• KCI Concrete Journal
• /
• v.13 no.1
• /
• pp.3-9
• /
• 2001

This research concerns the effect of kaolin as material of cement admixture. which has the advantage of low price and high adaptability. Kaolin, a kind of soil, is well known as a raw material of pottery. which is widely scat-tered on the earth (especially in Korea). This research shows the method and process for activating kaolin to have the properties of a cement admixture through experiment. In the experiments, kaolin is baked in high temperature and then cooled suddenly to be activated. The temperature zone and time span, on which kaolin is activated are examined. The research looks over the effect of the activated kaolin based on several criteria regarding to chemical and physical characteristic of general admixtures. The results of this research are as follows; kaolin start activation at the temperature above 50$0^{\circ}C$ and make ends of activation at the temperature below 95$0^{\circ}C$ and there was little effect by the change of duration. It is concluded that compressive strength can be increased by putting activated kaolin in the concrete and the activated kaolin is good for water resistance and anti-chemical , and that it is effective for protecting the leakage of hazardous article like Cl- and for protecting damage by an organic salt like acid. The activated kaolin of proper temperature and time is effective in compressive strength, salt resistance and acid resistance. The adaptability of activated kaolin as a cement admixture was shown through this research.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.10
• /
• pp.821-827
• /
• 2003

Reduced-scale experimental study was carried out on the heat flow behavior which flows under the sloped ceiling in underground fire. Temperature and flow velocity were measured to characterize the ceiling jet along the sloped stairway ceiling. The methanol fuel was used as a model fire source giving 2.2 and 3.4 kW, with changing the slope angle of stairway adopting of 15, 25, 35, and 45 deg. Based on the experimental data, excess temperature and velocity along the sloped stairway ceiling were examined which are usefully applicable to estimate the activating conditions of heat detector and sprinkler head mounted on the sloped ceiling. Excess temperature in upper exit of the sloped stairway was also examined to analyze the soffit which delays the smoke diffusion. The result shows that the activating conditions of heat detector and sprinkler in the sloped stairway ceiling have to be considered differently in a point of about 30 deg.

• Resources Recycling
• /
• v.12 no.3
• /
• pp.13-24
• /
• 2003

The production characteristics of activated carbon from waste walnut shell have been investigated by taking activation temperature, activation time, amount of activating agent, and kind of activating agent as the major influential factors. The adsorption capacity of the activated carbon which was produced using phosphoric acid as the activating agent increased with activation temperature and showed its greatest value at about $550^{\circ}C$. Yield for activated carbon was observed to decrease continuously as the activation temperature was raised. The optimal activation time for the highest adsorption capacity was found to be about 2 hr, and as the activation time increased the yield for activated carbon was showed to decrease continuously. The increase in the amount of activating agent resulted in the increase of the yield for activated carbon, however, excessive amount of activating agent deteriorated its adsorption capacity reversely. The variations of the microstructure of activated carbon observed by SEM with several influential factors, correlated very well with its changes in the adsorbability with the same factors and the kind of activating agent was found to play an important role in the determination of the adsorption capacity of activated carbon. To investigate the adsorption characteristics of the produced activated carbon, the adsorption reactions of $Cu^{2+}$ ion were examined using the produced activated carbon as the adsorbent. In general, the kinetics of the adsorption of $Cu^{2+}$ ion was observed to follow a 2nd-order reaction and the rate constant for adsorption reaction increased as the initial concentration of adsorbate was diminished. The equilibrium adsorption of $Cu^{2+}$ was explained well with Freundlich model and its adsorption reaction was found to be endothermic. The activation energy for adsorption was calculated to be 13.07 kcal/mol, which implied that the adsorption reaction was very irreversible, and several thermodynamic parameters of adsorption reaction were estimated using van't. Hoff equation and thermodynamic relationships.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.76-81
• /
• 2002

The dramatic increase in the depth of a weld bead penetration has been demonstrated by welding a stainless steel in GTA (Gas-Tungsten-Arc) process with activating flux which consists of oxides and halides. However, there is no commonly agreed mechanism fer the effect of flux on the process. In order to make clear the mechanism, each behavior of the arc md the weld pool in GTA process with activating flux is observed in comparison with a conventional GTA process. A constricted anode root is shown in GTA process with the activating flux, whereas a diffuse anode root is shown in the conventional process. These anode roots are related strongly to metal vapor from the weld pool and the metal vapor is also related to temperature distributions on the weld pool surface. Furthermore, it is suggested that a balance between the Marangoni force and the drag force of the cathode jet should dominate the direction of re-circulatory flow in the weld pool. The electromagnetic force encourages the inward re-circulatory flow due to the constricted anode root in the case with flux. The difference in flow direction in the weld pool changes the geometry or depth/width ratio of weld bead penetration.

• Resources Recycling
• /
• v.15 no.2 s.70
• /
• pp.50-57
• /
• 2006

Production of activated carbon from woody fish parking cases has been studied using waste sulfuric acid as an activating agent for the purpose or promoted recycling of woody fishing port wastes. The adsorption capacity of produced activated carbon was observed to increase with activation temperature and reached its maximum at ca. $650^{\circ}C$ under the experimental conditions. However, the adsorption capacity of activated carbon became deteriorated above this temperature due to the thermal degeneration of its structure. Optimal activation time was found to be about 120 minutes and 1:3 weight ratio of raw material and activating agent was appropriate for increased adsorption capacity of activated carbon under the conditions of $550^{\circ}C$ and 60 minutes of activation time. Regarding the effect of the concentration of activating agent on activation, ca. 1.2 M of sulfuric acid was observed to be proper for an optimal activation or raw material. Comparison of the activation power of sulfuric acid with nitric acid showed that sulfuric acid was superior to nitric acid, however, with regard to the yield of activated carbon there was no significant difference between the two activating agents. The degree of dispersion of carbon particles was shown to be relatively high in neutral condition and the produced activated carbon was considered to be effectively employed for the treatment of metal ions in wastewater due to its negative surface charge in aqueous condition.

• Journal of Forest and Environmental Science
• /
• v.23 no.1
• /
• pp.51-55
• /
• 2007

The effect of ratio between chemical activating agent and raw material in the preparation of activated carbons from wood has been studied. Pinus koraiensis wood and zinc chloride ($ZnCl_2$) were used for materials in this study. Mixtures of wood and zinc chloride were heated under nitrogen flow in the temperature ranging from room-temperature to $600^{\circ}C$ for 1 hr using thermogravimetric technique. During heat treatment, activated carbons with various pore size and specific surface properties were obtained. The maximum BET surface area and total pore volume were $1468m^2/g$ and 1.74 cc/g, respectively, at the mixture ratio of 1 (wood powder) to 5 ($ZnCl_2$). It can be concluded that the differences in the properties of the activated carbons were related significantly with the ratio of chemical activating regent.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.2
• /
• pp.121-132
• /
• 1997

The thermal behavior of' concrete can be ch;lracterized from a knowledge of concrete ternperatu1.e at early ages, environmental conditions, and cement hydration in the mixture. 'l'o account for thost. interactions, a computer model was developed for prwlicting the temperature pr.ol'ile in hnrdcning c o n c r c t ~ st.r~icture in terms of material and tmvironmcntal factors. The cerncnt hydration cha~.acteristics such as the activating energy, total heat 1ihei.atr.d. anti th\ulcorner degree of' hydration. can represent the internal heat gc,neration. In this study. th(> activating c1ncrgy and the tlcgree of' hydration curve were determined well fmm the rnortn~. compressive strength tests while total amount of heat liberated was determined by tht> isothermal calorimctcr method. The main purpose of' this study is to correlate measured tt>mperaturr distributions in a concrete st1,ucture during thc hardening process with the ~ c s u l t s computed f'ro~n theoretical considrl.ations. Using twodimensional heat transfer model, first. the importance of several parameters will be identified by a parametric analysis. Then, the tcmpcmture distribution of thc cylindrical concrete specimen in the laboratory was mensuwti and compared with that yielded by thc theoretical considel.ations.

• International Journal of Highway Engineering
• /
• v.15 no.2
• /
• pp.95-103
• /
• 2013

PURPOSES : To investigate the fundamental characteristics of blast-furnace slag mortar that was hardened with activating chemicals to capture and sequester carbon dioxide. METHODS : Various mix proportions were considered to find an appropriate stregnth development in regards with various dosages of activating chemicals, calcium hydroxides and sodium silicates, and curing conditions, air-dried, wet and underwater conditions. Flow characteristics was investigated and setting time of the mortar was measured. At different ages of 3, 7 and 28days, strength development was investigated for all the mix variables. At each age, samples were analyzed with XRD. RESULTS : The measured flow values showed the mortar lost its flowability as the activating chemicals amount increased in the scale of mole concentration. The setting time of the mortar was relatively shorter than OPC mortar but the initial curing condition was important, such as temperature. The amount of activating chemicals was found not to be critical in the sense of setting time. The strength increased with the increased amount of chemicals. The XRD analysis results showed that portlandite peaks reduced and clacite increased as the age increased. This may mean the $Ca(OH)_2$ keeps absorbing $CO_2$ in the air during curing period. CONCLUSIONS : The carbon capturing and sequestering activated blast-furnace slag mortar showed successful strength gain to be used for road system materials and its carbon absorbing property was verified though XRD analysis.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.10a
• /
• pp.143-150
• /
• 1997

The maturity concept was adopted to predict the strength of concrete, which was subjected to same temperature conditions and variable curing conditions. Penetration test and compressive test were conducted to measure the initial and final setting time and the compressible strength of concrete specimen, respectively. Also, the temperature and time were recorded at some intervals of time for calculating the maturity. The initial and final setting were delayed as the w/c ratio increased and curing temperature decreased. The activating energy decreased as the w/c ratio increased. The relationships at the relative strength and the maturity were proposed at different w/c ratio for the same temperature curing condition, and these were applied for the variable curing conditions. The results indicated that the difference between the strength of the proposed and the specimen was big at 1 days's age but quite similar after 3 day's age.

• Carbon letters
• /
• v.4 no.3
• /
• pp.126-132
• /
• 2003

Granular Activated Carbon (GAC) has been proven to be an excellent material for many industrial applications. A systematic study has been carried out of the kinetics of physical as well as chemical activation of phenolic resin chars. Physical activation was carried out using $CO_2$ and chemical activation using KOH as activating agent. There are number of factors which influence the rate of activation. The activation temperature and residence time at HTT varied in the range $550{\sim}1000^{\circ}C$ and $\frac{1}{2}{\sim}8$ hrs respectively. Kinetic studies show that the rate of chemical activation is 10 times faster than physical activation even at much lower temperature. Above study show that the chemical activation process is suitable to prepare granular activated carbon with very high surface area i.e.$ 2895\;m^2/g$ in short duration of time i.e. 1 to 2 hrs at lower temperature i.e. $750^{\circ}C$ from phenolic resins.