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Advanced Studies in Structure Materials—2nd Edition

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A special issue of Buildings (ISSN 2075-5309). This special issue belongs to the section "Building Materials, and Repair & Renovation".

Deadline for manuscript submissions: closed (28 February 2026) | Viewed by 16385

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Special Issue Editors

Dr. Yang Li

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Institute of Water Resources and Hydro-Electric Engineering, Xi’an University of Technology, Xi’an 710048, China
Interests: mechanical and durability performance of hydraulic concrete; repair techniques for hydraulic structures; novel repair materials; service life prediction modeling; hydrodynamic framework
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Prof. Dr. Ruijun Wang

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State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Shanxi 710048, China
Interests: hydraulic structures materials; building materials properties and simulation
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Dr. Yiping Luo

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State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Shanxi 710048, China
Interests: concrete materials; geotechnical engineering; transmission structure
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Dr. Xiaochun Lu

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Guest Editor

College of Hydraulic and Environmental Engineering, China Three Gorges University, Yichang 443005, China
Interests: hydraulic structures materials
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Dr. Li Li

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Guest Editor

College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China
Interests: fiber reinforced concrete; geopolymer concrete
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Special Issue Information

Dear Colleagues,

Concrete, mortar, and geo-materials are commonly used building materials for various hydraulic structures. As we all know, the operating conditions and working environment of hydraulic structures such as dams, spillways, weirs, culverts, and canals are very complex. During the operation period, they are not only affected by various loads in different ways but are also subjected to natural factors such as abrasion, freeze–thaw, infiltration, carbonization, chemical erosion, and so on in a relatively harsh environment. These environments easily cause decay and aging of the physical and mechanical properties of building materials, thereby shortening the service life of hydraulic structures and even threatening the safe operation of hydraulic structures. Therefore, for some old and ill hydraulic structures, it is necessary to adopt high-performance repair materials and repair processes to ensure their safe operation. With the construction of high dams and reservoirs around the world, higher requirements will be placed on the material properties and restoration of hydraulic structures in the future, and there is a need to develop hydraulic structures materials.

The main aim of this Special Issue "Advanced Studies in Structure Materials" in Buildings is to provide a platform for the discussion of the major research challenges and achievements in the development of novel hydraulic structures materials. We warmly invite authors to submit their papers for potential inclusion in this Special Issue on concrete, repair materials, mortar, sustainable materials, and geo-materials in hydraulic structures such as dams, spillways, weirs, culverts, and canals.

Dr. Yang Li
Prof. Dr. Ruijun Wang
Dr. Yiping Luo
Dr. Xiaochun Lu
Dr. Li Li
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Buildings is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

structures concrete
durability
repair materials
sustainable materials
structures mortar
freeze–thaw
sulfate attack
mechanical property
geo-materials
environmental factor

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Published Papers (10 papers)

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Research

21 pages, 4966 KB

Open AccessArticle

Study on the Compression Performance of Prefabricated Reinforced Welded Hollow Sphere Joints

by Gang Liang, Miaotong Cheng, Yunhe Liu, Mingtao Li and Tao Gao

Buildings 2026, 16(7), 1364; https://doi.org/10.3390/buildings16071364 - 30 Mar 2026

Viewed by 247

Abstract

To address the challenges encountered during the in situ welding reinforcement process of hollow spherical joints, including complex construction, limited quality control, and low efficiency, this study proposed a prefabricated reinforced hollow spherical joint. A three-dimensional finite element (FE) model was developed and validated against experimental results to quantify the effects of T-rib web width (b), web thickness (t₁), ferrule thickness (t₂), hollow-sphere diameter (D), and bolt pretension (f_v) on the bearing capacity of the prefabricated joint. Based on these analyses, a predictive model was established for the axial compressive bearing capacity of the prefabricated joint. The results showed that, under compression, the reinforcing components primarily provided a supporting role to the hollow sphere, thereby improving the buckling resistance of the prefabricated joint under compression. The reinforcement mechanism primarily relied on friction between the ferrule and the steel stub for load transfer, with the available frictional resistance governed primarily by bolt pretension and the stiffness of the reinforcing components. When sufficient friction existed between the ferrule and the steel tube, increasing the T-rib web width from 0 mm to 80 mm improved the bearing capacity of the prefabricated joint by 33%. At a T-rib flange height (h)-to-web width ratio of h/b = 1.0, the T-rib satisfied the reinforcement requirement through its inherent strength and stiffness. As the hollow-sphere diameter-to-thickness ratio decreased, the incremental gain in bearing capacity diminished. A predictive model was proposed for compressive bearing capacity by accounting for the support provided by the reinforcing components and the effects of hollow-sphere diameter, steel-tube diameter, and the tube-to-sphere diameter ratio. The proposed model predicted the FE results with errors within ±10%, and the findings can provide a practical reference for designing the compressive bearing capacity of prefabricated reinforced hollow spherical joints. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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25 pages, 9313 KB

Open AccessArticle

Effect of Salt Frost Cycles on the Normal Bond Behavior of the CFRP–Concrete Interface

by Hao Cheng, Yushi Yin, Tian Su and Dongjun Chen

Buildings 2026, 16(3), 586; https://doi.org/10.3390/buildings16030586 - 30 Jan 2026

Viewed by 494

Abstract

The durability of the carbon fiber-reinforced polymer (CFRP)–concrete interface is a critical indicator for assessing the service life of composite structures in cold regions. This study systematically investigates the normal bond behavior under coupled deicing salt and freeze–thaw cycles through single-sided salt-frost tests on 126 specimens. The influence of surface roughness, number of freeze–thaw cycles, concrete strength grade, and CFRP material type was systematically evaluated. The results demonstrate that bond behavior is positively correlated with surface roughness, with the f₂ interface exhibiting optimal performance and increasing the ultimate capacity by up to 76.61% compared to the smooth interface. CFRP cloth showed superior bond retention compared to CFRP plates, which experienced a bond strength loss rate up to 26.90% higher than cloth specimens after six cycles. A critical performance threshold was identified between six and eight cycles, where the failure mode transitioned from cohesive adhesive failure to brittle interfacial debonding. Concrete matrix strength had a negligible effect compared to the dominant environmental damage. A two-parameter prediction model based on cycle count and roughness was established with high accuracy. SEM analysis confirmed that epoxy resin cracking, fiber–matrix debonding, and microcrack propagation in the concrete surface layer were the fundamental causes of macroscopic mechanical degradation. These findings provide a theoretical foundation for optimizing interface treatment and predicting the structural integrity of CFRP-strengthened systems in salt-frost regions. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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20 pages, 12987 KB

Open AccessArticle

Seismic Responses in Shaking Table Tests of Spatial Crossing Tunnels

by Zhiqiang Lv, Jiacheng Li and Jiaxu Jin

Buildings 2026, 16(2), 312; https://doi.org/10.3390/buildings16020312 - 11 Jan 2026

Viewed by 328

Abstract

To study the complex dynamic response characteristics of spatial crossing tunnels under seismic loads, shaking table model tests were carried out for typical spatial parallel, orthogonal, and oblique crossing tunnels. The propagation and energy distribution characteristics of seismic waves were quantitatively analyzed according to the fundamental frequency, acceleration, and strain response of the system. The results show the following: the addition of a tunnel structure significantly reduces the natural frequency of the system. In spatial crossing tunnel engineering, the axial acceleration responses of the arch top and arch bottom of the tunnel both exhibit the characteristic of a linear distribution, presenting a ‘linear’ shape. For spatial parallel-type and spatial orthogonal-type tunnels, the peak acceleration at the same measurement point of the overcrossing tunnel under the same working condition is generally greater than that of the undercrossing tunnel. However, for the spatial oblique intersection-type structure, the result is just the opposite, that is, the peak acceleration of the overcrossing tunnel is generally less than that of the undercrossing tunnel. For spatial crossing tunnels, unlike the amplification effect of acceleration in a single tunnel, due to the reflection and refraction of seismic waves between the two tunnels, a ‘superposition effect’ of acceleration is generated in space, resulting in an abnormal increase in the acceleration response within the crossing section, which is prone to becoming a weak link in the seismic resistance of the tunnel structure. The strain response of both spatially parallel and orthogonal overcrossing tunnels is greater at the central section than that of undercrossing tunnels and less on both sides. The strain response of the spatial oblique intersection-type overcrossing tunnel is generally greater than that of the undercrossing tunnel. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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17 pages, 2616 KB

Open AccessArticle

Investigation of the Dynamic Characterization of Traditional and Modern Building Materials Using an Impact Excitation Test

by Anil Ozdemir

Buildings 2025, 15(15), 2682; https://doi.org/10.3390/buildings15152682 - 30 Jul 2025

Cited by 2 | Viewed by 1105

Abstract

This study presents a comprehensive non-destructive evaluation of a broad range of construction materials using the impulse excitation of vibration (IEV) technique. Tested specimens included low- and normal-strength concrete, fiber-reinforced concrete (with basalt, polypropylene, and glass fibers), lime mortars (NHL-2 and -3.5), plaster, and clay bricks (light and dark). Compressive and flexural strength tests complemented dynamic resonance testing on the same samples to ensure full mechanical characterization. Flexural and torsional resonance frequencies were used to calculate dynamic elastic modulus, shear modulus, and Poisson’s ratio. Strong correlations were observed between dynamic elastic modulus and shear modulus, supporting the compatibility of dynamic results with the classical elasticity theory. Flexural frequencies were more sensitive to material differences than torsional ones. Fiber additives, particularly basalt and polypropylene, significantly improved dynamic stiffness, increasing the dynamic elastic modulus/compressive strength ratio by up to 23%. In contrast, normal-strength concrete exhibited limited stiffness improvement despite higher strength. These findings highlight the reliability of IEV in mechanical properties across diverse material types and provide comparative reference data for concrete and masonry applications. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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21 pages, 4748 KB

Open AccessArticle

Investigation on Thermal Conductivity of Soil Under Freeze–Thaw Action Based on Machine Learning Models

by Yuwei Chen, Yadi Min, Haiqiang Jiang, Jing Luo, Mengxin Liu, Enliang Wang, Xingchao Liu, Ke Shi and Xiaoqi Li

Buildings 2025, 15(5), 750; https://doi.org/10.3390/buildings15050750 - 25 Feb 2025

Cited by 3 | Viewed by 1643

Abstract

Thermal conductivity is a crucial factor for the soil, which is significantly affected by environmental conditions. Based on the variation in the thermal conductivity and the influencing factors of silty clay obtained by the freeze–thaw cycle test, this paper adopted four machine learning models optimized by particle swarm optimization (PSO), including the artificial neural network model (ANN), random forest model (RF), support vector machine model (SVM), and extreme gradient boosting model (XGBoost) to predict the thermal conductivity of the soil. Meanwhile, mean absolute error (MAE), root mean square error (RMSE), and correlation coefficient(R²) were used to evaluate the accuracy of the models. The accuracy of the machine learning model and empirical model were also compared. Then, the Monte Carlo simulation was used to analyze the stability of the models. The research results showed that the predicted performance of the machine learning models is significantly better than the empirical models. Among all the machine learning models, the R² of the PSO-ANN model is above 0.95, while both RMSE and MAE values are below 0.02 (W·m⁻¹·K⁻¹). In addition, the stability order of the machine learning models is PSO-XGBoost, PSO-ANN, PSO-RF, and PSO-SVM. Therefore, comprehensively considering the accuracy and stability of the four machine learning models, the PSO-ANN model is recommended to predict soil’s thermal conductivity under freeze–thaw action. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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16 pages, 6602 KB

Open AccessArticle

Experimental Study of Alkali-Activated Cementitious Materials Using Thermally Activated Red Mud: Effect of the Si/Al Ratio on Fresh and Mechanical Properties

by Kai Guo, Haifeng Dong, Junyi Zhang, Liqing Zhang and Zhiping Li

Buildings 2025, 15(4), 565; https://doi.org/10.3390/buildings15040565 - 12 Feb 2025

Cited by 21 | Viewed by 3242

Abstract

Bayer red mud (RM)-based geopolymers are economical and ecofriendly alternatives to cement because of their superior performance. This study investigated alkali-activated cementitious materials by combining RM, fly ash (FA) and slag, and the mixtures were used to produce ecofriendly composites. The influence of the Si/Al molar ratio (3.30–3.79) on the initial properties (setting time and flowability) and hardened properties (compressive strength, drying shrinkage and water permeability) of the composite materials was studied. The Na₂O content was fixed at 4 wt%, and the thermal activation temperature was 800 °C. The phase evolution and geopolymerization mechanism of the effect of the initial Si/Al molar ratio on the material properties was investigated by FTIR, XRD, TG–DTG and SEM–EDS. The results of M1.2Si333 indicated that the compressive strength of the blends can reach 33.5 MPa at 28 days, with a drying shrinkage rate of 1.20%. Compressive strength decreases, while drying shrinkage increases with a higher initial Si/Al ratio. Microstructural analyses revealed that a low Si/Al ratio and alkali activator modulus enhance the dissolution of precursors to form C–(A)–S–H gels, which increase the compressive strength. The results promoted the application of RM-based geopolymer-engineered cementitious composite and enhanced the resource efficiency of the bauxite residue. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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19 pages, 5918 KB

Open AccessArticle

Impact of Various Erosive Environments on the Durability of POM Fiber-Reinforced Ultra-High-Performance Concrete

by Jingliang Dong, Yingliang Zong, Xiaopeng Shang, Xiaolei Chen, Zhen Tu, Ren Jiang and Zebing Zhu

Buildings 2024, 14(12), 4048; https://doi.org/10.3390/buildings14124048 - 20 Dec 2024

Cited by 4 | Viewed by 1291

Abstract

To address the durability challenges faced by traditional concrete in marine environments, this study focuses on polyoxymethylene (POM) fiber-reinforced ultra-high-performance concrete (PFUHPC) and, for the first time, systematically investigates the inhibitory effects of POM fibers on microstructural degradation and mechanical performance deterioration of ultra-high-performance concrete under various erosive environments. The results indicated the following: (1) The mass loss rate and compressive strength degradation in PFUHPC under different erosive environments initially increased and then decreased, demonstrating that the inclusion of POM fibers delayed corrosion and significantly improved the durability and stability of the material’s performance. (2) Compared to the natural environment, after 180 days of immersion in different erosive environments (seawater immersion, wet–dry cycles in seawater, chloride salt immersion, sulfate salt immersion, and complex salt immersion), the compressive strength degradations were observed to be 4.8%, 9.7%, 6.8%, 11.7%, and 10.7%. (3) Microscopic analysis after 180 days revealed that the main corrosion products were gypsum, ettringite, and Friedel’s salt (calcium chloroaluminate). Under the environments of seawater immersion and cyclic wetting and drying, the low concentrations of chloride and sulfate ions resulted in fewer corrosion products and a denser matrix. The primary corrosion product under the chloride salt immersion was Friedel’s salt, which led to surface cracking and microporosity, while under the sulfate immersion, gypsum and ettringite were predominant, resulting in more porous and loosely bound hydration products and more severe corrosions. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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24 pages, 9725 KB

Open AccessArticle

Development and Characterization of Alkali-Activated Lithium Slag-Fly Ash Composite Cement

by Jingliang Dong, Zhen Tu, Xiaopeng Shang, Hao Wu, Zhiping Li and Haibin Ding

Buildings 2024, 14(12), 3766; https://doi.org/10.3390/buildings14123766 - 26 Nov 2024

Cited by 2 | Viewed by 1994

Abstract

As the demand for environmental sustainability grows in the global construction industry, traditional cement production faces significant challenges due to high energy consumption and substantial CO₂ emissions. Therefore, developing low-carbon, high-performance alternative cementitious materials has become a research focus. This paper proposes a new low-carbon cement (alkali-activated lithium slag-fly ash composite cement, ALFC) as a substitute for traditional cement. First, the alkali activation reactivity of lithium slag (LS) is enhanced through calcination and grinding, revealing the reasons behind its improved reactivity. Then, alkali-activated LS and fly ash were partially used to replace cement to prepare ALFC, and the effects of the water-to-binder ratio (W/B), LS content, and NaOH addition on the flowability and mechanical properties of ALFC were investigated. XRD, SEM/EDS, and TG/DTG analyses were conducted to examine its hydration products and microstructure, revealing the hydration mechanism. The results show that the flowability of ALFC increases with W/B but decreases with a higher LS content. When W/B is 0.325 and the LS content is 25 wt.%, flowability reaches 200 mm, meeting construction requirements. LS calcined at 700 °C for 1 h significantly enhanced ALFC’s 90-day flexural and compressive strengths by 39.73% and 58.47%, respectively. The primary hydration products of ALFC are C-S-H, N-A-S-H, and C-A-S-H gels, with their content increasing as the NaOH concentration rises. The optimal NaOH concentration and LS content for ALFC are 2 mol/L and 25 wt.%, respectively. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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19 pages, 9143 KB

Open AccessArticle

Evaluation of Dynamic Mechanical Properties of Steel-Fiber-Reinforced Concrete Subjected to Freeze–Thaw Cycles

by Ruijun Wang, Nan Tian, Jun Liu, Ruibao Jin, Gang Liang, Yan Li, Jing Hu, Hekuan Zhou, Yaofei Jia and Yanxiong Liu

Buildings 2024, 14(9), 2880; https://doi.org/10.3390/buildings14092880 - 12 Sep 2024

Cited by 4 | Viewed by 2560

Abstract

This study investigates the structural characteristics of SFRC with different amounts of steel fibers following exposure to freeze–thaw cycles, while taking into account various levels of confinement pressure and rates of deformation. The focus of the research is to examine the dynamic mechanical properties of SFRC exposed to freeze–thaw cycles. The inclusion of steel fibers improves the strength of concrete during freeze–thaw cycles, with 1% steel fiber content being the most effective. Strain rate and confining pressure significantly impact the strength and failure mode of SFRC. The strength of concrete increases linearly with the strain rate. With no confining pressure, the cracks in the concrete specimen align with the direction of the applied stress. And with confining pressure, concrete exhibits diagonal shear failure. Microstructural analysis results from scanning electron microscopy are consistent with the macroscopic properties. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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22 pages, 8482 KB

Open AccessArticle

Mesoscopic Numerical Simulation of Freeze–Thaw Damage in Hydraulic Concrete

by Ruijun Wang, Yunhui Liu, Jun Liu, Yang Li, Ruibao Jin, Gang Liang, Ningning Yu, Jing Hu, Hekuan Zhou, Yaofei Jia and Yanxiong Liu

Buildings 2024, 14(9), 2694; https://doi.org/10.3390/buildings14092694 - 28 Aug 2024

Cited by 4 | Viewed by 2222

Abstract

To investigate the impact of freeze–thaw damage on the mechanical properties of concrete, this study utilized Python in combination with ABAQUS 2016 to generate a two-dimensional meso-scale model of concrete. Uniaxial compression tests were conducted on the concrete after freeze–thaw cycles to study the evolution of its mechanical properties. Using “relative compressive strength” as a variable, the relationships between this variable and the parameters of the freeze–thaw damage model were determined, leading to the establishment of the freeze–thaw damage model and the simulation of compressive tests on concrete after freeze–thaw cycles. This study also explored the changes in the mechanical properties of concrete with variations in ITZ parameters and coarse aggregate content. The conclusions drawn are as follows: A comparison with experimental data showed that the model ensures that the relative error of each mechanical property parameter does not exceed 7%, verifying the model’s rationality. Increasing the ratio of ITZ parameters improved the mechanical properties of the ITZ, enhancing the overall mechanical performance, but had almost no effect on the elastic modulus. Compared to ratios of 0.7 and 0.8, concrete with a ratio of 0.9 showed slower rates of decrease in compressive strength and elastic modulus and slower rates of increase in peak compressive strain after freeze–thaw cycles. The increase in coarse aggregate content had a similar effect on the strength and freeze–thaw resistance of concrete as the ratio of ITZ parameters. Concrete with a coarse aggregate content of 60% exhibited slower rates of change in mechanical properties after freeze–thaw cycles. Full article

(This article belongs to the Special Issue Advanced Studies in Structure Materials—2nd Edition)

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