• Journal of Korean Neurosurgical Society
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• 제52권5호
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• pp.435-440
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• 2012

Objective : The purpose of this study is to find the optimal stiffness and volume of bone cement and their biomechanical effects on the adjacent vertebrae to determine a better strategy for conducting vertebroplasty. Methods : A three-dimensional finite-element model of a functional spinal unit was developed using computed tomography scans of a normal motion segment, comprising the T11, T12 and L1 vertebrae. Volumes of bone cement, with appropriate mechanical properties, were inserted into the trabecular core of the T12 vertebra. Parametric studies were done by varying the volume and stiffness of the bone cement. Results : When the bone cement filling volume reached 30% of the volume of a vertebral body, the level of stiffness was restored to that of normal bone, and when higher bone cement exceeded 30% of the volume, the result was stiffness in excess of that of normal bone. When the bone cement volume was varied, local stress in the bony structures (cortical shell, trabecular bone and endplate) of each vertebra monotonically increased. Low-modulus bone cement has the effect of reducing strain in the augmented body, but only in cases of relatively high volumes of bone cement (>50%). Furthermore, varying the stiffness of bone cement has a negligible effect on the stress distribution of vertebral bodies. Conclusion : The volume of cement was considered to be the most important determinant in endplate fracture. Changing the stiffness of bone cement has a negligible effect on the stress distribution of vertebral bodies.

• Computers and Concrete
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• 제13권3호
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• pp.309-323
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• 2014

Based on the compositions and structures of cement-based materials, the geometrical models of the tortuosity of transport paths in hardened cement pastes, mortar and concrete, which are associated with the capillary porosity, cement hydration degree, mixture particle shape, aggregate volume fraction and water-cement ratio, are established by using a geometric approach. Numerical simulations are carried out to investigate the effects of material parameters such as water-cement ratio, volume fraction of the mixtures, shape and size of aggregates and cement hydration degree, on the tortuosity of transport paths in hardened cement pastes, mortar and concrete. Results indicate that the transport tortuosity in cement-based materials decreases with the increasing of water-cement ratio, and increases with the cement hydration degree, the volume fraction of cement and aggregate, the shape factor and diameter of aggregates, and the material parameters related to cement pastes, such as the water-cement ratio, cement hydration degree and cement volume fraction, are the primary factors that influence the transport tortuosity of cement-based materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.567-572
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• 2002

This research investigates experimentally an effect on the quality performances of the high flowing concrete according to binder types. The purpose of this study is to determine the optimum mix proportion of the high flowing concrete having good flowability, viscosity and no-segregation. For this purpose, two types using belite cement＋lime stone powder(LSP) and furnace slag cement+lime stone powder are selected and tested by design factors including water cement ratio, fine and coarse aggregate volume ratio. As test results of this study, the optimum mix proportion for binder types is as followings. 1) One type based belite cement ; water cement ratio $51^{\circ}C$, fine aggregate volume ratio $43^{\circ}C$ and coarse aggregate volume ratio $53^{\circ}C$, replacement ratio of LSP $42.7^{\circ}C$. 2) Another type based slag cement : water cement ratio $41^{\circ}C$, fine aggregate volume ratio $47^{\circ}C$ and coarse aggregate volume ratio $53^{\circ}C$, replacement ratio of LSP $13.5^{\circ}C$.

• Journal of Korean Neurosurgical Society
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• 제48권2호
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• pp.125-128
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• 2010

Objective : The purpose of this study was to determine the optimal volume of injected cement and its distribution when used to treat vertebral compression fractures, and to identify factors related to subsequent vertebral fractures. Methods : A retrospective analysis of newly developing vertebral fractures after percutaneous vertebroplasty was done. The inclusion criteria were that the fracture was a single first onset fracture with exclusion of pathologic fractures. Forty-three patients were included in the study with a minimum follow up period of six months. Patients were dichotomized for the analysis by volume of cement, initial vertebral height loss, bone marrow density, and endplate-to-endplate cement augmentation. Results : None of the four study variables was found to be significantly associated with the occurrence of a subsequent vertebral compression fracture. In particular, and injected cement volume of more or less that 3.5 cc was not associated with occurrence (p = 0.2523). No relation was observed between initial vertebral height loss and bone marrow density (p = 0.1652, 0.2064). Furthermore, endplate-to-endplate cement augmentation was also not found to be significantly associated with a subsequent fracture (p = 0.2860) by Fisher's exact test. Conclusion : Neither volume of cement, initial vertebral height loss, bone marrow density, or endplate-to-endplate cement augmentation was found to be significantly related to the occurrence of a subsequent vertebral compression fracture. Our findings suggest that as much cement as possible without causing leakage should be used.

• 한국환경복원기술학회지
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• 제5권6호
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• pp.9-13
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• 2002

This study has been performed to investigate the physical and mechanical characteristics of compaction, volume change and compressive strength for reinforced soil mixed with cement. And confirm the reinforcing effects with admixture such as cement. To this end, a series of compaction test and compression test was conducted for clayey soil(CL) and cement reinforced soil. In order to determine proper moisture content and mixing ratio, pilot test was carried out for soil and cement reinforced soil. And the mixing ratio of cement admixture was fixed 3%, 6%, 9% and 12% by the weight of dry soil. As the experimental results, the maximum dry unit weight(${\gamma}_{dmax}$) was increased with the mixing ratio and then shown the peak at 10% reinforced soil, but the optimum moisture content(OMC) and the volume change was decreased with the ratio increase. And the compressive strength volume change was decreased with mixing ratio increased.

• Investigative Magnetic Resonance Imaging
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• 제21권3호
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• pp.148-153
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• 2017

Purpose: To identify the differences between injected cement volumes during vertebroplasty procedures according to the enhancement pattern of pre-procedure magnetic resonance imaging (MRI) findings. Materials and Methods: Thirty-two patients who underwent 52 vertebroplasty procedures as well as pre-procedure contrast-enhanced spine MRI in the authors' institution were reviewed retrospectively. The 52 procedures were divided into two groups according to different enhancement patterns shown by pre-procedure MR imaging [E(+) and E(-)]. The volumes of the enhancing/non-enhancing portions of the fractured vertebral body shown by pre-procedural MR imaging were calculated and compared to the volumes of the injected cement during the vertebroplasty procedures. Results: The 52 injections included 28 (56%) in Group E(+) and 24 (44%) in Group E(-). The actual volume ratio of the injected cement to the volume of the non-enhanced or enhanced region calculated based on the contrast-enhanced MRI was $0.22{\pm}0.11(cc/cm^3)$ in the E(+) group and $0.93{\pm}0.62(cc/cm^3)$ in the E(-) group. The average amount of injected cement was significantly different between Group E(+) and Group E(-) (P < 0.001). In addition, the ratio of the injected cement amount to the volume of the enhanced or non-enhanced portion based on the contrast-enhanced MRI in Group E(-) was significantly higher than that of Group E(+) (P < 0.001). Conclusion: Different enhancement patterns shown by pre-procedure MRI can predictors of the injected cement volume during vertebroplasty procedures for osteoporotic fractures.

• Computers and Concrete
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• 제7권1호
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• pp.17-38
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• 2010

This research aimed to investigate the influence of high-volume mineral admixtures (MAs), i.e., fly ash and slag, on the hydration characteristics and microstructures of cement pastes. Degree of cement hydration was quantified by the loss-on-ignition technique and degree of pozzolanic reaction was determined by a selective dissolution method. The influence of MAs on the pore structure of paste was measured by mercury intrusion porosimetry. The results showed that the hydration properties of the blended pastes were a function of water to binder ratio, cement replacement level by MAs, and curing age. Pastes containing fly ash exhibited strongly reduced early strength, especially for mix with 45% fly ash. Moreover, at a similar cement replacement level, slag incorporated cement paste showed higher degrees of cement hydration and pozzolanic reaction than that of fly ash incorporated cement paste. Thus, the present study demonstrates that high substitution rates of slag for cement result in better effects on the short- and long-term hydration properties of cement pastes.

• 콘크리트학회논문집
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• 제27권2호
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• pp.177-184
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• 2015

시멘트를 대체하여 고로슬래그 미분말을 건설재료로 대량으로 활용하기 위해서는 잠재수경성을 향상시켜 조기강도를 개선시킬 수 있는 적절한 활성화제가 필요하다. 이 연구에서는 경석고와 황산나트륨을 이용하여 하이볼륨 고로슬래그 시멘트의 수화특성에 대한 연구를 수행하였다. 수화특성을 평가하기 위해 고로슬래그 미분말을 전체 바인더의 80%로 고정하였으며, 나머지 20%를 시멘트와 활성화제로 구성하였다. 경석고와 황산나트륨의 치환율(1~7%)에 따른 응결, 압축강도, 미소수화열 및 미세구조 특성을 시멘트만을 사용한 경우와 비교하여 분석하였다. 이 연구에서는 경석고와 황산나트륨을 활성화제로 사용한 경우, 하이볼륨 고로슬래그 미분말의 조기 수화특성을 향상을 위해 필요한 $SO_3$ 함량을 전체 바인더 중량대비 약 3~5% 제안하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권5호
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• pp.95-102
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• 2022

최근, 전세계적으로 온실 가스의 저감에 관심이 높아지면서 건설 산업에서도 FA를 대량 치환하는 HVFAC의 사용을 위한 연구가 수행되고 있다. 시멘트의 수화도와 FA 반응도의 정량적인 측정은 HVFAC의 강도발현 메커니즘을 명확히 이해할 수 있게 한다. FA가 포함된 시멘트 페이스트의 수화 및 포졸란 반응은 매우 복잡하고 수화 생성물의 조성을 정확하게 결정할 수 없으므로 간단한 방법으로 반응도를 설명하는 것은 매우 어렵다. 따라서, 이 연구는 재령에 따른 하이볼륨 FA 시멘트의 수화 특성을 조사하였다. 시멘트의 수화도와 FA의 반응도는 재령에 따른 선택용해법과 페이스트의 비증발 수량을 통해 평가하였다. 또한 HVFA 모르타르 시편을 이용하여 연령에 따른 압축강도를 측정하였다. 실험결과 FA의 치환율이 증가할수록 시멘트의 수화도는 증가하나 FA의 반응성은 감소하는 것으로 나타났다.

• 시멘트
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• 통권42호
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• pp.84-91
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• 1971