The public value of contaminated soil remediation in Janghang copper smelter of Korea

Lim, S.Y.,Min, S.H.,Yoo, S.H. Butterworth Scientific, [etc.] 2016 RESOURCES POLICY Vol.50 No.-

The Korean government planned to remediate the soil contaminated with heavy metals, such as arsenic, cadmium, and lead, in Janghang copper smelter (JCS). The policy-makers are demanding a figure about the public value of the remediation. Therefore, this paper describes an attempt to measure the public value, applying the contingent valuation (CV) method. To this end, we conducted a CV survey of 1000 households in Korea in 2015. We used a one-and-one-half-bounded dichotomous choice question to derive the willingness to pay (WTP) responses, and utilized a spike model to analyze zero WTP responses. The mean WTP was computed to be KRW 1627 (USD 1.37) per household per year and statistically meaningful at the 1% level. Expanding the value to the national population gives us KRW 30.4 billion (USD 25.7 million) per year. The present value of the total public value for the next ten years reaches KRW 241.7 billion (USD 204.0 million), using a social discount rate of 5.5%. We can conclude that Korean households are ready to shoulder some of the financial burden for contaminated soil remediation in JCS. Moreover, we conducted economic feasibility analysis of the remediation and found that it is socially profitable.

Evaluation of corrosion resistance properties of N, N'-Dimethyl ethanolamine corrosion inhibitor in saturated Ca(OH)₂ solution with different concentrations of chloride ions by electrochemical experiments

Ryu, H.S.,Singh, J.K.,Yang, H.M.,Lee, H.S.,Ismail, M.A. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.114 No.-

Steel rebars attain passivity in concrete environment. Passive film can be destroyed by acidification through carbonation and chloride ions from NaCl in concrete. There are different techniques have been employed to mitigate the corrosion problem of steel rebars embedded in concrete. Among different methods inhibitors are very popular and frequently used. Commercially available N, N'-Dimethyl ethanol amine (DMEA) inhibitor is studied in different concentrations of NaCl in saturated Ca(OH)<SUB>2</SUB> solution. The performance of inhibitor was evaluated by potential time, electrochemical impedance spectroscopy and potentiodynamic techniques. DMEA inhibitor is showing 63-74% efficiency and effectively reduces the corrosion rate.

Evaluation of compressive strength development and carbonation depth of high volume slag-blended concrete

Han-Seung, L.,Wang, X.Y. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.124 No.-

Compressive strength development and carbonation are critical topics for using high volume slag concrete rationally. The objective of this study is to present a numerical procedure that evaluates compressive strength and carbonation depth of high volume slag concrete. This numerical procedure consists of a blended hydration model and a carbonation reaction model. The amount of carbonatable materials, such as calcium hydroxide (CH) and calcium silicate hydrate (CSH), is calculated using the blended hydration model. Compressive strength development of cement-slag blends is evaluated from CSH content. By considering the effects of material properties and environmental conditions, the carbonation reaction model analyzes the diffusivity of carbon dioxide and the carbonation depth of concrete. The results of the analysis show that regarding compressive strength, the contribution of slag mixes prepared at a lower water to binder ratio was greater than the contribution of slag mixes prepared at a higher water to binder ratio. Regarding carbonation, with an increase in slag content or reducing the initial curing period, carbonation depth increases. The results of this study are useful for optimum mixing proportional design and carbonation durability design of concrete incorporating a high volume slag.

Pore blocking characteristics of corrosion products formed on Aluminum coating produced by arc thermal metal spray process in 3.5wt.% NaCl solution

Lee, H.S.,Singh, J.K.,Park, J.H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.113 No.-

Arc thermal metal spray coating is very efficient process to protect the steel from corrosion in industrial, humid and saline/coastal environments. This paper incorporates the experimental results for the performance of Aluminum coating deposited on mild steel substrate by arc thermal metal spray. Different electrochemical techniques, FE-SEM, Raman spectroscopy and XRD were used to assess the performance of deposited coating. Electrochemical studies revealed the enhanced corrosion resistance properties of coating in 3.5wt.% NaCl solution. The formation of α-Al(OH)<SUB>3</SUB> on coating substrate during exposure periods block the pores of coating and impede the penetration of corrosive species to react with substrate.

Size effect in normal- and high-strength amorphous metallic and steel fiber reinforced concrete beams

Yoo, D.Y.,Banthia, N.,Yang, J.M.,Yoon, Y.S. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.121 No.-

In this study, the size effect on the flexural behavior of amorphous metallic fiber reinforced concrete (AM-FRC) was investigated. For this, several AM-FRC beams having three different sizes were fabricated with different values of water-to-cementitious material (w/cm) ratio and fiber volume fraction. In order to estimate the implication of fiber type on the size effect, steel fiber reinforced concrete (SFRC) having the same mixture proportion as that of the AM-FRC and 0.75% by volume of hooked-end steel fibers were also fabricated and tested. The experimental results showed that lower flexural performance including flexural strength, normalized deflection capacity, and normalized toughness was obtained with an increase in the specimen size, regardless of w/cm ratio and volume content and type of fibers. High-strength concrete was more sensitive to the size effect on flexural strength than normal-strength concrete, whereas less sensitivity to the size effect was observed with an increase in the fiber volume content. The effectiveness of using hooked-end steel fibers in reducing the size effect was greater for high-strength concrete compared to normal-strength concrete, due to the better fiber bond performance.

Estimation of rheological properties of UHPC using mini slump test

Choi, M.S.,Lee, J.S.,Ryu, K.S.,Koh, K.T.,Kwon, S.H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.106 No.-

This paper reports a method for estimating the rheological properties of ultra-high performance concrete (UHPC) by applying a mini slump test that can be used easily on-site. Computational fluid dynamic (CFD) analysis of the mini slump test within the scope of viscosity and yield stress of UHPC was performed and a simple equation that expresses the correlation between the variation of the spreading diameter over time obtained from the analysis and the rheological properties was proposed. The mini slump test was carried out on four types of UHPC mixtures and the rheological properties were estimated from the proposed equation, and verified by a comparison with the viscosity and yield stress measured directly using a rheometer. The comparison showed that the rheological properties of UHPC could be estimated quantitatively using mini slump test.

Compressive strength, resistance to chloride-ion penetration and freezing/thawing of slag-replaced concrete and cementless slag concrete containing desulfurization slag activator

Lee, B.,Kim, G.,Nam, J.,Cho, B.,Hama, Y.,Kim, R. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.128 No.-

In this research, desulfurization slag (DS), a byproduct generated during steel production, was used as an activator for ground granulated blast-furnace slag (GGBS), and the compressive strength, resistance to chloride-ion penetration and freezing/thawing of slag-replaced concrete and cementless slag concrete containing DS activator was evaluated. The experimental results indicated that DS affects the strength development of slag-replaced concrete and cementless slag concrete when used as an activator. Moreover, a constant increase in the compressive strength was observed during the long-term aging of cementless slag concrete with a DS and anhydrous gypsum mixture. However, the transformation of ettringite to monosulfate was not effective; a large quantity of ettringite was observed at a long-term age of 910days in the cementless slag concrete. In addition, a high resistance to chloride-ion penetration was obtained for high-volume slag concrete. The resistance to chloride-ion penetration was greater in cementless slag concrete. On the other hand, cementless slag concrete, which had a high volume of capillary pores, had the lowest resistance to freezing/thawing.

Effects of amorphous metallic fibers on the properties of asphalt concrete

Yang, J.M.,Kim, J.K.,Yoo, D.Y. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.128 No.-

This study aims to examine the effects of amorphous metallic fibers on various properties of asphalt concrete (AC), such as internal porosity, resistance to moisture-related damage, dynamic stability, indirect tensile strength, flexural strength, strain capacity, and toughness. For this, several AC samples with various fiber volume fractions were fabricated and tested. The implications of asphalt binder content on the properties of AC with fibers were also investigated. Test results indicated that the air void content in AC increased with the incorporation of amorphous metallic fibers, so that higher asphalt binder content was required for AC with fibers to achieve 4% porosity or less in comparison to AC without fibers. Indirect tensile strength and flexural strength of AC decreased with the inclusion of fibers, and its moisture-related damage was more pronounced when fibers were incorporated. On the other hand, the dynamic stability, strain capacity at a moderate temperature, and thermal conductivity of AC were improved by using amorphous metallic fibers. Finally, the self-healing of completely broken AC containing amorphous metallic fibers was successfully achieved with induction heat and restraint.

Utilization of excavated soil in coal ash-based controlled low strength material (CLSM)

Kim, Y.s.,Do, T.M.,Kim, H.k.,Kang, G. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.124 No.-

Coal ash generated from the combustion process of thermal power plants and excavated soil from construction sites in Jeolla Province (South Korea) have significant environmental and economic impacts. The aim of this study is to evaluate the feasibility of controlled low strength material (CLSM) production using wastes (e.g., ponded ash, fly ash, and excavated soil) and cementless binder as full replacement of Portland cement in CLSM mixtures by assessing its engineering properties. First, control mixtures were produced with Portland cement or cementless binder, Class F fly ash, ponded ash, and water. Then, for other mixtures, excavated soil substituted for ponded ash in amounts of 10, 20, 30, and 40% by weight. The bleeding, flowability, and initial setting time of fresh CLSM mixtures were measured; afterward, they were hardened and tested for compressive strength, water absorption, and corrosivity. It was found that the engineering properties of CLSM with excavated soil, possibly up to 30%, satisfied the specifications of ACI 229R. In particular, it was found that an increase in excavated soil content as replacement could lead to an improvement in the stability (bleeding rate) of the proposed CLSM mixtures. Finally, it is worth noting that cementless binder could be feasibly used to completely replace Portland cement in CLSM production.

Effect of cement powder based self-healing solid capsule on the quality of mortar

Oh, Sung-Rok,Choi, Yun Wang,Kim, Yong Jic Butterworth Scientific ; 2019 Construction and Building Materials Vol.214 No.-

<P> In this study, self-healing solid capsule (SHC) were prepared by using cement powder for crack self-healing of concrete structure. The plain mix was selected that considering the loss ratio of capsule and dispersibility. Mixing rate of solid capsule were 5, 10 and 15% based on cement mass. The mortar with solid capsule were investigated for the basic quality such as flow, air content, compressive strength, splitting tensile strength, elastic moduli and dry shrinkage. The focus of this paper is to evaluate the effect of solid capsule mixing on the quality of mortar instead of self-healing effects of solid capsule. Experimental results show that the flowability decreases and the air content increases as the mixing rate of SHC increase. And the compressive, splitting tensile strength and elastic moduli tended to decreases as the mixing rate of SHC increase. The effect of particle size show that the flowability increases and the air content decreases as the particle size of SHC becomes larger. And, the compressive, splitting tensile strength and elastic moduli tended to increases as the particle size of SHC becomes larger. </P>