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Influence of recycled polyethylene terephthalate fibres on plastic shrinkage and mechanical properties

Necat ÖZAŞIK; Özgür EREN

《结构与土木工程前沿（英文）》 2022年 第16卷 第6期   页码 792-802 doi: 10.1007/s11709-022-0849-6

摘要： Polyethylene terephthalate bottles production has drastically increased year after year due to high versatility of polyethylene terephthalate plastics and considerable consumption of beverages. In tandem with that increase, the major concern of society has been the improper disposal of this non-biodegradable material to the environment. To deal with this concern, recycled polyethylene terephthalate bottles were incorporated in concrete as fibre reinforcements in this study. The objective of this research is to evaluate the mechanical properties of recycled polyethylene terephthalate fibre reinforced concrete (RPFRC) in comparison with control concrete without fibres. polyethylene terephthalate fibres with three different diameters (0.45, 0.65, and 1.0 mm) and two lengths (20 and 30 mm) were added at various proportions (0.5%, 1.0%, 1.5% and 2.0%) by volume of concrete in order to determine the effect of fibres initially on compressive, flexural and splitting tensile strengths of concrete. The results revealed that none of the fibres have detrimental effects up to 1% volume fraction, however further addition caused slight reductions on mechanical properties in some conditions. Plastic shrinkage resistance and impact resistance tests were also performed according to related standards. Polyethylene terephthalate fibres were observed to have marked improvements on those properties. Such a good performance could be attributed primarily to the bridging effect of fibres.

关键词： recycled PET     fibre-reinforced concrete     mechanical properties     plastic shrinkage     impact energy    

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Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

《结构与土木工程前沿（英文）》 2022年 第16卷 第11期   页码 1453-1473 doi: 10.1007/s11709-022-0877-2

摘要： Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.

关键词： manufactured sand     fresh concrete     microfines     admixtures     shrinkage     cracking    

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Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent

Beibei SUN, Hao WU, Weimin SONG, Zhe LI, Jia YU

《结构与土木工程前沿（英文）》 2020年 第14卷 第5期   页码 1274-1284 doi: 10.1007/s11709-020-0656-x

摘要： Superabsorbent Polymer (SAP) has emerged as a topic of considerable interest in recent years. The present study systematically and quantitively investigated the effect of SAP on hydration, autogenous shrinkage, mechanical properties, and microstructure of cement mortars. Influences of SAP on hydration heat and autogenous shrinkage were studied by utilizing TAM AIR technology and a non-contact autogenous shrinkage test method. Scanning Electron Microscope (SEM) was employed to assess the microstructure evolution. Although SAP decreased the peak rate of hydration heat and retarded the hydration, it significantly increased the cumulative heat, indicating SAP helps promote the hydration. Hydration promotion caused by SAP mainly occurred in the deceleration period and attenuation period. SAP can significantly mitigate the autogenous shrinkage when the content ranged from 0 to 0.5%. Microstructure characteristics showed that pores and gaps were introduced when SAP was added. The microstructure difference caused by SAP contributed to the inferior mechanical behaviors of cement mortars treated by SAP.

关键词： Superabsorbent Polymer     mechanical properties     hydration heat     autogenous shrinkage     microstructure    

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Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

K. S. SIVAKUMARAN,R. M. KOROL,Xiao FAN

《结构与土木工程前沿（英文）》 2014年 第8卷 第3期   页码 282-291 doi: 10.1007/s11709-014-0269-3

摘要： This paper experimentally investigates the energy absorption potential of two types of concrete floors, namely, normal density concrete and structural low-density concrete, containing secondary (shrinkage and temperature) reinforcements. The test program considered the following secondary reinforcements: 1) traditional welded-wire steel mesh, 2) steel fiber and 3) poly composite fiber. To estimate the extent to which crushing of floor slab materials would help absorb energy, a series of concrete penetration tests employing patch loading was undertaken on scaled down model slabs. Each concrete-secondary reinforcement combination considered slabs of 50 mm in depth with square plan dimensions ranging from 50 to 500 mm, resulting in a total of 30 test specimens. The first part of the paper discusses the test specimens, the test setup, and the test procedure. The second part of the paper presents the experimental results and establishes the energy absorption of different concrete- secondary reinforcement combinations. Sieve analysis results of the crushed specimens were used to derive a “work index” value that relates the pulverized particle size distributions to energy inputs. The work index values of concrete-secondary reinforcement systems can be used to assess the energy dissipation potential associated with such floor slabs in buildings undergoing progressive collapse. The results indicate that floors with secondary reinforcements could play an important role in helping arrest global progressive collapse.

关键词： concrete floors     structural low-density concrete     shrinkage and temperature reinforcements     energy absorption     penetration tests     sieve analysis    

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Effect of concrete creep and shrinkage on tall hybrid-structures and its countermeasures

Pusheng SHEN, Hui FANG, Xinhong XIA

《结构与土木工程前沿（英文）》 2009年 第3卷 第2期   页码 234-239 doi: 10.1007/s11709-009-0020-7

摘要： This paper aims to study the different vertical displacements in tall hybrid-structures and the corresponding engineering measures. First, the method to calculate the different vertical displacements in tall hybrid-structures is presented. This method takes into account the effects of construction process by applying loads sequentially story by story. Based on the concrete creep and shrinkage calculation formula in American Concrete Institute (ACI) code, with the assumption that loads are increased linearly in members, the creep and shrinkage effects of members are analyzed by adopting two parameters named average load-aged coefficient and average age-last coefficient. The effects of steel ratio on members creep are analyzed by age-adjusted module method (AEMM). The effects that core-tube were constructed in advance to outer steel frame were also considered. Then, based on the sample calculation, the measures to effectively reduce the different vertical displacements in hybrid-structures are proposed. This method is simple and practical in the calculation of different vertical displacements in tall and super-tall hybrid-structures.

关键词： creep     shrinkage     construction process     hybrid-structure    

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A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 36-45 doi: 10.1007/s11709-014-0243-0

摘要： This study presents the results of an experimental investigation that compares the mechanical properties, fracture behavior, creep, and shrinkage of a chemically-based self-consolidating concrete (SCC) mix with that of a corresponding conventional concrete (CC) mix. The CC and SCC mix designs followed conventional proportioning in terms of aggregate type and content, cement content, air content, water-cementitiuos materials ( / ) ratio, and workability. Then, using only chemical admixtures, the authors converted the CC mix to an SCC mix with all of the necessary passing, filling, flowability, and stability requirements typically found in SCC. The high fluidity was achieved with a polycarboxylate-based high-range water-reducing admixture, while the enhanced stability was accomplished with an organic, polymer-based viscosity-modifying admixture. The comparison indicated that the SCC and CC mixes had virtually identical tensile splitting strengths, flexural strengths, creep, and shrinkage. However, the SCC mix showed higher compressive strengths and fracture energies than the corresponding CC mix.

关键词： admixture     conventional concrete (CC)     creep     fracture mechanic     mechanical Properties     self-consolidating concrete (SCC)     shrinkage    

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Moving policy and regulation forward for single-use plastic alternatives

《环境科学与工程前沿（英文）》 2021年 第15卷 第3期 doi: 10.1007/s11783-021-1423-5

摘要： Single-use plastics are often used once or cannot be reused for extended periods. They are widely consumed with the rapid development of social economy. The waste generated by single-use plastics threatens ecosystem health by entering the environment and ultimately restricts sustainable human development. The innovation of sustainable and environmentally friendly single-use plastic alternative materials and the joint participation of governments, enterprises and the public are promising technologies and management approaches that can solve the problem of single-use plastics wastes. The development of single-use plastic alternative products can be promoted fundamentally only by improving relevant legislation and standards, providing differentiated industrial policies, encouraging scientific and technological innovation and expanding public participation.

关键词： Single-use plastic alternatives     Policy     Regulation     Sustainable development    

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Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste

Feneuil BLANDINE, Karin HABERMEHI-CWIRZEN, Andrzej CWIRZEN

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 255-255 doi: 10.1007/s11709-017-0395-9

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现代混凝土收缩开裂的评估方法与控制关键技术 Article

刘加平, 田倩, 王育江, 李华, 徐文

《工程（英文）》 2021年 第7卷 第3期   页码 348-357 doi: 10.1016/j.eng.2021.01.006

摘要：

现代混凝土组成日趋复杂、收缩加大、结构约束增强，导致收缩开裂问题突出，严重影响构筑物的服役性能和使用寿命。本文以胶凝材料体系水化程度作为材料与环境温湿度交互作用的基本状态变量，提出了复杂胶凝材料体系水化反应活化能的计算方法，建立了水化-温度-湿度-约束耦合作用模型，实现了多种收缩的耦合计算和开裂风险的量化评估；介绍了水化温升抑制、全过程补偿收缩和化学减缩三项关键技术的作用机理及效果，这些技术能够有针对性地降低混凝土的温降收缩、自收缩和干燥收缩；在此基础上，提出了高抗裂混凝土的设计方法，采用该方法后，全过程控制开裂风险系数小于阈值；最后介绍了典型的工程应用案例，结果表明，采用所提出的方法和技术能够显著抑制甚至避免实际工程中收缩裂缝的产生。

关键词： 现代混凝土     收缩     水化程度     抑制技术     开裂风险    

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Current scenario and challenges of plastic pollution in Bangladesh: a focus on farmlands and terrestrial

《环境科学与工程前沿（英文）》 2023年 第17卷 第6期 doi: 10.1007/s11783-023-1666-4

摘要：

● A global snapshot of plastic waste generation and disposal is analysed.

关键词： Plastic waste     Farmlands     Terrestrial ecosystem     Marine life    

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广义塑性力学及其运用

郑颖人,孔亮

《中国工程科学》 2005年 第7卷 第11期   页码 21-36

摘要：

分析了经典塑性力学用于岩土类材料的问题，它采用了3个不符合岩土材料变形机制的假设。从固体力学原理直接导出广义塑性位势理论，将经典塑性力学改造为更一般的塑性力学——广义塑性力学。广义塑性力学采用了塑性力学中的分量理论，能反映应力路径转折的影响，并避免了采用正交流动法则所引起的过大剪胀等不合理现象，也不会产生当前非关联流动法则中任意假定塑性势面引起的误差。给出了广义塑性力学的屈服面理论、硬化定律和应力-应变关系，并建立了考虑应力主轴旋转的广义塑性位势理论。屈服条件是状态参数，也是试验参数，只能由试验给出。应用表明，广义塑性力学可作为岩土材料的建模理论，还可应用于诸如极限分析等土力学的诸多领域，具有广阔的应用前景。

关键词： 岩土塑性力学     广义塑性力学     塑性势     屈服面     本构模型    

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Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 86-98 doi: 10.1007/s11709-021-0793-x

摘要： One of the strategic materials used in earth-fill embankment dams and in modifying and preventing groundwater flow is plastic concrete (PlC). PlC is comprised of aggregates, water, cement, and bentonite. Natural zeolite (NZ) is a relatively abundant mineral resource and in this research, the microstructure, unconfined strength, triaxial behavior, and permeability of PlC made with 0%, 10%, 15%, 20%, and 25% replacement of cement by NZ were studied. Specimens of PIC-NZ were subjected to confined conditions and three different confining pressures of 200, 350, and 500 kPa were used to investigate their mechanical behavior and permeability. To study the effect of sulfate ions on the properties of PlC-NZ specimens, the specimens were cured in one of two different environments: normal condition and in the presence of sulfate ions. Results showed that increasing the zeolite content decreases the unconfined strength, elastic modulus, and peak strength of PlC-NZ specimens at the early ages of curing. However, at the later ages, increasing the zeolite content increases unconfined strength as well as the peak strength and elastic modulus. Specimens cured in the presence of sulfate ions indicated lower permeability, higher unconfined strength, elastic modulus, and peak strength due to having lower porosity.

关键词： plastic concrete     sulfate resistance     natural zeolite     triaxial compression test     SEM     permeability    

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Preventing masks from becoming the next plastic problem

《环境科学与工程前沿（英文）》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1413-7

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The road to sustainable use and waste management of plastics in Portugal

《环境科学与工程前沿（英文）》 2022年 第16卷 第1期   页码 5-5 doi: 10.1007/s11783-021-1439-x

摘要：

• Portugal recycles 34% of the 40 kg/hab year of plastic packaging waste.

关键词： Single-use plastics     Plastic packaging     Plastic waste     Waste management     Waste shipment     Lightweight plastic bags    

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Effect of RC wall on the development of plastic rotation in the beams of RC frame structures

Amar KAHIL, Aghiles NEKMOUCHE, Said BOUKAIS, Mohand HAMIZI, Naceur Eddine HANNACHI

《结构与土木工程前沿（英文）》 2018年 第12卷 第3期   页码 318-330 doi: 10.1007/s11709-017-0420-z

摘要：

The objective of this study is, to interpret the influence of reinforced concrete walls addition in reinforced concrete frame structures considering behavior laws that reflects the actual behavior of such structures, by means of Castem2000computer code (pushover analysis). A finite element model is proposed in this study, using the TAKEDA modified behavior model with Timoshenko beams elements. This model is validated initially on experimental model. Then the work has focused on the behavior of a RC frame with 3 levels and three bays to better visualize the behavior of plastic hinges. Once the plastic hinge control parameters are identified (plastic rotation, ultimate curvature), a strengthening by introduction of reinforced concrete walls (RC/wall) at the ends of the reinforced concrete frame (RC/frame) has been performed. The results show that these RC walls significantly improve the behavior, by a relocation of efforts towards the central part of the beams.

关键词： RC/frame     RC/wall     moment curvature     plastic rotation     plastic hinge     pushover analysis     global models    

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标题 作者 时间 类型 操作

Influence of recycled polyethylene terephthalate fibres on plastic shrinkage and mechanical properties

Necat ÖZAŞIK; Özgür EREN

期刊论文

Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

Branavan ARULMOLY; Chaminda KONTHESINGHA; Anura NANAYAKKARA

期刊论文

Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent

Beibei SUN, Hao WU, Weimin SONG, Zhe LI, Jia YU

期刊论文

Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

K. S. SIVAKUMARAN,R. M. KOROL,Xiao FAN

期刊论文

Effect of concrete creep and shrinkage on tall hybrid-structures and its countermeasures

Pusheng SHEN, Hui FANG, Xinhong XIA

期刊论文

A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

期刊论文

Moving policy and regulation forward for single-use plastic alternatives

期刊论文

Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste

Feneuil BLANDINE, Karin HABERMEHI-CWIRZEN, Andrzej CWIRZEN

期刊论文

现代混凝土收缩开裂的评估方法与控制关键技术

刘加平, 田倩, 王育江, 李华, 徐文

期刊论文

Current scenario and challenges of plastic pollution in Bangladesh: a focus on farmlands and terrestrial

期刊论文

广义塑性力学及其运用

郑颖人,孔亮

期刊论文

Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

期刊论文

Preventing masks from becoming the next plastic problem

期刊论文

The road to sustainable use and waste management of plastics in Portugal

期刊论文

Effect of RC wall on the development of plastic rotation in the beams of RC frame structures

Amar KAHIL, Aghiles NEKMOUCHE, Said BOUKAIS, Mohand HAMIZI, Naceur Eddine HANNACHI

期刊论文