Column Mode Research Articles

Life-cycle seismic performance assessment of aging RC bridges considering multi-failure modes of bridge columns

Corrosion of steel reinforcements is a major factor causing seismic performance deterioration of reinforced concrete (RC) bridges. More critically, corrosion could induce failure mode shift of the bridge columns as evidenced by some recent experimental studies. This phenomenon has not been well considered in existing studies regarding seismic performance assessment of aging RC bridges. This paper presents seismic fragility analysis of aging RC bridges in a life-cycle context considering failure mode shift of the bridge columns. A numerical model that can capture shear capacity deterioration and flexure-shear coupling behaviors of the corroded columns are developed and validated with experimental tests results. A two-span RC bridge is selected to conduct seismic fragility analysis at variant corrosion time. Time-variant structural capacity of the bridge columns are investigated with the developed numerical model. Seismic fragility curves of the bridge component as well as the bridge system are developed via dynamic analysis using near fault ground motions. Results indicate that the bridge columns will experience failure mode shift due to corrosion effects. The columns will fail in flexure-shear mode at severer corrosion levels although they were initially ductile-designed. Seismic fragility of the bridge significantly increases in case of flexure-shear failure of the columns. The results highlight the importance of considering the potential shear failure of the bridge columns in life-cycle seismic performance assessment of aging RC bridges.

Removal of tetracycline using modified wheat straw from solution in batch and column modes

A novel adsorbent (Zr-WS) was developed from the chemical modification of wheat straw with diethylenetriamine, chloroacetic acid and zirconium (Zr) and its efficacy for adsorption property was assessed using tetracycline (TC) as model pollutant. The materials were characterized by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and the results indicated that zirconium was successfully loaded on the surface of wheat straw. The adsorption property of TC was performed in batch mode and fixed-bed column mode. The TC uptake was influenced by several factors such as pH, salts, temperature and contact time in batch mode. The adsorption quantity of Zr-WS toward TC was to 77.2 mg·g−1 from equilibrium study at 303 K. Freundlich model was suitable to fit the equilibrium data while Elovich model was better to predict the kinetic process. The adsorption of TC onto Zr-WS was a physical and chemical reaction with endothermic and entropy increasing. The fixed-bed adsorption results showed that high column, high TC concentration and low flow rate were beneficial to the adsorption quantity. Yan model could describe the column adsorption behavior well. There were coordination complexation and ion exchange in the adsorption process. There was some property of regeneration using 0.1 mol·L−1 hydrogen chloride solution as eluting agent. Therefore, Zr-WS could be promising as a new material to remove tetracycline from water.

Bayesian Theory-Based Seismic Failure Modes Identification of Reinforced Concrete Columns

ABSTRACT The aim of this research is to develop a probability method that can identify the flexure, shear or flexural-shear failure of RC columns. A total of 336 columns of cyclic load test results were collected, and a probabilistic model was constructed using the Bayesian procedure. Then, the model was simplified by Bayesian updating. The boundaries for each failure mode were selected through an internal search optimization. The results show that the Bayesian methodology can accurately predict the seismic failure modes of RC columns and the comparison of the identification with other methods underscore the validity of Bayesian method.

Synthesis, characterization, and adsorption properties of collagen and attapulgite‐filled copolymer biocomposites: Batch and column studies

AbstractSeveral biocomposites were synthesized by copolymerizing hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) at varied molar ratios in the presence of different wt% of collagen (CLG) and attapulgite (APG) clay. The structure and properties of the biocomposite adsorbents were characterized by Fourier transform infrared apectroscopy, nuclear magnetic resonance, X‐ray photo electron spectroscopy, X‐ray diffraction, scanning electron microscope, transfer electron microscopy, energy‐dispersive X‐ray analysis, differential thermal analysis–thermogravimetric analysis, point zero charge analysis, mechanical properties, and pH reversibility tests. The synthesis variables were optimized with a central composite design of response surface methodology (RSM). The biocomposite prepared with an optimized composition of 1.5 wt% CLG, 1.7 wt% APG, and 5:1 molar ratio of HEMA:IA showed an adsorption capacity (Qe, mg/g) of 674.4/602.4 for methylene blue (MB)/Rose Bengal (RB) dye from a feed containing 200 mg/L of MB + RB dye mixture in batch mode. In a fixed bed in column mode, the optimized biocomposite showed a removal% of 82.8/71.3 for 100 mg/L inlet concentration, 20 ml/min flow rate, and 20 mm bed height with a breakthrough time of 23/31 min and a mass transfer coefficient (kmtc × 105 cm/s) of 8.36/7.67 for MB/RB as single dye solution.

Removal of arsenic from aqueous solution by novel iron and iron–zirconium modified activated carbon derived from chemical carbonization of Tectona grandis sawdust: Isotherm, kinetic, thermodynamic and breakthrough curve modelling

The aim of the present study was: development of activated carbon modified with iron (Fe@AC) and modified with iron and zirconium (Fe–Zr@AC) from the Tectona grandis sawdust (TGS) waste biomass and its potential applicability for the removal of As (III) from contaminated water by batch and column mode. The biomass waste was pre-treated with ferric chloride (FeCl3) and the mixture of FeCl3 and zirconium oxide (ZrO2) and then pyrolyzed at 500 °C for 2 h. The properties of both bioadsorbents were comprehensively characterized by using Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), Particle Size analysis (PSA), point of zero charge (pHZPC), Brunauer–Emmett–Teller (BET) to prove successful impregnation of the Fe and Zr on the surface of AC of TGS. FTIR analysis clearly indicates the Fe and Fe–Zr complexation on biosorbents surface and biosorption of As (III). The results revealed that maximum As (III) removal was achieved 86.35% by Fe–Zr@AC (3 g/L dose, pH-7.0, temperature-25 °C and concentration 0.5 mg/L). However, maximum removal of As (III) was attained ~75% by Fe@AC (with dose-4g/L, pH-7.0, temperature-25 °C and concentration 0.5 mg/L) at the initial concentration of 0.5 mg/L of As (III). Fe–Zr@AC exhibits higher efficiency with qmax value 1.206 mg/g than Fe@AC with the qmax value 0.679 mg/g for the removal of As(III). While in the column study, Fe–Zr@AC exhibited 98.8% removal at flow rate of 5 mL/min and bed height of 5 cm. Biosorption Isotherm and Kinetics were fitted good with Langmuir isotherm (R2 ≥ 0.99) and followed pseudo-second-order (R2 ≥ 0.99). The regeneration study indicates that the prepared biosorbents efficiently recycled up to five cycles. Therefore, Fe@AC and Fe–Zr@AC derived from TGS has been showed to be novel, effective, and economical biosorbent. The collective benefits of easy development, good affinity towards As (III), good separability, reusability, and inexpensive of magnetized Fe@AC and Fe–Zr@AC make it a novel biosorbent. The application of Fe–Zr@AC for the removal of As (III) from the water was very efficient its concentration in the solution after treatment was found below the 10 μg/L as per the guideline WHO.

Evaluation of BenzoDODA grafted polymeric resin for rapid and reliable assaying of plutonium in sediment samples

The paper reports a new rapid radioanalytical procedure for the determination of plutonium (Pu) in sediments by solid phase extraction chromatography (SPEC) using Bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) grafted resin, abbreviated as Benzodioxodiamide (BenzoDODA) grafted resin. The resin was synthesized and evaluated for its sorption behaviour towards Pu in batch and column mode to determine its efficacy for selective recovery of Pu from sediment samples. The analytical procedure was based on the radiochemical separation of samples by acid digestion, followed by preconcentration of actinides by co-precipitation with Fe(OH)3 and finally selective recovery of Pu by SPEC using a column filled with BenzoDODA grafted resin. Pu was then radiometrically assayed by preparing alpha disc sources with electro-deposition followed by alpha spectrometry. The method was further validated with IAEA reference materials. This method gives reliable and reproducible results for the activity concentration of Pu in sediment samples within 24 h.

Recovery of Zinc from Municipal Solid Waste Incineration Fly Ash

In recent years, over one million tons of Municipal Solid Waste (MSW) incineration fly ash has been generated annually Taiwan. Only a small percentage of the ash was used as raw material for other utilities besides landfill. Fly ash contains many harmful heavy metals, such as Cd and Cr, among others; however, fly ash also contains many valuable metals, including as Zn, Pb, and Ga.To recover Zn from fly ash, in this work, an experiment was first designed to determine the physical and chemical properties of the fly ash. Then, treatment processes, including water leaching, acid leaching, and ion exchange were conducted.Test samples were subjected to scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), and atomic absorption spectroscopy (AAS) to determine their physical and chemical properties. Then, water leaching was conducted under optimal experimental conditions. Thereafter, acid leaching was performed using two different acids (hydrochloric and sulfuric) to extract the target metal ions, and finally the ion exchange process was deployed to concentrate and recover the target metal ions.Ultimately, an optimal process to recover zinc from MSW incineration fly ash was developed in this work. An aqueous solution containing approximately 1 wt% zinc was obtained by leaching with sulfuric acid. Zn was then concentrated using a chelating resin IRC-747 in column mode.

Physical Simulation for Effect Seasons and Fertilizer on Solidified Fabric Peat Soil; A Soil Column Model Study

Soil stabilization is a method to improve the weakness of fabric peat soil structure which is a result of larger particle size pore. Therefore, the fabric peat soil is solidified using mixture of cement, fly ash and bottom. The present study aimed to investigate a physical simulation of soil column model as a response for affecting the wet and dry seasons and fertilizer on the solidified fabric peat soil. The column mode was investigated by analysis the water leaching micronutrient using atomic adsorption spectroscopy (AAS). The results revealed that the nitrate has the highest concentration (35.55 mg/L) on Run 3 (Fibric, rainwater, solidified peat and fertilizer) at upper area in the dry season. In comparison, potassium (K) recorded the lowest concentrations (1.14 mg / L) on Run 2 (fibric, rainwater and fertilizer) at upper area in the wet season. The highest (22.92 mg/L) and lowest (0.10 mg/L) calcium was recorded on Run 3 and Run 2 with both at upper area in wet season. These findings indicated that the chemical binder used as stabilization soil influenced the nutrient quality especially calcium which is one of the major compound materials in cement.

Performance of square steel tubular stub columns in-filled with fly ash and silica fume self-compacting concrete under concentric loading

Concrete filled steel tube (CFST) column is a composite member comprising of structural hollow steel tube and concrete core. This paper evaluates the effect of fly ash (FA) and silica fume (SF) on square CFST stub columns’ behavior under concentric loading. The self-compacting concrete (SCC) grade used is M60 with the addition of 50% FA and 10% SF as a partial replacement of Portland cement. The performances of the fly ash-silica fume selfcompacting (FSS) CFST columns are examined through the axial compression capacity, the load-shortening response, and the failure mode of stub columns. The axial load of the FSS CFST columns is compared with the international design codes to validate the available design codes’ accuracy. The results yield that the FSS CFST columns’ ultimate axial load capacities range between 1408.80 kN and 808.70 kN, while the reference CFST columns’ capacities range between 1332.80 kN and 789.20 kN. FSS concrete improves the concrete contribution ratio and strength index of the square CFST stub columns. However, reference CFST columns demonstrate better ductility than FSS CFST columns. This is attributed to the brittleness of the FSS concrete. All the square CFST stub columns fail via local buckling. Eurocode 4 slightly over predicts the square CFST columns’ ultimate capacity by an average of 4.58%. The American Concrete Institute (ACI) code, on the other hand, over predicts the axial capacity of the CFST stub columns by an average of 17.46%.

Separation of iodine using neem oil-cashew nut shell liquid based-phenol formaldehyde resin modified lignocellulosic biomatrices: Batch and column study

BackgroundManagement and separation of radioactive iodine from wastewater of nuclear power plants is time-dependent and needs lot of efforts. Changes of surface chemistry due to radioactive irradiations are the major issue for developing an efficient adsorbent for separation of radionuclei from wastewater. MethodsThis article presented a promising case of separation of non-radioactive iodine from aqueous solution using neem oil phenolic resin treated lignocellulosic biomass. The resin was prepared with some ingredients with known properties of radiation absorption. FindingsThe data pointed that the treated biomass has the efficacy of iodine separation from aqueous solution within wide range of pH. The iodine sorption followed the Langmuir isotherm indicating a monolayer surface adsorption reaction. The maximum iodine removal efficacy of the resin treated biomass was 3.64 mg/g. The iodine adsorption was found to follow the pseudo second order reaction. The kinetic analysis also indicated that both surface adsorption and intraparticle diffusion were likely to control the rate of iodine-adsorbent. The treated adsorbent also showed iodine removal efficacy in column mode. The resin used for the treatment of lignocellulosic biomass was prepared using cashew nut shell liquid and phenol-formaldehyde that are known for their radiation adsorption and antioxidant properties. Thus, neem oil cashew nut shell liquid containing phenol formaldehyde resin treated biomass is expected to be stable under radioactive radiation. As radioactive iodine generation is a common phenomenon for nuclear power plant the bio-based chemical modified lignocellulosic adsorbent could be a promising alternative. However, more detail investigations with radioactive iodine containing real wastewater from nuclear power plant is needed for validation of our statement.

English

Treatment of effluents from batik producing enterprises to removal dyes and other impurities is inevitable as these enterprises are becoming ubiquitous in many cities in Tanzania. Wastewater from batik production processes are discharged haphazardly without treatment. In this study, preliminary results on adsorption potential of defatted Moringa oleifera crude seed extract (DMOCSE) and fuel wood ash (FWA) for dye and chemical oxygen demand (COD) in batik processing wastewater (BPW) are presented. Batch and column adsorption studies were conducted using varied dye concentrations, adsorbents dosage, contact time and pH. 7% (w/v) DMOCSE at the dosage of 15 to 25 ml/L produced minimum residual dye in BPW with initial color ranging from 480 to 675 mgpt-Co/L. Optimum contact time for DMOCSE ranged from 1.5 to 2.5 h and pH 7.5 to 9.5 with 75.5 to 93% dye removal efficiency. FWA at optimum dosage of 25 g/l, contact time of 1.5 to 3 h and pH 8.5 to 11.5 removed 78.8 to 84% of dye. FWA and DMOCSE reduced 98 and 64% of COD. The FWA packed column with depth of 20 and 25 cm achieved 99% dye removal after 4 to 6 h of retention time. The findings reveal that DMOCSE and FWA have potential to treat BPW in both batch and column mode. Key words: Dye-rich wastewater, impurities removal, natural adsorbent.

Impacts of secondary ice production on Arctic mixed-phase clouds based on ARM observations and CAM6 single-column model simulations

Abstract. For decades, measured ice crystal number concentrations have been found to be orders of magnitude higher than measured ice-nucleating particle number concentrations in moderately cold clouds. This observed discrepancy reveals the existence of secondary ice production (SIP) in addition to the primary ice nucleation. However, the importance of SIP relative to primary ice nucleation remains highly unclear. Furthermore, most weather and climate models do not represent SIP processes well, leading to large biases in simulated cloud properties. This study demonstrates a first attempt to represent different SIP mechanisms (frozen raindrop shattering, ice–ice collisional breakup, and rime splintering) in a global climate model (GCM). The model is run in the single column mode to facilitate comparisons with the Department of Energy (DOE)'s Atmospheric Radiation Measurement (ARM) Mixed-Phase Arctic Cloud Experiment (M-PACE) observations. We show the important role of SIP in four types of clouds during M-PACE (i.e., multilayer, single-layer stratus, transition, and frontal clouds), with the maximum enhancement in ice crystal number concentrations up to 4 orders of magnitude in moderately supercooled clouds. We reveal that SIP is the dominant source of ice crystals near the cloud base for the long-lived Arctic single-layer mixed-phase clouds. The model with SIP improves the occurrence and phase partitioning of the mixed-phase clouds, reverses the vertical distribution pattern of ice number concentrations, and provides a better agreement with observations. The findings of this study highlight the importance of considering SIP in GCMs.

Seismic behavior of steel reinforced concrete L-shaped columns under compression-bending-shear-torsion combined action

The L-shaped column is usually used as a corner column in buildings, which can be one of the weak members in the structural system. Because of the asymmetry of an L-shaped column, it is more complex in structural layout and mechanical performance. To study the seismic performance of steel reinforced concrete (SRC) L-shaped columns under compression-bending-shear-torsion combined action, twelve SRC L-shaped columns were tested in this paper. The main variables included the shaped-steel layout, the torsion-bending ratio and the ratio of limb height to limb thickness. Based on the test results, the failure modes, hysteretic curves, ductility, stiffness degradation and energy dissipation were compared and analyzed. The results show that the failure modes of SRC L-shaped columns mainly depended on the torsion-bending ratio, which could be divided into bending failure, bending-shear failure and bending-torsion failure. The shaped-steel layout had an effect on the final damage degree of the specimens. Increasing the torsion-bending ratio could improve the torsion resistance of the specimen, but the bending capacity became weaker and the stiffness degradation was faster. The ductility and energy dissipation of SRC L-shaped columns could be enhanced by reducing the ratio of limb height to limb thickness. Comprehensive analysis showed that the empty-web T-section SRC L-shaped column had superior seismic performance under compression-bending-shear-torsion combined action.

Online In-Tube Solid-Phase Microextraction Coupled to Liquid Chromatography-Tandem Mass Spectrometry for the Determination of Tobacco-Specific Nitrosamines in Hair Samples.

Active and passive smoking are serious public health concerns Assessment of tobacco smoke exposure using effective biomarkers is needed. In this study, we developed a simultaneous determination method of five tobacco-specific nitrosamines (TSNAs) in hair by online in-tube solid-phase microextraction (SPME) coupled to liquid chromatography-tandem mass spectrometry (LC–MS/MS). TSNAs were extracted and concentrated on Supel-Q PLOT capillary by in-tube SPME and separated and detected within 5 min by LC–MS/MS using Capcell Pak C18 MGIII column and positive ion mode multiple reaction monitoring systems. These operations were fully automated by an online program. The calibration curves of TSNAs showed good linearity in the range of 0.5–1000 pg mL–1 using their stable isotope-labeled internal standards. Moreover, the limits of detection (S/N = 3) of TSNAs were in the range of 0.02–1.14 pg mL–1, and intra-day and inter-day precisions were below 7.3% and 9.2% (n = 5), respectively. The developed method is highly sensitive and specific and can easily measure TSNA levels using 5 mg hair samples. This method was used to assess long-term exposure levels to tobacco smoke in smokers and non-smokers.

TWO-STAGE SUPPORT VECTOR MACHINE METHOD FOR FAILURE MODE CLASSIFICATION OF REINFORCEDCONCRETE COLUMNS

A two-stage support vector machine (SVM) method for the failure mode classification of reinforced concrete (RC) columns is proposed. A two-stage SVM model is established to classify the seismic failure modes of RC columns according to three failure modes, namely, flexure failure, flexure-shear failure and shear failure. The optimal values of model parameters (i.e., penalty parameters and kernel function parameter) of the two-stage SVM model are determined by using ten-fold cross-validation and grid-search based on 270 experimental data. Subsequently, the characteristic parameters including the axial load ratio, shear span ratio, hoop spacing to depth ratio (s/h0), longitudinal reinforcement index and transverse reinforcement index on the seismic failure modes of RC columns are analyzed by the support vector machine-recursive feature elimination (SVM-RFE). The classification accuracy of the proposed classification method is validated by comparing with two classical machine learning methods and five traditional classification methods. The results indicate that the accuracy of the proposed method is generally higher than 90% for three failure modes, which is 10% higher than the classical machine learning methods and 20% higher than the traditional classification methods. The shear-span ratio and longitudinal reinforcement index have significant influences on whether the RC column fails in flexure. They are followed by the transverse reinforcement index and s/h0, while the axial load ratio has negligible influence. The longitudinal reinforcement index has significant influence on whether the RC column fails in flexure-shear. It is followed by the shear-span ratio and s/h0, while the transverse reinforcement index and axial load ratio have negligible influence.

Experimental investigation on the post-fire performance of reactive powder concrete columns

The increased use of reactive powder concrete (RPC) in concrete structures has attracted attention towards the structural behavior of RPC in fires. This work examines experimentally the performance of RPC and NSC columns subjected to 25% of the ultimate load and exposed to direct fire flame for a period of 30 and 60 min at various temperature levels. The paper aims to evaluate the maximum temperature level and fire duration that can be withstood by this type of concrete columns. The results show that the failure mode of RPC columns without reinforcement is a sudden shear failure, whereas the failure mode of reinforced RPC columns is a crushing failure with rupture of certain ties. The RPC columns at high temperatures spall intensively; additionally, the ultimate strength clearly decreases compared to the NSC columns at the same conditions.

Biochar caged zirconium ferrite nanocomposites for the adsorptive removal of Reactive Blue 19 dye in a batch and column reactors and conditions optimizaton

Abstract Biochar caged zirconium ferrite (BC-ZrFe2O5) nanocomposites were fabricated and their adsorption capacity for Reactive Blue 19 (RB19) dye was evaluated in a fixed-bed column and batch sorption mode. The adsorption of dye onto BC-ZrFe2O5 NCs followed pseudo-second-order kinetics (R 2 = 0.998) and among isotherms, the experimental data was best fitted to Sips model as compared to Freundlich and Langmuir isotherms models. The influence of flow-rate (3–5 mL min−1), inlet RB19 dye concentration (20–100 mg L−1) and quantity of BC-ZrFe2O5 NCs (0.5–1.5 g) on fixed-bed sorption was elucidated by Box-Behnken experimental design. The saturation times (C t /C o = 0.95) and breakthrough (C t /C o = 0.05) were higher at lower flow-rates and higher dose of BC-ZrFe2O5 NCs. The saturation times decreased, but breakthrough was increased with the initial RB19 dye concentration. The treated volume was higher at low sorbent dose and influent concentration. Fractional bed utilization (FBU) increased with RB19 dye concentration and flow rates at low dose of BC-ZrFe2O5 NCs. Yan model was fitted best to breakthrough curves data as compared to Bohart-Adams and Thomas models. Results revealed that BC-ZrFe2O5 nanocomposite has promising adsorption efficiency and could be used for the adsorption of dyes from textile effluents.

Synthesis and characterization of polyaniline composites with silica gel, styrene-divinyl benzene resin beads, calcium alginate and tetraethoxy silane substrates

Initially, Polyaniline (PAni) was synthesized in the powder form by chemical oxidative polymerization of aniline with ammonium persulphate in HCl medium. Further, composites of PAni with beads of silica gel, styrene-divinyl benzene resin beads and calcium alginate were prepared by in-situ chemical polymerization of aniline. Pre-formed base-PAni and tetraethoxysilane were used as precursors for the synthesis of PAni-siloxane composite disks. Ion exchange capacity of PAni powder was found to be 3.25 ± 0.084 meq g−1. PAni powder and its composites were characterized by elemental analysis, UV–visible and FTIR spectroscopy, TG-DSC, SEM, molecular weight and ion exchange capacity measurements. All the composites, except the alginate, were found to be thermally more stable than the powder form of PAni. The composite beads can be applied for future studies in the column mode of operations. Preliminary evaluation of the PAni-siloxane disc for arsenic sorption from aqueous solutions showed promising results. These disks are easy to handle, durable and the sorbed species can be directly quantified, i.e., without post-sorption processing, by energy dispersive X-ray fluorescence spectrometry.

Modelling and efficiency assessment of the up flow fixed bed process packed with Moringa oleifera for continuous Cd(II) removal from drinking water

The biosorption ability of ‘Moringa oleifera ‘seed powder for the expulsion of cadmium from wastewater was investigated by performing packed column tests. Column tests were conducted as a function of biosorbent dose, influent flow rate and feed sorbate concentration. The findings from column operations revealed that values of maximum cadmium uptake, exhaustion and breakthrough time enhances with rise in bed depth, reduces with rise in feed volumetric flowrate and initial cadmium concentration. At 6 g of Moringa oleifera dose, 2 mL/min of flow rate and 300 µg/L of influent cadmium, the cadmium uptake capacity was found to be 65.44, µg/g. The continuous packed column data for cadmium were well fitted to the Thomas model with the regression coefficient ranges 0.966–0.993. Moreover, the qth values obtained from Thomas model are similar to the experimental breakthrough capacities qexp. The FTIR results reveals that the Moringa oleifera seed contains various active functional groups which are appears to be played a significant role in biosorption of cadmium ions. From practical view, the Moringa oleifera seed could be utilized as safe, inexpensive, sustainable and eco-friendly biosorbent for the elimination of cadmium from drinking water using continuous column mode and also this technology could be considered as an ideal for household usage in rural communities.

MECHANICAL PERFORMANCE OF RECYCLED AGGREGATE SELF-CONSOLIDATING CONCRETE COLUMN

The utilization of recycled concrete aggregate (RCA) can reduce the environmental impact and decreases the cost of concrete. In this study, a comprehensive assessment of self-consolidating concrete (SCC) using RCA as partial or total replacement of coarse aggregate was conducted. Recycled concrete aggregate self-consolidating concrete (RCA-SCC) mixtures with varied water-to-cement (W/C) ratios (0.28–0.46), sand-to-aggregate (S/A) ratios (48–52%), fly ash (FA) contents (20–40%), RCA replacement ratios (0–100%), and water reducer contents (0–1.5%) were designed and tested. 5 groups of the RCA-SCC columns with different W/C and replacement ratios of RCA were also investigated. The slump flow, the J-ring flow and the cubic compressive strength, and the compressive behaviors of the RCA-SCC columns were studied. Results indicated that W/C ratio was the dominant parameter in RCA-SCC mixture, and the failure modes of the RCA-SCC columns were similar to those of the conventional concrete columns. Based on the experimental results, the mechanical performance of RCA-SCC columns was evaluated quantitatively, and a stress–strain relation model for predicting the axial compressive behavior of RCA-SCC column was proposed. This study will provide a reference for the engineering application of the environment-friendly SCC using RCA that are derived from tested or returned concretes with better performance.