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Long term performance of recycled concrete beams with different water-cement ratio and recycled aggregate replacement rate

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Frontiers of Structural and Civil Engineering 2022年第3期16卷 302-315页

作者： Jingwei YING Feiming SU Shuangren CHEN School of Civil Engineering and Architecture Guangxi UniversityNanning 530004China Key Laboratory of Engineering Disaster Prevention and Structural Safety of China Ministry of Education Guangxi Key Laboratory of Disaster Prevention and Engineering SafetySchool of Civil Engineering and ArchitectureGuangxi UniversityNanning530004China

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 ***,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 *** 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 *** showed that the damage pattern of RAC was the same as that of natural aggregate concrete(NAC),but the brittleness was more *** brittleness of concrete before failure can be reduced more effectively by adjusting the replacement rate of RCA than by adjusting the water-cement *** 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

Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

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Frontiers of Structural and Civil Engineering 2020年第2期14卷 554-568页

作者： Yasmin MURAD Wassel AL BODOUR Ahmed ASHTEYAT Civil Engineering Department The University of JordanAmman 11942.Jordan

An experimental and numerical program is carried out in this research to investigate the influence of CFRP sheets on the cyclic behavior of unconfined connections made with recycled *** is partially replaced by silica fume,iron flling and pulverised fuel ash using two different percentages:15%and 20%.Each specimen is partially loaded at the first stage and then specimens are repaired using CFRP *** repaired specimens are then laterally loaded until *** addition,a finite element model is built in ABAQUS and verfed using the experimental *** experimental results have shown that the repaired specimens have regained almost double the capacity of the un-repaired specimens and hence the adopted repair configuration is recommended for retroftting seismically vulnerable RC *** cement replacement percentage by silica fume,fuel ash or iron flling from 15%to 20%has reduced joint carrying capacity and weakened the *** is recommended using 15%pulverised fuel ash or silica fume as cement partial replacement to enhance the strength and ultimate drift of beam-column joints under cyclic *** filling concrete is also recommended but the enhancement is relatively less than that found with pulverised fuel ash concrete and silica fume concrete.

关键词： retrofitting CFRP sheets recycled concrete pulverised fuel ash silica fume cyclic beam-column connections

Study on Carbonation Damage Constitutive Curve and Microscopic Damage Mechanism of Tailing recycled concrete

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Journal of Renewable Materials 2021年第8期9卷 1413-1432页

作者： Tao Li Sheliang Wang Fan Xu Binbin Li Bin Dang Meng Zhan Zhiqi Wang College of Urban Rural Planning and Architectural EngineeringShangluo UniversityShangluo726000China School of Civil Engineering Xi’an University of Architecture and TechnologyXi’an710055China Key Laboratory of Structure Engineering and Earthquake Resistance Ministry of Education(XAUAT)Xi’an University of Architecture and TechnologyXi’an710055China College of Architecture Engineering Huanghuai UniversityZhumadian463000China China Construction Third Engineering Bureau Green Industry Investment Co. Ltd.Wuhan430070China

To improve the resource utilization of recycled aggregate concrete(RAC)and make use of the unique pozzolanic activation characteristics of iron ore tailing(IOT),the constitutive curves of tailing recycled concrete(TRC)before and after carbonization were analyzed theoretically,experimentally and ***,according to the experimental data,the damage constitutive and related damage parameters of TRC were theoretically established by Weibull probability distribution ***,the comprehensive damage parameter b under different working conditions was ***,the damage mechanism was formed by EDS and *** results showed that the damage constitutive model based on Weibull probability distribution function was in good agreement with the experimental *** each carbonization period,the b first decreased and then rose with the increase of tailings *** its content was 30%,the b values of TRC were minimized,which were 22.14%,20.99%,25.39%lower than those of NAC,and 41.09%,34.89%,35.44%lower than those of RAC,indicating that IOT had a relatively good optimization effect on the constitutive curve of *** microscopic analysis results also proved that the IOT addition with a proper amount would improve the matrix structure of RAC and increased its compactness,but when the content was higher,it would also cause harmful cracks in its matrix structure and reduced its ***,the optimal tailing content was about 30%.This paper provided a new method for damage constitutive calculation and analysis of TRC before and after carbonization.

关键词： Tailings recycled concrete carbonation damage constitution damage mechanism

Analysis of a landfill cover without geomembrane using varied particle sizes of recycled concrete

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第5期15卷 1263-1273页

作者： Charles Wang Wai Ng Cheuk Lam Ng Junjun Ni Haowen Guo Qi Zhang Qiang Xue Rui Chen Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyHong KongChina School of Transportation Southeast UniversityNanjingChina State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Department of Civil and Environmental Engineering Shenzhen Graduate SchoolHarbin Institute of TechnologyShenzhenChina

Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates(RCAs)without geomembrane in both laboratory and ***,no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs(FRC)and coarse-grained RCAs(CRC)that can be used for the three-layer landfill cover *** aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of *** numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm,its saturated permeability increases by 10 *** a result,a larger amount of rainwater infiltrates into the cover system,causing a higher lateral diversion in both the top FRC and middle CRC *** further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 *** the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall *** implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of *** it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible,this study provides an upper limit to the particle size that can be used in the bottom layer(D10 not larger than 0.02 mm).With this limit,the three-layer system can still minimize the water percolation to meet the design criterion(30 mm/yr)even under a 100-year return period of rainfall in humid climates.

关键词： Capillary barrier Landfill cover Particle size recycled concrete

Research Progress on the Influence of Varying Fiber Contents on Mechanical Properties of recycled concrete

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Structural Durability & Health Monitoring 2023年第3期17卷 239-255页

作者： Zhenqing Shi Guomin Sun Jianyong Pang College of Civil and Architecture Engineering Chuzhou UniversityChuzhouChina Engineering Research Center of Underground Mine Construction Ministry of Education(Anhui University of Science and Technology)HuainanChina

Applying recycled concrete for engineered projects not only protects the ecological environment but also improves the utilization rate of waste concrete to satisfy sustainable development ***,the mechanical properties of recycled concrete are not as good as those of ordinary *** enhance the former’s performance and increase its popularity and application in engineeringﬁelds,notable advances have been made by using steel,synthetic,plant,and mineralﬁber *** materials are added to recycled concrete to improve its mechanical *** have shown that(1)steelﬁbers have a distinct reinforcing effect and improve the strength,toughness,and elastic modulus of recycled concrete;(2)the addition of syntheticﬁbers can improve the tension,crack resistance,and durability of concrete,but the size effect needs to be further explored and elaborated;(3)plantﬁber concrete is lightweight and environmentally friendly and provides high toughness and good thermal insulation,but theﬁbers corrode in alkaline environments;in addition,plantﬁbers have high water absorption capacity,which leads to wet expansion and dry shrinkage phenomena,which need to be further studied;and(4)the cost of basaltﬁber,a mineralﬁber,is relatively low,and a suitable basalt content can improve the mechanical properties of recycled concrete to a certain extent.

关键词： recycled concrete fibers mechanical properties overview

Analysis of Sulfate Corrosion Resistance and Reliability of recycled concrete

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Wuhan University Journal of Natural Sciences 2020年第3期25卷 208-216页

作者： QIAO Hongxia ZHU Xiangchen CHEN Kefan PENG Kuan College of Civil Engineering Lanzhou University of TechnologyLanzhou 730000GansuChina

In order to study the effect of different recycled fine aggregate and recycled coarse aggregate substitution rate on the sulfate resistance of recycled concrete under dry-wet cycle conditions,the substitution rate of recycled fine aggregate and recycled coarse aggregate was designed to be 0%/0%,10%/0%,0%/25%,10%/25%,0%/50%and 10%/50%of the six groups of mixture *** mass loss rate and relative dynamic modulus of each group of test blocks were tested respectively and the optimal ratio was *** Wiener distribution probability method was used to establish the reliability function to optimize the remaining life of the *** results show that the dynamic elastic modulus and mass show a trend of increasing first and then decreasing during the dry-wet cycles of *** recycled concrete has the strongest resistance to sulfate attack under the substitution rate of recycled fine aggregate and recycled coarse aggregate is 10%and 0%,and the test blocks will be damaged after being subjected to 182 times of dry-wet cycles of *** effect of recycled coarse aggregate on the sulfate attack resistance of the test block is more obvious than that of the recycled fine aggregate,which leads to the durability of the concrete being greatly reduced.

关键词： recycled concrete dry-wet cycles of sulfate the Wiener distribution probability microscopic reaction mechanism

Durability of recycled concrete Aggregate in Aggressive Environments

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Journal of Civil Engineering and Architecture 2016年第10期10卷 1097-1102页

作者： Zainab Aamer Shamsulddin College of Engineering A Hraqia University Baghdad 10001 Iraq

The main purpose of this research is to study the durability of recycled concrete as a partial replacement of coarse aggregate in corrosive environment. 10%, 20%, 30% and 40% by weight were used for recycled concrete. concrete samples exposed to 10% concentration dilute sulfuric acid solution for 180 days. Mechanical tests such as compressive and tensile strength tests, physical tests such as ultrasonic pulse velocity, bulk density, porosity, specific gravity and water absorption tests were done to the samples after curing in normal water for 28 days and after submerged in dilute sulfuric acid for 180 days. Degradation increased with increasing of replacement. Test results showed that 10% and 20% partial replacement of recycled concrete aggregate still closely to reference samples. Noticeable deterioration was shown in mechanical and physical properties for 30% and 40% partial replacement of recycled concrete aggregate.

关键词： recycled concrete sulfuric acid compressive strength tensile strength durability partial replacement.

Bond Behavior between recycled concrete Containing CDW and Different Types of Steel Bars

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Journal of Architectural Environment & Structural Engineering Research 2021年第2期4卷 1-7页

作者： Carine N.S.Reis Paulo Lima Mônica B.Leite Department of Technology Post-graduation Program of Civil and Environmental EngineeringState University of Feira de SantanaBahiaBrazil

The operation of reinforced concrete structures is directly associated with the adhesion between the steel bar and the concrete,which allows the internal forces to be transferred to the reinforcement during the process of loading the structural *** modification of the concrete composition,with the introduction of recycled aggregate from construction and demolition waste(CDW),affects the steel-concrete interface and can modify the bonding stress,which is also influenced by the type and diameter of the bar *** this work,the influence of the recycled fine aggregate(RFA)and types of steel bar on the steel-concrete bond was experimentally evaluated using the pullout *** concrete and recycled concrete,with RFA replacement level of 25%,were *** types of steel rebars(i.e.,plain and deformed)with diameters of 10.0 and 16.0 mm were considered in this *** results indicate a reduction in the adhesion stress with the introduction of recycled aggregate,but this trend is influenced by the diameter of the bar *** use of ribbed bars modifies the stress bon-slip behavior,with an increase in the average bond strength,which is also observed with the reduction of the diameter of the bar.

关键词： Construction and demolition waste(CDW) recycled concrete Steel-concrete bond behavior

The Behavior of recycled concrete through the Application of an Isotropic Damage Model

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Open Journal of Civil Engineering 2015年第3期5卷 339-351页

作者： Marcelo Pedreira da Silva Magno Teixeira Mota Anderson de Souza Matos Gadea Monica Batista Leite Koji de Jesus Nagahama Civil and Environmental Engineering Post-Graduate Program State University of Feira de SantanaFeira de SantanaBrazil

The main goal of this paper is to describe the mechanical behavior of the CDW recycled concrete in compression, using an isotropic damage model adapted to the variation of the replacement rate of natural aggregates by recycled ones. The isotropic model by Mazars was used as a constitutive equation for the CDW concrete and its adjustment parameters, A and B, were written as quadratic polynomials according to the aggregates replacement rate. The model was evaluated for conventional and recycled concretes. For the latter ones, the aggregates replacement ratios evaluated were 50% and 100%. The results show good approximation between the analytical and numerical values obtained with the adapted isotropic damage model and experimental concrete results for both compressive and flexural strength.

关键词： recycled concrete Construction and Demolition Waste Isotropic Damage Mazars Isotropic Model