• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.10a
• /
• pp.131-136
• /
• 1999

In this study, novel activated silicate grout solution for injection grouting was prepared by the reaction of ordinary waterglass with alkaline earth metal salts mixture by means of the high-speed stirring method with strong shearing force, and its chemical and physical properties were investigated. The variation of its gelation time plotted with the amount of dilution water showed that this novel silicate had better gelation characteristics in comparison with ordinary waterglass. And some other engineering characteristics of this grout such as durability and mechanical properties were investigated experimentally. The whole experimental results established that this novel silicate grout was a good alternative with an existing ordinary waterglass grouting method.

• Journal of the Korean Ceramic Society
• /
• v.31 no.5
• /
• pp.538-542
• /
• 1994

The kinetics and mechanism on the hydration of granulated blastfurnace slag-sodium silicate systems were studied by ignition loss, unreacted slag determination, XRD, DTA and SEM(EDS). From this experiment the following results were obtained. The amount of slag reaction was increased with the content of sodium silicate and also C-S-H, C4AH13, and C2ASH8 were formed to be the main products up to 28 days of hydration. Sodium silicate was not only an activator for slag hydration but also a binder in the hydration. The amount of slag reaction activated by sodium silicate was a nearly same for Ca(OH)2 activated slag, but it was smaller one than that activated by NaOH. However there was no difference in hydration products.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.627-630
• /
• 2005

This paper examines degradation properties of alkali-activated alumino-silicate composite body by NAS solution exposed to high temperature. Activators include sodium hydroxides and sodium silicate solution. In the result of experiment, flexural and compressive strength of AAS base mortar exposed to high temperature ($400\~600^{\circ}C$) was higher than alumina cement base mortar. Particularly, In case of compressive strength, alumina cement base mortar was decreased by about $60\~70\%$. While, AAS base mortar exposed to high temperature ($400\~600^{\circ}C$) was higher than that curing by room temperature. The above results showed that AAS base inorganic binder has a good mechanical properties exposed to high temperature($400\~600$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.11
• /
• pp.1020-1024
• /
• 2006

Europium$(Eu^{2+}\;or\;Eu^{3+})$-activated calcium aluminium silicate phosphors were synthesized for the first time and the structures and luminescence characteristics of these phosphors were investigated. The phosphors in this study emitted blue, green, and even red light depending on the starting milterials and annealing conditions for synthesis. In addition, the structure was also changed when the different starting materials were used. When $CaCO_3$ was used as a starting material, tetragonal $Ca_2Al_2SiO_7$ was formed. However, pure green light was emitted when the annealing was conducted in reduced atmosphere and red one was emitted by annealing in air. In the case of $CaSiO_3$ as a starting material, triclinic $CaAl_2Si_2O_8$ was formed and only pure blue emission was observed. Moreover, this blue phosphor exhibited higher intensity than that of commercial YAG:Ce phosphor, which showed the possibility of application on the phosphor for new light source such as a UV-LED.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.32-35
• /
• 2006

For the white UV-LED applications, $Eu^{2+}$-activated calcium aluminium silicate phosphors were synthesized for the first time and the structures and luminescence characteristics of these phosphors were investigated. The phosphors in this study emitted blue. green or blue-green light depending on the starting materials for synthesis. In addition, the structure was also changed when the different starting materials were used. When CaO and $CaCO_3$ was used as a starting material. tetragonal $Ca_2Al_2SiO_7$ was formed and blue-green and pure green light was emitted. respectively. However. in the case of $CaSiO_3$, triclinic $CaAl_2Si2O_8$ was formed and only pure blue emission was detected. The maximum emission intensity was obtained from $CaAl_2Si_2O_8:Eu^{2+}$ phosphors, which intensity was about 1.4 times higher than that of YAG:$Ce^{3+}$ phosphor used for blue LED.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.12 no.4
• /
• pp.59-66
• /
• 2012

This study is interested in identifying the effectiveness of alkali-activated fire protection material compounds including the alkali-activator such as potassium hydroxide, sodium silicate and fly ash as the fire resistant finishing materials. Also, this paper is concerned with change in compressive strength and pore structure of the alkali-activated fire protection material at high temperatures. The testing methods of fire protection materials in high temperature properties are make use of TG-DSC and mercury intrusion porosimetry measurements. This study results show that compressive strength is rapidly degraded depending on a rise of heating temperature. Porosity showed a tendency to increase irrespective of specimen types. This is due to both the outbreak of collapse of gel comprising the cement and a micro crack by heating. However, alkali-activated fire protection material composed of potassium hydroxide, sodium silicate and fly ash has the thermal stability of the slight decrease of compressive strength and porosity at high temperature. These thermal stability is caused by the ceramic binding capacity induced by alkali activation reaction by the reason of the thermal analysis result not showing the decomposition of calcium hydrate.

• Journal of the Korea Concrete Institute
• /
• v.24 no.6
• /
• pp.745-752
• /
• 2012

This paper studies the effect of the compressive strength for combined alkali-activated slag mortars. The effect of activators such as alkali type and dosage factor on the strength was investigated. The alkalis combinations made using five caustic alkalis (sodium hydroxide (NaOH, A series), calcium hydroxide ($Ca(OH)_2$, B series), magnesium hydroxide ($Mg(OH)_2$, C series), aluminum hydroxide ($Al(OH)_3$, D series), and potassium hydroxide (KOH, E series)) with sodium carbonate ($Na_2CO_3$) were evaluated. The mixtures were combined in different dosage at 1M, 2M, and 3M. The study results showed that the compressive strength of combined alkali-activated slag mortars tended to increase with increasing sodium carbonate. The strength of combined alkali-activated slag mortars was better than that of control cases (without sodium carbonate). The result from scanning electron microscopy (SEM) analysis confirmed that there were reaction products of calcium silicate hydrate (C-S-H) and alumina-silicate gels from combined alkali-activated slag specimens.

• Journal of the Korean Chemical Society
• /
• v.48 no.3
• /
• pp.273-282
• /
• 2004

The synthetic technology of improved polyaluminiumchloride (IPAC) similar to characteristics of PACS was established with minimum expense for modifying existing production line. The conditions for activating silicate was studied before the synthesis of IPAC, and the IPAC was synthesised with raw materials such as aluminumhydroxide and concentrated hydrochloric acid, followed by adding activated silicate and alginate. The specification of product, chemical structure, and coagulating properties were tested by using specification testing method, instrumental analytical method, and Jar tester, respectively. As a result, the product, IPAC, contained aluminium oxide content more than 17%, and no precipitation was shown at all while the IPAC solution was preserved, and the larger floc and faster coagulation were represented compared to existing PAC under the same conditions. It was suggested that these synthetic technology could be applied to the existing production line for producing PAC without approximately cost raising factor because of adding sulfuric acid-activated silicate instead of sodium sulfate.

• Applied Chemistry for Engineering
• /
• v.19 no.4
• /
• pp.445-451
• /
• 2008

In order to regenerate the activated carbon polluted by volatile organic compounds (VOCs) using microwave, adsorption and desorption characteristics of benzene over activated carbon (AC) coated with insulating materials were investigated. Physical characteristics of activated carbon and insulator-coated ACs were investigated by means of $N_2$ gas adsorption and scanning electron microscopy (SEM). The amount of VOC adsorbed showed a positive relationship with the specific surface area of the ACs, and spark discharge over insulator-coated ACs did not occur. Potassium silicate (PS) was the best binder for coating of insulating materials on AC. Amount of benzene desorbed by microwave irradiation was dependent on output power of microwave. Nearly same performance was obtained even though the adsorption-desorption operation under microwave irradiation was repeated 5 times. Finally, it was known that the microwave heating was a very effective mean for regenerating the polluted AC.

• Computers and Concrete
• /
• v.17 no.4
• /
• pp.523-539
• /
• 2016

Alkali-activated binder (AAB) is increasingly being considered as an eco-friendly and sustainable alternative to portland cement (PC). The present study evaluates 30 different AAB mixtures containing fly ash and/or slag activated by sodium hydroxide and sodium silicate by correlating their properties from micro to specimen level using regression. A model is developed to predict compressive strength of AAB as a function of volume fractions of microstructural phases (physicochemical properties) and ultrasonic pulse velocity (elastic properties and density). The predicted models are ranked and then compared with the experimental data. The correlations were found to be quite reasonable (R2 = 0.89) for all the mixtures tested and can be used to estimate the compressive strengths for similar AAB mixtures.