scholarly journals Confinement Effect and Efficiency of Concentrically Loaded RACFCST Stub Columns

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 154
Author(s):  
En Wang ◽  
Yicen Liu ◽  
Fei Lyu ◽  
Faxing Ding ◽  
Yunlong Xu
Keyword(s):  
Bearing Capacity ◽  
Ultimate Bearing Capacity ◽  
Recycled Aggregate Concrete ◽  
Confinement Effect ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Replacement Ratio ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Stub Columns

Recycled aggregate concrete-filled steel tubular (RACFST) columns are widely recognized as efficient structural members that can reduce the environmental impact of the building industry and improve the mechanical behavior of recycled aggregate concrete (RAC). The objective of this study is to investigate the behavior of recycled aggregate concrete-filled circular steel tubular (RACFCST) stub columns subjected to the axial loading. Three-dimensional finite element (FE) models were established using a triaxial plastic-damage constitutive model of RAC considering the replacement ratio of recycled aggregates. The FE analytical results revealed that the decreased ultimate bearing capacity of RACFCST stub columns compared with conventional concrete infilled steel tubular (CFST) columns was mainly due to the weakened confinement effect and efficiency. This trend will become more apparent with the larger replacement ratio of recycled aggregates. A practical design formula of the ultimate bearing capacity of RACFCST stub columns subjected to axial load was proposed on the basis of the reasonably simplified cross-sectional stress nephogram at the ultimate state. The derivation process incorporated the equilibrium condition and the superposition theory. The proposed equation was evaluated by comparing its accuracy and accessibility to some well-known design formulae proposed by other researchers and some widely used design codes.

scholarly journals Numerical Study on Confinement Effect and Efficiency of Concentrically Loaded RACFRST Stub Columns

2021 ◽  
Vol 8 ◽  
Author(s):  
Yicen Liu ◽  
Fei Lyu ◽  
Faxing Ding ◽  
En Wang ◽  
Yunlong Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Steel Tube ◽  
Recycled Aggregate Concrete ◽  
Confinement Effect ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Superposition Method ◽  
Aggregate Concrete ◽  
Stub Columns

The mechanical behaviors of recycled aggregate concrete (RAC) are upgraded by outer steel tube confinement, and the performance of recycled aggregate concrete-filled steel tubular (RACFST) columns is similar to that of the traditional concrete-filled steel tube (CFST) columns. The purpose of this study is to investigate the behaviors of recycled aggregate concrete-filled rectangular steel tubular (RACFRST) stub columns under axial loading. Three-dimensional finite element (FE) models were established, which utilized a triaxial plastic-damage constitutive RAC model considering the replacement ratio of recycled aggregates. The finite element analysis results indicated that the lessened ultimate bearing capacity of RACFRST stub columns compared with their traditional concrete infilled counterparts was mainly due to the weakened confinement effect and confinement efficiency. A simplified formula of the bearing capacity of concentrically loaded RACFRST stub columns was proposed. The cross-sectional stress nephogram was reasonably simplified by the limited state of infilled concrete. The basics of proposed formula were the equilibrium condition and the superposition method. Finally, the formula for the bearing capacity of RACFRST stub columns was evaluated by comparing its accuracy and feasibility to some design formulae proposed by specialists and some design codes of different regions.

Experimental Research on Behavior of Axially Square CFRP Steel Tubular Confined Recycled Aggregate Concrete Long Columns

2015 ◽  
Vol 744-746 ◽  
pp. 93-95
Author(s):  
Jiong Feng Liang ◽  
Ping Hua Yi ◽  
Jian Bao Wang
Keyword(s):  
Bearing Capacity ◽  
Coarse Aggregate ◽  
Slenderness Ratio ◽  
Ultimate Bearing Capacity ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Replacement Ratio ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate

Seven axially square CFRP steel tubular confined recycled aggregate concrete long columns were experimentally investigated to study their static behavior. The influence of the slenderness ratio, recycled coarse aggregate replacement ratio, layers of CFRP jackets effect on the performance of axial compression. The test results show that the higher the recycled coarse aggregate content and the slenderness ratio, the greater the specimen ultimate bearing capacity is smaller, and the more the layers of CFRP jackets, the greater the specimen ultimate bearing capacity.

Experimental Study on Compressive Strength of Recycled Aggregate Concrete with Different Replacement Ratios

2012 ◽  
Vol 174-177 ◽  
pp. 1277-1280 ◽  
Author(s):  
Hai Yong Cai ◽  
Min Zhang ◽  
Ling Bo Dang
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
Failure Mode ◽  
Failure Process ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Replacement Ratio ◽  
Aggregate Concrete

Compressive strengths of recycled aggregate concrete(RAC) with different recycled aggregates(RA) replacement ratios at 7d, 28d, 60d ages are investigated respectively. Failure process and failure mode of RAC are analyzed, influences on compressive strength with same mix ratio and different RA replacement ratios are analyzed, and the reason is investigated in this paper. The experimental results indicate that compressive strength of recycled concrete at 28d age can reach the standard generally, it is feasible to mix concrete with recycled aggregates, compressive strength with 50% replacement ratio is relatively high.

scholarly journals Geopolymer Recycled Aggregate Concrete: From Experiments to Empirical Models

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1180
Author(s):  
Hoai-Bao Le ◽  
Quoc-Bao Bui ◽  
Luping Tang
Keyword(s):  
Sodium Hydroxide Solution ◽  
Empirical Models ◽  
Recycled Aggregate Concrete ◽  
Curing Temperature ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
River Sand ◽  
Conventional Concrete ◽  
Aggregate Concrete

Ordinary cement concrete is a popular material with numerous advantages when compared to other construction materials; however, ordinary concrete is also criticized from the public point of view due to the CO2 emission (during the cement manufacture) and the consumption of natural resources (for the aggregates). In the context of sustainable development and circular economy, the recycling of materials and the use of alternative binders which have less environmental impacts than cement are challenges for the construction sector. This paper presents a study on non-conventional concrete using recycled aggregates and alkali-activated binder. The specimens were prepared from low calcium fly ash (FA, an industrial by-product), sodium silicate solution, sodium hydroxide solution, fine aggregate from river sand, and recycled coarse aggregate. First, influences of different factors were investigated: the ratio between alkaline activated solution (AAS) and FA, and the curing temperature and the lignosulfonate superplasticizer. The interfacial transition zone of geopolymer recycled aggregate concrete (GRAC) was evaluated by microscopic analyses. Then, two empirical models, which are the modified versions of Feret’s and De Larrard’s models, respectively, for cement concretes, were investigated for the prediction of GRAC compressive strength; the parameters of these models were identified. The results showed the positive behaviour of GRAC investigated and the relevancy of the models proposed.

scholarly journals Elasto-Damage Constitutive Modelling of Recycled Aggregate Concrete

2020 ◽  
Vol 7 ◽  
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Percentage Increase ◽  
Test Results ◽  
Conventional Concrete ◽  
Critical Energy Release Rate ◽  
Aggregate Concrete ◽  
Finite Element Software ◽  
Concrete Model

Use of recycled aggregates in concrete has proved to be beneficial in attaining sustainable construction without compromising overall material and structural performance when compared with concrete containing natural aggregates. However, use of the recycled aggregates in concrete have resulted in reduction in compressive and tensile strengths with the recycled aggregates percentage increase in concrete. Furthermore, it is important to note that most of the finite element software used in the construction industry use concrete model derived from the test results of the conventional concrete, therefore, they may not always predict safe solution for recycled aggregates concrete (RAC). Therefore, in this investigation elasto-damage, proposed by Khan and Zahra, for natural aggregate concrete (NAC) was modified to incorporate the influence of recycled aggregates on the behaviour of concrete. Model use four parameters α, β, γ critical energy release rate (Rc) to predict the behaviour of recycled aggregate concrete for multi axial stress states. Parameters α, β and γ are used to predict the different behavior of concrete in tension and compression while Rc controls the damage growth rate. These parameters are defined as a function of concrete compressive strength (fc/) and its initial elastic modulus (Eo). Existing test results for uniaxial compressive state of stress were used to validate this model and it was found that it predicts better post cracking and post peak-behaviour of RAC as compared to the commercially available models for conventional concrete

scholarly journals Virtual Revision on Compressive Srength of Conventional Concrete and Recycled Aggregate Concrete Consisting Treated Recycled Aggregate

2019 ◽  
Vol 8 (3) ◽  
pp. 3439-3443
Keyword(s):  
Experimental Studies ◽  
Strength Properties ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Natural Aggregate

Use of reused aggregate in concrete can be useful for the ecological protection and economical terms. The application of recycled has been started in many construction projects. Paper hear says the basic properties of recycled concrete aggregate. It similarly relates the properties with natural aggregate, similarly the properties of recycled aggregates concrete were also determined and explained here. For the concrete grades of M25 and M30, the recycled aggregate concrete is produced by changing the natural aggregate, by recycled aggregate in conventional concrete with 5%, 10% and 15% of weight of natural aggregates. Experimental studies were carried out on influence of recycled aggregate treatment and comparison of strength properties of conventional cement concrete and recycled aggregate concrete at the curing of 7days and 28 days. They are two types of treatments under the considerations for recycled aggregates are Abrasion of recycled aggregate and chemical immersion

scholarly journals Recycled Aggregates Concrete Compressive Strength Prediction Using Artificial Neural Networks (ANNs)

2021 ◽  
Vol 6 (2) ◽  
pp. 17
Author(s):  
Mohamad Ali Ridho B K A ◽  
Chayut Ngamkhanong ◽  
Yubin Wu ◽  
Sakdirat Kaewunruen
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Strength Prediction ◽  
Concrete Compressive Strength ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Ann Models

The recycled aggregate is an alternative with great potential to replace the conventional concrete alongside with other benefits such as minimising the usage of natural resources in exploitation to produce new conventional concrete. Eventually, this will lead to reducing the construction waste, carbon footprints and energy consumption. This paper aims to study the recycled aggregate concrete compressive strength using Artificial Neural Network (ANN) which has been proven to be a powerful tool for use in predicting the mechanical properties of concrete. Three different ANN models where 1 hidden layer with 50 number of neurons, 2 hidden layers with (50 10) number of neurons and 2 hidden layers (modified activation function) with (60 3) number of neurons are constructed with the aid of Levenberg-Marquardt (LM) algorithm, trained and tested using 1030 datasets collected from related literature. The 8 input parameters such as cement, blast furnace slag, fly ash, water, superplasticizer, coarse aggregate, fine aggregate, and age are used in training the ANN models. The number of hidden layers, number of neurons and type of algorithm affect the prediction accuracy. The predicted recycled aggregates compressive strength shows the compositions of the admixtures such as binders, water–cement ratio and blast furnace–fly ash ratio greatly affect the recycled aggregates mechanical properties. The results show that the compressive strength prediction of the recycled aggregate concrete is predictable with a very high accuracy using the proposed ANN-based model. The proposed ANN-based model can be used further for optimising the proportion of waste material and other ingredients for different targets of concrete compressive strength.

scholarly journals Effects of Concrete Grades on Strength Characteristics of Metakaolin Modified Recycled Aggregate Concrete

2021 ◽  
Vol 18 (3) ◽  
pp. 184-193
Author(s):  
A.U. Adebanjo ◽  
B.I.O. Dahunsi ◽  
J.O. Labiran
Keyword(s):  
Specific Gravity ◽  
Water Absorption ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Concrete Production ◽  
Aggregate Impact Value ◽  
Control Samples

In this study, locally produced Metakaolin (MK) was used as an admixture in recycled aggregate concrete of grades M 25 and M 30. The content of MK varied from 0-15% at 5% intervals. The physical and mechanical properties (bulk density, specific gravity, water absorption, aggregate crushing value and aggregate impact value) of aggregates were determined, the chemical composition as well as reactivity of MK was evaluated using X-Ray Fluorescence (XRF) technique and modified Chappelle test. The workability  (slump) and strength (compressive and split tensile) properties of fresh and hardened RAC were examined relative to that of conventional concrete. The results of the experiments revealed that the specific gravity (SG), water absorption and aggregate impact value of recycled aggregates (RA) were 2.23, 5.35% and 32%, respectively. The MK used had an optimum reactivity of 2060.8 mg of Ca(OH)2 fixed at a temperature of 660 oC. The slump values for M 25 and M 30 control specimens were 72 mm and 65 mm, respectively while the slump values of MK modified RAC decreased from 67-45 mm for M 25 and 55-35 mm for M 30 as MK increased from 0-15%. The 56th-day compressive strength of the control samples was 21.73 N/mm2 for M 25 and 26.8 N/mm2 for M 30, respectively, while RAC samples ranged from 14.96 - 17.04 N/mm2 for M 25 and 20.55 - 22.67 N/mm2 for M 30 whereas the split tensile strength for the control samples was 2.71 N/mm2 and 3.06 N/mm2 for the two grades in that sequence, while those of RAC ranged from 2.26-2.49 N/mm2 for M 25 and 2.62 – 2.84 N/mm2 for M 30. Despite the fact that metakaolin modified RAC had lower strength properties than conventional concrete, the use of 10% metakaolin as a RA modifier in concrete production will provide a sustainable alternative to conventional aggregates in concrete mix design.

Chloride Resistance of Recycled Aggregate Concrete under Wetting-Drying Cycles

2016 ◽  
Vol 724 ◽  
pp. 3-7 ◽  
Author(s):  
Bing Qi ◽  
Jian Ming Gao ◽  
Da Man Shen
Keyword(s):  
Chloride Content ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Chloride Diffusion ◽  
Replacement Ratio ◽  
Aggregate Concrete ◽  
Coarse Aggregates ◽  
Free Chloride ◽  
Chloride Resistance

Recycled aggregates concrete (RAC) becomes an important participant in recycled materials. This study was performed in order to evaluate the effect of recycled coarse aggregates (RCA) on the chloride resistance of concretes with different coarse aggregates replacement ratio under wetting–drying cycles. Composition influence on the concrete were studied with different the addition of admixtures. The results indicate that the free chloride content decreased with the increasing of depth, whist it increased with the increasing replacement ratio of RCA at the same depth. Wetting–drying cycles accelerated the process of chloride diffusion. It was also found that the addition of admixtures can improve the ability of chloride resistance of concrete.

scholarly journals Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

2021 ◽  
Vol 13 (10) ◽  
pp. 5741
Author(s):  
Muhammad Junaid Munir ◽  
Syed Minhaj Saleem Kazmi ◽  
Yu-Fei Wu ◽  
Xiaoshan Lin ◽  
Muhammad Riaz Ahmad
Keyword(s):  
Axial Stress ◽  
Peak Stress ◽  
Polypropylene Fibre ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Peak Strain ◽  
Stress Strain ◽  
Polypropylene Fibres ◽  
Aggregate Concrete

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

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