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Effects of coarse and fine aggregates on long-term mechanical properties of sea sand recycled aggregate

《结构与土木工程前沿(英文)》 2021年 第15卷 第3期   页码 754-772 doi: 10.1007/s11709-021-0711-2

摘要: Typical effects of coarse and fine aggregates on the long-term properties of sea sand recycled aggregate concrete (SSRAC) are analyzed by a series of axial compression tests. Two different types of fine (coarse) aggregates are considered: sea sand and river sand (natural and recycled coarse aggregates). Variations in SSRAC properties at different ages are investigated. A novel test system is developed via axial compression experiments and the digital image correlation method to obtain the deformation field and crack development of concrete. Supportive results show that the compressive strength of SSRAC increase with decreasing recycled coarse aggregate replacement percentage and increasing sea sand chloride ion content. The elastic modulus of SSRAC increases with age. However, the Poisson’s ratio reduces after 2 years. Typical axial stress–strain curves of SSRAC vary with age. Generally, the effect of coarse aggregates on the axial deformation of SSRAC is clear; however, the deformation differences between coarse aggregate and cement mortar reduce by adopting sea sand. The aggregate type changes the crack characteristics and propagation of SSRAC. Finally, an analytical expression is suggested to construct the long-term stress–strain curve of SSRAC.

关键词: sea sand recycled aggregate concrete     recycled coarse aggregate replacement percentage     sea sand chloride ion content     long-term mechanical properties     stress–strain curve    

Punching shear behavior of recycled aggregate concrete slabs with and without steel fibres

Jianzhuang XIAO, Wan WANG, Zhengjiu ZHOU, Mathews M. TAWANA

《结构与土木工程前沿(英文)》 2019年 第13卷 第3期   页码 725-740 doi: 10.1007/s11709-018-0510-6

摘要: A study on the punching shear behavior of 8 slabs with recycled aggregate concrete (RAC) was carried out. The two main factors considered were the recycled coarse aggregate (RCA) replacement percentage and the steel fibre volumetric ratio. The failure pattern, load-displacement curves, energy consumption and the punching shear capacity of the slabs were intensively investigated. It was concluded that the punching shear capacity, ductility and energy consumption decreased with the increase of RCA replacement percentage. Research findings indicated that the incorporation of steel fibres could not only improve the energy dissipation capacity and the punching shear capacity of the slab, but also effectively improve the integrity of the slab tension surface and thereby changing the trend from typical punching failure pattern to bending-punching failure pattern. On the basis of the test, the punching shear capacity formula of RAC slabs with and without steel fibres was proposed and discussed.

关键词: recycled aggregate concrete     steel fibres     slab     punching shear     recycled coarse aggregates replacement percentage    

Chloride diffusion in concrete with carbonated recycled coarse aggregates under biaxial compression

《结构与土木工程前沿(英文)》 2023年 第17卷 第4期   页码 637-648 doi: 10.1007/s11709-023-0902-0

摘要: Chloride attack on concrete structures is affected by the complex stress state inside concrete, and the effect of recycled aggregates renders this process more complex. Enhancing the chloride resistance of recycled concrete in a complex environment via carbonization facilitates the popularization and application of recycled concrete and alleviates the greenhouse effect. In this study, the chloride ion diffusion and deformation properties of recycled concrete after carbonization are investigated using a chloride salt load-coupling device. The results obtained demonstrate that the chloride ion diffusivity of recycled concrete first decreases and then increases as the compressive load increases, which is consistent with the behavior of concrete, in that it first undergoes compressive deformation, followed by crack propagation. Carbonation enhances the performance of the recycled aggregates and reduces their porosity, thereby reducing the chloride diffusion coefficient of the recycled concrete under different compressive load combinations. The variation in the chloride ion diffusivity of the carbonized recycled aggregate concrete with the load is consistent with a theoretical formula.

关键词: recycled concrete     carbonated recycled coarse aggregate     biaxial compression     chloride diffusion     stress level    

Long term performance of recycled concrete beams with different water–cement ratio and recycled aggregatereplacement rate

Jingwei YING; Feiming SU; Shuangren CHEN

《结构与土木工程前沿(英文)》 2022年 第16卷 第3期   页码 302-315 doi: 10.1007/s11709-022-0803-7

摘要: The purpose of this study is to reveal the service performance of recycled aggregate concrete (RAC) components for different values of water−cement ratio and replacement rate of recycled coarse aggregate (RCA). Generally, the concrete strength decreases with the increase of the replacement rate of RCA, in order to meet the strength requirements when changing the replacement rate of RCA, it is necessary to change the water−cement ratio at the same time. Therefore, the axial compressive strengths of prism with 25 mix proportions, the short-term mechanical properties and long-term deformation properties of reinforced concrete beams were tested respectively by changing water−cement ratio and RCA replacement rate. The bearing capacity and the strain nephogram of samples under different loads were obtained using the Digital Image Correlation (DIC) method, and a self-made gravity loading experimental device was used for long-term deformation investigation. Results showed that the damage pattern of RAC was the same as that of natural aggregate concrete (NAC), but the brittleness was more pronounced. The brittleness of concrete before failure can be reduced more effectively by adjusting the replacement rate of RCA than by adjusting the water−cement ratio. The water−cement ratio has an evident influence on the axial compressive strength and early creep of concrete, while the replacement rate of RCA has a remarkable effect on the long-term deformation of the concrete beams.

关键词: recycled concrete     beam     the replacement rate of recycled coarse aggregate     water–cement ratio     digital image correlation    

Stress-strain relationship of recycled self-compacting concrete filled steel tubular column subjected

Feng YU, Cheng QIN, Shilong WANG, Junjie JIANG, Yuan FANG

《结构与土木工程前沿(英文)》 2020年 第14卷 第3期   页码 760-772 doi: 10.1007/s11709-020-0618-3

摘要: As a typical compression member, the concrete-filled steel tube has been widely used in civil engineering structures. However, little research on recycled self-compacting concrete filled circular steel tubular (RSCCFCST) columns subjected to eccentric load was reported. In this study, 21 specimens were designed and experimental studies on the stress-strain relationship of were carried out to study the mechanical behaviors. Recycled coarse aggregate replacement ratio, concrete strength grade, length to diameter ratio and eccentric distance of specimens were considered as the main experimental parameters to carry out eccentric compression tests. The corresponding stress-strain relationship curves were used to analyze the influence of concerned parameters on eccentric load-bearing capacity of RSCCFCST columns. The experimental results show that the strain of the eccentric compression stress-strain curves increase with the increase of recycled coarse aggregate replacement ratio and concrete strength grade. With increase of eccentric distance, the ductility of specimens increases while the bearing capacity decreases. Moreover, a phenomenological model of RSCCFCST columns is proposed, which exhibits versatile ability to capture the process during loading. The present study is expected to further understanding the behaviors and to provide guidance of RSCCFCST columns in design and engineering applications.

关键词: concrete filled circular steel tubular columns     recycled self-compacting concrete     eccentric compression     recycled coarse aggregate replacement ratio     stress-strain relationship    

电中性固体表面上多条肽链的吸附过程——粗粒化模拟研究 Research

裘若桑, 肖杰, 陈晓东

《工程(英文)》 2020年 第6卷 第2期   页码 185-194 doi: 10.1016/j.eng.2018.12.012

摘要:

蛋白质在固体表面的吸附过程涉及诸多复杂的分子间相互作用,因此到目前为止仍然无法做到精准调控。通过模拟计算,可以获取固-液界面分子尺度的蛋白质移动机理,从而为预测蛋白质吸附和结垢现象提供可靠的理论依据。本研究通过多尺度粗粒化模型对多条疏水的丙氨酸十二肽在金表面的聚集和吸附过程进行了分析。大约有一半(46.6%)的丙氨酸十二肽可以组成聚集体。30.0%的独立肽链会被快速地吸附到固体表面。这些在表面吸附的肽链经过一段时间的爬行,其中的一些(51.0%)能与吸附在表面的或是游离在溶液中的肽链融合,从而形成吸附在表面的聚集体。这些在固-液界面吸附的肽链使得固体表面性质发生变化。这一变化可能会进一步影响之后溶液中肽链和聚集体在金表面的吸附。本研究揭示的多条肽链吸附机理有希望为进一步研究多个蛋白质分子在固体表面的吸附机理提供理论基础。

关键词: 肽链     聚集体     吸附     粗粒化计算    

Recycled glass replacement as fine aggregate in self-compacting concrete

Yasser SHARIFI, Mahmoud HOUSHIAR, Behnam AGHEBATI

《结构与土木工程前沿(英文)》 2013年 第7卷 第4期   页码 419-428 doi: 10.1007/s11709-013-0224-8

摘要: With increasing environmental pressure to reduce solid waste and to recycle as much as possible, the concrete industry has adopted a number of methods to achieve this goal by replacement of waste glass with concrete composition materials. Due to differences in mixture design, placement and consolidation techniques, the strength and durability of Self Compacting Concrete (SCC) may be different than those of conventional concrete. Therefore, replacement of waste glass with fine aggregate in SCC should deeply be investigated compared to conventional concretes. The aim of the present study is to investigate the effect of glass replacement with fine aggregate on the SCC properties. In present study, fine aggregate has been replaced with waste glass in six different weight ratios ranging from 0% to 50%. Fresh results indicate that the flow-ability characteristics have been increased as the waste glass incorporated to paste volume. Nevertheless, compressive, flexural and splitting strengths of concrete containing waste glass have been shown to decrease when the content of waste glass is increased. The strength reduction of concrete in different glass replacement ratios is not remarkable, thus it can be produced SCC with waste glass as fine aggregate in a standard manner.

关键词: Self Compacting Concrete (SCC)     recycle glass     fine aggregate     fresh and hardened properties    

hardened properties of high-strength concrete incorporating byproduct fine crushed aggregate as partial replacement

Dammika P. K. WELLALA, Ashish Kumer SAHA, Prabir Kumar SARKER, Vinod RAJAYOGAN

《结构与土木工程前沿(英文)》 2021年 第15卷 第1期   页码 124-135 doi: 10.1007/s11709-020-0673-9

摘要: This paper presents the fresh and hardened properties of high-strength concrete comprising byproduct fine crushed aggregates (FCAs) sourced from the crushing of three different types of rocks, namely granophyre, basalt, and granite. The lowest void contents of the combined fine aggregates were observed when 40% to 60% of natural sand is replaced by the FCAs. By the replacement of 40% FCAs, the slump and bleeding of concrete with a water-to-cement ratio of 0.45 decreased by approximately 15% and 50%, respectively, owing to the relatively high fines content of the FCAs. The 28 d compressive strength of concrete was 50 MPa when 40% FCAs were used. The slight decrease in tensile strength from the FCAs is attributed to the flakiness of the particles. The correlations between the splitting tensile and compressive strengths of normal concrete provided in the AS 3600 and ACI 318 design standards are applicable for concrete using the FCAs as partial replacement of sand. The maximum 56 d drying shrinkage is 520 microstrains, which is significantly less than the recommended limit of 1000 microstrains by AS 3600 for concrete. Therefore, the use of these byproduct FCAs can be considered as a sustainable alternative option for the production of high-strength green concrete.

关键词: fine crushed aggregates     quarry dust     compressive strength     splitting tensile strength     drying shrinkage    

Quantification of coarse aggregate shape in concrete

Xianglin GU,Yvonne TRAN,Li HONG

《结构与土木工程前沿(英文)》 2014年 第8卷 第3期   页码 308-321 doi: 10.1007/s11709-014-0266-6

摘要: The objective of this study is to choose indices for the characterization of aggregate form and angularity for large scale application. For this purpose, several parameters for aggregate form and angularity featured in previous research are presented. Then, based on these established parameters, 200 coarse quartzite aggregates are analyzed herein by using image processing technology. This paper also analyzes the statistical distributions of parameters for aggregate form and angularity as well as the correlation between form and angularity parameters. It was determined that the parameters for form or angularity of coarse aggregates could be fitted by either normal distribution or log-normal distribution at a 95% confidence level. Some of the form parameters were influenced by changes in angularity characteristics, while aspect ratio and angularity using outline slope, area ratio and radius angularity index, and aspect ratio and angularity index were independent of each other, respectively; and consequently, the independent parameters could be used to quantify the aggregate form and angularity for the purpose to study the influence of aggregate shape on the mechanical behavior of concrete. Furthermore, results from this study’s in-depth investigations showed that the aspect ratio and the angularity index can further understanding of the effects of coarse aggregates form and angularity on concrete mechanical properties, respectively. Finally, coarse aggregates with the same content, type and surfaces texture, but different aspect ratios and angularity indices were used to study the influence of coarse aggregate form and angularity on the behavior of concrete. It was revealed that the splitting tensile strength of concrete increased with increases in the aspect ratio or angularity index of coarse aggregates.

关键词: coarse aggregate     form     angularity     digital image analysis     statistical distribution     splitting tensile strength    

MICROBIAL NECROMASS WITHIN AGGREGATES STABILIZES PHYSICALLY-PROTECTED C RESPONSE TO CROPLAND MANAGEMENT

《农业科学与工程前沿(英文)》 2023年 第10卷 第2期   页码 198-209 doi: 10.15302/J-FASE-2023498

摘要:

● The contribution of fungal necromass C to SOC increased with aggregate sizes.

关键词: cropland management     microbial necromass     soil aggregates     soil carbon sequestration     soil organic matter    

Experimental research on seismic behavior of recycled concrete frame under varying cyclic loading

SUN Yuedong, XIAO Jianzhuang, ZHOU Deyuan

《结构与土木工程前沿(英文)》 2008年 第2卷 第4期   页码 302-308 doi: 10.1007/s11709-008-0050-6

摘要: A study is conducted on the seismic behavior of one natural concrete frame and two recycled concrete frames with 100% recycled coarse aggregate whose scales are 1:2 entirely, and a comparative study is conducted under low-reversed cyclic lateral loading and different vertical loading. This work aims to estimate the failure mechanism, hysteresis loops, displacement ductility, deterioration of strength and stiffness and energy dissipation of recycled concrete frames under low-reversed cyclic loading as well as the influence of different vertical loading. Analysis on the basis of the experiment proves that it is entirely feasible to apply recycled concrete to practical engineering for the sake of its good seismic behaviors. Theoretical base is provided for further study and practical application of recycled concrete structure.

关键词: different     aggregate     stiffness     practical application     % recycled    

Analysis of Sydney’s recycled water schemes

Zhuo CHEN, Huu Hao NGO, Wenshan GUO, Xiaochang WANG

《环境科学与工程前沿(英文)》 2013年 第7卷 第4期   页码 608-615 doi: 10.1007/s11783-012-0468-x

摘要: Recycled water provides a viable opportunity to partially supplement fresh water supplies as well as substantially alleviate environmental loads. Currently, thousands of recycled water schemes have been successfully conducted in a number of countries and Sydney is one of the leading cities, which has made massive effort to apply water reclamation, recycling and reuse. This study aims to make a comprehensive analysis of recycled water schemes in Sydney for a wide range of end uses such as landscape irrigation, industrial process uses and residential uses (e.g., golf course irrigation, industrial cooling water reuse, toilet flushing and clothes washing etc.). For each representative recycled water scheme, this study investigates the involved wastewater treatment technologies, the effluent quality compared with specified guideline values and public attitudes toward different end uses. Based on these obtained data, multi criteria analysis (MCA) in terms of risk, cost-benefit, environmental and social aspects can be performed. Consequently, from the analytical results, the good prospects of further expansion and exploration of current and new end uses were identified toward the integrated water planning and management. The analyses could also help decision makers in making a sound judgment for future recycled water projects.

关键词: recycled water schemes     end use     water quality     public attitudes     integrated water planning and management    

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columns

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

《结构与土木工程前沿(英文)》 2022年 第16卷 第7期   页码 817-842 doi: 10.1007/s11709-022-0844-y

摘要: To research the axial compression behavior of steel reinforced recycled concrete (SRRC) short columns confined by carbon fiber reinforced plastics (CFRP) strips, nine scaled specimens of SRRC short columns were fabricated and tested under axial compression loading. Subsequently, the failure process and failure modes were observed, and load-displacement curves as well as the strain of various materials were analyzed. The effects on the substitution percentage of recycled coarse aggregate (RCA), width of CFRP strips, spacing of CFRP strips and strength of recycled aggregate concrete (RAC) on the axial compression properties of columns were also analyzed in the experimental investigation. Furthermore, the finite element model of columns which can consider the adverse influence of RCA and the constraint effect of CFRP strips was founded by ABAQUS software and the nonlinear parameter analysis of columns was also implemented in this study. The results show that the first to reach the yield state was the profile steel in the columns, then the longitudinal rebars and stirrups yielded successively, and finally RAC was crushed as well as the CFRP strips was also broken. The replacement rate of RCA has little effect on the columns, and with the substitution rate of RCA from 0 to 100%, the bearing capacity of columns decreased by only 4.8%. Increasing the CFRP strips width or decreasing the CFRP strips spacing could enhance the axial bearing capacity of columns, the maximum increase was 10.5% or 11.4%, and the ductility of columns was significantly enhanced. Obviously, CFRP strips are conducive to enhance the axial bearing capacity and deformation capacity of columns. On this basis, considering the restraint effect of CFRP strips and the adverse effects of RCA, the revised formulas for calculating the axial bearing capacity of SRRC short columns confined by CFRP strips were proposed.

关键词: steel reinforced recycled concrete     CFRP strips     short columns     axial compression behavior     recycled aggregate concrete    

Industrial bio-based plant aggregates as hygric and insulating construction materials for energy efficient

Yunhong Jiang, Mike Lawrence, Meng Zhang, Jiandong Cui

《化学科学与工程前沿(英文)》 2022年 第16卷 第10期   页码 1532-1532 doi: 10.1007/s11705-020-1960-7

摘要: In this paper, the bulk density, microstructure, porosity and pore size distribution of the selected aggregates, including hemp shiv, flax shiv, rape shiv and wheat straw, are fully studied due to these properties are highly related to their excellent characteristics and more or less linked to the properties of the final product. The scanning electron microscope results showed all the selected aggregates have a highly porous and complex hierarchical structure, whereas the arrangement of pores and the thickness of cell wall are significantly different among these aggregates. All the selected aggregates had a low bulk density ranging from 30 to 130 kg∙m and a high porosity between 75.81% and 88.74%. The thermal conductivity of the selected bio-aggregates ranged from 0.04 to 0.06 W∙m ∙K . The thermal conductivity of the selected aggregates was not only depending on the bulk density of the sample but also depending on the raw material. Hemp shiv, rape shiv and flax shiv were excellent hygric regulators with moisture buffer value ( ) ranging from 2.07 to 2.36 g∙m ∙%RH , whereas, wheat straw had a lower MBV value ranging from 1.76 to 1.97 g∙m ∙%RH . The results showed that particle size does not affect the value. The value increases linearly with bulk density.

关键词: bio-based aggregates     density     porosity     thermal conductivity     hygric properties    

Effect of fly ash replacement level on the fracture behavior of concrete

Mahdi AREZOUMANDI, Jeffery S. VOLZ

《结构与土木工程前沿(英文)》 2013年 第7卷 第4期   页码 411-418 doi: 10.1007/s11709-013-0228-4

摘要: The production of portland cement–the key ingredient in concrete–generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed manmade material on the planet. One method of reducing concrete’s contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the cement. ?This study presents the results of an experimental investigation that evaluates effect of fly ash replacement level on the fracture energy of concrete. This study includes four mixes with 0%, 30%, 50%, and 70% fly ash as a cement replacement. This experimental program consisted of 32 fracture beams to study the fracture behavior of concrete. The experimental fracture energies were compared with the fracture energy provisions of different design codes and also different analytical equations. Furthermore, statistical data analyses (parametric and non-parametric) were performed to evaluate whether or not there is any statistically significant difference between the experimental fracture energies of different mixes. Results of these statistical tests show that the mix with higher level of fly ash replacement level has higher fracture energy.

关键词: concrete     fracture energy     fly ash    

标题 作者 时间 类型 操作

Effects of coarse and fine aggregates on long-term mechanical properties of sea sand recycled aggregate

期刊论文

Punching shear behavior of recycled aggregate concrete slabs with and without steel fibres

Jianzhuang XIAO, Wan WANG, Zhengjiu ZHOU, Mathews M. TAWANA

期刊论文

Chloride diffusion in concrete with carbonated recycled coarse aggregates under biaxial compression

期刊论文

Long term performance of recycled concrete beams with different water–cement ratio and recycled aggregatereplacement rate

Jingwei YING; Feiming SU; Shuangren CHEN

期刊论文

Stress-strain relationship of recycled self-compacting concrete filled steel tubular column subjected

Feng YU, Cheng QIN, Shilong WANG, Junjie JIANG, Yuan FANG

期刊论文

电中性固体表面上多条肽链的吸附过程——粗粒化模拟研究

裘若桑, 肖杰, 陈晓东

期刊论文

Recycled glass replacement as fine aggregate in self-compacting concrete

Yasser SHARIFI, Mahmoud HOUSHIAR, Behnam AGHEBATI

期刊论文

hardened properties of high-strength concrete incorporating byproduct fine crushed aggregate as partial replacement

Dammika P. K. WELLALA, Ashish Kumer SAHA, Prabir Kumar SARKER, Vinod RAJAYOGAN

期刊论文

Quantification of coarse aggregate shape in concrete

Xianglin GU,Yvonne TRAN,Li HONG

期刊论文

MICROBIAL NECROMASS WITHIN AGGREGATES STABILIZES PHYSICALLY-PROTECTED C RESPONSE TO CROPLAND MANAGEMENT

期刊论文

Experimental research on seismic behavior of recycled concrete frame under varying cyclic loading

SUN Yuedong, XIAO Jianzhuang, ZHOU Deyuan

期刊论文

Analysis of Sydney’s recycled water schemes

Zhuo CHEN, Huu Hao NGO, Wenshan GUO, Xiaochang WANG

期刊论文

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columns

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

期刊论文

Industrial bio-based plant aggregates as hygric and insulating construction materials for energy efficient

Yunhong Jiang, Mike Lawrence, Meng Zhang, Jiandong Cui

期刊论文

Effect of fly ash replacement level on the fracture behavior of concrete

Mahdi AREZOUMANDI, Jeffery S. VOLZ

期刊论文