Seung-Young So

Comparison of Deterministic Calculation and Fuzzy Arithmetic for Two Prediction Model Equations of Corrosion Initiation

abstract The existing deterministic solution for prediction model of corrosion initiation cannot reflect input variable uncertainties very well. Thus there is a growing tendency for a stochastic model based on the probabilistic method to be developed and applied. This paper presents an approach to the fuzzy arithmetic based modeling of the chloride-induced corrosion of reinforcement in concrete structures that takes into account the uncertainties in the physical models of chloride penetration into concrete and corrosion of steel reinforcement, as well as the uncertainties in the governing parameters, including concrete diffusivity, concrete cover depth, surface chloride concentration and critical chloride level for corrosion initiation. There are a lot of models for predicting the onset time of reinforcement corrosion of structures exposed to corrosion environment. In this work, the RILEM model formula and Cranks solution of Ficks second law of diffusion are used. The parameters of the models are regarded as fuzzy numbers with proper membership function adapted to statistical data of the governing parameters, while the fuzziness of the corrosion time is determined by the fuzzy arithmetic of the interval arithmetic and extension principle. An analysis is implemented by comparing the deterministic calculation with fuzzy arithmetic for the above two prediction models.

Properties of Strength and Pore Structure of Reactive Powder Concrete Exposed to High Temperature

This paper discusses the properties of strength and pore structure of reactive powder concrete (RPC) with various contents of cement, silica fume, and polypropylene (PP) fiber exposed to high temperatures. A series of fire tests were conducted on various RPC specimens with compressive strengths of 100 to 150 MPa (14,504 to 21,756 psi). The specimens were made with various contents of PP fiber and cement at various silica fume-cement ratios (SF/C) (0.25, 0.30, and 0.40). The explosive spalling and residual mechanical properties of RPC exposed to high temperature and the change of pore structure and hydrate products in the RPC specimens before and after the fire tests were investigated. It was confirmed that the addition of PP fiber was effective in preventing the explosive spalling of the RPC specimens in the fire tests, and that more than 2.0 kg/m³ (3.38 lb/yd³) was required, which was greater than the amount in high-performance concrete. The results also indicated that the RPC specimens were more susceptible to explosive spalling as the cement content and SF/C increased. Increased cement and silica fume contents led to the formation of denser microstructures, and thus the buildup of internal vapor pressure at an elevated temperature. The explosive spalling of the RPC specimens was closely related to the pore-volume proportion (capillary porosity) of 0.1 to 100 µm (0.395 to 395 × 10⁻⁵ in.) to total pore volume in the matrix; this relationship should therefore be studied further.

Hydration Reaction of Non-Sintering Cement Using Inorganic Industrial Waste as Activator

Greenhouse gas reduction will be highlighted as the most pending question in the cement industry in future because the production of Portland cement not only consumes limestone, clay, coal, and electricity, but also release waste gases such as , and NOX, which can contribute to the greenhouse effect and acid rain. To meet the increase of cement demand and simultaneously comply with the Kyoto Protocol, cement that gives less discharge should be urgently developed. This study aims to manufacture non-sintering cement(NSC) by adding phosphogypsum(PG) and waste lime(WL) to granulated blast furnace slag(GBFS) as sulfate and alkali activators. This study also Investigates the hydration reaction of NSC through analysis of scanning electron microscopy(SEM), X-ray diffraction(XRD), differential thermal analysis(DTA), and pH. Results obtained from analysis of the hydrate have shown that the glassy films of GBFS are destroyed by the activation of alkali and sulfate, ions eluted from the inside of GBFS react with PG and produce ettringite, and consequently the remaining component in GBFS slowly produced C-5-H(I) gel. Here, PG is considered not only to play the role of simple activator, but also to work as a binder reacting with GBFS.

Properties of Cement Mortar with Phosphogpysum under Steam Curing Condition

The purpose of this study is to utilize waste PG as an admixture for concrete products cured by steam. For the study, waste PG was classified into 4 forms (dehydrate, 𝛽-hemihydrate, III-anhydrite, and II-anhydrite), which were calcined at various temperatures. Also, various admixtures were prepared with PG, fly-ash (FA), and granulated blast-furnace slag (BFS). The basic properties of cement mortars containing these admixtures were analyzed and examined through X-ray diffraction, scanning electron microscopy, compressive strength, and acid corrosion resistance. According to the results, cement mortars made with III-anhydrite of waste PG and BFS exhibited strength similar to that of cement mortars made with II-anhydrite. Therefore, III-anhydrite PG calcined at lower temperature can be used as a steam curing admixture for concrete second production.

Analysis of Influence Factors for the Pozzolanic Activity and Material Characteristic of the Calcined Paper Sludge

The purpose of this study is to investigate the influencing factors for pozzolanic activity and material characteristics of calcined paper sludge. Calcined paper sludge (CPS) was produced by various parameters such as temperature and time of calcination, cooling methods, basicity and fineness, and its chemical and mineral characteristics were investigated using X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses. The pozzolanic activity of the CPS was also investigated by using an API (assessed pozzolanic activity index) test. From the results of XRD, new phases such as anorthite and gehlenite by crystallization of CAS appeared at CPS above 800 °C. These new phases have higher chemical and thermal stability than calcite or kaolinite. This may have a negative effect on the pozzolanic activity of CPS. The results of the API (%) test clearly showed that the pozzolanic activity of CPS was highest at a calcination temperature of 700 °C, a calcination time of 2 hours and the cooling method of water quenching.

Modeling of Carbon Mortar Color Expression Using Artificial Neural Network

Colored concrete uses pigments and white Portland cement (WPC) to perform decorative functions together with structural function. Pigments are used in permanent coloring of concrete with colors different from the natural color of the cement or the aggregates with mixing WPC. In this study, an artificial neural networks study was carried out to predict the color evaluation of black mortar using pigment and carbon black. A data set of a laboratory work, in which a total of 9 mortars were produced, was utilized in the Artificial Neural Networks (ANNs) study. The mortar mixture parameters were nine different pigment and carbon black ratios. Each mortar was measured at ten locations on the surface and averaged. Color can be evaluated by measurements of tristimulus values L* , a* and b* , represented in the chromatic space CIELAB. The L* value is a measure of luminosity (0 darkness), from completely opaque (0) to completely transparent (100); a* is a measure of redness (-a* greenness) and b* of yellowness (-b* blueness). ANN model is constructed, trained and tested using these data. The data used in the ANN model are arranged in a format of three input parameters that cover the pigment, carbon black and WPC and, an output parameter which is the color parameters of the black colored mortar. The results showed that ANN can be an alternative approach for the predicting the color parameters using mortar ingredients as input parameters.

The properties of cement-based mortar using grinding waste pottery powder and gypsum

The purpose of this work was searching of the formation of grain boundaries in metal-ceramics composites at various metal concentrations and sintering temperatures, influence of these boundaries on elastic moduli, coefficient absorption ultrasonic waves (USW) and thermo-conductivity to find the coupling of these properties and to estimate the optimal value of the metal concentration for achieve high quality of ready composites “corundum-stainless steel”. These boundaries are formed in the sintering process. In this work, cermets sintered in a high vacuum at different temperatures are investigated. Ðiermets (metal-ceramic composites) are modern construction materials used in different branches of industry. Their toughness and heat resistance are determined by their elastic and thermo-physical properties. In addition, these properties are significantly dependent on the grain boundaries in the material. The elastic moduli and absorption coefficient were measured by the ultrasonic method at room temperature; measurement of the thermal conductivity coefficient was carried out at temperature 200°C. In addition the samples structure was investigated by optical and scanning electron microscopy (SEM), cermets composition was determined by energydispersive X-ray spectroscopy method (EDS). We found two extremes for the concentration dependence of the elastic moduli (E and G) on the stainless steel concentrations, the nature of which is unknown. Similar dependence is observed also for the thermal conductivity coefficient and coefficient absorption ultrasonic waves. A discussion of the results is based on the structure cermet model as multiphase micro heterogeneous media with isotropic physical properties is also presented.R usage of 3D printing methods to fabricate all type of human organ has been considered. Among all of them, 3D printed scaffolds to be utilized as bone replacement implant have been investigated comprehensively. The advantage of this method is fabricating an implant with exact dimensions of the actual bone tissue. In addition, this method is faster than the conventional methods which surgeon used to apply to replace the injured or infected bone tissue. First of all, polycaprolactone with different concentrations of hydroxyapatite (0, 10%, 15% and 20%) were mixed completely. The HA/PCL composite was prepared with 40%, 50%, and 60% porosity. Then by using a spinneret, we transfer the HA/PCL composite to filament with a specific diameter (1.65-1.85 mm). We used these filaments to feed the 3D printer instrument. As a model, a femur bone of rabbit was used to design the scaffolds. The femur bone of rabbit was 3D scanned and transferred to Simplify 3D software to prepare the 3D printing pattern. The open source 3D printer printed the HA/PCL filament exactly similar to the rabbit bone. The mechanical properties of the 3D printed scaffold was determined and compared to femur rabbit bone. In terms of 3D printed scaffold characterization, the yield strength, stress-strain, force, stiffness, compressive modulus, and surface morphology of them have been studied.

Pozzolanicity of Calcined Sewage Sludge with Calcination and Fineness Conditions

This study discussed the pozzolanic properties of calcined sewage sludge (CSS) according to calcination and fineness conditions. The chemical and mineralogical analysis of CSS according to calcination temperature and time were carried out and compared with that of the existing pozzolanic materials such as fly-ash, blast furnance slag and meta-kaolin. Various mortars were made by mixing those CSS and Ca(OH)2 (1:1 wt. %), and their compressive strength and hydrates according to experimental factors such as fineness of CSS and curing age were also investigated in detail. The results show clearly the potentiality of calcined sewage sludge (CSS) as an admixture materials in concrete, but the CSS should be controlled by calcination temperature and time, and fineness etc. In this experimental condition, the calcination temperature of 800°C, calcination time of 2 hours and fineness of 5,000 cm 2 /g were optimum conditions in consideration of the mechanical properties and economic efficiency of CSS. The compressive strength of CSS mortars was higher than that of fly-ash mortars and blast furnace slag mortars, especially at the early ages. Then, the utilization of CSS in construction fields was greatly expected.

Antifungal Activity of Antifungal Mortars with Various Organic/Inorganic Antifungal Agents

This study discuss the antifungal performance of antifungal mortars with various organic and inorganic antifungal agent on the five kinds of mold: Chaetomium globosum, Aspergillus niger, Aureobasidium pullulans, Gliocladium virens and Penicillium pinophilum, which can be easily discovered in the interiors and exteriors of buildings. Various antifungal mortars using organic and inorganic antifungal agents were made in this study, and the antifungal performance, the durability of antifungal activity and chemical stability of them were investigated. As the results, the antifungal mortar with 10% Df-45 of organic antifungal agent exhibited the outstanding antifungal activity as well as the durability of antifungal activity. The antifungal mortars with inorganic antifungal agents presented overall the low antifungal activity and durability of antifungal activity, relatively.

Influence of Temperature on Chloride Ion Diffusion of Concrete

The long term integrity of concrete cask is very important for spent nuclear fuel dry storage system. However, there are serious concerns about early deterioration of concrete cask from creaking and corrosion of reinforcing steel by chloride ion because the cask is usually located in seaside, expecially by combined deterioration such as chloride ion and heat, carbonation. This study is to investigate the relation between temperature and chloride ion diffusion of concrete. Immersion tests using 3.5% NaCl solution that were controlled in four level of temperature, i.e. 20, 40, 65, and 90℃, were conducted for four months. The chloride ion diffusion coefficient of concrete was predicted based on the results of profiles of Cl- ion concentration with the depth direction of concrete specimens using the method of potentiometric titration by AgNO3. Test results indicate that the diffusion coefficient of chloride ion increases remarkably with increasing temperature, and there was a linear relation between the natural logarithm values of the diffusion coefficients and the reciprocal of the temperature from the Arrhenius plots. Activation energy of concrete in this study was about 46.6 (W/C = 40%), 41.7 (W/C = 50%), 30.7 (W/C = 60%) kJ/mol under a temperature of up to 90℃, and concrete with lower water-cement ratio has a tendency towards having higher temperature dependency.