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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (10 April 2023) | Viewed by 23942

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Special Issue Editors

Prof. Dr. Wei Wang

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Guest Editor

School of Civil Engineering, Shaoxing University, Shaoxing 312000, China
Interests: soil reinforcement materials; engineering management
Special Issues, Collections and Topics in MDPI journals

Dr. Taeseo Ku

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Guest Editor

Department of Civil and Environmental Engineering, Konkuk University, Seoul 05029, Korea
Interests: soil reinforcement materials; binary mixtures; sustainable and environmentally friendly material

Prof. Zhishu Yao

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Guest Editor

School of Civil Engineering and Architecture, Anhui University of Science and Technology, Huainan 232001, China
Interests: advanced building materials; structure of shaft wall; geothermal energy

Prof. Dr. Aizhao Zhou

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Guest Editor

School of Architecture and Civil Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
Interests: soil reinforcement technology; environmentally eco-friendly material; geothermal energy
Special Issues, Collections and Topics in MDPI journals

Dr. Xianwen Huang

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Guest Editor

1. School of Civil Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
2. Department of Civil & Environmental Engineering, National University of Singapore, Singapore 119077, Singapore
Interests: composite building material; binary mixtures; geothermal energy
Special Issues, Collections and Topics in MDPI journals

Dr. Xue Xin

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Guest Editor Assistant

1. School of Qilu Transporation, Shandong University, Jinan 250002, China
2. Department of Civil & Environmental Engineering, National University of Singapore, Singapore 119077, Singapore
Interests: functional road asphalt materials; pavement engineering intelligent monitoring

Special Issue Information

Dear Colleagues,

We are pleased to inform you that we have launched a new Special Issue of Materials (IF 3.748, JCR Q1), entitled “Mechanical Performance of Composite geomaterials”. This Special Issue aims to reveal the mechanical properties of geotechnical engineering-related composite geomaterials and the interaction between each component through analytical studies, experiments, numerical simulations, and field surveys.

Composite geomaterials play an essential role in geotechnical engineering, in which common composite geomaterials include cement composite geomaterials, asphalt composite geomaterials, and soil–rock mixture materials. By setting different mixing ratios and adding different novel materials and additives, the composites' microstructure and mechanical response characteristics will change, potentially improving the functional performance of composite material and economic returns. Therefore, this Special Issue aims to present novel scientific advances in composite geomaterials, numerical simulation technology, and case studies, thus illuminating the influence mechanism of each component in composite geomaterials to further promote the economic and environmentally friendly application of composite geomaterials.

This Special Issue will publish original high-quality research papers in the fields of:

Novel composite geomaterials;
In situ tests;
Case histories;
Numerical simulation;
Engineering design;
Environmentally friendly materials;
Multiscale analysis;
Mechanism under seepage flow.

Prof. Dr. Wei Wang
Dr. Taeseo Ku
Prof. Zhishu Yao
Prof. Dr. Aizhao Zhou
Dr. Xianwen Huang
Guest Editors

Dr. Xue Xin
Guest Editor Assistant

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 100 words) can be sent to the Editorial Office for announcement on this website.

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. Materials 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

composite geomaterials
cement-based materials
environmentally eco-friendly material
influential mechanism
binary mixtures

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Published Papers (14 papers)

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Research

13 pages, 4061 KiB

Open AccessArticle

Protective Performance of Coated Reinforcement in Coral Concrete under Dry/Wet Cycling

by Hongji Cao, Qing Wu, Muhammad Akbar, Ning Yang and Zahoor Hussain

Materials 2023, 16(11), 4037; https://doi.org/10.3390/ma16114037 - 29 May 2023

Cited by 4 | Viewed by 1370

Abstract

The actual protective performance of the coated reinforcement in coral concrete was investigated by measuring the chloride ion diffusion coefficient, electrochemical analysis, and numerical simulation. The test results show that the corrosion rate of coated reinforcement in coral concrete under the action of wet and dry cycles is kept at a low level, and the Rp value is always greater than 250 kΩ·cm² during the test period, which is in the uncorroded state and has good protection performance. Moreover, the chloride ion diffusion coefficient D is in accordance with the power function relationship with the wet and dry cycle time, and a time-varying model of chloride ion concentration on the surface of coral concrete is established. The surface chloride ion concentration of coral concrete reinforcement was modeled as a time-varying model; the cathodic zone of coral concrete members was the most active, increasing from 0 V to 0.14 V from 0 to 20 years, with a large increase in potential difference before the 7th year, and a significant decrease in the increase after the 7th year. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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18 pages, 26518 KiB

Open AccessArticle

Experimental Study on the Effect of Limestone Powder Content on the Dynamic and Static Mechanical Properties of Seawater Coral Aggregate Concrete (SCAC)

by Juan Qi, Lili Jiang, Ming Zhu, Chaomin Mu and Rui Li

Materials 2023, 16(9), 3381; https://doi.org/10.3390/ma16093381 - 26 Apr 2023

Cited by 9 | Viewed by 1590

Abstract

The development of island construction concrete can serve as a basis for the development and utilization of island resources. Complying with the principle of using local materials to configure seawater coral aggregate concrete (SCAC) that is able to meet the requirements of island and reef engineering construction could effectively shorten the construction period and cost of island and reef engineering construction. In this paper, quasi-static mechanical experiments and dynamic mechanical experiments were carried out on SCAC with different limestone powder contents. High-speed photography technology and Digital Image Correlation (DIC) were used to monitor the dynamic failure process and strain field of SCAC, and the influence of limestone powder content on the dynamic and static mechanical properties of SCAC was investigated. The results showed that, when the limestone powder content was 20% and 16%, the quasi-static compressive strength and quasi-static tensile strength exhibited the best improvement. Additionally, with increasing limestone powder content, the dynamic tensile strength of SCAC first showed and increasing trend and then a decreasing trend, reaching its maximum value when the limestone powder content was 16%. Moreover, the maximum strain value of SCAC with the same limestone powder content increased with increasing strain rate grade, showing an obvious effect on strain rate. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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12 pages, 4119 KiB

Open AccessArticle

Study on Modification and Mechanism of Construction Waste to Solidified Silt

by Yannan Shi, Haoxuan Weng, Jiongqi Yu and Yongfan Gong

Materials 2023, 16(7), 2780; https://doi.org/10.3390/ma16072780 - 30 Mar 2023

Cited by 1 | Viewed by 1489

Abstract

A large amount of silt may be produced in river and lake regulation. It not only occupies land but also pollutes the environment. Therefore, it is urgent to seek effective disposal and utilization methods. Based on the problems of poor stability of stabilized soil and its tendency to soften easily in water, as well as its low strength with low curing agent dosage, this paper proposes a method to improve stabilized soil’s solidification effect by adding materials such as cement, lime, fly ash, triethanolamine, sodium hydroxide, sodium silicate, etc., while mixing different grain diameters and quantities of building waste materials and ordinary sand. Using construction waste and ordinary sand as a comparative test, the curing mechanism of construction waste debris on the mechanical properties, permeability, and microstructure of solidified sludge was studied through unconfined compression tests, dry and wet cycle tests, permeability tests, and micro-structure tests such as XRD, MIP, and SEM. The test results show that the strength increases 8.5%~72.1% by adding building waste materials, and it grew with the increase in particle size and amount. It reduced the content of large pore size of solidified sediment and optimized the internal pore structure. At the same time, it formed a new structure filled by rigid skeleton material. Thus, it improved its unit section stress, built up the curing effect and water stability. The findings of this study can be used to modify solidified silt to improve stability and compaction characteristics. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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16 pages, 3807 KiB

Open AccessArticle

Experimental Study of Stress and Deformation of Reclaimed Asphalt Concrete at Different Temperatures

by Jing Zhang, Mingyuan Zhou, Juan Liu and Xianwen Huang

Materials 2023, 16(3), 1323; https://doi.org/10.3390/ma16031323 - 3 Feb 2023

Cited by 2 | Viewed by 1923

Abstract

Asphalt concrete has been used as a material for dam core walls because of its impermeability, durability and reliability. Firstly, asphalt is a temperature-sensitive material, and many of its characteristics are related to temperature. Secondly, because of the increasing construction height of the dam, the pressure on the asphalt concrete core wall is also great. Finally, for the purpose of resource utilization, it is necessary to verify whether the reclaimed asphalt concrete can be used in dam construction. Therefore, it is necessary to study the stress and deformation characteristics of recycled asphalt concrete under different temperatures and confining pressures. In this study, three groups of triaxial tests of reclaimed asphalt concrete were carried out for the first time in a new temperature-controlled room. Duncan Zhang’s E-v model was used to fit the test results. The results show that the stress–strain curves of reclaimed asphalt concrete show softening characteristics at low temperatures and low confining pressure. It evolves to a hardening type with the increase in temperature and confining pressure. The bulk curve is first contracts but is followed by dilatancy. The dilatancy characteristics become more obvious at low temperatures and low confining pressure. With the increase in temperature and confining pressure, the dilatancy characteristics will weaken. Duncan Zhang’s E-v model has a good fitting effect on the stress–strain relationship but a poor fitting effect on the volumetric curve. The research of this paper can better combine the utilization of waste resources with engineering and achieve the aim of resource-saving and waste utilization under the premise of ensuring the safety of the engineering Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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20 pages, 5891 KiB

Open AccessArticle

Study of Chloride Ion Diffusion in Coral Aggregate Seawater Concrete with Different Water–Cement Ratios under Load

by Guangmin Dai, Qing Wu, Kailong Lu, Shiliang Ma, Wei Wang, Hao Zhou, Chenggong Cai, Zuocheng Han and Jiaming Chen

Materials 2023, 16(2), 869; https://doi.org/10.3390/ma16020869 - 16 Jan 2023

Cited by 2 | Viewed by 1678

Abstract

This study was conducted to investigate the chloride ion transport in coral aggregate seawater concrete (CASC) with varying water–cement ratios under different loads. The ultimate compressive strength was obtained by conducting compression testing of three groups of CASC with different water–cement ratios. Steady loads of 0%, 10%, and 20% of their respective ultimate compressive strengths were applied to the concrete specimens with different water–cement ratios. After being subjected to a seawater erosion test for 30, 60, 90, 120, and 180 days, the chloride ion concentration at different depths was measured to determine the chloride ion diffusion coefficient. Meanwhile, the chloride ion diffusion coefficients of CASC were verified by comparing them with results obtained from numerical simulations performed using COMSOL software. The test results show that the internal pore space of CASC expands, leading to acceleration of the chloride ion transport rate when applied loads are increased. The initial chloride ion concentration of CASC rises as the water–cement ratio rises, and the concentration gradient formed with artificial seawater lowers, decreasing the chloride ion transport rate. When the water cement ratio decreases and the load increases, the diffusion coefficient increases. Using the numerical simulation method of COMSOL software, it was proved that the model has good applicability and accuracy in predicting chloride ion transport in CASC. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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12 pages, 2085 KiB

Open AccessArticle

Modification Effect of Nano-Clay on Mechanical Behavior of Composite Geomaterials: Cement, Nano-Silica and Coastal Soft Soil

by Yaying Wang, Wei Wang, Yinuo Zhao, Na Li, Jiale Luo, Asefa Mulugeta Belete and Jiang Ping

Materials 2022, 15(24), 8735; https://doi.org/10.3390/ma15248735 - 7 Dec 2022

Cited by 8 | Viewed by 1324

Abstract

To study the modification effect of nano-clay and nano-SiO₂ on cement-reinforced coastal soft soil, the effects of the nano-SiO₂ and nano-clay on the mechanical properties of cement soil were studied through unconfined compressive and unconsolidated undrained shear tests, and the Duncan–Chang model was used to fit the test results. Results show that adding nano-clay and nano-SiO₂ to cement soil improved its compressive and shear strength. The compressive strength and shear strength increased by 18–57% and 3–32%, respectively, with the increase in nano-clay content in a content range of 0–10%. Additionally, nano-clay can enhance the ductility of cement soil. Moreover, nano-clay and nano-SiO₂ improve the shear strength by increasing the internal friction angle by 1°–2° and cohesion of 9–25%, and the cement-stabilized coastal soft soil enhanced by nano-SiO₂ and nano-clay conforms to the Duncan–Chang model well. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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17 pages, 5942 KiB

Open AccessArticle

Experimental Study on the Effects of Matric Suction on Shear Properties of Polypropylene Fiber Reinforced Unsaturated Clay

by Ruiqian Wu, Guang Yang, Shaohe Li and Qichen Xiang

Materials 2022, 15(22), 8223; https://doi.org/10.3390/ma15228223 - 19 Nov 2022

Cited by 2 | Viewed by 1547

Abstract

Matric suction has an important effect on the behavior of unsaturated soils, and polypropylene fibers are often used to improve soil. In order to probe into the mechanism of matric suction and fiber reinforcement, triaxial shear tests are carried out with changing matric suction and net confining pressure. Unsaturated clay in the Shaoxing section of East Zhejiang Grand Canal is selected with polypropylene fiber as a reinforcement material in the tests. The results show that the total cohesion intercept and effective internal friction angle of soil increase with the increase in matric suction, while the adsorption internal friction angle decreases gradually. Similarly, the contribution of matric suction to shear strength decreases. The total cohesion intercept is more sensitive to matric suction. As the length of fiber is 12 mm, the shear strength parameters of soil will be improved accordingly, which makes the fiber reinforcement achieve the best. The stress–strain relationship is approximately hyperbolic and strain hardening. The characteristics of strain hardening are more obvious with the increase in matric suction, and the soil specimens present plastic failure. The volumetric strain of specimen is more sensitive to the changing net confining pressure. It increases with the increase in net confining pressure, and increases linearly as the matric suction is zero. The failure modes of triaxial tests are divided into tensile failure and friction failure. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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15 pages, 3395 KiB

Open AccessArticle

Experimental Study on the Mechanical Properties of Diatomite-Modified Coastal Cement Soil

by Jiyuan Fang, Yunfeng Wang, Kefa Wang, Wenhao Dai, Yanfei Yu and Cuihong Li

Materials 2022, 15(21), 7857; https://doi.org/10.3390/ma15217857 - 7 Nov 2022

Cited by 6 | Viewed by 1931

Abstract

Diatomite is a non-metallic mineral resource rich in SiO₂, which can be used to modify coastal cement soil. In order to explore the mechanical modification effect of diatomite on coastal cement soil at the age of 7 days, based on coastal cement soil with cement content of 5% (mass fraction), diatomite of 0%, 5%, 10%, 15% and 20% (mass fraction) was mixed for modification. Through the unconfined compressive strength test, the triaxial unconsolidated undrained test, backscattered electron imaging (BSE), and energy-dispersive spectroscopy (EDS) technology, the influence of diatomite content and confining pressure on the peak strength of modified coastal cement soil was explored. The empirical formula between the peak strength of the DE specimen and the content of diatomite and confining pressure was established by curve fitting, and the fitting effect was ideal. When diatomite was mixed with coastal cement soil, the optimal dosage of diatomite was 5% from the perspective of mechanical properties and economic benefits of the maximum growth rate of compression and shear. The unconfined compressive strength test showed that the peak strength and elastic modulus of the modified coastal cement soil with 5% diatomite content were 37% and 57% higher than those of cement soil, respectively. The triaxial unconsolidated undrained test showed that the internal friction angle of the modified coastal cement soil was stable at about 30°, and cohesion of DE-5, DE-10, DE-15, and DE-20 increased by 28%, 48%, 78%, and 97%, respectively, compared to cement soil. The microscopic test found that the pore distribution of modified coastal cement soil is closely related to the strength change. The results show that the addition of diatomite can effectively improve the mechanical properties of soil-cement. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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16 pages, 3852 KiB

Open AccessArticle

Theoretical Research on Diffusion Radius of Cement-Based Materials Considering the Pore Characteristics of Porous Media

by Bao Xie, Hua Cheng, Xuesong Wang, Zhishu Yao, Chuanxin Rong, Ruihe Zhou, Liangliang Zhang, Longhui Guo, Hong Yu, Wei Xiong and Xusong Xiang

Materials 2022, 15(21), 7763; https://doi.org/10.3390/ma15217763 - 3 Nov 2022

Cited by 5 | Viewed by 1803

Abstract

In engineering, loose sandy (gravelly) strata are often filled with cement-based grout to form a mixed material with a certain strength and impermeability, so as to improve the mechanical properties of sandy (gravelly) strata. The tortuosity effect of sandy (gravelly) strata and the time-varying viscosity of slurry play a key role in penetration grouting projects. In order to better understand the influence of the above factors on the penetration and diffusion mechanism of power-law slurry, based on the capillary laminar flow model, this research obtained the seepage motion equation of power-law slurry, the time-varying constitutive equations of tortuosity and power-law fluid viscosity were introduced, and the spherical diffusion equation of penetration grouting considering both the tortuosity of porous media and time-varying slurry viscosity was established, which had already been verified by existing experiments. In addition, the time-varying factors of grouting pressure, the physical parameters of the injected soil layer, and slurry viscosity on penetration grouting diffusion law and the influencing factors were analyzed. The results show that considering the tortuosity of sandy (gravelly) strata and the time-varying of slurry viscosity at the same time, the error is smaller than the existing theoretical error, only 13~19%. The diffusion range of penetration grouting in the sandy (gravelly) strata is controlled by the tortuosity of sandy (gravelly) strata, the water–cement ratio of slurry, and grouting pressure. The tortuosity of sandy (gravelly) strata is inversely proportional to the diffusion radius of the slurry, and the water–cement ratio of slurry and grouting pressure are positively correlated with the diffusion radius. In sandy (gravelly) strata with a smaller particle size, the tortuosity effect of porous media dominates the slurry pressure attenuation. When the particle size is larger, the primary controlling factor of slurry pressure attenuation is the tortuosity effect of porous media in the initial stage and the time-varying viscosity of slurry in the later stage. The research results are of great significance to guide the penetration grouting of sandy (gravelly) strata. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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13 pages, 3439 KiB

Open AccessArticle

Energy Dissipation and Dynamic Fragmentation of Alkali-Activated Rubber Mortar under Multi-Factor Coupling Effect

by Yuhang Shi, Qinyong Ma, Zifang Xu, Dongdong Ma, Xuan Yang and Yuqi Gu

Materials 2022, 15(21), 7718; https://doi.org/10.3390/ma15217718 - 2 Nov 2022

Cited by 2 | Viewed by 1397

Abstract

Recycled rubber aggregate (RRA) made from ground tire rubber has been promoted for its light weight and shock resistance. The high alkalinity of alkali-activated slag mortar has a modification effect on the surface of RRA. This paper studies the performance of alkali-activated slag mortar using RRA as aggregate (RASM), which has significance for applications in low-carbon building materials. The orthogonal test analysis method was used to analyze the significance and correlation of the main variables of the test. The dynamic energy absorption capacity and crushing state of RASM under the synergistic effect of various factors were studied using the separating Hopkinson pressure bar (SHPB) test system. The energy absorption characteristics and failure modes of RASM were analyzed by SEM and microscopic pore characterization. The results show that the increase of the alkali equivalent of the mix ratio will increase the peak value of the absorption energy of the specimen. When the size of the RRA is between 0.48 mm~0.3 mm, the dynamic energy absorption of the specimen will reach its peak value. Although the increase in the total volume of RRA will reduce the energy absorption capacity of RASM specimens, its crack resistance is enhanced. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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13 pages, 2207 KiB

Open AccessArticle

Shear Behavior of Recycled Fine Aggregate Reinforced by Nano-MgO Modified Cement

by Ting Zhu, Yitong Shou, Xiaoqing Chen, Beifeng Lv, Xianwen Huang, Yanfei Yu and Cuihong Li

Materials 2022, 15(20), 7188; https://doi.org/10.3390/ma15207188 - 15 Oct 2022

Cited by 2 | Viewed by 1339

Abstract

In order to study the mechanical modification effect of nano-MgO on cement-reinforced recycled fine aggregate (CRA), direct shear tests and triaxial shear tests were carried out. In the test of recycled fine aggregate reinforced by nano-MgO modified cement (MCRA), the cement content was fixed at 2%, and the nano-MgO content varied between 0%, 0.5%, 1.0%, 1.5% and 2.0%. The test results showed that adding nano-MgO can greatly increase both the direct shear strength and triaxial shear strength of MCRA. This increase in direct shear strength was mainly attributed to the increase in cohesion. However, this increase in triaxial shear strength was attributed to the simultaneous increase in the cohesion and friction angle. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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16 pages, 2800 KiB

Open AccessArticle

The Fingerprint Identification of Asphalt Aging Based on ¹H-NMR and Chemometrics Analysis

by Wenxin Wu, Chenlong Wang, Pinhui Zhao, Linyan Xiu, Liang Fan, Fei Bi, Xiaoqing Song and Xu Zhou

Materials 2022, 15(19), 6825; https://doi.org/10.3390/ma15196825 - 1 Oct 2022

Cited by 3 | Viewed by 1440

Abstract

In this study, the chemical structure of asphalt aging was analyzed and identified based on ¹H-NMR quantitative technology and chemometrics analysis. The characteristic full component information of 30 samples before and after aging from 5 different oil sources was measured by ¹H-NMR, and the results were converted into a data matrix. This study used PCA, HAC, OPLS-DA, and Fisher discriminant analysis to evaluate the change rules of the chemical composition of asphalt from different oil sources after aging. The results showed that the ¹H-NMR spectra of 30 asphalt samples were very similar, and hydrogen could be divided into 4 categories according to the chemical shift: H_A, H_α, H_β, and H_γ. The shapes of ¹H-NMR of asphalt samples from different oil sources showed slight differences, while the shapes of the ¹H-NMR spectra of asphalt samples with different aging degrees from the same oil source was basically the same. The results of PCA and HAC analysis showed that the samples of the same asphalt and asphalt with similar oil sources before and after aging were still in the same category, and the spatial distance was very close, while the spatial distance of asphalts from different oil sources was very different. The Fisher discriminant function established by PCA and HAC can be used to distinguish asphalt samples from different oil sources with an accuracy of up to 100%. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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17 pages, 3649 KiB

Open AccessArticle

Mechanical Properties and Energy Evolution of Fractured Sandstone under Cyclic Loading

by Xinwei Li, Zhishu Yao, Xianwen Huang, Xiaohu Liu, Yu Fang and Yongjie Xu

Materials 2022, 15(17), 6116; https://doi.org/10.3390/ma15176116 - 2 Sep 2022

Cited by 3 | Viewed by 1633

Abstract

Affected by fracture distribution, sandstone shows different deformation and energy evolution characteristics under cyclic loading and unloading conditions. Therefore, uniaxial cyclic loading tests were conducted on fractured sandstone with different angles. The deformation characteristics and the evolution law of energy indexes with the peak load and crack angles were obtained under cyclic loading. Studies have shown that: The deformation modulus of sandstone first increases and then decreases, and the lateral expansion coefficient is positively correlated with the peak load. Based on the viscoelastic deformation theory, an energy analysis model considering damping energy and damage energy is established. The dissipated energy can be divided into the damping energy consumed to overcome rock viscoelasticity and damage energy causing damage by viscoelastic deformation theory. Based on this model, the relationship between elastic property, damping energy, damage energy and fracture angle is obtained, and the damage energy increases slowly first and then rapidly. The research results provide a reference for predicting the damage and failure of rock. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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16 pages, 7017 KiB

Open AccessArticle

Experimental Study on PVA-MgO Composite Improvement of Sandy Soil

by Zhongyao Li, Zhewei Zhao, Haiping Shi, Jiahuan Li, Cheng Zhao and Peiqing Wang

Materials 2022, 15(16), 5609; https://doi.org/10.3390/ma15165609 - 16 Aug 2022

Cited by 1 | Viewed by 1694

Abstract

Materials with violent hydration reaction such as cement are used to solidify sandy soil slopes, which will cause destructive damage to the ecology of the slopes. In this paper, polyvinyl alcohol (PVA) and activated magnesium oxide (MgO) are used to improve sandy soil, and the effects of the dosage and curing age of modifiers on the mechanical properties of solidified sandy soil are studied. The dry–wet durability of the composite improved sandy soil is analyzed using a dry–wet cycle test, and the improvement mechanism of PVA and activated magnesium oxide is revealed using an electron microscope. The results show that the curing effect of polyvinyl alcohol and activated magnesium oxide on sand particles is better than that of polyvinyl alcohol alone. The compressive strength of improved soil samples increases with the increase of curing time, and magnesium oxide as an improved material needs appropriate reaction conditions to give full play to its role. The compressive strength of composite improved samples increases first and then decreases during the dry–wet cycle. Through the observation of microstructure, it can be seen that the cementing material wraps and connects the sand particles, and the cementing material of the sample after the dry–wet cycle develops more completely; if the magnesium oxide content is high, cracks may appear inside the sample. Full article

(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)

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