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22 pages, 9596 KiB

Open AccessArticle

Damage and Crack Propagation Mechanism of Q345 Specimen Based on Peridynamics with Temperature and Bolt Holes

by Jinhai Zhao, Huanhuan Sun and Xinfeng Zhang

Buildings 2024, 14(10), 3220; https://doi.org/10.3390/buildings14103220 - 10 Oct 2024

Viewed by 493

With the increasing demand for the performance and design refinement of steel structures (including houses, bridges, and infrastructure), many structures have adopted ultimate bearing capacity in service. The design service lives of steel building structures are generally more than 50 years, and most [...] Read more.

With the increasing demand for the performance and design refinement of steel structures (including houses, bridges, and infrastructure), many structures have adopted ultimate bearing capacity in service. The design service lives of steel building structures are generally more than 50 years, and most of them contain bolted connections, which suffer from extreme conditions such as fire (high temperature) during service. When the structure contains defects or cracks and bolt holes, it is easy to produce stress concentration at the defect location, which leads to crack nucleation and crack propagation, reduces the bearing capacity of the structure, and causes the collapse of the structure and causes disasters. In the process of structural damage and crack propagation, the traditional method has some disadvantages, such as stress singularity, the mesh needing to be redivided, and the crack being restricted to mesh; however, the integral method of peridynamics (PD) can completely avoid these problems. Therefore, in this paper, the constitutive equation of PD in high temperature is derived according to the variation law of steel material properties when changed by temperature increase and peridynamics parameters; the damage and crack expansion characteristics of Q345 steel specimens with bolt holes and a central double-crack at 20 °C, 200 °C, 400 °C, and 600 °C were analyzed to clarify the structural damage and failure mechanism. This study is helpful for providing theoretical support for the design of high-temperature steel structures, improving the stability of the structure, and ensuring the bearing capacity of the structure and the safety of people’s lives and property. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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18 pages, 3929 KiB

Open AccessArticle

Preparation Method and Benefit Analysis for Unburned Brick Using Construction Solid Waste from Residue Soil

by Xingzhong Nong, Linren Zhou, Lihua Zhai and Feng Gu

Buildings 2024, 14(10), 3213; https://doi.org/10.3390/buildings14103213 - 9 Oct 2024

Viewed by 535

Abstract

Highly efficient resource utilization of construction solid waste has significant environmental and socioeconomic benefits. In this study, a fabrication method and process optimization of unburned brick from construction residue soil were investigated based on experiments. The effects of cementing the material content, the [...] Read more.

Highly efficient resource utilization of construction solid waste has significant environmental and socioeconomic benefits. In this study, a fabrication method and process optimization of unburned brick from construction residue soil were investigated based on experiments. The effects of cementing the material content, the raw material treatment process, the brick moisture content, and the molding method on the compressive strength of unburned brick were studied and discussed. The experimental results show that 5–20% of ordinary cement can produce a strength grade of 5 MPa–20 MPa for unburned brick, and the utilization rate of the residue soil is greater than 80%. In the case of well-dispersed residual particles, complete drying and rolling are not necessary, and soil particle size within 5 mm is beneficial for obtaining proper sand grading and low mud content, which will improve the strength of unburned brick. The pressure for the press forming of unburned brick should be 10 MPa, and the optimal moisture content of the residue-soil mixture is about 13%. The proposed residue-soil unburned brick has remarkable environmental and economic benefits with low carbon emissions, low cost, and high profit. The methods proposed and optimized in this study can provide important technical support for realizing the large-scale production of residue-soil unburned brick. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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20 pages, 5766 KiB

Open AccessArticle

Bearing Capacity of Hybrid (Steel and GFRP) Reinforced Columns under Eccentric Loading: Theory and Experiment

by Lei Pang, Zebin Han, Jie Xiao, Zexuan Liu, Wenjun Qu and Sansheng Dong

Buildings 2024, 14(8), 2472; https://doi.org/10.3390/buildings14082472 - 10 Aug 2024

Cited by 1 | Viewed by 971

Abstract

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the [...] Read more.

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the damage process and failure mode of these hybrid RC columns was similar to those in the conventional steel-reinforced concrete columns. The mode of failure for all specimens is characterized as large eccentricity compression failure, and the ultimate bearing capacity of the columns decreases with the increase in eccentricity. However, the impact of the varying axial stiffness ratio between GFRP and steel bars on the bearing capacity can be considered negligible. In addition, based on theoretical analysis, two boundary states for distinguishing failure mode and the formulae for calculating ultimate bearing capacity in different failure modes of eccentrically loaded hybrid RC columns are proposed. The computed results agree well with test results. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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21 pages, 6435 KiB

Open AccessArticle

Experimental Study and Analysis of the Effects of Mud on the Compressive Strength of Unburned Brick Using Engineering Residue Soil

by Xingzhong Nong, Linren Zhou, Yuehua Liang and Taojun Wang

Buildings 2024, 14(7), 1949; https://doi.org/10.3390/buildings14071949 - 27 Jun 2024

Cited by 2 | Viewed by 732

Abstract

Engineering residue soil, a prominent type of construction solid waste, can offer considerable environmental and socioeconomic benefits if efficiently utilized. Unburned brick represents an environmentally friendly and high-value approach to reusing this residue soil. Mud, a primary constituent of residue soil, typically hinders [...] Read more.

Engineering residue soil, a prominent type of construction solid waste, can offer considerable environmental and socioeconomic benefits if efficiently utilized. Unburned brick represents an environmentally friendly and high-value approach to reusing this residue soil. Mud, a primary constituent of residue soil, typically hinders the performance of unburned brick using cement-based materials. This study investigates the effects of mud on the performance of unburned brick made from engineering residue soil based on experimental tests and mechanism analysis. The residue soil is silty clay sourced from the alluvial soil layer in South China. A comprehensive analysis of the physical and chemical properties of the residue soil and mud is conducted to assess the feasibility of using them in unburned brick production. Using ordinary Portland cement as the cementitious material, the unburned residue soil bricks are produced via semi-dry static-press forming and natural curing. The influence of mud type and content on the compressive strength of the unburned brick made with engineering residue soil is investigated and discussed. This experimental study reveals that the influence of mud on unburned brick’s compressive strength is negligible. However, excessively low mud content reduces brick compactness, impairs brick formation, and leads to lower compressive strength. Within the range of solidification, unburned brick’s compressive strength initially increases and then decreases with increasing mud content, with an optimal mud content of approximately 25%. As engineering residue soil often contains a high mud content, reducing it effectively enhances the compressive strength of unburned bricks. Through experiments and mechanism analysis, this research clarifies the impact of mud on the strength and performance of unburned residue soil bricks, providing important theoretical insights and practical guidance for the production of unburned products and promoting the efficient and environmentally friendly resource utilization of engineering residue soil. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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13 pages, 3202 KiB

Open AccessArticle

Design Approach on Bearing Capacity of the Cross-Bracing with Different Types of Joint Connection in Steel Lattice Transmission Towers

by Jiajing Xu, Songyang He, Xing Huang, Dagang Han, Xiangyun Liu, Jiubin Sun, Jing Wang, Lu Yao and Shaofeng Zhang

Buildings 2024, 14(6), 1784; https://doi.org/10.3390/buildings14061784 - 13 Jun 2024

Viewed by 643

Abstract

This paper presents an evaluation of the bearing capacity of cross-bracing in steel transmission tower structures. Design guidelines (ASCE 10-15, BS EN 50341-1, GB 50017-2017, and DL/T 5486-2020) related to the buckling capacity of the cross-bracing are summarized and compared with the experimental [...] Read more.

This paper presents an evaluation of the bearing capacity of cross-bracing in steel transmission tower structures. Design guidelines (ASCE 10-15, BS EN 50341-1, GB 50017-2017, and DL/T 5486-2020) related to the buckling capacity of the cross-bracing are summarized and compared with the experimental results. The current design provisions obtained the bearing capacity from the equivalent slenderness ratio, and then the stability coefficient and buckling capacity were derived. The calculated bearing capacity based on the design code tends to be overly progressive for smaller slenderness ratios (particularly those below 100), except for EN 50341-1-2012. Conversely, for larger slenderness ratios, ASCE 10-15 and DL/T 5486-2020 Class A design codes lean towards being overly progressive, while GB 50017-2017 and EN 50341-1-2012 codes tend to be more conservative. The design standard appears to exhibit unsafe predictions for Class A and B connections with low slenderness ratios and Class C connections. It needs to be noted that the effects of torsional stiffness and joint connection type are not considered in the current design codes, which are proved to be nonnegligible by the test results. In this paper, the bearing capacity calculation formula is proposed by introducing a modified effective length coefficient (K), and both the torsional stiffness and joint connection type are taken into account. The modified bearing capacity is verified with the test results; the correlation coefficient is 0.997, and the coefficient of variation is 0.04. It can provide a reference for the engineering design of steel lattice transmission tower structures. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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Schematic diagram of the members in lattice transmission towers. Full article ">Figure 2
Schematic diagram of buckling modes [<a href="#B20-buildings-14-01784" class="html-bibr">20</a>]. (a) Flexural buckling along axis-uu; (b) flexural buckling along axis-vv; (c) torsional buckling; (d) flexural–torsional buckling. Full article ">Figure 3
Schematic of end restraints. Full article ">Figure 4
Notations of the steel angle section. yy/zz: geometric axis of the cross-section parallel to the leg; uu: major/strong principal axis (associated with weak axis displacement); vv: minor/weak principal axis (associated with strong axis displacement). Full article ">Figure 5
Comparison between experimental and calculated results with different end restraints. Full article ">Figure 6
The comparison between test results and the column curve in the design code. Full article ">Figure 7
The comparison between experimental and modified results. Full article ">

14 pages, 2405 KiB

Open AccessArticle

A Hydration-Based Integrated Model to Evaluate Properties Development and Sustainability of Oyster Shell Powder–Cement Binary Composites

by Seung-Jun Kwon and Xiao-Yong Wang

Buildings 2024, 14(6), 1578; https://doi.org/10.3390/buildings14061578 - 30 May 2024

Cited by 1 | Viewed by 673

Abstract

Currently, oyster shell powder (OSP) is becoming more widely used in the production of cement-based materials. The purpose of this study is to propose a predictive model that can predict the properties of concrete materials incorporating oyster shell powder. The methods of this [...] Read more.

Currently, oyster shell powder (OSP) is becoming more widely used in the production of cement-based materials. The purpose of this study is to propose a predictive model that can predict the properties of concrete materials incorporating oyster shell powder. The methods of this prediction model are given as follows. First, based on the measurement results of the heat of hydration in the first 7 days, the prediction parameters of the hydration model are obtained. Secondly, based on the hydration model, the measured results of the heat of hydration were extrapolated, and the heat of hydration from the start of stirring to day 28 was calculated. From the calculation results, the developments of compressive strength, ultrasonic velocity, and surface electrical resistivity were estimated. Finally, we evaluated the CO₂ emissions of concrete incorporating oyster shell powder. The CO₂ emissions corresponding to unit compressive strength and unit surface electrical resistivity were calculated. The important conclusions of the prediction model are given as follows. First, for different substitution amounts of oyster shell powder, the model result shows that the ultimate value of the heat of hydration corresponding to the unit cement mass is the same, i.e., 454.27 J/g. While the substitution amount of oyster shell powder increases from 0% to 30%, the model result shows that the cumulative 28-day hydration heat for 1 g cement increases the powder amount from 405.7 J/g to 419.3 J/g. Secondly, as the amount of substituted oyster shell powder increases from 0% to 30%, the model result shows that the cumulative 28-day heat of hydration per gram of cementitious material decreases this amount from 405.7 J/g to 293.4 J/g. Compressive strength, ultrasonic pulse velocity, and surface electrical resistivity can all be expressed as exponential functions of the heat of hydration. For compressive strength, ultrasonic pulse velocity, and surface electrical resistivity, the coefficients of determination for the simulation results and experimental results are 0.8396, 0.7195, and 0.9408, respectively. Finally, as the amount of substituted oyster shell powder increases from 0% to 30%, the model result shows that the CO₂ emission per unit of compressive strength increases from 10.18 kg/MPa to 16.51 kg/MPa. As the amount increases from 0% to 30%, the model result shows that the CO₂ emission corresponding to the unit surface electrical resistivity does not change significantly. In summary, the importance of this model is that it can predict various properties of concrete mixed with oyster shell powder, reduce the number of experiments, and promote the engineering application of oyster shell powder concrete. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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Analysis of cumulative heat normalized by cement. (a) Cumulative heat normalized by cement–0%OSP. (b) Cumulative heat normalized by cement–15%OSP. (c) Cumulative heat normalized by cement–30%OSP. Full article ">Figure 2
Calculation results of hydration heat from mixing to 28 days. (a) Cumulative hydration heat normalized by cement mass. (b) Hydration degree of cement. (c) Cumulative hydration heat normalized by binder mass. Full article ">Figure 3
Property predictions using cumulative hydration heat. (a) Relation between cumulative hydration heat and compressive strength. (b) Relation between cumulative hydration heat and UPV. (c) Relation between cumulative hydration heat and surface electrical resistivity. Full article ">Figure 4
Analysis of sustainability of cement–OSP binary composite. (a) CO2 emissions of 1 m3 mortar. (b) CO2 emissions of unit compressive strength. (c) CO2 emissions of unit surface electrical resistivity. Full article ">Figure A1
Cumulative hydration heat of 1 g binder. Full article ">Figure A2
Cumulative hydration heat of 1 g cement. Full article ">

19 pages, 65974 KiB

Open AccessArticle

Experimental Study on the Performance of Glass/Basalt Fiber Reinforced Concrete Unidirectional Plate under Impact Load

by Liancheng Li, Jueliang Chen, Siyu Liu, Xin Huang and Hui Chen

Buildings 2024, 14(5), 1367; https://doi.org/10.3390/buildings14051367 - 10 May 2024

Cited by 1 | Viewed by 924

Abstract

Fiber-reinforced composite materials have emerged as essential solutions for addressing the durability challenges of traditional reinforced concrete, owing to their lightweight nature, high strength, ease of construction, superior tensile capacity, robust corrosion resistance, and excellent electromagnetic insulation properties. This paper delves into the [...] Read more.

Fiber-reinforced composite materials have emerged as essential solutions for addressing the durability challenges of traditional reinforced concrete, owing to their lightweight nature, high strength, ease of construction, superior tensile capacity, robust corrosion resistance, and excellent electromagnetic insulation properties. This paper delves into the influence of loading rate and fiber bar type on the mechanical characteristics of concrete one-way plates through impact experiments on such plates fitted with glass/basalt fiber bars at varying drop weight heights. The test results reveal a direct correlation between increasing loading rates and escalating damage in fiber-reinforced concrete one-way plates, reflected in the progressive rise in peak deflection and residual displacement at the mid-span of the specimens. Notably, when subjected to higher impact loads, glass fiber-reinforced concrete specimens exhibit amplified deformation and intricate crack formations, consequently diminishing the overall deformation resistance of the plate. Furthermore, glass/basalt fiber-reinforced composites demonstrate notable vibration damping qualities, characterized by substantial residual displacement, minimal rebound, and rapid decay following vibration stimulation. Overall, glass fiber-reinforced one-way plates display marginally superior impact resistance compared to their basalt fiber-reinforced counterparts. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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21 pages, 3031 KiB

Open AccessArticle

Effect of Calcium Aluminate and Carbide Slag on Mechanical Property and Hydration Mechanism of Supersulfated Cement

by Guangzheng Qi, Qiang Zhang and Zhengning Sun

Buildings 2024, 14(4), 930; https://doi.org/10.3390/buildings14040930 - 28 Mar 2024

Viewed by 975

Abstract

Supersulfated cement (SSC), a low-carbon, energy-efficient, eco-friendly cementitious material, is mainly made from industrial byproducts. However, SSC’s slow early strength development leads to inadequate initial hardening and reduced durability, which restricts its practical application. This study investigated the potential enhancement of SSC by [...] Read more.

Supersulfated cement (SSC), a low-carbon, energy-efficient, eco-friendly cementitious material, is mainly made from industrial byproducts. However, SSC’s slow early strength development leads to inadequate initial hardening and reduced durability, which restricts its practical application. This study investigated the potential enhancement of SSC by incorporating calcium aluminate (CA) and carbide slag (CS) alongside anhydrite as activators to address its slow early strength development. The effects of varying CA and CS proportions on the mechanical property and hydration mechanism of CA-CS-SSC were examined. Results indicate that employing 1% CA and 4% CS as alkaline activators effectively activates slag hydration in the 1CA-4CS-SSC, achieving a compressive strength of 9.7 MPa at 1 day. Despite the limited improvement in early compressive strength of other mixtures with higher CA and lower CS proportions in the CA-CS-SSC system, all mixtures exhibited enhanced compressive strength during long-term hydration. After 90 days, ettringite formation in the CA-CS-SSC system decelerated, whereas anhydrite remained. Concurrently, the formation of C-S-H continued to increase, promoting late compressive strength. The mechanism for enhancing the early compressive strength of the CA-CS-SSC system is attributed to the swift hydration of CA with anhydrite, dissolution of fine slag particles, and reaction with anhydrite under conditions with suitable alkali content to augment the ettringite production. This process also generates a C-S-H and OH-hydrotalcite to fill the void in the skeleton structure formed by ettringite, resulting in a dense microstructure that improves early compressive strength. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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18 pages, 7414 KiB

Open AccessArticle

A Study on the Factors Influencing High Backfill Slope Reinforced with Anti-Slide Piles under Static Load Based on Numerical Simulation

by Baogui Zhou, Huabin Zhong, Kaipeng Yang, Xueqiang Yang, Chifeng Cai, Jie Xiao, Yongjian Liu and Bingxiang Yuan

Buildings 2024, 14(3), 799; https://doi.org/10.3390/buildings14030799 - 15 Mar 2024

Cited by 1 | Viewed by 1011

Abstract

Based on a real engineering case, this study employs the MIDAS finite element software to model the reinforced high embankment slope using anti-sliding piles. The accuracy of the finite element method is verified by comparing calculated outcomes with field monitoring data. Expanding on [...] Read more.

Based on a real engineering case, this study employs the MIDAS finite element software to model the reinforced high embankment slope using anti-sliding piles. The accuracy of the finite element method is verified by comparing calculated outcomes with field monitoring data. Expanding on this foundation, an analysis of factors influencing the reinforced high embankment slope is undertaken to scrutinize the impact of diverse elements on the slope and ascertain the optimal reinforcement strategy. The results reveal the following: The principal displacement observed in the high embankment slope is a vertical settlement, which escalates with the backfill height. Notably, the highest settlement does not manifest at the summit of the initial slope; instead, it emerges close to the summits of the subsequent two slopes. However, the maximum horizontal displacement at the slope’s zenith diminishes as the fill height increases—a trend that aligns with both field observations and finite element computations. The examination of the influence of anti-sliding pile reinforcement on the high embankment slope unveils that factors like the length, diameter, spacing, and positioning of the anti-sliding piles exert minor impacts on vertical settlement, while variations in the parameters of the anti-sliding piles significantly affect the slope’s horizontal displacement. When using anti-sliding piles to reinforce multi-level high embankment slopes, factoring in the extent of horizontal displacement variation and potential cost savings, the optimal parameters for the anti-sliding piles are a length of 15 m, a diameter of 1.5 m, and a spacing of 2.5 m, presenting the most effective combination to ensure superior slope stability and support. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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17 pages, 5975 KiB

Open AccessArticle

Experimental Investigation on the Influence of Strength Grade on the Surface Fractal Dimension of Concrete under Sulfuric Acid Attack

by Jie Xiao, Hehui Zeng, Huanqiang Huang, Lingfei Liu, Long Li, Bingxiang Yuan and Zucai Zhong

Buildings 2024, 14(3), 713; https://doi.org/10.3390/buildings14030713 - 7 Mar 2024

Cited by 10 | Viewed by 1242

Abstract

The corrosion of alkaline concrete materials exposed to a sulfuric acid environment is becoming more and more prevalent, and its damage assessment is becoming more and more imperative. This study aims to describe the corroded surfaces of concrete with different strength grades (C30, [...] Read more.

The corrosion of alkaline concrete materials exposed to a sulfuric acid environment is becoming more and more prevalent, and its damage assessment is becoming more and more imperative. This study aims to describe the corroded surfaces of concrete with different strength grades (C30, C50, C80) in sulfuric acid environments in terms of their three-dimensional fractal dimension. Three kinds of concrete with varying strength grades, namely C30, C50, and C80, were immersed in a sulfuric acid solution with pH ≈ 0.85 for four distinct corrosion durations, specifically 0, 28, 56, and 165 days, in accelerated corrosion tests. The 3D laser scanning technique was utilized to capture the 3D coordinates of the surface points of the concrete cylinder before and after corrosion. The fractal dimension of concrete’s uneven surface before and after corrosion was computed via the cube covering method, and the mass loss of the concrete specimen was also obtained. The outcomes demonstrate that the three-dimensional fractal dimension provides a new method for characterizing the degree of corrosion deterioration of concrete samples affected by sulfuric acid via laser scanning technology. From the perspective of the appearance, mass loss, and fractal dimension of a rough surface in the sulfuric acid environment at a pH level of approximately 0.85, the degree of the corrosion deterioration of concrete is ranked from high to low as C80 > C50 > C30. These fractal dimensions of the concrete’s corroded surfaces with various strength grades increase rapidly in the initial period. However, as the corrosion time progresses, the growth rate of the corroded surface fractal dimension gradually decelerates and tends towards stability, which accords with the law of exponential function. The widespread belief is that the higher the strength grade of concrete, the better its durability; however, this pattern varies in sulfuric acid corrosive environments. Therefore, based on this research, it is recommended that in extremely acidic environments (i.e., very low pH), more attention should be paid to high-strength grades of concrete. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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18 pages, 4998 KiB

Open AccessArticle

Flexural Behavior of Alkali-Activated Ultra-High-Performance Geopolymer Concrete Beams

by Jie Su, Jiandong Tan, Kai Li and Zhi Fang

Buildings 2024, 14(3), 701; https://doi.org/10.3390/buildings14030701 - 6 Mar 2024

Viewed by 1246

Abstract

Ultra-high-performance geopolymer concrete (UHPGC) emerges as a sustainable and cost-effective alternative to Portland cement-based UHPC, offering similar mechanical properties while significantly reducing carbon footprint and energy consumption. Research on UHPGC components is extremely scarce. This study focuses on the flexural and crack behavior [...] Read more.

Ultra-high-performance geopolymer concrete (UHPGC) emerges as a sustainable and cost-effective alternative to Portland cement-based UHPC, offering similar mechanical properties while significantly reducing carbon footprint and energy consumption. Research on UHPGC components is extremely scarce. This study focuses on the flexural and crack behavior of UHPGC beams with different steel fiber contents and longitudinal reinforcement ratios. Five UHPGC beams were tested under four-point bending. The test results were evaluated in terms of the failure mode, load–deflection relationship, flexural capacity, ductility, average crack spacing, and short-term flexural stiffness. The results show that all the UHPGC beams failed due to crack localization. Increases in the reinforcement ratio and steel fiber content had favorable effects on the flexural capacity and flexural stiffness. When the reinforcement ratio increased from 1.18% to 2.32%, the flexural capacity and flexural stiffness increased by 60.5% and 12.3%, respectively. As the steel fiber content increased from 1.5% to 2.5%, the flexural capacity and flexural stiffness increased by 4.7% and 4.4%, respectively. Furthermore, the flexural capacity, flexural stiffness, and crack spacing of the UHPGC beams were evaluated using existing methods. The results indicate that the existing methods can effectively predict flexural capacity and flexural stiffness in UHPGC beams but overestimate crack spacing. This study will provide a reference for the structural design of UHPGC. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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16 pages, 4543 KiB

Open AccessArticle

Assessment of CO₂ Capture in FA/GGBS-Blended Cement Systems: From Cement Paste to Commercial Products

by Jingxian Liu, Yingyu Wu, Fulin Qu, Hanbing Zhao and Yilin Su

Buildings 2024, 14(1), 154; https://doi.org/10.3390/buildings14010154 - 8 Jan 2024

Cited by 2 | Viewed by 1879

Abstract

The cement industry’s intricate production process, including kiln heating and fossil fuel use, contributes 5–8% of global CO₂ emissions, marking it as a significant carbon emitter in construction. This study focuses on quantifying CO₂ capture potential in blended cement systems through [...] Read more.

The cement industry’s intricate production process, including kiln heating and fossil fuel use, contributes 5–8% of global CO₂ emissions, marking it as a significant carbon emitter in construction. This study focuses on quantifying CO₂ capture potential in blended cement systems through the utilisation of phenolphthalein and thermalgravimetric methodologies. Its primary objective is to assess the CO₂ absorption capacity of these blended systems’ pastes. Initial evaluation involves calculating the carbon capture capacity within the paste, subsequently extended to estimate CO₂ content in the resultant concrete products. The findings indicate that incorporating ground granulated blast-furnace slag (GGBS) or an ettringite-based expansive agent did not notably elevate carbonation depth, irrespective of their fineness. Conversely, the introduction of fly ash (FA) notably augmented the carbonation depth, leading to a substantial 36.4% rise in captured CO₂ content. The observed distinctions in carbonation behaviour primarily stem from variances in pore structure, attributable to distinct hydration characteristics between GGBS and FA. Thermal analysis confirms the increased stabilisation of CO₂ in FA blends, highlighting the crucial influence of material composition on carbonation and emission reduction. Incorporating both GGBS and FA notably diminishes binder emissions, constituting almost half of PC-concrete emissions. Initially, 60% GGBS shows lower emissions than 50% FA, but when considering CO₂ capture, this emission dynamic significantly changes, emphasising the intricate influence of additives on emission patterns. This underscores the complexity of evaluating carbonation-induced emissions in cementitious systems. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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15 pages, 5512 KiB

Open AccessArticle

Mechanical Behavior of Compression-Compacted Dry Concrete Paver Blocks Making Use of Sea Sand and Seawater

by Pengcheng Guo, Qicheng Wang, Jia Liu, Tengfei Wang, Junliang Zhao and Dongyan Wu

Buildings 2023, 13(12), 2979; https://doi.org/10.3390/buildings13122979 - 29 Nov 2023

Cited by 1 | Viewed by 1286

Abstract

Dry concrete is a kind of concrete whose fresh mixture has almost no flowability and is widely used in the production of small-size unreinforced compression-compacted concrete blocks in plants. Considering the shortage of natural river sand and freshwater for concrete production, this study [...] Read more.

Dry concrete is a kind of concrete whose fresh mixture has almost no flowability and is widely used in the production of small-size unreinforced compression-compacted concrete blocks in plants. Considering the shortage of natural river sand and freshwater for concrete production, this study proposes that sea sand and seawater can be directly used in the manufacture of compression-compacted dry concrete paver blocks. The idea was verified in the laboratory to find suitable mix proportions and forming pressure, which are two key parameters for the production of paver blocks. Furthermore, the effect of sea sand replacement ratio and seawater replacement ratio is investigated, where compression and flexural tensile tests were conducted on lab-made paver blocks at different ages. The experimental results reveal that both the compressive and flexural tensile strengths of paver blocks increased when sea sand and seawater were adopted. It is finally suggested that sea sand and seawater are suitable for the production of unreinforced paver blocks with enhanced mechanical performance. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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13 pages, 2203 KiB

Open AccessArticle

Study on Resourceful Treatment and Carbon Reduction Intensity of Metro Shield Slag: An Example of a Tunnel Interval of Shenzhen Line 13

by Gang Chen, Wei Li, Fangsheng Yang, Taibo Cao, Zezhou Wu, Yun Lu and Chenwei Wu

Buildings 2023, 13(11), 2816; https://doi.org/10.3390/buildings13112816 - 10 Nov 2023

Cited by 3 | Viewed by 1195

Abstract

At present, the scale of subway construction in Chinese cities has reached a new height, and the shield slag produced by it has also surged year by year. Untreated subway shield slag not only occupies the space resources of the country, but also [...] Read more.

At present, the scale of subway construction in Chinese cities has reached a new height, and the shield slag produced by it has also surged year by year. Untreated subway shield slag not only occupies the space resources of the country, but also carries CO₂, which causes negative impacts on the environment and which, as a result, is not conducive to the realization of the goal of the national “double-carbon” strategy. Therefore, how to effectively manage the shield slag produced by subway construction has become a scientific problem that needs to be solved urgently. In order to scientifically dispose of metro shield slag and quantify the carbon reduction intensity of its disposal, based on the new shield slag integrated recycling technology, and taking a tunnel interval of Shenzhen Line 13 as an example, this study systematically sorted out the shield slag disposal process, clarified the management path of the on-site resource utilization of slag, and quantitatively compared the carbon emissions before and after the treatment as well as carbon reduction intensity. The results show that the on-site disposal process is basically feasible, and that, it is possible to achieve a shield structure slag reduction of resource products and mud cake water content of less than 40% of the target, in the case of 160,000 m³ of shield structure slag resource utilization after a total carbon reduction of about 4240.13 t CO₂, of which each preparation of 1 m³ of recycled bricks can bring about a benefit of carbon reduction of 240.09 kg CO₂. Compared with the conventional mud head truck slag disposal, shield structure slag resource utilization can save a utilization cost of about 10.4 million yuan, meaning that, in terms of economic and social levels, this method can achieve good benefits. This case verifies the feasibility of the new technology, and the results of the study can provide experience for other metro projects’ shield slag resource utilization, and provide stakeholders with a shield slag recycling management strategy for government departments to scientifically formulate metro shield slag management policy to provide data support. Full article

(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)

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