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Multi-Scale Structural Characterization of Cement-Based Composites

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

Deadline for manuscript submissions: closed (20 August 2023) | Viewed by 34095

Special Issue Editors

College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Interests: microstructures; cement-based materials; characterization methods; durability
Special Issues, Collections and Topics in MDPI journals
School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China
Interests: mass transport; durability; microstructures; NMR
Special Issues, Collections and Topics in MDPI journals
China Building Materials Academy, Beijing 100024, China
Interests: non-destructive material characterization; frost damage; electrical resistivity; durability, 3D-printed cement composites
Special Issues, Collections and Topics in MDPI journals
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Interests: textile-reinforced concrete composites; UHPC; FRC; dynamic behaviour
Special Issues, Collections and Topics in MDPI journals
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China
Interests: concrete; construction materials; corrosion resistant technology; structure dynamics; geopolymer
Special Issues, Collections and Topics in MDPI journals
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Interests: life-cycle assessmemt; low-carbon cement; strain-hardening composites
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues,

Cement-based composites, which play important roles in civil structures and infrastructure, have recently attracted increasing attention from both scientific and engineer communities. Due to the complexities of the raw materials, design codes, casting methods, curing conditions, and serving environments, the structural characterization of cement-based composites involves significant challenges. The multi-scale nature of cement-based composites causes near-insuperable obstacles for their microstructure characterization, as the commonly used techniques (such as SEM and XCT) have limited scopes in terms of structural characterization. Furthermore, the sustainability requirements for cement-based materials in terms of reducing CO2 emmissions and other environmental impacts make the large-scale uses of solid wastes and the development of highly durable concrete necessary. Additionally, 3D-printed concrete requires viscous fresh materials, involving a layer–layer structure that is different from that of ordinary in-situ-cast concrete. The transport of water and ions in porous cement-based composites relies on the pore structure and the interactions between the species and the cement skeleton. The multi-scale structural characterization of cement-based compsites would help in developing smarter, more sustainble, and more durable materials for civil structures and infrastructure. Therefore, we propose a Special Issue of Materials, including—but not limited to—the topics shown below:

(1) Advanced techniques for multi-scale structural characterization of cement-based composites;

(2) Advanced knowledge of multi-scale structures of cement-based composites;

(3) Multi-scale structural design, fabrication, and synthesis for cement-based composites;

(4) Multi-scale structural characterization of smart, 3D-printed, and sustainable cement-based composites;

(5) Multi-scale, structure-associated mechanical and durability performance assessment for cement-based composites;

(6) Structure changes of cement-based composites in harsh environments.

We warmly welcome researchers and engineers to submit contributions to this Special Issue.

Dr. Qiang Zeng
Dr. Chunsheng Zhou
Dr. Zhendi Wang
Dr. Jiyang Wang
Dr. Dongming Yan
Dr. Shaoqin Ruan
Guest Editors

Manuscript Submission Information

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Keywords

  • cement-based composites
  • structural characterization
  • multi-scale
  • advanced techniques
  • performances
  • environments

Published Papers (21 papers)

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Research

14 pages, 6950 KiB  
Article
Effects of Three-Dimensional Graphene–Carbon Nanotube Hybrid on the Mechanical Properties and Microstructure of Cement Paste
by Xin Zhao, Li Qiu, Deyu Kong, Yangfei Huang and Jintao Liu
Materials 2023, 16(19), 6571; https://doi.org/10.3390/ma16196571 - 06 Oct 2023
Viewed by 721
Abstract
This work experimentally studies the mechanical properties and microstructure of cementitious composites reinforced with a three-dimensional graphene–carbon nanotube (CNT) hybrid. Firstly, the graphene–CNT (GC) hybrid is dispersed in cement pastes using ultrasonication and surfactant, and then, the effect of the GC hybrid on [...] Read more.
This work experimentally studies the mechanical properties and microstructure of cementitious composites reinforced with a three-dimensional graphene–carbon nanotube (CNT) hybrid. Firstly, the graphene–CNT (GC) hybrid is dispersed in cement pastes using ultrasonication and surfactant, and then, the effect of the GC hybrid on the early hydration of the cement pastes is investigated. The experimental results show that adding the GC hybrid shortens the setting stage of cement hydration and accelerates the early hydration process. Moreover, the macro- and micro-mechanical properties of each group are evaluated. The 7- and 28-day strength of the cement pastes improves with addition of the GC hybrid. Finally, the microstructural analysis demonstrates that the GC hybrid is reasonably well distributed in cement and forms a spatial network, which could bridge the cracks and compact the cementitious matrix. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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15 pages, 2339 KiB  
Article
Mechanical Performance and Chloride Penetration of Calcium Sulfoaluminate Concrete in Marine Tidal Zone
by Xudong Tang, Shulin Zhan, Qiang Xu and Kui He
Materials 2023, 16(7), 2905; https://doi.org/10.3390/ma16072905 - 06 Apr 2023
Cited by 2 | Viewed by 922
Abstract
The enhancement of the durability of sulfoaluminate cement (CSA) in marine environments is of great importance. To this end, an investigation was carried out involving the placement of CSA concrete in the tidal zone of Zhairuoshan Island, Zhoushan, China, and subjected to a [...] Read more.
The enhancement of the durability of sulfoaluminate cement (CSA) in marine environments is of great importance. To this end, an investigation was carried out involving the placement of CSA concrete in the tidal zone of Zhairuoshan Island, Zhoushan, China, and subjected to a 20-month marine tidal exposure test. The comparison was made with ordinary Portland cement (OPC) concrete to evaluate the effectiveness of the former. The test findings indicate that the compressive strength of both types of concrete is reduced by seawater dry-wet cycling, and the porosity of the surface concrete is increased. However, the compressive strength of CSA concrete is observed to be more stable under long-term drying–wetting cycles. When the ettringite in the CSA surface concrete is decomposed due to carbonization and alkalinity reduction, its products will react with Ca2+ and SO42− in seawater to regenerate ettringite to fill in the concrete pores, making the concrete strength more stable and hindering chlorine penetration. Furthermore, CSA concrete exhibits a higher capillary absorption capacity than OPC concrete, which results in chloride accumulation on its surface. However, the diffusion capacity of chloride in CSA concrete is significantly lower than that in OPC concrete. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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15 pages, 5107 KiB  
Article
Nondestructive Evaluation for Hydration and Setting Time of Gypsum Modified Calcium Sulfoaluminate Cement Paste
by Yubin Jun, Yu-Rhee Ahn, Dongho Jeon and Hong Jae Yim
Materials 2023, 16(3), 920; https://doi.org/10.3390/ma16030920 - 18 Jan 2023
Viewed by 1081
Abstract
Calcium sulfoaluminate (CSA) cement is a promising solution for reducing CO2 emissions. While previous studies have attempted to investigate the usefulness of CSA cement via various approaches, early age nondestructive evaluations for the setting and hydration of CSA cement mixtures have not [...] Read more.
Calcium sulfoaluminate (CSA) cement is a promising solution for reducing CO2 emissions. While previous studies have attempted to investigate the usefulness of CSA cement via various approaches, early age nondestructive evaluations for the setting and hydration of CSA cement mixtures have not been reported. In this study, we measured the ultrasonic pulse velocity and electrical resistivity of early age CSA cement paste. Six types of samples were prepared according to different water-to-solid ratios and different amounts of gypsum. In addition, various microstructural analyses were performed to understand CSA cement hydration with the obtained nondestructive parameters. Consequently, the effect of added gypsum in CSA cement paste was discussed in terms of ye’elimite dissolution and the precipitation of ettringite, and different pore distributions produced by added gypsum were discussed in terms of compressive strength. The 5% addition of gypsum in CSA cement paste enhanced the hydration evolution, such as ettringite, and it can induce the faster setting time up to 6 h and strength development during 24 h. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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23 pages, 6328 KiB  
Article
Influence of Bonding Area on Dynamic Failure Behavior of Notched Reinforced Concrete Beams
by Min Song, Zhiyong Wang, Jie Zhang and Zhihua Wang
Materials 2023, 16(2), 507; https://doi.org/10.3390/ma16020507 - 04 Jan 2023
Viewed by 941
Abstract
To study the effect of the bonding area on the dynamic failure process of a reinforced concrete beam with the same reinforcement ratio, the experimental and numerical researches on the impact response of notched reinforced concrete beams in the low-velocity regime (≤2.5 m/s) [...] Read more.
To study the effect of the bonding area on the dynamic failure process of a reinforced concrete beam with the same reinforcement ratio, the experimental and numerical researches on the impact response of notched reinforced concrete beams in the low-velocity regime (≤2.5 m/s) are presented. The tests are carried out with a drop hammer impact testing machine and then the structural responses under different impact velocities are analyzed. Additionally, the dynamic three-point bending simulation for specimens with different bonding areas, but the same reinforcement ratio is conducted. In this numerical model, the parameters of a cohesive model verified from a steel bar pullout test are applied to the bonding layer to simulate the bond-slip behavior of steel bars. Then, the energy dissipation for each component (e.g., concrete, a steel bar, and the bonding layer) are compared and discussed. The dynamic experimental results suggest that the energy absorbed during the impact process increases with the growth of the impact velocity, while the effect of the impact velocity on the reaction force can be ignored. The numerical results indicate that the failure pattern changes from a bending failure to shear failure with the increase in the bonding area and impact velocity. With the growth of the bonding area, the steel bars reach the plastic stage easily and the internal energy dissipation of the bonding layer decreases, which protects the bonding effect between the steel bar and concrete effectively. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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12 pages, 2323 KiB  
Article
Bending Analysis of Multiferroic Semiconductor Composite Beam towards Smart Cement-Based Materials
by Yun Wang, Yifan Huang, Chunli Zhang and Rongqiao Xu
Materials 2023, 16(1), 421; https://doi.org/10.3390/ma16010421 - 02 Jan 2023
Cited by 1 | Viewed by 1129
Abstract
A beam-like structure of antisymmetric laminated multiferroic piezoelectric semiconductor (LMPS), which consists of two piezomagnetic (PM) and two piezoelectric semiconductor (PS) layers is proposed. The structure could be in pure flexure deformation under an applied magnetic field. Through this deformation mode and the [...] Read more.
A beam-like structure of antisymmetric laminated multiferroic piezoelectric semiconductor (LMPS), which consists of two piezomagnetic (PM) and two piezoelectric semiconductor (PS) layers is proposed. The structure could be in pure flexure deformation under an applied magnetic field. Through this deformation mode and the induced polarization field through the magneto-electro-semiconductive (MES) coupling mechanism, the semiconducting properties of PS layers can be manipulated by the applied magnetic field. In order to better understand and quantitatively describe this deformation mode, the one-dimensional governing equations for the LMPS beam are developed based on the three-dimensional theory. The analytical solutions are then presented for the LMPS cantilever beam with open-circuit conditions. The multi-field coupling responses of the LMPS cantilever beam under the longitudinal magnetic field are investigated. Numerical results show that the amplitude of each physical quantity is proportional to the applied magnetic field, and the thickness ratio of the PS phase plays a significant role in the MES coupling behaviors of the LMPS beam. The proposed structure can be integrated into cement structures but also fabricated cement-based multiferroic PS composite materials and structures. It provides an important material and structure basis for developing structural health monitoring systems in the fields of civil and transportation infrastructures. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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16 pages, 3179 KiB  
Article
Long-Term Performance of Concrete Made with Different Types of Cement under Severe Sulfate Exposure
by Ahmed M. Tahwia, Rowyda M. Fouda, Mohamed Abd Elrahman and Osama Youssf
Materials 2023, 16(1), 240; https://doi.org/10.3390/ma16010240 - 27 Dec 2022
Cited by 4 | Viewed by 2174
Abstract
Concrete sulfate attack is of great interest as it represents one of the main reasons of concrete deterioration and poor durability for concrete structures. In this research, the effect of different cement types on concrete sulfate resistance was investigated. This included three concrete [...] Read more.
Concrete sulfate attack is of great interest as it represents one of the main reasons of concrete deterioration and poor durability for concrete structures. In this research, the effect of different cement types on concrete sulfate resistance was investigated. This included three concrete classes, namely, low strength concrete, medium strength concrete, and high strength concrete. Blast furnace cement (BFC), sulfate resisting Portland cement (CEM I-SR5), and ordinary Portland cement (OPC) were used in a total of eighteen concrete mixes. Three binder contents of 250 kg/m3, 350 kg/m3, and 450 kg/m3 and a constant silica fume (SF) content were applied in this experimental study. The water/binder (w/b) ratio was varied between 0.4 and 0.8. Concrete specimens were immersed in highly severe effective sodium sulfate solutions (10,000 ppm) for 180 days after standard curing for 28 days. The fresh concrete performance was evaluated through a slump test to attain proper workability. Concrete compressive strength and mass change at 28 days and 180 days were measured before and after immersion in the solution to evaluate the long-term effect of sulfate attack on the proposed concrete durability. Scanning electron microscopy (SEM) analysis was conducted to study the concrete microstructure and its deterioration stages. The obtained results revealed that BFC cement has the best resistance to aggressive sulfate attacks. The strength deterioration of BFC cement was 3.5% with w/b of 0.4 and it increased to about 7.8% when increasing the w/b ratio to 0.6, which are comparable to other types of cement used. The findings of this research confirmed that the quality of concrete, specifically its composition of low permeability, is the best and recommended protection against sulfate attack. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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14 pages, 3347 KiB  
Article
Influence of Structural Characterization of C3S-C3A Paste under Sulfate Attack
by Qicai Zhao, Tao He, Gaozhan Zhang, Yang Li, Guocheng Rong and Qingjun Ding
Materials 2023, 16(1), 77; https://doi.org/10.3390/ma16010077 - 21 Dec 2022
Cited by 2 | Viewed by 1064
Abstract
The durability of C3S-C3A paste with varied C3A content (0%, 5%, 10%, and 20%) against sulfate attack at various attack ages (3 d, 7 d, 28 d, and 180 d) was investigated in this study through the [...] Read more.
The durability of C3S-C3A paste with varied C3A content (0%, 5%, 10%, and 20%) against sulfate attack at various attack ages (3 d, 7 d, 28 d, and 180 d) was investigated in this study through the examinations of corrosion product composition, Ca/Si and Al/Si of calcium-(aluminum)-silicate-hydrate (C-(A)-S-H) gel, formation and evolution of microstructure, migration and transformation of Al containing phase products, and pore structure. The results indicated that sulfate attack can promote the hydration reaction in C3S-C3A paste, thus accelerating the production of C-(A)-S-H gel in the paste. With the increase of C3A content, the acceleration effect becomes more significant. In addition, sulfate attack led to the dealumination and decalcification of C-(A)-S-H gel, resulting in the reduction of the gelling power of C-(A)-S-H gel. The degree of dealumination and decalcification of C-(A)-S-H gel increases with the increase of C3A content. At the same time, free Al and Ca promote the formation of expansive products such as ettringite and gypsum. Finally, under the action of sulfate, the pore characterization of C3S-C3A paste deteriorated, showing a decrease in specific surface area, cumulative pore volume and average pore diameter. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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14 pages, 3404 KiB  
Article
Tensile Behavior of Basalt Textile Reinforced Concrete: Effect of Test Setups and Textile Ratios
by Chenglin Wan, Jiyang Wang, Shubin Wang, Xiaohua Ji, Yu Peng and Hongmei Zhang
Materials 2022, 15(24), 8975; https://doi.org/10.3390/ma15248975 - 15 Dec 2022
Cited by 1 | Viewed by 911
Abstract
The clevis-grip tensile test is usually employed to evaluate the mechanical properties of textile reinforced concrete (TRC) composites, which is actually a bond test and is unsuitable for determining reliable design parameters. Thus, the clevis-grip tensile test needs further improvement to obtain foreseeable [...] Read more.
The clevis-grip tensile test is usually employed to evaluate the mechanical properties of textile reinforced concrete (TRC) composites, which is actually a bond test and is unsuitable for determining reliable design parameters. Thus, the clevis-grip tensile test needs further improvement to obtain foreseeable results concerning TRC tensile behavior. This paper presents the experimental results of twenty-one tension tests performed on basalt TRC (BTRC) thin plates with different test setups, i.e., clevis-grip and improved clevis-grip, and with different textile ratios. The influences of test setups and textile ratios on crack patterns, failure mode, and tensile stress-strain curves with characteristic parameters were analyzed in depth to judge the feasibility of the new test setup. The results indicated that with the new test setup, BTRC composites exhibited textile rupture at failure; in addition, multi-cracks occurred to the BTRC composites as the textile ratio exceeded 1.44%. In this case, the obtained results relied on textile properties, which can be considered reliable for design purposes. The modified ACK model with a textile utilization rate of 50% provided accurate predictions for the tensile stress-strain behavior of the BTRC composite derived from the improved test setup. The proposed test setup enables the adequate utilization of BTRC composite and the reliability of obtained results related to the occurrence of textile rupture; nevertheless, further work is required to better understand the key parameters affecting the textile utilization rate, such as the strength of the concrete matrix. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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15 pages, 6128 KiB  
Article
Mechanical Properties of Polyethylene Fiber Reinforced Ultra High Performance Concrete (UHPC)
by Xin Zhao, Lei Cai, Xiaohua Ji, Wei Zeng and Jintao Liu
Materials 2022, 15(24), 8734; https://doi.org/10.3390/ma15248734 - 07 Dec 2022
Cited by 6 | Viewed by 1593
Abstract
Ultra-high performance concrete (UHPC) is a kind of cement-based material with ultra-high strength, high toughness and excellent durability. However, the tensile strain capacity of UHPC is often below 0.5%, and the mode of single crack failure is the main failure pattern, which limits [...] Read more.
Ultra-high performance concrete (UHPC) is a kind of cement-based material with ultra-high strength, high toughness and excellent durability. However, the tensile strain capacity of UHPC is often below 0.5%, and the mode of single crack failure is the main failure pattern, which limits the development of UHPC. In order to overcome the weakness of the relatively low strain capacity of UHPC, five types of polyethylene (PE) fibers with different geometrical and mechanical parameters (length, diameter and elastic modulus) were added into the matrix, and the corresponding mechanical behavior was investigated. The experimental results showed that the high fiber length and fiber diameter of PE fibers are a benefit for the compressive strength and tensile strength of UHPC. The increase of the fiber diameter and elastic modulus remarkably attributed to the increase in the tensile strain capacity of UHPC. With the increase of the fiber diameter and elastic modulus, the overall energy absorption capacity G and the energy absorption capacity of the substrate prior to the softening section ga of UHPC were both enhanced. The diameter of PE fiber was the main factor affecting the energy consumption of UHPC. Among the five types of PE fiber, PF fiber (PF fiber is PF type polyethylene fiber; Fiber length: 15 mm; Fiber diameter: 27 μm; Elastic Modulus: 117 GPa) is the optimal fiber to increase the tensile mechanical behavior of UHPC. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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19 pages, 4246 KiB  
Article
The Effect of Harsh Environmental Conditions on Concrete Plastic Shrinkage Cracks: Case Study Saudi Arabia
by Talal O. Alshammari, Maurizio Guadagnini and Kypros Pilakoutas
Materials 2022, 15(23), 8622; https://doi.org/10.3390/ma15238622 - 02 Dec 2022
Cited by 1 | Viewed by 1470
Abstract
Due to climate change and population expansion, concrete structures are progressively being subjected to more extreme environments. As the environment affects plastic shrinkage directly, there is a need to understand the effect of environmental changes on plastic shrinkage cracking. This paper examines the [...] Read more.
Due to climate change and population expansion, concrete structures are progressively being subjected to more extreme environments. As the environment affects plastic shrinkage directly, there is a need to understand the effect of environmental changes on plastic shrinkage cracking. This paper examines the plastic shrinkage crack development parametrically at low, mid, and high drying environmental conditions, corresponding to different environments in three Saudi cities. The effects of water-cement ratios and quantities of recycled tire steel fibers (RTSF) in concrete are also investigated. The different environmental conditions for the plastic shrinkage tests were simulated in a specially designed chamber as per ASTM C1579, 2006. A digital image processing (DIP) technique was used to monitor crack initiation and development. Through the use of the crack reduction ratio (CRR), it was found that 30 kg/m3 of RTSF can control plastic shrinkage cracks at low and mid conditions. For the more extreme (high) conditions, the use of 40 kg/m3 of RTSF fiber was sufficient to completely eliminate surface plastic shrinkage cracks. This work can help develop more sustainable concrete structures in a wider set of environmental conditions and help mitigate the impact of climate change on concrete infrastructure. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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13 pages, 2669 KiB  
Article
Hydration Behavior of Magnesium Potassium Phosphate Cement: Experimental Study and Thermodynamic Modeling
by Jinrui Zhang, Wenjun Niu, Zhen Liu, Youzhi Yang, Wujian Long, Yuanyuan Zhang and Biqin Dong
Materials 2022, 15(23), 8496; https://doi.org/10.3390/ma15238496 - 29 Nov 2022
Cited by 1 | Viewed by 1144
Abstract
The microstructure and performance of magnesium potassium phosphate cement (MKPC), a kind of magnesium phosphate cement (MPC), are determined by the hydration products. In this paper, the hydration behavior of MKPC is investigated through various material characterization methods and thermodynamic modeling, including X-ray [...] Read more.
The microstructure and performance of magnesium potassium phosphate cement (MKPC), a kind of magnesium phosphate cement (MPC), are determined by the hydration products. In this paper, the hydration behavior of MKPC is investigated through various material characterization methods and thermodynamic modeling, including X-ray diffraction (XRD), thermogravimetric and differential scanning calorimeter (TG/DSC), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and GEMS software. The results of XRD, TG/DSC and SEM all indicate that K-struvite (MgKPO4·6H2O) is the main hydration product of MKPC. When the curing age is 1 day and 28 days, the TG data indicate that the mass loss of MKPC in the range of 60–200 °C is 17.76% and 17.82%, respectively. The MIP results show that the porosity of MKPC is 29.63% and 29.61% at the curing age of 1 day and 28 days, respectively, which indicates that the structure of MKPC becomes denser with the increase in curing age. In addition, the cumulative pore volume of MKPC at the curing age of 28 days is 2.8% lower than that at 1 day, and the pore diameters are shifted toward the small pores. Furthermore, the thermodynamic modeling is well suited to make an analysis of the hydration behavior of MKPC. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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14 pages, 3715 KiB  
Article
Corrosion Crack Morphology and Creep Analysis of Members Based on Meso-Scale Corrosion Penetration
by Bin Zeng, Yiping Yang, Fuyuan Gong and Koichi Maekawa
Materials 2022, 15(20), 7338; https://doi.org/10.3390/ma15207338 - 20 Oct 2022
Cited by 2 | Viewed by 1200
Abstract
In this paper, to study the development of load-carrying capacity and long-term creep performance of reinforced concrete beams under different corrosion patterns, the rate-dependent model of concrete is used as the basis to consider the creep development process from the meso-scale level. The [...] Read more.
In this paper, to study the development of load-carrying capacity and long-term creep performance of reinforced concrete beams under different corrosion patterns, the rate-dependent model of concrete is used as the basis to consider the creep development process from the meso-scale level. The porosity mechanics method is used to simulate the generation and penetration process of corrosion products. Three corrosion conditions are set: bottom longitudinal reinforcement corrosion, top longitudinal reinforcement corrosion and all reinforcement corrosion. The corrosion rate is used as the variable in each corrosion condition. The results show that: (1) the greater the corrosion rate in all conditions, the lower the bearing capacity. In addition, the corrosion of top longitudinal reinforcement causes the damage form of the beam to change to brittle damage; (2) the creep coefficient decreases with the increase in corrosion rate in all working conditions, but the main factor for this phenomenon is the obvious increase in initial deformation. Consequently, it is not suitable to follow the conventional creep concept (deformation development/initial deformation) for the development of plastic deformation of damaged members. It is more reasonable to use the global deflection to describe the long-term deformation of corrosion-damaged members. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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17 pages, 5820 KiB  
Article
Early-Stage Geopolymerization Process of Metakaolin-Based Geopolymer
by Xiuyu Zhu, Hao Qian, Hongxiao Wu, Quan Zhou, Huiping Feng, Qiang Zeng, Ye Tian, Shengqian Ruan, Yajun Zhang, Shikun Chen and Dongming Yan
Materials 2022, 15(17), 6125; https://doi.org/10.3390/ma15176125 - 03 Sep 2022
Cited by 7 | Viewed by 1579
Abstract
The geopolymerization of aluminosilicate materials in alkaline environments is a complex physicochemical process that greatly influences the microstructure and engineering performances. This work aims to reveal the geopolymerization process of metakaolin-based geopolymer (MKG) in the first 5 d. Physicochemical characteristics of different evolution [...] Read more.
The geopolymerization of aluminosilicate materials in alkaline environments is a complex physicochemical process that greatly influences the microstructure and engineering performances. This work aims to reveal the geopolymerization process of metakaolin-based geopolymer (MKG) in the first 5 d. Physicochemical characteristics of different evolution stages are disposed of in chronological order. The evolutions of electrical resistivity, dehydration process, volume deformation, and ionic concentration are comprehensively analyzed. Results show that chemical dissolution produces large dismantled fragments rather than small free monomers. The formation of a solid matrix follows the “spatial filling rule”, which means that gels grow by locking swelling fragments to form a framework, then densely filling residual space. Based on chemical models, early geopolymerization of MKG can be divided into six stages from the physicochemical perspective as dismantling, locking fixation, free filling, limited filling, second dissolution, and local mending. Those findings expand the understanding of the phase evolution of the early geopolymerization process; thus, the microstructure of MKG can be better manipulated, and its engineering performances can be improved. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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16 pages, 4333 KiB  
Article
Salt Scaling Resistance of Variable w/c Ratio Air-Entrained Concretes Modified with Polycarboxylates as a Proper Consequence of Air Void System
by Aneta Nowak-Michta
Materials 2022, 15(17), 5839; https://doi.org/10.3390/ma15175839 - 24 Aug 2022
Cited by 1 | Viewed by 1089
Abstract
The values of the air void parameters in hardened concrete (spacing factor L ≤ 0.200 mm and micro air content A300 ≥ 1.5%), determined on the basis of the Powers model, in concretes produced today do not always guarantee the frost resistance [...] Read more.
The values of the air void parameters in hardened concrete (spacing factor L ≤ 0.200 mm and micro air content A300 ≥ 1.5%), determined on the basis of the Powers model, in concretes produced today do not always guarantee the frost resistance of the concrete, especially when in surface impact with the participation of de-icing agents. The literature indicates that the modified polycarboxylates used to liquefy concrete mixes are one of the factors involved in changing the air void system; therefore, the aim of the article was to determine the dependence of the air void parameters and the resistance to scaling of concretes liquefied to a constant consistency by the use of modified polycarboxylates in the spectrum of variability of the ratio w/c = 0.53 ÷ 0.30. In the research program, twelve concrete mixes were made with a constant proportion of aggregate and paste: six air-entrained—with a constant air content of 5.5 ± 0.5%—and six non-air-entrained. The air void parameters were determined in accordance with EN 480-11, while the resistance to scaling was determined in accordance with CEN/TS 12390-9 and assessed according to the criteria of SS 137244. The analysis of the test results showed that liquefaction with modified polycarboxylates did not affect the w/c limit values, enabling obtaining concretes resistant to scaling. They are, respectively, 0.35 in the non-air-entrained concretes and 0.50 in the air-entrained concretes with an air content of 5.5 ± 0.5. Moreover, the commonly used criterion for ensuring the frost resistance of air-entrained concretes, L ≤ 0.200 mm and A300 ≥ 1.5%, requires supplementing with the minimum value of the w/c ≤ 0.50. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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18 pages, 5727 KiB  
Article
Prediction of Ultrasonic Pulse Velocity for Cement, Mortar, and Concrete through a Multiscale Homogenization Approach
by Jingluo Jiang, Dawei Zhang, Fuyuan Gong and Dian Zhi
Materials 2022, 15(9), 3241; https://doi.org/10.3390/ma15093241 - 30 Apr 2022
Cited by 8 | Viewed by 1592
Abstract
Ultrasonic testing (UT) is an important method for concrete, and ultrasonic pulse velocity is commonly used to evaluate the quality of concrete materials in existing studies. The ultrasonic pulse velocity of concrete materials is affected by many factors; therefore, it is necessary to [...] Read more.
Ultrasonic testing (UT) is an important method for concrete, and ultrasonic pulse velocity is commonly used to evaluate the quality of concrete materials in existing studies. The ultrasonic pulse velocity of concrete materials is affected by many factors; therefore, it is necessary to establish a quantitative prediction model for the ultrasonic pulse velocity of concrete materials. Based on the multiscale homogenization method, concrete material is divided into different scales of homogenized materials, namely cement paste, mortar, and concrete. Then, a multiscale ultrasonic pulse velocity model is established through a combination of elasticity formulation and the hydration model. At the three scales of cement paste, mortar, and concrete, the elastic parameters and ultrasonic pulse velocity were predicted with the water-to-cement ratio of 0.35, 0.5, and 0.65, respectively. The ultrasonic pulse velocity of concrete with different water-to-cement ratios and different ages were measured in the test and predicted by the model. The results show that the predicted value of ultrasonic pulse velocity is within the error range of ±1.5% of the measured ultrasonic pulse velocity, suggesting that the established prediction model of ultrasonic pulse velocity can reliably predict the velocity change in concrete materials. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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17 pages, 3416 KiB  
Article
Effect of Ornamental Stone Waste Incorporation on the Rheology, Hydration, Microstructure, and CO2 Emissions of Ordinary Portland Cement
by Taylana Piccinini Scolaro, Laura Silvestro, Artur Spat Ruviaro, Afonso R. G. de Azevedo, Sergio Neves Monteiro and Fernando Pelisser
Materials 2022, 15(2), 401; https://doi.org/10.3390/ma15020401 - 06 Jan 2022
Cited by 6 | Viewed by 1414
Abstract
The ornamental stone industry generates large amounts of waste thus creating environmental and human health hazards. Thus, pastes with 0–30 wt.% ornamental stone waste (OSW) incorporated into ordinary Portland cement (OPC) were produced and their rheological properties, hydration kinetics, and mechanical properties were [...] Read more.
The ornamental stone industry generates large amounts of waste thus creating environmental and human health hazards. Thus, pastes with 0–30 wt.% ornamental stone waste (OSW) incorporated into ordinary Portland cement (OPC) were produced and their rheological properties, hydration kinetics, and mechanical properties were evaluated. The CO2 equivalent emissions related to the pastes production were estimated for each composition. The results showed that the paste with 10 wt.% of OSW exhibited similar yield stress compared to the plain OPC paste, while pastes with 20 and 30 wt.% displayed reduced yield stresses up to 15%. OSW slightly enhanced the hydration kinetics compared to plain OPC, increasing the main heat flow peak and 90-h cumulative heat values. The incorporation of OSW reduced the 1-, 3-, and 28-days compressive strength of the pastes. Water absorption results agreed with the 28 days compressive strength results, indicating that OSW increased the volume of permeable voids. Finally, OSW incorporation progressively reduced the CO2 emission per m3 of OPC paste, reaching a 31% reduction for the highest 30 wt.% OSW content. Overall, incorporating up to 10 wt.% with OSW led to pastes with comparable fresh and hardened properties as comported to plain OPC paste. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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14 pages, 3651 KiB  
Article
Investigation on Variables Contributing to the Synthesis of C-S-H/PCE Nanocomposites by Co-Precipitation Method
by Ziyang You and Jing Xu
Materials 2021, 14(24), 7673; https://doi.org/10.3390/ma14247673 - 12 Dec 2021
Cited by 6 | Viewed by 2554
Abstract
The usage of nanoscale calcium silicate hydrate (nano C-S-H) proved to have an excellent promotion effect on the early performance of concrete as nano C-S-H with ultra-fine particle size can act as seeding for cement hydration. Therefore, it is of importance to tune [...] Read more.
The usage of nanoscale calcium silicate hydrate (nano C-S-H) proved to have an excellent promotion effect on the early performance of concrete as nano C-S-H with ultra-fine particle size can act as seeding for cement hydration. Therefore, it is of importance to tune the particle size during the synthesis process of nano C-S-H. In this paper, the influence of several variables of the particle size distribution (PSD) of nano C-S-H synthesized by chemical co-precipitation method with the aid of polycarboxylate (PCE) was studied by orthogonal experimental design. In addition, the composition, microstructure, and morphology of the C-S-H/PCE nanocomposites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectrum. The results showed that the concentration of reactants had a significant impact on the PSD of C-S-H/PCE nanocomposites, followed by the dosage of dispersant. Ultrasonic treatment was effective in breaking the C-S-H/PCE aggregates with unstable agglomeration structures. The change in synthetic variables had a negligible effect on the composition of the C-S-H/PCE nanocomposites but had a significant influence on the crystallinity and morphology of the composites. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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21 pages, 6837 KiB  
Article
Influence of Ultrasonication of Functionalized Carbon Nanotubes on the Rheology, Hydration, and Compressive Strength of Portland Cement Pastes
by Laura Silvestro, Artur Ruviaro, Geannina Lima, Paulo de Matos, Afonso R. G. de Azevedo, Sérgio Neves Monteiro and Philippe Gleize
Materials 2021, 14(18), 5248; https://doi.org/10.3390/ma14185248 - 13 Sep 2021
Cited by 22 | Viewed by 2452
Abstract
The functionalization process usually increases the localized defects of carbon nanotubes (CNT). Thus, the ultrasonication parameters used for dispersing non-functionalized CNT should be carefully evaluated to verify if they are adequate in dispersing functionalized CNT. Although ultrasonication is widely used for non-functionalized CNT, [...] Read more.
The functionalization process usually increases the localized defects of carbon nanotubes (CNT). Thus, the ultrasonication parameters used for dispersing non-functionalized CNT should be carefully evaluated to verify if they are adequate in dispersing functionalized CNT. Although ultrasonication is widely used for non-functionalized CNT, the effect of this dispersing process of functionalized CNT has not been thoroughly investigated. Thus, this work investigated the effect of ultrasonication on functionalized CNT + superplasticizer (SP) aqueous dispersions by ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). Furthermore, Portland cement pastes with additions of 0.05% and 0.1% CNT by cement weight and ultrasonication amplitudes of 0%, 50% and 80% were evaluated through rheometry, isothermal calorimetry, compressive strength at 1, 7 and 28 days, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). FTIR results from CNT + SP dispersions indicated that ultrasonication may negatively affect SP molecules and CNT graphene structure. The increase in CNT content and amplitude of ultrasonication gradually increased the static and dynamic yield stress of paste but did not significantly affect its hydration kinetics. Compressive strength results indicated that the optimum CNT content was 0.05% by cement weight, which increased the strength of composite by up to 15.8% compared with the plain paste. CNT ultrasonication neither increases the degree of hydration of cement nor the mechanical performance of composite when compared with mixes containing unsonicated CNT. Overall, ultrasonication of functionalized CNT is not efficient in improving the fresh and hardened performance of cementitious composites. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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13 pages, 4520 KiB  
Article
Influences of Air-Voids on the Performance of 3D Printing Cementitious Materials
by Yujun Che, Shengwen Tang, Huashan Yang, Weiwei Li and Mengyuan Shi
Materials 2021, 14(16), 4438; https://doi.org/10.3390/ma14164438 - 08 Aug 2021
Cited by 5 | Viewed by 2871
Abstract
This paper focuses on inspecting the influences of anti-foaming agent (AFA) on the performance of 3D printing cementitious materials (3DPC). The mini-slump, spreading diameter, yield stress, and strength of 3DPC were evaluated. Additionally, the air-void content, air-void morphology, and air-void size distribution of [...] Read more.
This paper focuses on inspecting the influences of anti-foaming agent (AFA) on the performance of 3D printing cementitious materials (3DPC). The mini-slump, spreading diameter, yield stress, and strength of 3DPC were evaluated. Additionally, the air-void content, air-void morphology, and air-void size distribution of mortar with and without 0.05% AFA were assessed through image analysis. The mechanical performance and air-void structure of 3D printed samples were also investigated and compared to that of conventionally mould cast samples. Test results show that an optimal AFA content enables 3DPC to achieve favorable workability and mechanical performance. The addition of AFA exhibits lower air-void content in 3DPC than that of the sample without the AFA addition. This reduction in air-void content is further strengthened by the results of strength analysis. Electron microscope analysis shows that the use of AFA results in the suppressed formation of large air-voids during the process of fresh 3DPC. Moreover, the air-void morphology substantially influenced the mechanical performance of hardened 3DPC. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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16 pages, 5068 KiB  
Article
Prediction of Healing Performance of Autogenous Healing Concrete Using Machine Learning
by Xu Huang, Mirna Wasouf, Jessada Sresakoolchai and Sakdirat Kaewunruen
Materials 2021, 14(15), 4068; https://doi.org/10.3390/ma14154068 - 21 Jul 2021
Cited by 18 | Viewed by 2444
Abstract
Cracks typically develop in concrete due to shrinkage, loading actions, and weather conditions; and may occur anytime in its life span. Autogenous healing concrete is a type of self-healing concrete that can automatically heal cracks based on physical or chemical reactions in concrete [...] Read more.
Cracks typically develop in concrete due to shrinkage, loading actions, and weather conditions; and may occur anytime in its life span. Autogenous healing concrete is a type of self-healing concrete that can automatically heal cracks based on physical or chemical reactions in concrete matrix. It is imperative to investigate the healing performance that autogenous healing concrete possesses, to assess the extent of the cracking and to predict the extent of healing. In the research of self-healing concrete, testing the healing performance of concrete in a laboratory is costly, and a mass of instances may be needed to explore reliable concrete design. This study is thus the world’s first to establish six types of machine learning algorithms, which are capable of predicting the healing performance (HP) of self-healing concrete. These algorithms involve an artificial neural network (ANN), a k-nearest neighbours (kNN), a gradient boosting regression (GBR), a decision tree regression (DTR), a support vector regression (SVR) and a random forest (RF). Parameters of these algorithms are tuned utilising grid search algorithm (GSA) and genetic algorithm (GA). The prediction performance indicated by coefficient of determination (R2) and root mean square error (RMSE) measures of these algorithms are evaluated on the basis of 1417 data sets from the open literature. The results show that GSA-GBR performs higher prediction performance (R2GSA-GBR = 0.958) and stronger robustness (RMSEGSA-GBR = 0.202) than the other five types of algorithms employed to predict the healing performance of autogenous healing concrete. Therefore, reliable prediction accuracy of the healing performance and efficient assistance on the design of autogenous healing concrete can be achieved. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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16 pages, 7433 KiB  
Article
Properties and Hydration Mechanism of Soda Residue-Activated Ground Granulated Blast Furnace Slag Cementitious Materials
by Yonghui Lin, Dongqiang Xu and Xianhui Zhao
Materials 2021, 14(11), 2883; https://doi.org/10.3390/ma14112883 - 27 May 2021
Cited by 14 | Viewed by 1949
Abstract
Soda residue (SR), an industrial solid waste, pollutes the environment due to its high alkalinity and chloride ion content. SR can be used as an alkali activator of ground granulated blast furnace slag (GGBFS). This study investigated the effects of four types of [...] Read more.
Soda residue (SR), an industrial solid waste, pollutes the environment due to its high alkalinity and chloride ion content. SR can be used as an alkali activator of ground granulated blast furnace slag (GGBFS). This study investigated the effects of four types of SR-activated GGBFS cementitious materials (pastes) with different mass ratios of SR to GGBFS (8:92, 16:84, 24:76, 34:68) on the physical properties, mechanical strength, and chloride binding capacity. The hydration mechanism of the pastes was also studied. Results showed that with the increasing addition of SR, the density of the pastes decreased, and more white aggregates of SR appeared causing the increase of water absorption and porosity of the pastes. The pastes with 16% SR addition had the maximum compressive strength (34.1 MPa, 28 d), so the optimum proportion of SR addition in the pastes was 16%. With the increases of SR addition, the amount of chloride element in the initial pastes increases. When the proportion of SR addition is 8%, the mass percentage of free chloride ion in the pastes at 28 d is 0.13%. The main hydration products of the pastes were C–S–H gels, ettringite, and Friedel’s salt, and the amount of ettringite varied with the amount of SR addition and curing time. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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