• Journal of Animal Environmental Science
• /
• v.7 no.1
• /
• pp.29-32
• /
• 2001

In this experiment porous calcium silicate (PCS) powder prepared by using a 50 mesh sieve was spread on top of chick droppings to investigate the odor from the manure. Zeolite was used as a comparative purpose. Reduction in ammonia production from chick droppings shortly after the PCS and zeolite application was evident (P<0.05), but there were no difference among treatments afterwards. hydrogen sulfide level was significantly lowered by both PCS and zeolite treatment(P<0.05).

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.8
• /
• pp.909-914
• /
• 2007

Fluorine compounds are the essential chemicals for wet processes of semiconductor and LCD production line. Problems of conventional treatments for fluoride wastewater are their high operation costs and low fluoride removal capacity. In this study, cement paste containing various Ca-bearing hydrates such as portlandite, calcium silicate hydrate(CSH), and ettringite was investigated for fluoride removal. The objectives of this study are to assess the feasibility of using cement paste cured mixture of cement and water as an alternative agent for treatment of fluoride wastewater and to investigate fluoride removal capacity of the cement paste. The performance of cement paste was comparable to that of lime in the kinetic test. In column experiment where the effluent fluoride concentrations were below 0.5 mg/L. Then the leached calcium reached the maximum level of 800 mg/L. The nitrate reduced to the level of less than 10 mg/L. Nitrate in the wastewater was exchanged with interlayer sulfate of these cement hydrate LDHs. Phosphate concentration could be reduced to 10 mg/L by forming calcium phosphate. These results indicate that the cement paste generally has advantageous characteristics as an economical and viable substitute for lime to remove fluoride.

• Cement
• /
• s.92
• /
• pp.41-54
• /
• 1983

Calcium Silicate의 생성 및 분해에 미치는 $K_2SO_4$와 $MgSO_4$의 영향을 비교 검토하였으며 Calcium Silicate의 생성을 최대로 하는 $SO_3$, MgO와 $K_2O$의 최적비를 반응표면분석기법으로 조사하였다. $K_2SO_4$의 혼합비 증감에 따라 $C_3S$의 생성촉진에 미치는 영향은 없었다. $C_3S$의 조합원료에 $CaSO_4$를 4.0wt$\%$이상 첨가시 $CaSO_4$는 $C_2S$주위에 Sulphate reaction rim을 형성함으로써 $C_2S$와 CaO의 반응을 방해해 $C_3S$의 생성을 억제하였으나 적당량의 MgO가 첨가되면 $CaSO_4$가 4.0wt$/%$이상이라도 $C_3S$의 생성은 억제되지 않았다. $C_3S$의 생성을 최대로 하기 위한 $SO_3$, MgO와 $K_2O$의 최적비를 반응표면분석기법을 이용하여 다음과 같은 결론을 얻었다. 1. $K_2SO_4$는 $K_2O$에 비해 소결에 미치는 영향이 적으므로 크링카에 고용되고 남은 $K_2O$는 전량 $K_2SO_4$로 전환시켜야한다. 2. $SO_3$와 $K_2O$의 최적비율은 1.5이다. 3. $CaSO_4$와 MgO의 최적비율을 유지하기 위해서는 $CaSO_4$중의 wt$\%SO_3$=0.7의 수준으로 Sulphate의 함량을 조절하여야 한다. 4. $SO_3$와 결합하고 남은 $K_2O$가 0wt$\%$인 경우는 $K_2SO_4$=2.3wt$\%$, MgO=1.5wt$\%$일때 $C_3S$의 생성이 최대로 된다. 5. $SO_3$와 결합하고 남은 $K_2O$가 2.0wt$\%$인 경우는 $K_2$$SO_4$=4.5wt$\%$, MgO=3.0wt$\%$일때 $C_3S$의 생성이 최대로 된다.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.6
• /
• pp.529-534
• /
• 2016

Calcium silicate inorganic insulating material is a porous material which is made of 90 wt% of cement. Unlike existing inorganic insulation materials, it is produced without high temperature curing process and also it costs much less than existing inorganic insulation materials. It is an innovative insulation material that supplemented disadvantages of conventional inorganic insulation material. Researches and developments about inorganic insulation materials have been actively researched abroad. Calcium silicate insulation has $0.13g/cm^3$ of specific gravity. Its heat conductivity is under 0.050W/mK, which it similar to conventional inorganic insulation. However, it has weak compressive strength compared to other inorganic insulation. The point of this research is to manifest that calcium silicate inorganic insulating material can have certain compressive strength after curing process with high insulating performance and to find out the proper curing methods and period.

• Resources Recycling
• /
• v.3 no.3
• /
• pp.27-31
• /
• 1994

We tested the limestone sludge produced in Pohang Iron & Steel Co., Ltd. as a filler powder for the effective use of portland cement. Hydration process was investigated by measuring the hydration rate, the amounts of non-evaporable water and compressive strength of cement-limestone sludge paste prepared by mixing limes-tone sludge with cement. The results obtained in this study can be summarized as follows: 1. There is no significant difference between the cases of adding up to 10% limestone sludge and those of unmixed cement system. However the reaction rate increases in the 5% limestone sludge system(due to the effects of fine). 2. The compressive strength increases proportionally with increasing the measured amount of non-evaporable water, Adding 5% limestone sludge also increases the strength a little higher, and the compressive strength and calcium silicate hydrates. In the case of the mixed limestone sludge, $2\theta$=$11.7^{\circ}$ peak appears in the samples of 28 days hydration. This peak indicted the presence of calcium carboaluminate hydrate. Although limestone sludge is generally regarded as a inert materials, some kinds of cement can produce a calcium carboaluminate by reacting with aluminate in cement pastes.

• International Journal of Concrete Structures and Materials
• /
• v.5 no.1
• /
• pp.3-10
• /
• 2011

Theoretical models for prediction of the mechanical properties of cement mortar are developed based on the morphology and interactions of cement hydration products, capillary pores and microcracks. The models account for intermolecular interactions involving the nano-scale calcium silicate hydrate (C-S-H) constituents of hydration products, and consider the effects of capillary pores as well as the microcracks within the hydrated cement paste and at the interfacial transition zone (ITZ). Cement mortar was modeled as a three-phase material composed of hydrated cement paste, fine aggregates and ITZ. The Hashin's bound model was used to predict the elastic modulus of mortar as a three-phase composite. Theoretical evaluation of fracture toughness indicated that the frictional pullout of fine aggregates makes major contribution to the fracture energy of cement mortar. Linear fracture mechanics principles were used to model the tensile strength of mortar. The predictions of theoretical models compared reasonably with empirical values.

• Journal of the Korean Ceramic Society
• /
• v.34 no.5
• /
• pp.491-499
• /
• 1997

High flexible lightweight composites containing tobermorite as a main mineral is produced using various amorphous silicates, lime, cement and fibers. Here, Mechanical properties of the composites were studied by observing microstructures of hydrates and fibers. Amorphous silicates having better hydraulicity retarded the crystallization of tobermorite due to better formation of C-S-H gel in water bath curing, but, difficult conversion from C-S-H gel to tobermorite in hydrothermal reaction. In the low molar ratio of CaO/SiO2 (0.67), faster crystalization was observed dued to more impurities such as Al2O3 alkali, resulting in improving mechanical properties due to small crystal size and many contact points. It was identified that a lot of calcium silicate hydates formed at surface of pulps increase bonding strength and the crack-resistance of matrix in the composites, but decrease hardness and compressive strength. The choice of amorpous silicates having better hydraulicity, low CaO/SiO2 adding each fibers bellow about 5% in the raw mixs and lower molding pressure should be needed at improve mechanical properties of composites.

• Restorative Dentistry and Endodontics
• /
• v.44 no.3
• /
• pp.30.1-30.6
• /
• 2019

We report the surgical endodontic treatment of a maxillary first premolar with a lateral lesion that originated from an accessory canal. Although lesions originating from accessory canals frequently heal with simple conventional endodontic therapy, some lesions may need additional and different treatment. In the present case, conventional root canal retreatment led to incomplete healing with the need for further treatment (i.e., surgery). Surgical endodontic management with a fast-setting calcium silicate cement was performed on the accessory canal using a dental operating microscope. At the patient's 9-month recall visit, the lesion was resolved upon radiography.

• Journal of the Korea Institute of Building Construction
• /
• v.24 no.2
• /
• pp.181-191
• /
• 2024

In the realm of cement manufacturing, concerted efforts are underway to mitigate the emission of greenhouse gases. A significant portion, approximately 60%, of these emissions during the cement clinker sintering process is attributed to the decarbonation of limestone, which serves as a fundamental ingredient in cement production. Prompted by these environmental concerns, there is an active pursuit of alternative technologies and admixtures for cement that can substitute for limestone. Concurrently, initiatives are being explored to harness technology within the cement industry for the capture of carbon dioxide from industrial emissions, facilitating its conversion into carbonate minerals via chemical processes. Parallel to these technological advances, economic growth has precipitated a surge in construction activities, culminating in a steady escalation of construction waste, notably waste concrete. This study is anchored in the innovative production of calcium silicate cement clinkers, utilizing finely powdered waste concrete, followed by a thorough analysis of their mineral phases. Through X-ray diffraction(XRD) analysis, it was observed that increasing the substitution level of waste concrete powder and the molar ratio of SiO₂ to (CaO+SiO₂) leads to a decrease in Belite and γ-Belite, whereas minerals associated with carbonation, such as wollastonite and rankinite, exhibited an upsurge. Furthermore, the formation of gehlenite in cement clinkers, especially at higher substitution levels of waste concrete powder and the aforementioned molar ratio, is attributed to a synthetic reaction with Al₂O₃ present in the waste concrete powder. Analysis of free-CaO content revealed a decrement with increasing substitution rate of waste concrete powder and the molar ratio of SiO₂/(CaO+SiO₂). The outcomes of this study substantiate the viability of fabricating calcium silicate cement clinkers employing waste concrete powder.

• Environmental Engineering Research
• /
• v.11 no.1
• /
• pp.54-61
• /
• 2006

An electron probe microanalysis (EPMA) investigation can provide quantitative and qualitative insight into the nature of the surface and bulk chemistry on solidified waste forms(SWF). The proportion of Pb in grain areas is below 0.3 wt. %, and the proportion near the border of the grain slightly increases to 0.98 wt. % but in the inter-particle areas farther from the grain, the concentration of Pb markedly increases. It is apparent that very little Pb diffuses into the tricalcium silicate($C_3S$) particles and most of the Pb exists as precipitates of sulfate, hydroxide, and carbonate in the cavity areas between $C_3S$ grains. Calcite additions on Pb-doped SWF are also observed to induce deeper incorporation of lead into the cement grains with EPMA line-analysis of cross-sections of cement grains. The line-analysis reveals the presence of $0.2{\sim}5$ weight % Pb over $5\;{\mu}m$ from cement grain boundaries. In the inter-particle areas, the ratio of Ca, Si, Al and S to Pb is relatively similar even at some distance from the grain border and the Pb (wt. %) ratio is reasonably constant throughout the whole inter-particles area. It is apparent that the enhanced development of C-S-H on addition of calcite can increasingly absorbs lead species within the silica matrix.