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Communication

A Study on the Pore and Strength Characteristics of an Eco-Friendly Sprayed Ultra High Performance Concrete with Manufactured Sand

by
Zhonghao Wang
1,2,
Xianjun Tan
2,*,
Jingqiang Yuan
2,
Chongge Wang
1 and
Yubiao Liu
2
1
College of Civil Engineering and Architecture, Shandong University of Science and Technology, Qingdao 266590, China
2
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(7), 3776; https://doi.org/10.3390/app15073776
Submission received: 17 February 2025 / Revised: 15 March 2025 / Accepted: 19 March 2025 / Published: 30 March 2025
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Abstract

:
Conventional shotcrete systems face critical limitations in adverse geological environments, including a delayed strength development (<5 MPa at 3 h), excessive rebounds (15–25%), and permeable macropore networks (>50 μm), often resulting in support failure for deeply buried tunnels. To address these challenges, this study systematically investigates the mechanical properties and pore characteristics of a manufactured sand-based sprayed UHPC at different spraying positions under simulated tunnel conditions. Our results demonstrate that the high-pressure air (0.8 MPa) driven spraying process optimizes its pore distribution, reducing large pores (>10 μm) and increasing harmless pores (<100 nm). Furthermore, the sprayed UHPC incorporating manufactured sand derived from tunnel slag not only maintains a 28-day compressive strength of 110.9 MPa but also reduces material costs and enhances sustainability. Field tests validate its low rebound rate (<5%) and rapid strength development (achieving a compressive strength of 30 MPa within 1 day), confirming its adaptability to complex geological conditions such as high-stress zones, thereby providing a novel method for support in complex geological conditions.

1. Introduction

During tunnel construction, the challenges of large deformation and intrusion frequently arise due to poor rock mass conditions and insufficient support strength, particularly in complex geological environments characterized by significant buried depth [1,2]. Bajaber et al. [3] have highlighted UHPC’s high strength and durability as a solution for enhancing tunnel supports in poor geological conditions. Sun et al. [4] have identified insufficient support strength and joint activation as key triggers for intrusive deformation in shallow tunnels under tectonic stress, which requires optimized materials and layouts. Shotcrete is a construction technique where concrete is sprayed onto a surface at high velocity using compressed air [5]. This method is capable of providing early load-bearing capacity for deformed rock strata, thereby offering a rapid solution for the stabilization of the surrounding rock mass [6,7]. This characteristic makes shotcrete a preferred method for primary or secondary support in underground engineering. However, the high porosity (19.6%) [8] and rebound rate (>15%) [9] of shotcrete hinder its effectiveness in controlling disasters such as collapse and large deformation when applied in unfavorable geological rock formations. Therefore, robust support materials with a specific strength and toughness are required to accommodate variations in rock masses while minimizing internal porosity to prevent water infiltration.
UHPC has garnered considerable attention due to its remarkable compressive strength, outstanding toughness, and minimal permeability [10]. These exceptional attributes are a result of its extremely low water–binder ratio (<0.25) and the substantial content of cementitious materials [11], which collectively bestow upon UHPC superior mechanical performance, high-level toughness, and low permeability (the compressive strength is greater than 100 MPa, and the tensile strength is greater than 5 MPa) [12,13]. These superior properties have led to its extensive applications in underground engineering and structural reinforcement [14]. However, the high content of cementitious materials and sand has increased its cost and reduced its sustainability. To further align with sustainable construction goals, the integration of manufactured sand into UHPC formulations has emerged as a pivotal innovation. Research demonstrates that replacing natural sand with manufactured sand not only mitigates environmental degradation caused by river sand mining but also optimizes particle gradation and interfacial bonding through its controllable particle size distribution and angular surface texture, thereby validating its superior compatibility with UHPC [15,16]. Sprayed UHPC integrates the advantages of both UHPC and shotcrete. It exhibits the outstanding mechanical properties and durability associated with UHPC, as well as featuring the flexibility of shotcrete, which makes it particularly well suited to intricate working conditions. Currently, only a few studies on sprayed UHPC have been conducted, mainly focusing on its rheological behavior and sprayability. These studies have aimed to improve the stability of wall-hanging and increase the spray’s thickness by adding various thickeners and cementitious materials [17,18]. Cui et al. [19] studied viscosity-enhancing agents in sprayed UHPC, showing improved rheology, enhanced compressive strength, and refined pore structure for durability. Chen et al. [20] linked molecular dynamics to rheology in wet-mix UHPC, proposing a cohesion-shear model for optimizing mix design. Al-Ameen et al. [21] highlighted fiber content/alignment in sprayed UHPC, balancing permeability reduction and mechanical gains against workability loss. Guler et al. [22] compared steel/synthetic fibers in wet-mix shotcrete, prioritizing steel for strength/toughness and synthetics for crack resistance. Nevertheless, research on the mechanical properties and micro-pore structure of sprayed UHPC, as well as its application in support structures for soft and broken rock masses, remains limited.
In this study, a UHPC formulation suitable for large-scale spraying was developed by incorporating manufactured sand (MS) and polypropylene (PP) fibers. A steel tunnel model with a diameter of 5.0 m was utilized to simulate the tunnel environment for laboratory spraying tests. The mechanical properties of both sprayed UHPC and cast UHPC were rigorously evaluated through compressive, flexural, and tensile strength tests. Additionally, the macroscopic porosity was analyzed using mercury intrusion porosimetry (MIP) and a scanning electron microscope (SEM) to gain deeper insights into the material’s pore structure. On this basis, on-site application tests in the engineering project were carried out to verify the applicability of sprayed UHPC.

2. Experimental Materials and Methods

2.1. Materials

The UHPC matrix in this study comprised Portland cement (PC, Type P·I 42.5), a water-retaining thixotropic agent (WRT), silica fume (SF), MS, a polycarboxylate-based superplasticizer (SP), polypropylene (PP) fibers, and mixing water. The PC, produced by the Tianshan Cement Plant in Xinjiang, conformed to the Chinese standard GB175-2007 (Common Portland Cement) [23]. Standard mortar specimens exhibited 28-day compressive and flexural strengths of 43.2 MPa and 6.5 MPa, respectively. The SF used in this study originated from Maoheng Co., Ltd. in Shihezi, Xinjiang, China, and its specific parameters were as follows: the specific surface area of SF was 19,300 m2/kg, and the SiO2 content was 92.8%. The WRT, developed in-house, demonstrated properties listed in Table 1. Derived from tunnel slag, MS served as a filler in the UHPC matrix, primarily composed of CaCO3 and SiO2, with a maximum particle size of less than 4.75 mm. The specific morphology and chemical composition can be found in Figure 1. The SP, a polycarboxylate-based admixture, achieved a water-reduction rate exceeding 35% and a solid content >34%, effectively lowering the water–binder ratio. The PP fibers, with a length of 10 ± 10% mm and an equivalent diameter of 0.1–0.4 mm, exhibited a tensile strength ≥400 MPa and elongation at break ≤30%.

2.2. Preparation of the Sprayed UHPC and Cast UHPC Specimens

The mixture proportion of the sprayed UHPC and cast UHPC matrix, based on the dense packing theory [24], was provided in Table 2. For both the spray and cast processes, the water–binder ratio was fixed at 0.18. The SP dosage was set at 2% by the mass of cementitious materials. Based on prior studies and preliminary experimental results, the optimal PP fiber content was determined as 2% by volume (equivalent to 18.2 kg/m3) [25]. The UHPC slurry was prepared using a 0.8 m3 horizontal forced action mixer, and the spraying machine used was the SPL6 wet-mix concrete sprayer, which was produced by the Henan Coal Science Research Institute, with a maximum pumping capacity of 6 m3/h. The spraying procedure is illustrated in Figure 2. The procedure included three stages:
(1)
Dry mixing of the PC, SF, WRT, and MS took place for 1–2 min at a speed of 65 rpm; the subsequent addition of water and SP with continued mixing for 6–8 min to form a homogeneous slurry; and a final incorporation of PP fibers with additional mixing for 2–3 min to ensure uniform dispersion occurred. After mixing, a flow expansion test was carried out to evaluate the concrete’s flowability. The total mixing time was controlled within 15 min, and the fresh slurry was required to be sprayed within 40 min.
(2)
Before commencing the spraying operation, the air compressor should be activated to maintain a constant pressure of 0.6 MPa in the air receiver tank. Subsequently, the UHPC slurry was poured into the hopper of the wet-spray machine, with the slurry pumping speed maintained at 3–5 m3/h. To ensure operational safety, the procedure requires that the high-pressure air be turned on before the UHPC slurry is pumped. Referencing the Chinese standard GB 50086–2015 [26], with the assistance of high-speed air, the UHPC slurry was sprayed into the mold (450 mm × 450 mm × 120 mm). During the spraying process, the spray nozzle should be perpendicular to the mold and maintain a distance of 1.3–1.7 m.
(3)
Following the completion of the spraying process, the specimens were demolded after 24 h, cut into the designated dimensions as shown in Figure 2, and placed in a standard curing room at a temperature of 20 ± 2 °C and a humidity of 95% until 28 days and 90 days had passed [27].

2.3. Experimental Methods

2.3.1. Mechanical Performance Tests

A SANS YAW-3000 pressure tester was employed to evaluate the compressive strength of the UHPC, while tensile and flexural strength tests were conducted using a universal testing machine at the State Key Laboratory of Geomechanics and Geotechnical Engineering, Chinese Academy of Sciences [28]. As shown in Figure 2A, cubic specimens (100 mm × 100 mm × 100 mm) were tested at 28 and 90 days for compressive strength according to GB/T50081-2019 [27], with a loading rate of 1.2 MPa/s and each group containing at least 6 samples. Flexural strength: Prismatic specimens (40 mm × 40 mm × 160 mm) followed T/CBMF 37–2018 [29] “Fundamental Characteristics and Test Methods of Ultra High Performance Concrete”, loaded at 0.1 mm/min. Tensile strength: Dog bone-shaped specimens were subjected to a controlled loading rate of 0.2 mm/min.

2.3.2. Porosity Test

The pore size measurement methods included MIP (100 nm–100 μm), nitrogen adsorption (2–100 nm), carbon dioxide adsorption (0.4–2 nm), SAXS/SANS (1–100 nm), and NMR (0.1–100,000 nm). Since MIP aligns with the pore size range of concrete, it was used to characterize the pores in sprayed UHPC [30].
As shown in Figure 2B, porosity characterization was conducted using a Micromeritics AutoPore IV 9500 porosimeter, wherein mercury was incrementally pressurized into the specimen’s pore network. To satisfy the stringent vacuum requirements for MIP analysis, sample preparation involved thermal drying at 80 °C until constant mass stabilization was achieved. A contact angle of 130° was configured for mercury–solid interactions. This protocol enabled the quantification of intrinsic structural parameters, including pore size distribution and volumetric porosity. The applied pressure regime spanned from 1.56 × 10−3 MPa to 227.53 MPa, corresponding to resolvable pore diameters ranging from 5 nm to 100 μm [31].

2.3.3. SEM Analysis

The SEM instrument utilized for the tests was the Zeiss Gemini Sigma 300 VP SEM from the State Key Laboratory of Geomechanics and Geotechnical Engineering, Chinese Academy of Sciences (Wuhan, China). Following the compressive strength tests, samples were randomly extracted from different regions of the crushed UHPC specimens. The broken specimens with sizes of about 10 mm were immersed into isopropanol for 72 h and then dried at 45 °C. These samples underwent vacuum treatment and platinum coating before being observed under SEM [32].

3. Experimental Results and Discussion

3.1. Mechanical Properties

The strength test results are presented in Figure 3 and the failure mode is shown in Figure 3c. The 28-day compressive strengths of sprayed UHPC at the foot (S-F), haunch (S-H), and vault (S-V) were 111.2 MPa, 110.9 MPa, and 110.6 MPa, respectively (the subsequent description follows the same order), while the compressive strength of cast UHPC was measured at 108.2 MPa. The 28-day flexural strengths of sprayed UHPC at S-F, S-H, and S-V were 11.8 MPa, 12.0 MPa, and 11.7 MPa, respectively, while the 28-day tensile strengths were 4.4 MPa, 4.3 MPa, and 4.3 MPa, respectively. The cast UHPC yielded flexural and tensile strengths of 12.3 MPa and 4.6 MPa, respectively. The mechanical properties of sprayed UHPC displayed minimal variation relative to those of the cast UHPC. The compressive strengths of sprayed UHPC at S-F, S-H, and S-V increased slightly as the curing age increased from 28 days to 90 days, with increases of 6.9 MPa, 6.1 MPa, and 5.3 MPa, respectively. These increases were lower than the 12.8 MPa recorded for cast UHPC.
This modest enhancement in mechanical properties may be attributed to the unique characteristics of the manufactured sand that was used in the sprayed UHPC mixture. The surface of manufactured sand particles is rough and angular, which significantly enhances the mechanical interlocking that occurs between the aggregate and the mortar, thereby effectively improving the interfacial bond performance [33]. Under the action of high-pressure air, the interlocking effect between the aggregate and the mortar becomes more pronounced, further promoting the densification of the interfacial transition zone (ITZ). This results in a more compact microstructure, thereby maintaining the outstanding mechanical properties of sprayed UHPC. Additionally, the incorporation of trace stone powder with a particle size of less than 75 μm filled voids within the concrete, thereby increasing the density of the matrix and enhancing the structural integrity of the sprayed UHPC [34,35]. Moreover, the sprayed UHPC experienced water loss over extended pumping distances and during atomization at the nozzle, leading to a decrease in the water-to-binder ratio. This temporarily enhanced the short-term mechanical properties. Concurrently, the use of an alkali free accelerator accelerated the hydration process and consumed a large amount of mixing water in the early stage of hydration [36], which was not conducive to the late hydration of the sprayed UHPC with a low water–binder ratio, and this was one of the reasons for the slow strength gain in the later stage [37,38,39].

3.2. The Porosity and Microstructure

As shown in Figure 4, the porosity of sprayed UHPC was found to be greater than that of cast UHPC at 28 days. The porosity values for sprayed UHPC at different locations were 8.6%, 8.6%, and 8.8%, while this was 7.4% for the cast UHPC. As the curing age increased from 28 days to 90 days, the porosity of the sprayed UHPC at different locations decreased to 7.7%, 7.9%, and 8.1%, while that of the UHPC decreased to 6.2%. This observation further explained the higher 90-day strength of the UHPC compared to the sprayed UHPC.
Although the sprayed UHPC had a slightly higher porosity at 28 days, its mechanical properties were not negatively affected due to its lower proportion of large harmful pores compared to the cast UHPC. Specifically, the proportions of the large pores (>10 μm) in the sprayed UHPC at S-F, S-W, and S-V were 14%, 20%, and 17%, respectively, which were significantly lower than the 32% observed in the cast UHPC. Meanwhile, the sprayed UHPC had a higher proportion of harmless pores smaller than 100 nm. Their values at S-F, S-H, and S-V were 70%, 65%, and 65%, respectively, while this was 53% for the cast UHPC. At 90 days, the proportion of harmful pores (>10 μm) in the UHPC was 6%, which was lower than the evaluated 8% for the sprayed UHPC across the different locations. This reduction in porosity correlated with superior mechanical properties.
As depicted in Figure 5A, the SEM images revealed that the sprayed UHPC possesses a denser microstructure. The surface bubbles were independent and isolated rather than interconnected. A low porosity, adequate pore distribution, and dense structure were critical factors contributing to the excellent mechanical performance of both the sprayed UHPC and the cast UHPC. The high pressure air not only brings about a dense structure for the sprayed UHPC but it also enhances fiber–matrix interfacial bonding. Figure 5B reveals that the slurry adhering to the sprayed UHPC was more abundant than on the cast UHPC surface. Therefore, the sprayed UHPC exhibits a stronger bond with the cementing material, resulting in a denser formed matrix. This characteristic enables it to dissipate more energy during the pull-out slip friction process compared with the cast UHPC.

3.3. Engineering Application

Engineering application tests were carried out at a diversion tunnel in the Xinjiang Uygur Autonomous Region, China. The tunnel has a maximum buried depth of 2268 m and encounters a complex geology characterized by folding, faults, and variable rock masses, posing challenges such as large deformation and rock bursts. In some sections, the deformation intrusion reaches 15 cm. This project evaluates the use of sprayed UHPC for tunnel lining to reduce thickness, construction time, and associated risks, and to address spatial constraints.
During on-site testing, PC, SF, WRT, MS, and PP fibers were mixed for 180 s in a mixer at a rotation speed of 95 rpm to create a pre-mix. At the designated tunnel section, the pre-mix was fed by a spiral conveyor into the mixer. Water and a SP were added, and the mixture was stirred at a rotation speed of 24.5 rpm for 360 s. The mixture was then placed in a hopper and pumped to the nozzle for spraying at a pumping rate of 4.9 m3/h and a pumping distance of 42 m. As shown in Figure 6f, the spraying sequence involved a single application between two steel arches, with a thickness of 12 cm. During the spraying process, the air pressure was set at 0.8 MPa, and the air volume was 11.6 m3/h. The nozzle used had a diameter of 5 cm and a length of 50 cm. The dosage of the accelerator increased from the arch waist to the arch top, being 3%, 3%, and 5.2%, respectively. Additionally, the distance between the nozzle and the initial lining surface was maintained at 1.3–1.7 m (as shown in Figure 6g,h). As shown in Figure 6j, overly close spraying caused significant surface flatness discrepancies. Increasing the spraying distance to >1.3 m and controlling the pumping rate at 5 m3/h achieved a spray surface flatness of less than 3 mm, meeting the requirements (Figure 6k). It should be noted that during the spraying process, the dosage of the accelerator should be carefully controlled to avoid excessive amounts. An excessive dosage would lead to an increase in the rebound rate, which is not conducive to construction quality and efficiency. After the spraying was completed, the surface was treated and the rebound measurement was carried out during non-construction periods.
The results show that the sprayed UHPC exhibits excellent workability, with a slump-flow of 601 mm. The mechanical properties are shown in Figure 7, and the results indicated that the strength reaches 1.5 MPa at 1 h and 3.9 MPa at 1.5 h after spraying, which is 1.25–3 times higher than conventional shotcrete (0.5–1.2 MPa). By 6 h, its strength reaches 10 MPa, which is 2.5–5 times the 6-h range of ordinary mixtures, demonstrating superior early age performance. The sprayed UHPC demonstrated a progressive strength development, achieving 20 MPa at 16 h, 25 MPa at 20 h, and ultimately reaching 30 MPa within 24 h (i.e., the strength of ordinary sprayed concrete at a 28-day curing age), the designed strength of 60 MPa is achieved within 48 h, with a rebound rate of less than 5%. The high early strength of the sprayed UHPC offered timely and effective support, reduced material waste, and enhanced economic benefits.

4. Conclusions

In this paper, a novel formulation of sprayed UHPC suitable for large-scale applications has been successfully developed. The mechanical properties and pore characteristics of sprayed UHPC were systematically investigated through controlled laboratory spray tests in a simulated tunnel environment and field applications. The main theoretical and practical contributions are summarized as follows:
(1)
The mechanical properties of the sprayed UHPC material were examined through a series of strength tests. Experimental results demonstrated that by incorporating manufactured sand into the UHPC matrix, the mechanical properties of sprayed UHPC are comparable to those of cast UHPC across various spraying orientations, confirming its structural reliability for practical applications. This study offers robust theoretical underpinnings and practical guidance for the development of sustainable green sprayed UHPC, effectively driving down UHPC costs and advancing its progress in environmental protection and resource recycling.
(2)
The pore characteristics of the sprayed UHPC material were revealed through advanced microstructural analysis using SEM. The pore structure was primarily characterized by isolated and non-interconnected micropores with diameters smaller than 100 nm. The high pressure air-driven spraying technique effectively prevented the formation of harmful macropores larger than 10 μm, thereby enhancing the mechanical properties of the material. This process simultaneously reduced early age porosity and improved pore connectivity in the UHPC, providing a critical reference for advancing research on enhancing UHPC durability through process optimization.
(3)
The early age strength development and low rebound rate of sprayed UHPC were validated through field tests. A compressive strength of 30 MPa was achieved within 24 h, reaching 60 MPa within 48 h, while the rebound rate remained consistently below 5%. The systematic refinement of indoor spraying process parameters, which integrates material fundamentals with engineering considerations, establishes a robust theoretical framework and actionable technical guidelines for implementing sprayed UHPC technologies. This study offers pivotal insights into the technological evolution of sprayed UHPC systems, thereby expanding their applicability in specialized domains such as tunneling and underground construction.

Author Contributions

Z.W.: Writing—original draft, Formal analysis, Data curation, Conceptualization. X.T.: Writing—review & editing, Methodology, Data curation, Conceptualization. J.Y.: Writing—review & editing. C.W.: Writing—review & editing, Conceptualization. Y.L.: Project administration. All authors have read and agreed to the published version of the manuscript.

Funding

The authors gratefully acknowledge support provided by the National Natural Science Foundation of China (Grant No. 52279119, 42293355, 51991392); the Science and Technology Planning Project of Xizang Autonomous Region, China (Grant No. XZ202201ZY0021G, No. XZ202401ZY0085); and the Youth Innovation Promotion Association CAS.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

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 conflict of interest.

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Figure 1. Properties of MS.
Figure 1. Properties of MS.
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Figure 2. (A). Experimental procedure and mechanical testing of sprayed UHPC. (B) Sprayed UHPC specimens used for MIP and SEM tests.
Figure 2. (A). Experimental procedure and mechanical testing of sprayed UHPC. (B) Sprayed UHPC specimens used for MIP and SEM tests.
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Figure 3. (a) Mechanical properties of sprayed UHPC at 28 days. (b) Mechanical properties of sprayed UHPC at 90 days. (c) Sprayed UHPC specimen failure modes at 28 days and 90 days.
Figure 3. (a) Mechanical properties of sprayed UHPC at 28 days. (b) Mechanical properties of sprayed UHPC at 90 days. (c) Sprayed UHPC specimen failure modes at 28 days and 90 days.
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Figure 4. Pore size characteristics of sprayed UHPC: Distribution and proportion at 28 and 90 days. (a,b) 28-day Pore Distribution Diagram, (c,d) 90-day Pore Distribution Diagram.
Figure 4. Pore size characteristics of sprayed UHPC: Distribution and proportion at 28 and 90 days. (a,b) 28-day Pore Distribution Diagram, (c,d) 90-day Pore Distribution Diagram.
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Figure 5. (A) Pore microstructure characteristics of sprayed UHPC and cast UHPC. (B) Fiber microstructure in sprayed UHPC and cast UHPC.
Figure 5. (A) Pore microstructure characteristics of sprayed UHPC and cast UHPC. (B) Fiber microstructure in sprayed UHPC and cast UHPC.
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Figure 6. Schematic illustration of integrated sprayed UHPC construction process flow and performance testing in tunnel support applications.
Figure 6. Schematic illustration of integrated sprayed UHPC construction process flow and performance testing in tunnel support applications.
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Figure 7. Mechanical property development curve of on-site sprayed UHPC.
Figure 7. Mechanical property development curve of on-site sprayed UHPC.
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Table 1. Primary technical specifications of WRT.
Table 1. Primary technical specifications of WRT.
WRTPrimary Technical Specifications
Chloride ion content≤0.6%
Alkali content≤1.0%
Compressive strength ratio≥100%
Fineness (85 μm Residue)≤10%
Setting Time Difference−90~+120 min
Table 2. Mixing ratios of cast UHPC and sprayed UHPC.
Table 2. Mixing ratios of cast UHPC and sprayed UHPC.
MaterialsSprayed UHPCCast UHPC
Portland Cement720720
Silica Fume200200
WRT100100
Manufactured sand10701070
Superplasticizer2021
Water-Binder0.180.18
Alkali-free accelerator160
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MDPI and ACS Style

Wang, Z.; Tan, X.; Yuan, J.; Wang, C.; Liu, Y. A Study on the Pore and Strength Characteristics of an Eco-Friendly Sprayed Ultra High Performance Concrete with Manufactured Sand. Appl. Sci. 2025, 15, 3776. https://doi.org/10.3390/app15073776

AMA Style

Wang Z, Tan X, Yuan J, Wang C, Liu Y. A Study on the Pore and Strength Characteristics of an Eco-Friendly Sprayed Ultra High Performance Concrete with Manufactured Sand. Applied Sciences. 2025; 15(7):3776. https://doi.org/10.3390/app15073776

Chicago/Turabian Style

Wang, Zhonghao, Xianjun Tan, Jingqiang Yuan, Chongge Wang, and Yubiao Liu. 2025. "A Study on the Pore and Strength Characteristics of an Eco-Friendly Sprayed Ultra High Performance Concrete with Manufactured Sand" Applied Sciences 15, no. 7: 3776. https://doi.org/10.3390/app15073776

APA Style

Wang, Z., Tan, X., Yuan, J., Wang, C., & Liu, Y. (2025). A Study on the Pore and Strength Characteristics of an Eco-Friendly Sprayed Ultra High Performance Concrete with Manufactured Sand. Applied Sciences, 15(7), 3776. https://doi.org/10.3390/app15073776

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