• 콘크리트학회논문집
• /
• 제12권1호
• /
• pp.45-52
• /
• 2000

The quality of cement mortar products largely depends on various work conditions, specially on the grading and grade shape of aggregates. However, the effect of grading and grade shape on the quality is not considered by both KS codes and production processes, resulting in the increase of the possibility of quality degradation. The objective of this study was to investigate the effect of grading and grade shape on the strength and absorption characteristics of cement mortar products. Flexural and compressive strength increased with the increase of fineness modulus and W/C. The strength increase was measured larger with river sand than with crushed sand. Absorption tended to decrease with the increase of fineness modulus and W/C, but did not affected by the source of sand.

• International Journal of Concrete Structures and Materials
• /
• 제5권2호
• /
• pp.119-123
• /
• 2011

Presented in the paper are findings of a project that examined the effect of slag grade and cement source on the performance of concrete mixtures. Slag cement contents were 20, 40, and 60 percent of the total cementitious material content. Two grades of slag cement were examined (Gr. 100 and Gr. 120) along with two sources of Type I cement. Compressive strength, durability, and permeability were measured. The results showed that the cement source affected the early age strength of the mixtures. At 28 days of age, mixtures containing Gr. 120 slag cement had higher compressive strengths than mixtures containing Gr. 100 slag cement, but by 90 days of age, the trend reversed. As for the chloride ion penetrability, mixtures cast with Gr. 100 slag cement passed fewer coulombs at 28 and 90 days of age than similar mixtures containing Gr. 120 slag. Mixtures containing Gr. 120 slag had the greatest durability factors.

• 미생물학회지
• /
• 제12권1호
• /
• pp.25-30
• /
• 1974

It was convinced that with a relatively small capital investment and with a low operating cost, appreciable amounts of cement copper could be produced from low-grade minerals by the application of a bacterial leaching method. For the recovery of cement copper from the impure pregnant solution, direct precipitation of copper with tin plates by a bacterial leaching method was feasible. The results obtained were as follows: 1)In order to remove the cement copper from the reducing metal, aeration and agitation method were more effective and economic than shaking method. 2)The rate of copper recovery from the pregnant solution was accerelated according to increasing quantities of reducing metal. However, the excess of reducing metal reduced the grade of cement copper. 3)Among the comparative experiments of copper recovery at each reaction temperature of $10^{\circ}C$, $20^{\circ}C$, and $30^{\circ}C$, the recovery rate of copper at $30^{\circ}C$from the pregnant solution was highest. 4)Direct cementation method on iron-containing metal was an excellent method for the recovery of cement copper in bacterial leaching.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
• /
• pp.106-107
• /
• 2014

This study dealt with an experimental study on development of tile grout cement complied with international standards criteria. Tile Grout Cement is divided two grade, 1 type and 2 type, in KS F 1592:2011. International Standards(ISO) is divided 9 grade. performance evaluation for cement content was measured according to KS L ISO 13007. water absorption test results are based on the cement content 30% were satisfied with International Standards criteria. strength test results are based on the cement content 25% were satisfied with International Standards criteria.

• Smart Structures and Systems
• /
• 제26권2호
• /
• pp.147-156
• /
• 2020

This numerical study demonstrates the porosity conditions and the intensity of the interactions with the aggressive agents. It is established that the density as well as the elastic modulus are correlated to ultrasonic velocity The following investigation assessed the effects of cement grade and porosity on tensile strength, flexural and compressive of Ultra High Performance Concrete (UHPC) as a numerical model in PLAXIS 2d Software. Initially, the existing strength-porosity equations were investigated. Furthermore, comparisons of the proposed equations with the existing models suggested the high accuracy of the proposed equations in predicting, cement grade concrete strength. The outcome obtained showed a ductile failure when un-corroded reinforced concrete demonstrates several bending-induced cracks transfer to the steel reinforcement. Moreover, the outcome also showed a brittle failure when wider but fewer transverse cracks occurred under bending loads. Sustained loading as well as initial pre-cracked condition during the corrosion development have shown to have significant impact on the corrosion behavior of concrete properties. Moreover, greater porosity was generally associated with lower compressive, flexural, and tensile strength. Higher cement grade, on the other hand, resulted in lower reduction in concrete strength. This finding highlighted the critical role of cement strength grade in determining the mechanical properties of concrete.

• Journal of Korean Neurosurgical Society
• /
• 제38권5호
• /
• pp.350-354
• /
• 2005

Objective : The aim of this study is to assess the immediate and long-term efficacy of percutaneous vertebroplasty for treating painful vertebral osteoporotic fractures. Methods : A retrospective review of 149patients who had undergone 167 vertebroplasty procedures for osteoporotic fractures was performed. Clinical, radiologic, and procedural datas were analyzed as parameters of prognostic significance, including age, sex, bone marrow density score, symptom duration, bone cement filling grade, number of fractured vertebrae, compression grade of vertebrae, leakage of bone cement, volume of bone cement injected and complications. Results : In 158 of the 167 procedures assessed, immediate pain relief was obtained [94.6%]. The extent of collapse of the vertebral body was assessed as a parameter for prognostic significance [p=0.015]. Three months postoperatively, no improvement of the pain was observed in four of the 167 procedures that had undergone the vertebroplasty [2%]. At long-term follow-up, the improvement of pain was not correlated with the compression grade of vertebrae [p=0.420]. Conclusion : The immediate outcome of vertebroplasty are less effective in vertebrae more collapsed.

• 대한치과의사협회지
• /
• 제12권8호
• /
• pp.613-617
• /
• 1974

The authors have studied the marginal leakage of various dental cements; Fynal cement (Caulk), Zinc cement (S.S. White) Carbo cement (Shofu, Poly-carboxylate cement), EBA cement (Opotow alumina cement), Propac (G-C's zinc oxide euginol cement), and Super cement (Shofu oxyphosphate zinc cement), by means of penetration of 2% methylene blue solution between orden crown restorations and human teeth in 150 cases. The result revealed as follow 1. None of the cements tested were free from dye penetration. 2. There was a wide difference in dye penetration among the trade brands of dental cement when immersed in dye solution before setting of cements. 3. EBA cement and Carbo cement showed comparatively low grade of dye penetration at the restorative margins.

• Restorative Dentistry and Endodontics
• /
• 제2권1호
• /
• pp.32-37
• /
• 1976

The author has studied comparatively the sealing quality of polycarboxylate cement, one of the newest dental cement systems, and zinc oxide eugenol cement by means of penetration of 2% methylene blue solution through the root apex of human teeth in 72 cases as time elapsed. Followings are the results obtained from this study. 1) In all groups, there was no increase in penetration related to increased time of immersion in the dye. 2) In polycarboxylate cement groups, there was a significant difference in depth of dye penetration of each tooth, but in zinc oxide eugenol cement group, there was a slight difference. 3) The depth of dye penetration of zinc oxide eugenol cement group is slightly lower than that of poly carboxylate cement groups. 4) In polycarboxylate cement groups, Carbolit cement group showed comparatively lower grade of dye penetration than Carbo cement group.

• 한국건설순환자원학회논문집
• /
• 제9권1호
• /
• pp.20-25
• /
• 2021

시멘트의 주 원료인 시멘트 클링커는 주원료로서 석회석을 사용하여 제조되며, 석회석의 품위에 따라 부원료의 사용이 변화되고, 시멘트 클링커의 생산에도 큰 영향을 미치게 된다. 본 연구에서는 시멘트 클링커 원료인 석회석의 CaO 함량의 변화가 Raw Mill 분쇄성과 시멘트 클링커의 소성성에 미치는 영향성을 파악하기 위하여, 석회석 CaO 함량을 변화시킨 조합원료의 분쇄시간 측정으로 분쇄성을 비교 검토하였고, 분쇄된 조합원료를 1350~1500℃의 범위에서 소성하여 소성성 지수 계산에 의한 시멘트 클링커의 소성성을 파악하였다. 석회석의 품위가 낮을수록 조합원료의 분쇄성은 저하하였고, 석회석의 CaO 함량이 낮을수록 소성온도에 따른 F-CaO의 변화가 크게 나타났다. 그에 따라 높은 B.I. 값이 계산되어, 낮은 시멘트 클링커 소성성을 나타내었다. 또한, 시멘트 클링커의 광물분석 결과에서는 소성온도의 증가로 F-CaO 값이 저하하는 경우, Belite 함량의 감소와 그에 따른 Alite 함량의 증가가 관찰되었다. Alite의 경우 석회석 CaO 함량이 증가함에 따라 R형의 비율은 감소하고 M형의 비율이 증가하였다.

• 소음진동
• /
• 제8권6호
• /
• pp.1078-1085
• /
• 1998

This study is carried out to investigate the characteristics of sound insulation performances for masonry walls. PC walls and ALC walls. For these purposes. 17 types of masonry walls were selected and tested in accordance with KS F 2808 at reverberation room The sound insulation performance of 8" cement block walls are graded with D-45 ∼ D-55 which are to be evaluated very favorable grade. 4" cement block walls are D-30 ∼ D-40. 1 B cement brick walls are D-40∼D-50 favorable grade. 0.5 B brick walls are D-30∼D-45. 150 mm PC wall is D-50. and ALC walls(150 mm, 200 mm) are D-30∼D-45.