Low Carbon and Green Materials in Construction

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

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 19018

Special Issue Editors

College of Civil Engineering, Tongji University, Shanghai 200092, China
Interests: recycled aggregate concrete; alkali-activated materials; carbonation; 3D concrete printing
Special Issues, Collections and Topics in MDPI journals
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong
Interests: sustainable concrete materials and technology; 3D printing of sustainable concrete
Special Issues, Collections and Topics in MDPI journals
Department of Civil and Environmental Engineering, Faculty of Construction and Environment, The Hong Kong Polytechnic University, Hong Kong 999077, China
Interests: cement hydration; durability; 3D concrete printing
School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, China
Interests: concrete durability; sulfuric acid corrosion; ultra-high performance concrete; fractal dimension characterization
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The amount of CO2 emissions caused by construction industry makes up about half of total CO2 emissions in the world, and a large portion is generated due to the production of construction materials. For example, the production of construction materials contributes to about 27% of total CO2 emissions in China. Therefore, the development of low-carbon materials in construction is very important in order to realize carbon neutrality.

A large amount of construction and demolition waste materials (e.g., waste concrete, brick, glass, wood, timber and so on) are generated every year. The recycling of construction and demolition wastes in construction materials can effectively reduce the amount of waste to landfill and save the natural sources. This is important for the sustainable development of the construction industry.

The aim of this Special Issue is to encourage scientists and researchers to publish their experimental and theoretical findings or solutions on low-carbon and green materials in construction. Topics for the Special Issue include (but are not limited to) the following:

  • Low-carbon concrete;
  • Recycled concrete;
  • Alkali-activated materials;
  • Ultra-high performance concrete;
  • 3D-printed concrete;
  • Carbonation.

Contributions are welcome.

Dr. Long Li
Dr. Shipeng Zhang
Dr. Xiaosheng Li
Dr. Jie Xiao
Guest Editors

Manuscript Submission Information

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

  • low-carbon materials
  • recycled concrete
  • alkali-activated materials
  • 3D concrete printing
  • carbonation
  • ultra-high performance concrete
  • mechanical properties
  • durability

Published Papers (13 papers)

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Research

16 pages, 4315 KiB  
Article
Research on the Bonding Performance of BFRP Bars with Reactive Powder Concrete
by Jie Xiao, Yikang Murong, Xiyuan Chen, Lingfei Liu, Keyi Zhai, Haibo Jiang, Linhai Huang and Guodong Wang
Buildings 2023, 13(8), 2083; https://doi.org/10.3390/buildings13082083 - 16 Aug 2023
Viewed by 540
Abstract
In recent years, replacing steel bars with basalt fiber-reinforced polymer (BFRP) bars and replacing ordinary concrete with reactive powder concrete (RPC) are considered effective solutions to the corrosion problem of steel bars in ordinary reinforced concrete structures. In order to study the bonding [...] Read more.
In recent years, replacing steel bars with basalt fiber-reinforced polymer (BFRP) bars and replacing ordinary concrete with reactive powder concrete (RPC) are considered effective solutions to the corrosion problem of steel bars in ordinary reinforced concrete structures. In order to study the bonding performance between BFRP bars and RPC, a total of 27 bonding specimens were tested by pull-out test. The effects of steel fiber volume content (0%, 1.5%, 2%), protective layer thickness (25 mm, 40 mm, 55 mm, 69 mm), and bond anchorage length of bars (3 d, 4 d, 5 d; d is the diameter of the bars) on the bond performance were studied. The experimental results indicated that the BFRP bar and reactive powder (RPC) concrete interface exhibited better bonding performance, and the steel fibers mixed in RPC can play the role of crack-blocking enhancement in the specimen, which improves the shear and tensile properties of the concrete, thus improving the bond strength between BFRP bar and RPC. Three failure modes were observed in the pull-out tests: BFRP bar shear failure, splitting failure, and concrete shear failure. The bond strengths of BFRP bars and RPC with 0%, 1.5%, and 2% steel fiber content were 24.2 MPa, 32.1 MPa, and 34.5 MPa, respectively. With the increase in bond anchorage length, the ultimate bond strength tended to increase first and then decrease. There may be an optimal bonding length between BFRP bar and reactive powder concrete, and when the optimal bonding length is exceeded, the bond strength decreases with the increase in bonding length. With the increase in the protective layer thickness, the improvement in the bond strength of the BFRP bar and RPC was not very significant. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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16 pages, 4695 KiB  
Article
Experimental Study on the Sulfuric Acid Corrosion Resistance of PHC Used for Pipe Pile and NSC Used in Engineering
by Jie Xiao, Huanqiang Huang, Hehui Zeng, Lingfei Liu, Long Li, Haibo Jiang, Zucai Zhong and Anyang Chen
Buildings 2023, 13(7), 1596; https://doi.org/10.3390/buildings13071596 - 24 Jun 2023
Cited by 1 | Viewed by 862
Abstract
In order to compare and investigate the sulfuric acid corrosion resistance of concrete for PHC pipe piles and two kinds of concrete commonly used in engineering, acid accelerated corrosion tests were conducted on specimens with three different strength grades of C30, C50, and [...] Read more.
In order to compare and investigate the sulfuric acid corrosion resistance of concrete for PHC pipe piles and two kinds of concrete commonly used in engineering, acid accelerated corrosion tests were conducted on specimens with three different strength grades of C30, C50, and C80 in a sulfuric acid solution with pH ≈ 0.85. The appearance of the specimens was observed, and the changes in mass loss percentage, corrosion depth, and stress–stain curves under uniaxial compressive loading were calculated and obtained with the corrosion time. From the comparison of corrosion depth and mass loss percentage of the concrete specimens with three different strength grades of C30, C50, and C80, it was found that the higher the strength grade of the concrete, the more severe the corrosion degree. The shapes of the stress–strain curves of three different strength grades of concrete specimens were basically the same. As the corrosion time was prolonged, the peak stress and the elastic modulus of concrete decreased. From the perspective of long-term corrosion, C80 specimens had a relatively smaller percentage of peak stress loss and a stronger resistance to peak stress loss. The research results provide references for the durability design of concrete structures and the prediction of concrete’s service life in a sulfuric acid environment. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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16 pages, 4046 KiB  
Article
Development and Characteristic of 3D-Printable Mortar with Waste Glass Powder
by Qi Deng, Shuai Zou, Yonghui Xi and Amardeep Singh
Buildings 2023, 13(6), 1476; https://doi.org/10.3390/buildings13061476 - 07 Jun 2023
Cited by 4 | Viewed by 1241
Abstract
Three-dimensional concrete printing (3DCP) is emerging as an innovative technology and shows promise to revolutionize conventional construction modes. However, the current 3D-printed concrete (3DPC) generally requires higher cement content than conventional concrete to ensure its rheology for printing. From the perspective of cleaner [...] Read more.
Three-dimensional concrete printing (3DCP) is emerging as an innovative technology and shows promise to revolutionize conventional construction modes. However, the current 3D-printed concrete (3DPC) generally requires higher cement content than conventional concrete to ensure its rheology for printing. From the perspective of cleaner production and reduce carbon emissions, this study explored the feasibility of replacing parts of cement with waste glass powder (WGP, 0%, 20%, 40%, and 60% by mass) and compared the properties of the developed 3DPC, including fluidity (flowable spread), rheology, heat of hydration, buildability, compressive strength, anisotropy, and drying shrinkage. The results showed that less than 40% WGP replacement had limited influence on the initial fluidity and static yield stress, as well as drying shrinkage, of 3DPC. Although the WGP inclusion decreased the compressive strength, it slowed down the fluidity loss and static yield stress increase, which could extend the workable time of the mixture for printing and improve buildability. The 40% WGP replacement was found increase to the buildability of the printing mixture from 150 mm to 155 mm. The printing mixture prepared with 60% WGP reduced the dying shrinkage by 50%. An exponential decay function between the fluidity and static yield stress was established so that the simple fluidity test could be used as an indicator of printability. The findings in this study provided a solution to reduce the consumption of cement in 3DPC, which could contribute to a greener production in the construction industry. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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19 pages, 10258 KiB  
Article
Experimental Study on Seismic Performance of CFRP-Strengthened Recycled Concrete Columns with Different Levels of Seismic Damage
by Shuai Song, Zhen Tian, Zhenyu Zhao, Xi Li, Jianfeng Zhao and Baishun Xu
Buildings 2023, 13(6), 1470; https://doi.org/10.3390/buildings13061470 - 06 Jun 2023
Viewed by 701
Abstract
To study the strengthening effect of carbon fiber composite materials (CFRP) on recycled concrete columns subjected to different levels of seismic damage, four column specimens were designed for pseudo-static tests. The four specimens were categorized as non-destructive without strengthening (prototype), non-destructive strengthening, medium [...] Read more.
To study the strengthening effect of carbon fiber composite materials (CFRP) on recycled concrete columns subjected to different levels of seismic damage, four column specimens were designed for pseudo-static tests. The four specimens were categorized as non-destructive without strengthening (prototype), non-destructive strengthening, medium seismic damage strengthening, and severe seismic damage strengthening based on the replacement rate of recycled aggregates and the level of seismic damage. The characteristics of the deformation damage and seismic performance indicators of each specimen were compared and analyzed. The results were verified on the OpenSees platform. A decrease was observed in the initial stiffness of the seismically damaged recycled concrete column specimens strengthened with CFRP, while the ductility, peak bearing capacity, and energy dissipation capacity of the specimens were improved. In addition, with the reduction in seismic damage, the ductility and energy dissipation capacity of the strengthened seismically damaged recycled concrete column specimens were enhanced to different degrees. In particular, the cumulative energy dissipation of the strengthened specimens exposed to medium seismic damage increased most significantly, by 32.5%. In general, the hysteretic curves of the strengthened specimens were full, and the average ductility coefficients were 4.1–6.8. CFRP strengthening was more effective for restoring and enhancing the performance of the recycled concrete column specimens with medium and lower seismic damage levels (displacement ratio ≤ 3%). Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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19 pages, 5958 KiB  
Article
Full-Scale Experimental Study on Flexural Performance of the New Precast UHPC Diaphragm Slab in Utility Tunnels
by Quan Cheng, Zhengwei Li, Shaowei Deng, Haibo Jiang, Yueqiang Tian and Jiayue Geng
Buildings 2023, 13(5), 1349; https://doi.org/10.3390/buildings13051349 - 22 May 2023
Viewed by 1070
Abstract
In this paper, a bending test of a precast ultra-high-performance concrete (UHPC) diaphragm slab was carried out. The test revealed that the flexural failure process of specimens under the action of a positive bending moment can be divided into three stages: the elastic, [...] Read more.
In this paper, a bending test of a precast ultra-high-performance concrete (UHPC) diaphragm slab was carried out. The test revealed that the flexural failure process of specimens under the action of a positive bending moment can be divided into three stages: the elastic, crack-propagation, and yield stages. The first stiffness reduction of the structure was caused by cracks at the bottom of the diaphragm slab, while the second stiffness drop resulted from the yielding of the bottom longitudinal rebars. During the loading process, the ultimate bearing capacity was 3.75 times higher than the design load value (150 kN vs. 40 kN). Additionally, a nonlinear finite element model was established using Abaqus software validated by the test and exploiting parameter analysis. Based on this model, the initial crack stress of the actual slab was determined to be 5.12 MPa. Parameter analysis indicated that the shear strength of the diaphragm slab was stronger than the flexural strength, and the diaphragm slab’s bearing capacity could be improved by increasing the ratio of bottom longitudinal reinforcement. This research confirmed that the new UHPC diaphragm slab used in Guangzhou Smart City is safe, and it also helped the design of similar UHPC slabs for utility tunnels. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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17 pages, 6682 KiB  
Article
Bond Stress Distribution and Bond–Slip Model of Deformed Steel Bars in Iron Tailing Sand Recycled Aggregate Concrete
by Qian Zhu, Jihao Chen, Yang He and Xialing Sun
Buildings 2023, 13(5), 1176; https://doi.org/10.3390/buildings13051176 - 28 Apr 2023
Cited by 3 | Viewed by 875
Abstract
In this study, the bond stress distribution and bond–slip model of steel bars and iron tailing sand recycled aggregate concrete (ITRAC) were investigated using central pullout tests on 33 steel bars and ITRAC bonded specimens. The results show three failure modes for the [...] Read more.
In this study, the bond stress distribution and bond–slip model of steel bars and iron tailing sand recycled aggregate concrete (ITRAC) were investigated using central pullout tests on 33 steel bars and ITRAC bonded specimens. The results show three failure modes for the bonded specimens: splitting, pullout, and splitting–pullout. Compared with the maximum bond strength of nature sand concrete (NAC), the maximum bond strength of the iron tailing concrete and ITRAC specimens increased by 23.12% and 6.08–23.96%, respectively. After adding 1% steel fiber, the maximum and residual bond strengths of ITRAC increased by 40.82% and 129.10%, respectively, compared with those of NAC. The maximum bond strength of ITRAC decreased after the configuration of the stirrups. The bond stress distribution characteristics of the ITRAC specimens resembled those of recycled aggregate concrete (RAC). Generally, two bond stress peaks emerged, and the uniformity of the bond stress distribution improved after adding RAC to the iron tailing sand (ITS). The results of the proposed ITRAC bond–slip constitutive model agreed with the test results. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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14 pages, 10959 KiB  
Article
Effect of Cementitious Material Composition on the Performance of Low-Carbon Foamed Lightweight Soil
by Cong Shen, Hao Liu, Huiwen Wan, Jixin Li, Peng Liu, Qiqing He and Jiaqi Xuan
Buildings 2023, 13(3), 759; https://doi.org/10.3390/buildings13030759 - 14 Mar 2023
Cited by 2 | Viewed by 926
Abstract
This study simulated the production process of low-carbon foamed lightweight soil (LCFLS) prepared using prefabricated foam technology in real engineering conditions. The preparation and properties of LCFLS with a wet density of 600 kg/m3 were systematically investigated. The effects of different mix [...] Read more.
This study simulated the production process of low-carbon foamed lightweight soil (LCFLS) prepared using prefabricated foam technology in real engineering conditions. The preparation and properties of LCFLS with a wet density of 600 kg/m3 were systematically investigated. The effects of different mix designs of large dosing granulated blast furnace slag and fly ash on the properties of LCFLS were investigated. The workability, rheological properties, and mechanical properties of LCFLS were studied. XRD, TG–DTG, and SEM were used to analyze the hydration mechanism of LCFLS. The results showed that fly ash could improve the flowability of LCFLS, while excessive fly ash could lead to foam and slurry delamination. Granulated blast furnace slag improved the mechanical properties of LCFLS, while excess granulated blast furnace slag caused the foam to break and merge, affecting the soil’s homogeneity. The higher the dynamic yield stress of the freshly mixed slurry, the better the homogeneity, and the smaller and more evenly distributed pore sizes formed after hardening. The main hydration products of LCFLS were C-S-H gel and CH, with small amounts of the carbonation products CaCO3, Hc, and Mc. The LCFLS prepared with 30% cement, 30% fly ash, and 40% granulated blast furnace slag had a flowability of 170–180 mm, with slight differences between wet and quasi-dry densities. The rheological properties of the slurry following the Bingham model showed a dynamic yield stress of 9.41 Pa, an average pore size after hardening of around 300 μm, and compressive strengths at 7 d and 28 d reaching 0.92 MPa and 2.04 MPa, respectively. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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17 pages, 2615 KiB  
Article
Contribution of Steel Fiber to the Mechanical Property Improvement of C80 Concrete Produced with a High Amount of Artificial Sand Powder
by Qingqing Xie, Dongxing Xuan, Bo Shen and Kejian Ma
Buildings 2023, 13(3), 602; https://doi.org/10.3390/buildings13030602 - 24 Feb 2023
Cited by 1 | Viewed by 865
Abstract
Due to the high price of river sand, its shortage and unsustainable extraction from the environment, artificial sand (AS) has been promoted as a fine aggregate for producing concrete. However, it has been acknowledged that a high content of limestone powder (LP), up [...] Read more.
Due to the high price of river sand, its shortage and unsustainable extraction from the environment, artificial sand (AS) has been promoted as a fine aggregate for producing concrete. However, it has been acknowledged that a high content of limestone powder (LP), up to 15 wt.%, as a by-product in AS coexists and it has an adverse impact on the mechanical properties of concrete. To compensate for the performance loss of C80 concrete with a high LP content to the applications of concrete on a large scale, this study evaluates the contribution of steel fiber content to the performance improvement of concrete by means of a developed statistical method. Experimental results show that when increasing the LP in concrete over 5%, it can influence axial compression, flexural intensity, splitting tension and the modulus of elasticity, in particular, presenting an obvious decrease in axial compressive intensity, splitting tension and modulus of elasticity. Incorporating steel fibers in such concrete prepared with a high amount of artificial sand powder is a way to compensate for its performance loss. Referring to the experimental results and probability theory, the probability density function of the characteristic value of mechanical characteristic of one type of concrete and the difference between the characteristic values of mechanical characteristics of any two concretes were developed to establish a scientific criterion that can be used to compare the sizes of any two characteristic probability values, which is superior to the comparative approach of arithmetic averages in publications. By adopting this method, the high-strength concrete with a high LP and steel fiber content could be applied in engineering practices from the point of view of its mechanical properties. Meanwhile, the study provides an evaluation method for other scientific research on the size comparison of any two stochastic physical variables. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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18 pages, 5588 KiB  
Article
Developing Low-pH 3D Printing Concrete Using Solid Wastes
by Xiao-Sheng Li, Long Li and Shuai Zou
Buildings 2023, 13(2), 454; https://doi.org/10.3390/buildings13020454 - 07 Feb 2023
Cited by 2 | Viewed by 1604
Abstract
Three-dimensional concrete printing technology provides the possibility to fabricate specific and eco-friendly concrete components for application on shorelines or in other areas, providing environmental protection. In this study, solid wastes in Hong Kong are employed for low-pH 3D printing concrete to further decrease [...] Read more.
Three-dimensional concrete printing technology provides the possibility to fabricate specific and eco-friendly concrete components for application on shorelines or in other areas, providing environmental protection. In this study, solid wastes in Hong Kong are employed for low-pH 3D printing concrete to further decrease the impact on the environment. The results indicate that WGP replacement in a classic low-pH recipe leads to lower yield stress and surface pH, as well as volume stability. The employment of slag improves workability and printability, but maintains the surface pH and drying shrinkage. The printing height is not merely determined by slump flow, and contributions from every binder on the surface pH are quantified based on simplified calculations. Reducing OPC and increasing SF in the classic low-pH recipe achieves the best printing performance and improved environmental friendliness. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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17 pages, 4087 KiB  
Article
Development of Ultrafine Mineral Admixture from Magnesium Slag and Sequestration of CO2
by Junhao Ye, Songhui Liu, Yue Zhao, Yuan Li, Jingrui Fang, Haibo Zhang and Xuemao Guan
Buildings 2023, 13(1), 204; https://doi.org/10.3390/buildings13010204 - 12 Jan 2023
Cited by 3 | Viewed by 1739
Abstract
To upcycle magnesium slag solid waste (MS) as well as sequester CO2, a new wet carbonation process was proposed to activate the volcanic ash activity of MS and use it as an ultrafine mineral admixture for cement. The effects of different [...] Read more.
To upcycle magnesium slag solid waste (MS) as well as sequester CO2, a new wet carbonation process was proposed to activate the volcanic ash activity of MS and use it as an ultrafine mineral admixture for cement. The effects of different carbonation times on the activity of MS were investigated, and the phase assemblage, as well as the changes in the microstructure and pore structure during the carbonation process, was also characterized using multiple techniques, such as TG-DTG, XRD, FT-IR, 29Si NMR spectrum, SEM, and BET, to further reveal the carbonation activation mechanism of MS under wet carbonation. Moreover, the effects of MS before and after carbonation on the compressive strength of the composite cement paste were investigated to verify the feasibility of carbonated MS as an ultrafine mineral admixture. The results show that the products of MS generated after a short carbonation reaction were mainly highly polymerized calcium–silicate–hydrate gel and a large amount of calcium carbonate in the form of calcite and aragonite with a size of about 1 μm. The CO2 sequestration rate of MS reached 22.14%. Compared to pure cement, carbonated MS can replace 30% of the cement clinker without compromising compressive strength. The above results offer potential possibilities for upgrading the utilization of MS and CO2 sequestration in the cement industry. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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12 pages, 29861 KiB  
Article
Mechanical Property and Dimensional Stability of Chopped Basalt Fiber-Reinforced Recycled Concrete and Modeling with Fuzzy Inference System
by Chu-Jie Jiao, Xiu-Cheng Zhang, Wei-Zhi Chen and Xue-Fei Chen
Buildings 2023, 13(1), 97; https://doi.org/10.3390/buildings13010097 - 30 Dec 2022
Cited by 3 | Viewed by 1150
Abstract
The rising amount of construction and demolition wastes (C & DWs) is triggering serious environmental and social problems globally. This study conducted an experimental investigation of basalt fiber (BF)-reinforced concrete with recycled aggregates (RAs) sourced from C & DWs. The flexural strength, the [...] Read more.
The rising amount of construction and demolition wastes (C & DWs) is triggering serious environmental and social problems globally. This study conducted an experimental investigation of basalt fiber (BF)-reinforced concrete with recycled aggregates (RAs) sourced from C & DWs. The flexural strength, the flexural to compressive strength ratio, and the drying shrinkage are set as indicators for the evaluation of the coupling effect of BF and RA in concrete. Results show that BF generated a significant effect on the flexural strength until the BF dosage was no higher than 1%. The excessive mixing amount of BF, though it still contributed to a positive effect on elevating the flexural strength, was of a reduced utility. Regarding the flexural to compressive strength ratio (denoted as ratio), BF and RA jointly produced a positive synergistic effect. In addition, the BF was verified as competent in curbing the adverse effect of RA incorporation upon the drying shrinkage. Relative to the benchmark concrete which contains 100% RA and no BF, 1% BF contributed to a 31.6% reduction in the drying shrinkage. The results prove that BF reinforcement is a feasible and promising approach to curb the drawbacks of RA concrete. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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21 pages, 11921 KiB  
Article
Recycling Old Concrete as Waste Concrete Powder for Use in Pervious Concrete: Effects on Permeability, Strength and Eco-Friendliness
by Hui Zhu Xie, Leo Gu Li, Feng Liu and Albert Kwok Hung Kwan
Buildings 2022, 12(12), 2172; https://doi.org/10.3390/buildings12122172 - 08 Dec 2022
Cited by 6 | Viewed by 2385
Abstract
The fine portion of crushed old concrete is difficult to be recycled for use in new concrete because it contains old cement paste, which generally has high porosity and low strength. Hence, in practice, the coarse portion is recycled as coarse aggregate and [...] Read more.
The fine portion of crushed old concrete is difficult to be recycled for use in new concrete because it contains old cement paste, which generally has high porosity and low strength. Hence, in practice, the coarse portion is recycled as coarse aggregate and the fine portion is mostly not recycled. Nevertheless, attempts have been made in recent years to recycle the fine portion as waste concrete powder (WCP) by grinding before use. In this research, WCP was used to make pervious concrete. The WCP was added using the paste replacement method (PR method) of replacing an equal volume of cementitious paste. A series of pervious concrete mixes containing 100% recycled coarse aggregate and having different amounts of WCP added were produced for testing of interconnected porosity, water permeability and strength. The results showed that the addition of WCP using the PR method can improve the interconnected porosity by 9% and water permeability by 18%, greatly enhance the strength by 86%, as well as decrease the cement consumption by 10% at the same time. Therefore, the addition of WCP as paste replacement has great potential to be applied to the production of eco-friendly high-performance pervious concrete. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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14 pages, 5707 KiB  
Article
Combined Effects of Sulfate and Chloride Attack on Steel Reinforced Mortar under Drying–Immersion Cycles
by Hongfang Sun, Hao Zou, Xinwei Li, Shazim Ali Memon, Binyang Yuan, Feng Xing, Xiaogang Zhang and Jie Ren
Buildings 2022, 12(8), 1252; https://doi.org/10.3390/buildings12081252 - 16 Aug 2022
Cited by 7 | Viewed by 1745
Abstract
In this study, X-ray microcomputed tomography (XCT) and nanoindentation techniques were used to evaluate the synergistic action between sulfate and chloride ingress under cyclic drying–immersion conditions on steel-reinforced mortars. Three salt solutions, namely 3% NaCl (Sc), 5% Na2SO4 (Ss), and [...] Read more.
In this study, X-ray microcomputed tomography (XCT) and nanoindentation techniques were used to evaluate the synergistic action between sulfate and chloride ingress under cyclic drying–immersion conditions on steel-reinforced mortars. Three salt solutions, namely 3% NaCl (Sc), 5% Na2SO4 (Ss), and 5% Na2SO4 + 3% NaCl (Scs), were used and 24 drying–immersion cycles were applied. The results showed that the chloride caused more severe corrosion on steel reinforcement than the sulfate while under the influence of Scs, and the presence of sulfate suppressed the steel corrosion caused by chloride. In terms the damage to the mortar cover, after 24 drying–immersion cycles, the sulfate caused the most severe damage (volume loss of approximately 7.1%) while the chloride resulted in the least damage (volume loss of approximately 2.6%). By comparing Ss and Scs, it was also found that chloride suppressed the sulfate attack by reducing the damage to the mortar cover (volume loss of approximately 6.3% for Scs). Moreover, the degradation of mortar specimens was found to be layer-dependent, as was the distribution of micro-mechanics. Regarding the micro-mechanics, the specimens of the three solutions performed differently in terms of the aforementioned properties, depending on which underlying mechanism was analyzed. This research could allow for a more accurate assessment of the factors influencing building structures in a typical aggressive marine environment. Full article
(This article belongs to the Special Issue Low Carbon and Green Materials in Construction)
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