In this study, the characteristics of grout mixed with charcoal as an expansive agent were examined to reduce the pre-hardening shrinkage of cementitious materials. This study compared and reviewed the application of CSA, a conventional expansive agent, to grout. The setting time, fluidity, compressive strength, and pre-hardening shrinkage/expansion were evaluated to explore the usability of charcoal as an expansive agent. The test results confirmed that, as the incorporation rate of charcoal increased, the pre-hardening expansion rate of the grout also increased, making it more effective for pre-hardening expansion than the conventional expansive agent CSA. However, when charcoal was used as an expansive agent, the compressive strength decreased after hardening, indicating the need for caution regarding the amount of charcoal used. Furthermore, the pre-hardening shrinkage and expansion rates of the various types of charcoal used in this study showed some differences, suggesting the need for further research on the internal pore volume and pore size of the charcoal.

Incineration bottom ash is generated by the incineration of solid waste. Household solid waste is increasing every year and so is incineration bottom ash. This is a problem to treat the incineration bottom ash because the ash has many toxic components. Cement composites can solve this problem and there are many studies for using the bottom ash as fine aggregate. To evaluate the usage of incineration bottom ash, compressive strength, mercury intrusion porosimetry, scanning electron microscopy-backscatter electron, X-ray diffraction, and toxicity characteristic leaching processes were performed. When using incineration bottom ash up to 20% of substitution, the compressive strength in all cases was increased. This study showed how the filler effect appeared well in the cement composites through the scanning electron microscopy-backscatter electron, and mercury intrusion porosimetry. X-ray diffraction indicated the possibility of an alkali-silica reaction of the aggregate with the components of incineration bottom ash. This problem is an obstacle to applying the incineration bottom ash as a fine aggregate. In addition, the toxicity characteristic leaching process was shown to be under the threshold of the Korean standard, however, this should nuanced by the consideration of amorphity. Comprehensively, incineration bottom ash could be used as a fine aggregate of up to 20% of substitution. However, the pre-treatment would need to eliminate or reduce alkali reactive components and heavy metals.

This experimental study investigated the durability degradation of concrete exposed to freezing and thawing and chloride intrusion. In order to observe the degree of the degradation, 24 MPa, 35 MPa and 60 MPa concretes were used with 4% and 12% calcium chloride solution as freezing water for scaling resistance and freeze - thaw resistance tests. The results show that 24 MPa and 35 MPa concrete had a relatively large decrease in durability due to the freeze-thaw resistance and scaling resistance, but the 60 MPa concrete was not deteriorated significantly. In addition, when the concentration of the solution of calcium chloride was 4%, the degradation of durability was most remarkable. The results of this study suggest when concrete structures such as bridges or roads expose to the environmental conditions, appropriate measures such as increasing the designed standard strength of concrete need to be deliberated and additional studies should be conducted.

The anti-corrosion performance of coating systems (cathode protection, organic coating, and duplex coating) applied to prevent the corrosion of offshore wind power plants was assessed. As an assessment method, the adhesion strength of each coating system was evaluated after exposing the coatings to the marine environment and an indoor salt spray test. It was confirmed that the adhesion strength varied depending on the exposure period, and the deterioration of adhesion strength was related to the fracture type of each coating layer. In addition, the fracture type of each coating system was analyzed and the adhesion strength was corrected according to the fracture type. The corrosion rates after exposure to the marine environment and indoor salt spray were compared and examined using the corrected values.

Temperature is an important factor that affects corrosion potential in rebars. The temperature effect must be removed from the corrosion potential for precise measurement of corrosion rates. To separate the temperature effect from the corrosion potential, in this study rebar specimens were not embedded in concrete but, instead, were placed in an uncontrolled air environment. Gaussian process regression (GPR) was applied to the temperature and the non-corrosion potential data in order to remove the temperature effect from the corrosion potential. The results indicated that the corrosion potential was affected by the temperature. Furthermore, the GPR models of all the experimental cases showed high coefficients of determination (R2 > 0.90) and low root mean square errors (RMSE < 0.08), meaning that these models had high reliability. The fitted GPR models were used to successfully remove the temperature effect from the corrosion potential. This demonstrates that the GPR method can be appropriately used to assess the temperature effect on rebar corrosion.

Increasing use of cement in the construction industry is causing an alarming increase in carbon dioxide (CO2) emissions, which is a serious environmental threat, it can be reduced by the addition of supplementary cementitious materials (SCMs). The commonly used SCMs like ground granulated blast furnace slag (GGBS), metakaolin (MK) and fly ash (FA) have been successfully used to replace the cement partially or completely. Polysilicon sludge obtained from the photovoltaic industry is also a type of waste material that can be used as SCM because it has high content of reactive SiO2. This study investigates the effects of replacing cement with polysilicon sludge in concrete. Different concrete specimens were made by replacing varying proportions of cement with polysilicon sludge and their properties, such as, fresh properties, compressive strength, heat release, chloride penetration, freeze/thaw resistance and microstructural investigations were determined. The results demonstrate that the polysilicon sludge can be used effectively to replace cement, and environmental threats associated with its disposal can be reduced.

In this study, heteropoly acid PVMo catalysts were supported on activated carbon with various composition of phosphoric acid (H3PO4), vanadium (V) pentoxide (V2O5) and molybdenum (VI) trioxide (MoO3). Catalytic performance was examined at 140 degrees C for 1hour in vapor formaldehyde. XRD and BET analyses were carried with the catalysts before and after the reaction. Formaldehyde conversion was increased with decreasing Mo and H3PO4 content and increasing V2O5 content. Acidity of the catalysts was investigated with NH3-TPD. Crystallinity of the catalysts was relatively low, and surface area was decreased after the reaction. In NH3-TPD result, the ratio of strong acid site corresponding to NH3 desorption between 400 degrees C and 500 degrees C was increased by decreasing MoO3 and H3PO4 content and increasing V2O5 content. Therefore, it was found that the strong acid site could affect the catalytic reactivity in vapor formaldehyde conversion.

The depletion of natural sand and production of the huge amount of cement in the construction industry are serious threats to the environment, which can be reduced by the utilization of by-products as cement replacement material. In this study, cement was replaced with fly ash up to 45% (by weight). In addition, the natural fine aggregate was replaced with air-cooled blast furnace slag aggregate (here referred to as slag aggregate) at a level of 50% and 100% (by weight). Polypropylene fiber was also added, at a dosage of 0.25% of binder weight. Mortar specimens were prepared and analyzed using tests for compressive, flexure, and splitting tensile strength, as well as for microhardness, and ultrasonic pulse velocity. In addition, the specimens were exposed to sulfate solution and investigated for changes in length, mass, and compressive strength. Electron microscopy and X-ray diffraction analysis were performed to examine the microstructure and phase changes of mortar specimens exposed to sulfate solution. The results indicate that mortar specimens made with 50% slag aggregate and 0.25 % fiber showed enhanced mechanical properties. The performance of slag aggregate mortars under sulfate attack was improved significantly.

Globally, concrete is the most widely used construction material. The composition of concrete plays an important role in controlling its overall performance. Concrete is composed of approximately 70%–80% aggregates, by volume. Therefore, it is mandatory to investigate the effect of aggregates on the performance of concrete. For this purpose, this study investigated the effect of three different coarse aggregates on the mechanical properties, durability, and microstructure of concrete. Concrete specimens were made using aggregates obtained from three regions with different mineralogies. The specimens were also made by replacing cement with silica fume. The specimens were analyzed in terms of compressive, flexural, and splitting tensile strengths, chloride penetration, carbonation, mercury intrusion porosimetry, and scanning electron microscopy. The results demonstrate that the specimens made with rougher coarse aggregates and silica fume had enhanced performance in comparison to those made with smoother aggregates.

We prepared activated charcoal-supported Co-Mo carbide catalysts to investigate the effects of solution pH and initial Co/Mo molar ratio. In the absence of Co, no Mo adsorption was observed at pH above the pH(zpc) of AC, whereas the introduction of Co at pH > 6 resulted in the co-precipitation of Mo and Co and facilitated Mo adsorption. CO conversions for CO methanation at 400 degrees C and 30 bar achieved over samples prepared at pH 3 were initially high but decreased with increasing reaction time, whereas CO conversions were maintained at >90% with increasing reaction time for samples prepared at pH > 6. XPS analysis of these high-performance catalysts revealed that the predominant state of surface Mo was Mo-0 rather than Mo4+ and Mo6+. Catalysts with maximum methanation activity, i.e., those with the highest surface Mo-0 content, were obtained at pH 7 and an initial Co/Mo molar ratio of 1.0. (C) 2019 Elsevier Ltd. All rights reserved.

Unsupported MoS2 catalysts were prepared for the methanation reaction by varying the pressure and temperature in the hydrothermal reaction by using ammonium tetrathiomolybdate (ATTM). The physical and chemical characteristics of the catalysts were analyzed by using XRD, SEM, TEM, BET, XPS, H2-TPR, and CO-TPD techniques. The catalyst particles were formed in the bent fringe shape by stacking the (0 0 2) planes, and consisted mostly of MoS2, with some Mo2S5 and MoS3. It was found that the BET surface and active sites such as surface Mo4+ and sulfur vacancies increased with increasing preparation pressure, which could contribute to the improvement of MoS2 catalytic activity. The increase in preparation temperature not only favored the decomposition of ATTM into MoS2, but also lowered the number of active sites accessible for the reaction. Thus, it was suggested that the preparation temperature should be controlled at 350 °C to improve the catalytic activity.

This study is an experimental study on the corrosion protection performance according to the configuration ratio of the Zn and Al. A metal spraying was used as the arc metal spraying method, a specimen was produced by varying the proportion ratio and coating thickness of the Zn and Al. Experimental methods visually observed to corrosion of the specimen for 1, 3, 7, 15 days was conducted in accordance with the CASS salt spray test. This study has confirmed that the performance of the corrosion protection improved against the increase in the Al content. Further, it was confirmed that excellent perfomance is exhibited when the coating thickness is secured over 80 µ m. In addition, the SEM analysis was performed to observe the cross-sectional shape of the metal spraying specimen after CASS testing. The analysis result showed that the deterioration of the metal spraying coating layer was reduced as the Al content increases.

Both polymerization modification and the use of functional additives for controlling air entrainment inside a polymer were examined for improving their performance in cement matrices. Functional additives were added to acrylic redispersible polymer powders at a glass-transition temperature of -11 degrees C, and the polymerization method was modified. The physical properties of cement mortars produced with these polymers were evaluated. The performance improved and the average polymer-particle size decreased when using the modified emulsion polymerization method, while the air content in the polymer cement mortars decreased with the use of defoamer as a functional additive. Moreover, better compressive, flexural, and adhesion strengths were achieved, and the use of polymers with improved performance resulted in enhanced waterproofing. Scanning electron microscopy and energy-dispersive spectroscopy confirmed the formation of carbon-based polymer films around the pores and cracks inside the cement mortars.

This study experimentally investigated the properties of bottom ash in cement specimens. The performances of hardened cement test specimens, prepared with unground or finely ground bottom ash, fly ash, or ordinary Portland cement, were compared. The fineness of bottom ash increased with grinding time. Testing in mortar mixes revealed that the compressive strengths of both wet and dry finely ground bottom ash increased with increasing fineness. The microstructural density of bottom ash increased and the porosity decreased as the grinding fineness increased. Finely ground bottom ash showed strong pozzolanic activity, demonstrating its applicability as a cement replacement.

본 연구는 화력발전소에서 배출되는 석탄회 중 바텀애시의 재활용에 대한 실험적 연구이다. 석탄회는 일반적으로 플라이애시, 바텀애시, 신더애시 등으로 구분된다. 이 중 플라이애시의 경우 콘크리트 재료 중 시멘트 대체재로 많은 양이 재활용되고 있다. 반면, 바텀애시의 경우 다공성 및 높은 흡수율 등의 특징에 의해 석탄회 중 재활용률이 가장 낮은 실정이다. 이에 본 연구에서는 바텀애시를 콘크리트의 잔골재로 0~30%까지 단계별로 치환하여 제조한 콘크리트에 대한 내구성능을 평가하였다. 바텀애시 잔골재를 사용한 콘크리트의 내구성능 평가 결과, 동결융해의 경우 바텀애시 혼입 유무와 관계없이 적정한 연행공기를 통해 저항성을 확보할 수 있었고 염소이온침투 저항성, 건조수축 및 중금속에 대한 영향을 검토한 결과 바텀애시 혼입량 증가에 따른 영향은 크지 않은 것으로 나타났다. 반면, 탄산화 촉진 실험결과 바텀애시 사용이 증가함에 따라 탄산화 침투가 다소 컸으나 적절한 배합설계를 통해서 바텀애시를 콘크리트 잔골재로 활용하는 것이 가능할 것으로 판단된다. This study is about the reuse of bottom ash, which is released as a necessity in thermal power plant. In general, coal-ash are classified as fly-ash, bottom-ash, cinder-ash. Of these, a large amount of fly ash is being recycled as cement substitutes. While, recycling rates of bottom ash are the lowest due to its porosity and high absorption. In this study, the durability of the concrete using bottom ash as a concrete fine aggregate was evaluated. The using level of the bottom ash ranges to step-by-step from 0% to 30%. According to the result of the durability test, regardless of the presence of the bottom ash, freeze-thaw durability could be secured by air entrainment. In case of the resistance to chloride ions penetration, the length change, and the effects on heavy metals, the replacement of bottom ash as fine aggregate was not critical. Although carbonation penetration was higher as the replacement level of bottom ash increased, the experiment showed that it could be possible to use bottom ash as concrete fine aggregate with proper mix design.

해양환경 및 공장지역과 같이 가혹한 부식환경에 놓인 강구조물은 사용수명을 증대시키기 위하여 다양한 방식 기술을 적용하여 건설되고 있다. 그 중 금속용사에 의한 방식기술은 일반적으로 널리 쓰이는 기술의 단점을 보완한 방식 기술이지만 완벽하다 할 수 없어 내식성 향상에 대한 연구개발이 절실한 상황이다. 본 연구에서는 금속용사에서 사용되는 금속 재료의 종류 및 용사 두께의 변화에 따른 내식성을 평가하였으며 전기화학적 방법인 부식전위 및 부식전류밀도 측정을 통하여 비교 고찰하였다. 금속용사 재료로는 아연(Zn) 및 알루미늄(Al)을 사용하여 비율을 조절하였고, 용사 두께는 $30{\sim}100{\mu}m$ 사이에서 구분하여 선정하였다. 검토 결과, 금속용사 재료로 Zn을 100% 사용한 경우에서 가장 낮은 부식전위가 측정된 것을 확인하였으며, Zn 85%-Al 15% 합금과 Al 100%의 경우에는 부식전류밀도가 감소하였다. 또한 용사재료에 관계없이 용사두께가 증가할수록 부식전위는 감소하였다. Steel structures exposed to extremely corrosive environment like marine environments and industrial area are generally manufactured by applying various protection treatment to increase their lifetime. Metal spraying is one of the protection methods to overcome some drawbacks of the widely employed technologies. Therefore, lots of research needs to be done to improve the corrosion resistance of steel structures. In this study, the corrosion resistance of steel structures was evaluated with the variation in the type and thickness of metal spray by measuring the corrosion potential and current density. As a raw material for spraying, Zn, Al and their mixture were employed to obtain coating thickness of $30{\sim}100{\mu}m$. Our data indicated that the pure zinc coating with $100{\mu}m$ showed the lowest corrosion potential. In the case of pure Al and Zn 85%-Al 15%, the corrosion potential and current density was decreased compared to pure zinc. It was found that the corrosion potential was decreased with the increase of coating thickness irrespective of the type of the coating.

With the purpose of investigating the influence of both fineness levels and replacement ratios of limestone filler on sodium sulfate attack, cement mortar and paste specimens incorporating the material were exposed to 5% sodium sulfate solution for 1 year. The resistance of mortar specimens to sulfate attack was evaluated by visual appearance, expansion and compressive strength measurements. Additionally, microstructural observations such as XRD and SEM/EDS were also performed on paste samples stored in similar conditions of sulfate attack. Experimental results demonstrated that the worst performance was noted in the mortar specimens with high replacement ratio as well as high fineness level of limestone filler, showing extensive surface damages in addition to significant expansion and strength loss. Thus, it was observed that both high replacement ratio and high fineness level have potentially a negative effect in resisting sodium sulfate attack. This phenomenon is likely attributed to thaumasite formation as a result of sulfate attack rather than gypsum formation. The present study may suggest useful information on both reasonable replacement ratio and fineness level for the application of limestone filler in sulfate environments.

In order to improve NOx storage and reduction (NSR) kinetics over Pt/Co/Ba/Al2O3 catalyst in the presence of SO2, Fe was added as a promoter to inhibit sulfation. A NOx analyzer was used to measure the NOx concentration of the gas phase and in-situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was dedicated to analyze the interaction between the adsorbed reactive species from the gas phase and solid catalyst surface. NSR results showed that the addition of Fe to Pt/Co/BaO/Al2O3 increased the NOx uptake. The presence of Fe inside catalyst contributed to enhancing the ability of resistance to SO2 exposure. In situ DRIFT study confirmed that Fe played a role as an active inhibitor to sulfation based on the decreased intensity of band at 1120cm−1. An isothermal temperature reduction (ITR) experiment at 300°C showed that Fe would work to improve the reduction ability of stored NOx in the lean cycle and catalyst regeneration during the rich cycle.