation of small amounts of cyanless MgO and fly ash produced self-healing ECC-MgO with stable durability. Samples with higher degree of pre-cracking under autoclave conditions had higher strength, confirming the potential of the system to self-heal. It was found that increasing the content of the slag material and the modulus of alkali activator induced stronger drying shrinkage in AAMs [28]. The collapse and rearrangement of the gels produced by polymerization reactions result in volume reduction, refinement of the internal pore structure, and increased capillary tensile stress. A material cannot fully rebound from drying shrinkage.
In summary, research on the effect of active MgO on the hydration reaction mechanisms of AAMs is still limited. Alkali-activated precursor materials are rich in MgO. In order to apply the concepts of green development and low-carbon energy conservation, different amounts of active MgO were added to solid waste: alkali-activated fly ash–slag materials, and NaOH, which is inexpensive, was selected as the alkali activator. The effects of MgO on the compensation for drying shrinkage, mechanical properties, pore structure, and microstructure of alkali-activated fly ash–slag materials were studied. The hydration reaction process of AAMs and MgO is shown in Figure 1. It is of great significance to improve the expansion effect of MgO to improve the stability and durability of AAMs and promote the application of low-carbon and environmentally friendly AAMs in engineering.

2. Materials and Methods

2.1. Materials

This experiment employed S95-grade granulated blast furnace slag, Class F fly ash, and Chinese ISO standard sand as raw materials. The active MgO was sourced from Wuhan Sanyuan Special Building Materials Co., Ltd., Wuhan, China. By controlling the calcination conditions, three different active MgO samples were obtained: rapid-reacting MgO (R-MgO, reaction time < 100 s), moderately reacting MgO (M-MgO, reaction time 100–200 s), and slowly reacting MgO (S-MgO, reaction time > 200 s). The chemical compositions of the fly ash, slag, and active MgO were determined through X-ray fluorescence analysis and are presented in Table 1. Their XRD patterns are presented in Figure 2.

2.2. Preparation Process

We dissolved sodium hydroxide (NaOH) solid in deionized water to prepare a NaOH solution. After stirring well, we let it stand for 24 h to allow the solution temperature to drop to room temperature and to compensate for any water loss due to evaporation. We added sodium silicate, which we ultrasonically stirred for 1 h to prepare the alkali activator. We placed fly ash, slag, standard sand, and active MgO materials in a mixer and stirred them at low speed for 30 min. Then, we added the alkali activator and stirred rapidly for 5 min to form a uniform paste. We quickly poured the freshly mixed paste into cube molds of 50 mm × 50 mm × 50 mm, rectangular molds of 40 mm × 40 mm × 160 mm, and special molds for testing drying shrinkage of 40 mm × 40 mm × 160 mm. After vibrating to ensure compaction, we sealed the molds with polyethylene film to prevent water evaporation [29]. The samples were cured under standard curing conditions (temperature 20 ± 2 °C, humidity 95 ± 1%) for 24 h before demolding and then sealed with polyethylene film and continuously cured under standard curing conditions until the experiment was finished. The active MgO content was designed to be 0%, 6%, 9%, 12%, and 15% (as a percentage of the total mass of fly ash, slag and active MgO). The Na2O concentration was 4%, the alkali activator modulus was 1.0, the liquid-to-solid ratio was 0.36, and the sand-to-binder ratio was 2. A total of 13 experimental groups were set up, with specific mix proportions shown in Table 2. The experimental flowchart is shown in Figure 3.

2.3. Testing Methods

2.3.1. Compressive Strength Tests

The tests of compressive strength and flexural strength were conducted at 3 d, 28 d and 90 d of the specimen’s curing. The tests were carried out using a WDW3300 100 KN universal testing machine with a loading speed of 0.5 mm/min. Three samples were tested in each group, and their average value was taken as the value of compressive strength, as shown in Figure 4a.

2.3.2. Drying Shrinkage Tests

After removing the mold, rectangular 40 mm × 40 mm × 160 mm samples were obtained. The straight line distance between the two ends was measured as the initial length (L0) using a dial comparator (accurate to 0.001 mm). The testing operation is shown in Figure 4b. The samples were transferred to a drying shrinkage humidity control box for cement materials for curing (temperature 20 ± 2 °C and relative humidity 60 ± 5 °C), and the length values were measured for curing ages of 2 d, 3 d, 7 d, 14 d, 21 d, 28 d, 42 d, 60 d and 90 d, recorded as Lt. The dying shrinkage rate of the alkali-activated materials was calculated based on the L0 and Lt, with Equation (1):
εs = (L0 − Lt)/160 × 100%

2.3.3. Microscopic Tests

Samples of the alkali-activated material were crushed and cored, and, after terminating hydration with isopropanol and low-temperature vacuum drying, they were subjected to MIP and SEM tests. The MIP test was conducted using an Autopore II 9220 mercury injection apparatus, with a test pore size range of 3 nm to 275 μm and a maximum mercury injection pressure of 430 MPa. The pore size distribution of the samples was continuously tested under pressure. The scanning electron microscope test (SEM test) was performed using a JSM-7800F field-emission scanning electron microscope, with magnifications of 2000× and 20,000×. By mapping and scanning micro areas of the samples, the amounts of elements Ca, Si, Al, and Mg were obtained. Before testing, the samples were coated with a layer of gold.

3. Results and Analysis

3.1. Mechanical Properties’ Analysis

The graph in Figure 5 illustrates the compressive strength of AAMS cured for 3 d, 28 d, and 90 d with reactive MgO. During the initial curing age, the incorporation of M-MgO and R-MgO did not significantly affect the compressive strength. However, the addition of R-MgO reduced the compressive strength, which decreased continuously with increasing content. Specifically, samples containing 6%, 9%, 12%, and 15% S-MgO exhibited decreases of 5.3%, 11.1%, 22.9%, and 27%, respectively. This is related to the lower reactivity of S-MgO, which resulted in a slower hydration rate and lower compressive strength in the early stages. As the curing progressed, with an increase in the content of reactive MgO, the 28-day samples all showed a trend of increasing compressive strength, followed by a decrease, with the highest values observed in the samples with a 9% content. This may have been due to MgO providing a large amount of Mg2+ for the formation of hydrotalcite. The formation of an appropriate amount of hydrotalcite enhances the compactness of the matrix, thereby increasing the compressive strength of the paste, while excessive hydrotalcite formation may reduce it [29]. The differences in the compressive strength of the 90-day samples were relatively small, which may have been related to the hydration degree of periclase [30]. The compressive strength of the 9% M-MgO samples at 3 d, 28 d, and 90 d were 33.7 MPa, 64.5 MPa, and 72.3 MPa, respectively, all higher than those of the S-MgO and R-MgO samples at the same curing age [28].
Figure 6 displays the flexural strength of the AAMs cured for 3 d, 28 d, and 90 d with active MgO. During the initial curing age, with an increase in the content of active MgO, the flexural strength of all samples showed a gradual decline, consistent with previous reports [31]. Specifically, samples with 15% contents of S-MgO, M-MgO, and R-MgO exhibited decreases of 29.9%, 27.1% and 24.4%, respectively. However, at a content of 9%, all reactive MgO samples showed a sudden increase in flexural strength. As the curing age increased, the flexural strengths of S-MgO, M-MgO, and R-MgO samples were all lower than that of the control group, but the samples with 9% reactive MgO still had a significant advantage. The flexural strengths of the 9% M-MgO samples at 3 d, 28 d, and 90 d were 6.6 MPa, 10.2 MPa, and 11.8 MPa, respectively, all higher than those of the S-MgO and R-MgO samples. The 9% M-MgO AAMs exhibited superior mechanical properties.

3.2. Analysis of the Change in Active-Mg-Compensated Drying Shrinkage

The addition of an alkali activator and the inherent characteristics of AAMs contribute to significant drying shrinkage [32,33]. MgO has been extensively studied in cement-based materials due to its excellent expansive properties [30,31,34,35,36,37]. Previous studies [18,38,39,40] have shown that the drying shrinkage of cement is approximately 800–1000 με, while that of AAMs is around 2000–6000 με. This is because the water in AAMs does not directly participate in the formation of aluminosilicate gels and exists as free water, which is prone to evaporation and loss [41]. Figure 7 presents the drying shrinkage of AAMs with reactive MgO at various curing ages. As the curing age increased, the drying shrinkage of each sample rapidly increased, and, after 28 days, it tended to stabilize and then slightly decreased, remaining relatively unchanged, which is consistent with previous reports [22]. Furthermore, with an increase in the content of reactive MgO, the degree of shrinkage of the samples continuously decreased, indicating that MgO is an excellent expansive agent. This is because the hydration product of MgO is brucite (Mg(OH)2), a very simple and stable crystal, whose solid-phase volume increases by 126%, effectively reducing the internal hydration heat and shrinkage of AAMs [21]. At a content of 15% and a curing age of 28 days, the shrinkage rates of the S-MgO, M-MgO, and R-MgO samples decreased by 15.8%, 19.1%, and 32.2%, respectively, with the R-MgO sample exhibiting excellent resistance to shrinkage.

3.3. MIP Analysis

The pore structure is a crucial structural characteristic of hardened cementitious material paste, influencing the mechanical properties and the supplementary shrinkage performance of the binding materials. It also reflects the hydration reaction degree of composite cementitious materials. In this study, mercury intrusion porosimetry (MIP) was utilized to analyze the evolution of the pore structure and pore size distribution in the AAMs under changing variables with curing age. To identify the changes in pores, the AAM pores were classified based on size into micropores (<0.01 μm), transition pores (0.01–0.1 μm), mesopores (0.1–1 μm), macropores (1–100 μm), and harmful pores (>100 μm) [42].
Figure 8a illustrates the pore volume of the M-MgO-activated AAMs. As the content of reactive M-MgO increased, the volume of macropores gradually decreased, while the volumes of the micropores and transition pores first increased and then decreased. The total pore volume showed an overall decreasing trend. The incorporation of active M-MgO reduced the AAMs’ pore volume, made the material more dense, and enhanced the mechanical properties.
Figure 8c depicts the influence of different types of active MgO on the AAMs’ pore volume. The cumulative pore volume of the materials in the R-MgO experimental group with a 9% content was markedly higher compared to that of both the control group and the S-MgO and M-MgO experimental groups. The impact of the different types of active MgO on the pore structure of the AAMs varied significantly. R-MgO effectively increased the AAMs’ pore volume, which explains the mechanism through which MgO mitigates the drying shrinkage of materials.
Figure 8e presents the pore distribution of the M-MgO experimental group at different ages. It can be observed that the pore volumes of various sizes at 3 d and 28 d were similar. However, as the curing age increased, significant changes occurred in the AAMs’ pore structure, with the pore volumes at 90 d being much greater than those at 3 d and 28 d, consistent with previous research results [26].

3.4. SEM Analysis

The microstructure morphology of the AAMs was observed using scanning electron microscopy (SEM) testing. Figure 9 shows the SEM photos of the active M-MgO AAMs. The degree of hydration of fly ash and slag, as well as the accumulation of hydration products, depended on the content of M-MgO. No significant unreacted fly ash microspheres were observed in the images, indicating that hydration products had largely formed. When the reactive M-MgO content was 6%, fewer flocculent and platelet-like products were observed, suggesting the presence of a large amount of unhydrated periclase and slag particles. As the M-MgO content increased, more hydration products such as brucite and hydrotalcite-like phases were formed in the reactive M-MgO AAMs.
Figure 10 shows SEM photos of the AAMs containing different types of active MgO. Numerous fine rods and flakes of brucite, numerous small spinel-like hydrotalcite-like products, and flocculent C-(A)-S-H gel were clearly observed. The AAMs containing reactive R-MgO exhibited multiple microcracks. R-MgO had high reactivity, a fast hydration rate, and a high degree of hydration, resulting in the production of numerous hydromagnesite and hydrotalcite-like phases, and the accumulation of these products tended to induce the formation of microcracks, thus adversely affecting the development of the long-term strength (>90 d) and durability of the materials.
To observe the changes in the microstructural morphology of the AAMs after the incorporation of M-MgO, scanning electron microscopy (SEM) tests were conducted on the AAFS-M9 experimental group materials with a 9% M-MgO content at different curing ages. Figure 11 shows the SEM photos of the reactive M-MgO AAMs at curing ages of 3 d, 28 d, and 90 d. With the increase in the standard curing age, significant changes occurred in the surface microstructure of the AAMs, as shown in the SEM images. At 3 d, the microstructure of the materials surface was relatively loose with fewer hydration products, and more fly ash, slag, and MgO particles were undergoing hydration. As the hydration reaction progressed further, at 28 d, the hydration products became more abundant, and the microstructure became denser. After 90 d, it can be seen that the microstructure exhibited a high degree of crystallinity, indicating a high degree of hydration reaction. The hydration products were more abundant and had accumulated to form a well-structured overall structure.

4. Conclusions

The effects of three types of active MgO on compensating for the drying shrinkage and mechanical properties of AAMs containing different amounts of MgO were investigated. The findings and prospects are summarized as follows:
(1)
The addition of active MgO can enhance the compressive strength of AAMs to some extent, but it decreases when the content is too high. The flexural strength exhibited a decreasing trend, except for a noticeable increase at a content of 9%. This study found that AAMs with 9% M-MgO exhibited superior mechanical properties.
(2)
The incorporation of active MgO induces significant expansion behavior in AAMs, which increases with content. The shrinkage rates of R-M-S MgO samples decreased to 15.8%, 19.1%, and 32.2%, indicating a positive correlation between the expansion behavior of AAMs and the activity of MgO.
(3)
High-temperature drying, high-altitude terrain, and wind can accelerate moisture evaporation within AAMs, promoting drying shrinkage and crack formation. Compared to methods such as using steel reinforcement to inhibit drying shrinkage, expansive MgO agents offer advantages such as lower cost, easier application, and significant effectiveness. As green materials, AAMs contribute to lowering carbon emissions, reducing energy consumption, saving energy, and reducing emissions.

Author Contributions

H.M.: Investigation, writing—review and editing; S.L.: data curation, writing—original draft; Z.L.: data curation; J.W.: data curation; X.Y.: data curation; X.N.: methodology, supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Natural Science Foundation of Hebei Province (E2022201011).

Data Availability Statement

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

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Reaction diagram of AAMs with MgO.
Figure 1. Reaction diagram of AAMs with MgO.
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Figure 2. XRD patterns of raw materials.
Figure 2. XRD patterns of raw materials.
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Figure 3. Flow chart of experiment.
Figure 3. Flow chart of experiment.
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Figure 4. AAMs tests. (a) Compressive strength. (b) drying shrinkage.
Figure 4. AAMs tests. (a) Compressive strength. (b) drying shrinkage.
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Figure 5. Compressive strength of MgO-activated AAMs containing: (a) S-MgO, (b) M-MgO, (c) R-MgO and (d) 9% active MgO.
Figure 5. Compressive strength of MgO-activated AAMs containing: (a) S-MgO, (b) M-MgO, (c) R-MgO and (d) 9% active MgO.
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Figure 6. Flexural strength of MgO-activated AAMs containing: (a) S-MgO, (b) M-MgO, (c) R-MgO and (d) 9% active MgO.
Figure 6. Flexural strength of MgO-activated AAMs containing: (a) S-MgO, (b) M-MgO, (c) R-MgO and (d) 9% active MgO.
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Figure 7. Drying shrinkage of MgO-activated AAMs containing: (a) S-MgO, (b) M-MgO, (c) R-MgO and (d) active MgO.
Figure 7. Drying shrinkage of MgO-activated AAMs containing: (a) S-MgO, (b) M-MgO, (c) R-MgO and (d) active MgO.
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Figure 8. Pore size distribution of MgO-activated AAMs containing: (a) M-MgO and (b) MgO for different (c) M-MgO and (d) MgO types; (e) M-MgO curing age, (f) MgO curing age.
Figure 8. Pore size distribution of MgO-activated AAMs containing: (a) M-MgO and (b) MgO for different (c) M-MgO and (d) MgO types; (e) M-MgO curing age, (f) MgO curing age.
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Figure 9. SEM photos of AAMs with different contents of active M-MgO. (a) AAFS. (b) AAFS-M6. (c) AAFS-M9. (d) AAFS-M12. (e) AAFS-M15.
Figure 9. SEM photos of AAMs with different contents of active M-MgO. (a) AAFS. (b) AAFS-M6. (c) AAFS-M9. (d) AAFS-M12. (e) AAFS-M15.
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Figure 10. SEM photos of AAMs with different types of active MgO. (a) AAFS-S9. (b) AAFS-M9. (c) AAFS-R9.
Figure 10. SEM photos of AAMs with different types of active MgO. (a) AAFS-S9. (b) AAFS-M9. (c) AAFS-R9.
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Figure 11. SEM photos of M-MgO AAMs at different curing ages: (a) 3 d, (b) 28 d and (c) 90 d.
Figure 11. SEM photos of M-MgO AAMs at different curing ages: (a) 3 d, (b) 28 d and (c) 90 d.
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Table 1. The main chemical composition of raw materials (wt%).
Table 1. The main chemical composition of raw materials (wt%).
MaterialCaOMgOAl2O3SiO2Fe2O3SO3LOI
Slag35.587.1616.3236.100.231.712.9
Fly ash2.660.2432.7955.714.43—0.97
R-MgO1.3192.650.7110.21.6
M-MgO1.390.920.52.20.80.12.2
S-MgO2.690.040.52.710.11.9
Table 2. Mix proportion of alkali-activated fly ash–slag materials.
Table 2. Mix proportion of alkali-activated fly ash–slag materials.
Sample No.Fly AshSlagMgO TypeMgO Content
AAFS50%50%—0
AAFS-S647%47%S6%
AAFS-S945.5%45.5%S9%
AAFS-S1244%44%S12%
AAFS-S1542.5%42.5%S15%
AAFS-M647%47%M6%
AAFS-M945.5%45.5%M9%
AAFS-M1244%44%M12%
AAFS-M1542.5%42.5%M15%
AAFS-R647%47%R6%
AAFS-R945.5%45.5%R9%
AAFS-R1244%44%R12%
AAFS-R1542.5%42.5%R15%
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MDPI and ACS Style

Ma, H.; Li, S.; Lei, Z.; Wu, J.; Yuan, X.; Niu, X. Effect of Active MgO on Compensated Drying Shrinkage and Mechanical Properties of Alkali-Activated Fly Ash–Slag Materials. Buildings 2025, 15, 256. https://doi.org/10.3390/buildings15020256

AMA Style

Ma H, Li S, Lei Z, Wu J, Yuan X, Niu X. Effect of Active MgO on Compensated Drying Shrinkage and Mechanical Properties of Alkali-Activated Fly Ash–Slag Materials. Buildings. 2025; 15(2):256. https://doi.org/10.3390/buildings15020256

Chicago/Turabian Style

Ma, Hongqiang, Shiru Li, Zelong Lei, Jialong Wu, Xinhua Yuan, and Xiaoyan Niu. 2025. "Effect of Active MgO on Compensated Drying Shrinkage and Mechanical Properties of Alkali-Activated Fly Ash–Slag Materials" Buildings 15, no. 2: 256. https://doi.org/10.3390/buildings15020256

APA Style

Ma, H., Li, S., Lei, Z., Wu, J., Yuan, X., & Niu, X. (2025). Effect of Active MgO on Compensated Drying Shrinkage and Mechanical Properties of Alkali-Activated Fly Ash–Slag Materials. Buildings, 15(2), 256. https://doi.org/10.3390/buildings15020256

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