Research

16 pages, 11744 KiB

Open AccessArticle

Mechanical Properties and Sulfate Freeze–Thaw Resistance of Calcium Carbonate Whisker-Reinforced Iron Ore Tailings Concrete

by Shufang Wang, Yangyang Gao and Kangning Liu

Buildings 2024, 14(4), 1004; https://doi.org/10.3390/buildings14041004 - 04 Apr 2024

Viewed by 475

Abstract

Iron ore tailings from iron ore mines pose environmental challenges. However, their reuse could provide significant environmental benefits. This study focused on producing clean concrete using iron ore tailings as crushed stone aggregate (IOTA) and calcium carbonate whiskers (CWs) as reinforcement. Five mixture [...] Read more.

Iron ore tailings from iron ore mines pose environmental challenges. However, their reuse could provide significant environmental benefits. This study focused on producing clean concrete using iron ore tailings as crushed stone aggregate (IOTA) and calcium carbonate whiskers (CWs) as reinforcement. Five mixture groups were prepared: normal concrete (NAC) with natural crushed stone aggregate (NA), iron ore tailings concrete (TAC) with IOTA, and CW (10%, 20%, and 30%)-reinforced TAC (TAC-CW). Mechanical properties like the compressive strength (f_cu) and splitting tensile strength (f_st), as well as sulfate freeze–thaw (F-T) cycle resistance, were thoroughly investigated. Additionally, pore structure and microstructure were characterized using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) techniques. The results showed that IOTA’s complete replacement of NA decreased concrete mechanical properties and frost resistance, but incorporating CWs effectively compensated for these losses. Specifically, the f_cu and f_st of TAC-CW20 with 20% CWs increased by 23.26% and 49.6% compared to TAC and were higher than those of NAC. With increasing F-T cycles, concrete internal pore structure significantly deteriorated, and corrosive products increased significantly, which was further confirmed by SEM. TAC-CW20 significantly optimized pore structure. Overall, the successful application of iron ore tailings as eco-friendly materials enhanced concrete performance and reduced the environmental impact of construction activities. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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23 pages, 7780 KiB

Open AccessArticle

The Influence of Composition Ratio on the Thermal Performance Parameters of Eutectic Phase Change Materials: Experimental Research and Theoretical Prediction

by Bo Liu, Sheliang Wang, Wurong Jia, Jiangsheng Xie, Zhe Lu, Honghao Ying and Yanwen Sun

Buildings 2023, 13(12), 3043; https://doi.org/10.3390/buildings13123043 - 07 Dec 2023

Cited by 1 | Viewed by 603

Abstract

Eutectic phase change material (EPCM), compared with single phase change material (PCM), is widely studied by many scholars due to its flexibility in practical engineering applications by the characteristic of changing phase change temperatures. However, there is still a lack of theoretical prediction [...] Read more.

Eutectic phase change material (EPCM), compared with single phase change material (PCM), is widely studied by many scholars due to its flexibility in practical engineering applications by the characteristic of changing phase change temperatures. However, there is still a lack of theoretical prediction research on the thermal performance parameters of EPCM. The existing theories about EPCM are unable to accurately predict its thermal performance parameters, which increases the difficulty of selecting the composition ratio of EPCM and affects its practical application. Based on a background of the accurate prediction of EPCM thermal parameters, 12 binary EPCMs, and 7 ternary EPCMs are prepared by mixing capric acid, n-octanoic acid and tetradecane with different proportions, respectively. By using the cooling curves and DSC test, the variation patterns in thermal performance parameters of EPCMs are studied. After comparing various thermodynamic models, the Schrader model was selected and combined with experimental results to compare and calculate the experimental and theoretical values of thermal performance parameters. The results show that the binary PCM reaches the minimum eutectic point of 1.42 °C at a mass ratio of 0.33:0.67 for capric acid to n-octanoic acid, while the ternary PCM reaches the minimum eutectic point of 0.34 °C at a mass ratio of 0.231:0.469:0.3 for capric acid, n-octanoic acid, and n-tetradecane. The latent heat of a EPCM is between the lowest and highest values of the latent heat of the constituent components, and its value increases with the enhancement of the overall thermal storage density of the material. The modified Schrader equations can effectively predict the phase change temperatures and latent heats of EPCMs at different composition ratios. The equation has a fitting accuracy of over 0.986 and a bias error of less than 6%, demonstrating excellent accuracy and providing a reliable theoretical basis for the proportion design and thermal parameter prediction of EPCM in actual engineering applications. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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15 pages, 5798 KiB

Open AccessArticle

Low-Field Nuclear Magnetic Resonance Investigation on Early Hydration Characterization of Cement Paste Mixed with Mineral Admixtures

by Yu-Juan Tang, Zi-Qi Shan, Guang-Ji Yin, Ling Miao, Sai-Sai Wang and Zhen-Ya Zhang

Buildings 2023, 13(9), 2318; https://doi.org/10.3390/buildings13092318 - 12 Sep 2023

Cited by 1 | Viewed by 913

Abstract

Mineral admixtures (MA), like fly ash (FA), silica fume (SF), and slag (S), are usually added to cement-based materials to improve their compactness and further enhance their mechanical properties, permeability resistance, and durability. In this study, low-field nuclear magnetic resonance (LF-NMR) is adopted [...] Read more.

Mineral admixtures (MA), like fly ash (FA), silica fume (SF), and slag (S), are usually added to cement-based materials to improve their compactness and further enhance their mechanical properties, permeability resistance, and durability. In this study, low-field nuclear magnetic resonance (LF-NMR) is adopted to explore the evolution of the early hydration characterization of cement-based materials with MA by testing the transverse relaxation time T2. Meanwhile, the effect of MA on mechanical properties is analyzed by measuring compressive and flexural strength. The results show that, in the early hydration (0–7 days), the T2 distribution shows a trend of gradually moving to a short relaxation time and changes from a double peak to a single main peak. The decrease in T2i (main peak vertex) means that the evaporated water is gradually distributed in smaller pores with more motion constraints. However, the type and content of MA have little effect on T2i. Porosity gradually decreases in the period of early hydration. The addition of MA causes the porosity to decrease, and the order influence is FA > S > SF, i.e., the porosities of cement paste with 0%MA, 10%FA + 10%SF, 10%FA + 10%S, and 20%FA at 7 days are 48%, 44.5%, 40.7%, and 40.2%, respectively. Additionally, the addition of MA to cement-based materials also decreases the early strength, and the influence order is FA > S > SF, i.e., the compression strength values of cement paste with 0%MA, 10%FA + 10%SF, 10%FA + 10%S, and 20%FA at 7 days are 47.8 MPa, 40.1 MPa, 38.6 MPa, and 37 MPa, respectively. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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18 pages, 13706 KiB

Open AccessArticle

Impact of Polypropylene Fiber on the Mechanical and Physical Properties of Pervious Concrete: An Experimental Investigation

by Jian Wu, Liangjie Hu, Chaoqun Hu, Yuxi Wang, Jian Zhou and Xue Li

Buildings 2023, 13(8), 1966; https://doi.org/10.3390/buildings13081966 - 01 Aug 2023

Viewed by 1137

Abstract

It is important to balance the characteristics of pervious concrete, such as mechanical, physical, and durability properties. To obtain a better performance, adding fibers is very effective. In this study, samples with different polypropylene fiber content (0 kg/m³, 3 kg/m³ [...] Read more.

It is important to balance the characteristics of pervious concrete, such as mechanical, physical, and durability properties. To obtain a better performance, adding fibers is very effective. In this study, samples with different polypropylene fiber content (0 kg/m³, 3 kg/m³, 6 kg/m³, and 9 kg/m³) were designed to test the strength, porosity, permeability, acid corrosion behavior, and low-temperature performance of pervious concrete. It can be found from the experimental results that, compared to the control samples (without the addition of fibers), when the mixing amount of fiber is 6 kg/m³, the cubic compressive strength, axial compressive strength, and flexural tensile strength increase by 35.32%, 37.16%, and 13.04%, respectively; the porosity and permeability coefficient decrease by 36.32 % and 49.30%, respectively; the strength of samples with acidic corrosion times of 0 d, 20 d, 40 d, and 60 d increased by 30.96%, 17.41%, 15.47%, and 20.87%, respectively; and the strength of samples at temperatures of −20 °C, −10 °C, 0 °C, and 25 °C decrease by 14.17%, 15.45%, 22.97%, and 30.96%, respectively. The meso-structure of pervious concrete is studied using industrial computed tomography (ICT) to investigate the relationships between the characteristics. It could be seen that the optimal dosage of polypropylene fiber is 6 kg/m³, which is more suitable for application in engineering. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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14 pages, 5354 KiB

Open AccessArticle

The Effect of ECC Materials on Seismic Performance of Beam—Column Subassemblies with Slabs

by Tingting Lu, Kai Guan, Jiaojiao Pan and Xingwen Liang

Buildings 2023, 13(8), 1942; https://doi.org/10.3390/buildings13081942 - 30 Jul 2023

Cited by 1 | Viewed by 538

Abstract

The main objective of this investigation was to study the influence of an Engineered Cementitious Composite (ECC) on the seismic performances of beam–column–slab subassemblies. Tests and simulations were conducted on several models. The bearing capacity of the ECC model was 15% higher than [...] Read more.

The main objective of this investigation was to study the influence of an Engineered Cementitious Composite (ECC) on the seismic performances of beam–column–slab subassemblies. Tests and simulations were conducted on several models. The bearing capacity of the ECC model was 15% higher than that of the RC member, the deformability increased by 19%, and the energy dissipation capability increased by 34%. The use of an ECC in the slab could reduce the contribution of the reinforced bars in the slab to the flexural strength of the beam. At a drift of 2%, the range of the yielding bars in the slab of the RC models was 5h to 6h. However, the yield range of reinforcement in the slab of the ECC models was nearly 3h. As a result, the ECC subassemblies were prone to reach a “strong column and weak beam” yield mechanism. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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12 pages, 3107 KiB

Open AccessArticle

Influence of Stone Powder Content from Manufactured Sand Concrete on Shrinkage, Cracking, Compressive Strength, and Penetration

by Mingming Zhang, Jin Xu, Meng Li and Xiaosa Yuan

Buildings 2023, 13(7), 1833; https://doi.org/10.3390/buildings13071833 - 20 Jul 2023

Cited by 3 | Viewed by 1042

Abstract

The market demand for manufactured sand has grown rapidly, and the solution to the problem of optimum stone powder content from manufactured sand concrete is imminent. The workability, early age shrinkage strain and cracking, strength, chloride ion penetration, and pore structures of concrete [...] Read more.

The market demand for manufactured sand has grown rapidly, and the solution to the problem of optimum stone powder content from manufactured sand concrete is imminent. The workability, early age shrinkage strain and cracking, strength, chloride ion penetration, and pore structures of concrete with different stone powder contents were tested to study the influence of stone powder content from manufactured sand concrete. The test results show that the addition of stone powder is beneficial in improving the working performance of manufactured sand concrete. But at the same time, it will increase the amount of concrete water reducer and the total shrinkage strain at an early age. The workability and durability of manufactured sand concrete can be significantly improved by adding an appropriate stone powder. However, excessive stone powder will lead to a reduction in the strength and durability of manufactured sand concrete. It is suggested that the best stone powder content of concrete with a water/cement ratio of 0.32 is 10%, and that of concrete with a water/cement ratio of 0.45 should be less than 20%. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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21 pages, 7430 KiB

Open AccessArticle

Nano-SiO₂ Recycled Concrete Anti-Sulfate Performance and Damage Mechanism Research

by Jia Luo, Sheliang Wang, Xiaoyi Quan, Jin Xu, Juntao Li, Kangning Liu, Fan Xu and Zhilong Hong

Buildings 2023, 13(6), 1429; https://doi.org/10.3390/buildings13061429 - 31 May 2023

Viewed by 915

Abstract

The use of construction waste for concrete is an effective way to reduce the environmental burden while improving the sustainability of construction materials. Nano-SiO₂ (NS) has excellent volcanic ash activity, which can effectively improve the strength of concrete. In this study, the [...] Read more.

The use of construction waste for concrete is an effective way to reduce the environmental burden while improving the sustainability of construction materials. Nano-SiO₂ (NS) has excellent volcanic ash activity, which can effectively improve the strength of concrete. In this study, the synergistic effects of NS and 30% recycled concrete aggregate (RCA) on the mass loss, compressive strength, ultrasonic sound velocity values and microstructure of RAC after 25, 50, 75 and 100 repetitions of a dry–wet cycle (DWC) of sulfuric acid were investigated. The results show that NS has a significant role in improving RAC performance. The RAC specimens showed the lowest mass loss rate, the highest compressive strength, the lowest ultrasonic velocity value and the best resistance to sulfate erosion when the NS doping was 4%. Meanwhile, under CT and SEM, RAC with NS has lower porosity and higher hydration, which can effectively inhibit the crack generation and has stable volume growth within 0–50 repetitions of DWC. In addition, the addition of NS improves not only the microstructure of the substrate but also the interfacial transition zone (ITZ). When 4% NS was added, the porosity was the lowest and the durability improvement was the best performance. This study not only improves the production performance of RAC but also provides a strong reference for the integrated application of nanomaterials in concrete. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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17 pages, 24303 KiB

Open AccessArticle

Development of Engineered Cementitious Composites (ECCs) Incorporating Iron Ore Tailings as Eco-Friendly Aggregates

by Kangning Liu, Sheliang Wang, Xiaoyi Quan, Jing Wu, Jin Xu, Nan Zhao and Bo Liu

Buildings 2023, 13(5), 1341; https://doi.org/10.3390/buildings13051341 - 20 May 2023

Cited by 3 | Viewed by 838

Abstract

In this study, iron ore tailings (IOTs) are used as aggregates to prepare iron-ore-tailing-engineered cementitious composites (IOT-ECCs) to achieve clean production. Some mechanical indexes, such as compressive strength (f_cu), four-point flexural strength (f_f), axial compressive strength ( [...] Read more.

In this study, iron ore tailings (IOTs) are used as aggregates to prepare iron-ore-tailing-engineered cementitious composites (IOT-ECCs) to achieve clean production. Some mechanical indexes, such as compressive strength (f_cu), four-point flexural strength (f_f), axial compressive strength (f_c), deformation properties, flexural toughness, and stress–strain behavior, are studied. The mass loss, f_cu loss, relative dynamic modulus elasticity (RDEM), and deterioration mechanism after the sulfate freeze–thaw (F-T) cycle are discussed in detail. In addition, pore structure analysis is performed using nuclear magnetic resonance (NMR), while a scanning electron microscope (SEM) is utilized to study the micro-morphology. The results showed that under the 20–80% IOT replacement ratio, IOT-ECCs exhibited improvements in their mechanical properties, pore structure, and resistance to sulfate freeze–thaw (F-T). The most notable mechanical properties and sulfate F-T resistance were demonstrated by the IOT-ECC with 40% IOTs (namely, IOT40-P2.0). Meanwhile, IOT40-P2.0 exhibited good pore structure as well as the bonding interface of the PF and the matrix. The pore structure and compactness of the matrix of IOT-ECCs gradually deteriorated as the F-T cycle increased. The research results will promote the application of IOTs in ECCs. Full article

(This article belongs to the Special Issue Durability, Physical and Mechanical Properties of Ecofriendly Cement and Concrete Composites)

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