• 한국지반공학회논문집
• /
• 제40권3호
• /
• pp.85-91
• /
• 2024

시멘트계열 재료를 이용한 지반보강 시 처리지반의 안정적 이용을 위하여 해당 재료의 양생과정 평가가 요구된다. 본 연구에서는 전자기적 물성 기반 시멘트 그라우트의 양생과정 평가를 위하여 시계열반사계(TDR) 측정시스템을 적용하였다. 시멘트 그라우트의 높은 전도성으로 인한 프로브 내 전극간 전기적 연결을 방지하기 위하여 코팅 프로브를 제작하였으며, 코팅 프로브로부터 실제 비유전율 평가를 위한 보정실험이 수행되었다. 코팅 프로브가 적용된 TDR 측정시스템으로부터 시멘트 그라우트의 양생과정을 평가하고자 지연제가 첨가된 물시멘트비 45%의 초속경시멘트 그라우트가 준비되었으며, 몰드 내 타설 직후 예비측정 및 배합 후 3~288시간 경과 시점에서 TDR 신호를 수집, 비유전율을 평가하였다. 실험 결과, 타설 직후의 시멘트 그라우트는 100 이상의 높은 비유전율 상태를 나타내었으나 양생시간이 경과함에 따라 급격한 감소 경향을 보였으며, 양생 144시간 시점부터의 비유전율은 약 13.8로 수렴하여 해당 시간을 양생 완료시점으로 판단하였다. 본 연구에서 이용된 코팅 프로브 TDR 측정시스템은 전도성 재료에 대한 적용성과 더불어 전자기적 물성 기반 시멘트계열 지반보강재 양생과정 모니터링에 활용될 수 있을 것이라 기대된다.

• Advances in concrete construction
• /
• 제9권3호
• /
• pp.279-287
• /
• 2020

This paper focuses on the engineering properties of Bentonite-Cement-Sodium silicate (BCS) grout, which was prepared by partially replacing the ordinary Portland cement in Cement-Sodium silicate grout with lithium bentonite (Li-bent) and sodium bentonite (Na-bent), respectively. The effect of different Water-to-Solid ratio (W/S) and various replacement percentages of bentonite on the apparent viscosity, bleeding, setting time, and early compressive strength of BCS grout were investigated. The XRD method was used to detect its hydration products. The results showed that both bentonites played a positive role in the stability of BCS grout, increased its apparent viscosity. Na-bent prolonged the setting time of BCS, while 5% of Li-bent shortened the setting time of BCS. The XRD analysis indicated that the hydration products between the mixture containing Na-bent and Li-bent did not differ much. Using bentonite as supplementary cementitious material (SCM) to replace partial cement is a promising way to cut down on carbon dioxide emissions and to produce low-cost, eco-friendly, non-toxic, and water-resistant grout. In addition, Li-bent was superior to Na-bent in improving the strength and the thickening of BCS grouts.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.579-582
• /
• 2009

The thermal conductivity and viscosity(or workability) of graphite-added bentonite grouts and cementitious grouts have been evaluated and compared to determine the suitability of these materials for backfilling vertical boreholes of ground heat exchangers. Seven bentonite grouts from different product sources and a portland cement grout with various mixture ratios were considered in this paper. As a new additive for grout, we choose graphite which has high thermal conductivity. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or with an addition of Graphite compared with that of silica sand. In case of cementitious grout also increase the thermal conductivity and decrease the workability dramatically though an addition of Graphite. Therefore, we cautiously select the amount of graphite and mixture ratio of bentonite and cement considering not only thermal conductivity but also viscosity for the optimum condition of backfilling material.

• Nuclear Engineering and Technology
• /
• 제43권5호
• /
• pp.459-468
• /
• 2011

The current solution to the problem of using cementitious material for sealing purposes in a final radioactive waste repository is to develop a low-pH cement grout. In this study, the material properties of a low-pH cement grout based on a recipe used at ONKALO are investigated by considering such factors as pH variation, compressive strength, dynamic modulus, and hydraulic conductivity by using silica fume and micro-cement. From the pH measurements of the hardened cement grout, the required pH (< pH 11) is obtained after 130 days of curing. Although the engineering properties of the low-pH cement grout used in this study are inferior to those of conventional high-pH cement grout, the utilization of silica fume and micro-cement effectively meets the long-term environmental and durability requirements for cement grout in a radioactive waste repository.

• 한국건축시공학회지
• /
• 제24권2호
• /
• pp.215-226
• /
• 2024

본 연구에서는 초고분말 플라이 애시가 다량 치환된 자기감지형 그라우트의 성능을 검토하기 위하여 실험적 연구를 진행하였다. 또한 기존의 대표적인 산업부산물인 고로슬래그 미분말과 플라이 애시를 동일한 양으로 치환하여 굳지 않은 그라우트의 유동특성, 경화 그라우트에서 압축강도, 길이변화율, 전기적 특성을 평가하였다. 실험결과 초고분말 플라이 애시 치환시 소성점도가 크게 낮아져 유동성이 향상되었으며, 압축강도도 플레인보다 초기재령에서부터 높게 나타났다. 또한 전기적 특성에서도 FCR-Stress, FCR-Strain의 관계가 유사하게 나타났다.

• Steel and Composite Structures
• /
• 제44권6호
• /
• pp.883-898
• /
• 2022

A hollow-core partially-encased composite beam, named HPEC beam, is investigated in this paper. HPEC beam comprises I-beam, longitudinal reinforcement, stirrup, foam formwork, and cementitious grout. The foam formwork is located on both sides of the web, and cementitious grout is cast within the steel flange. To investigate the shear performance of HPEC beams, static loading tests of six HPEC beams and three control beams were conducted. The shear span ratio and the number of studs on the shear behavior of the HPECspecimens were studied. The failure mechanism was studied by analyzing the curves of shear force versus both deflection and strain. Based on the shear span ratio (𝜆), two typical shear failure modes were observed: shear compression failure when 1.6 ≤ 𝜆 ≤ 2; and diagonal compression failure when 𝜆 ≤ 1.15. Shear studs welded on the flange can significantly increase the shear capacity and integrity of HPEC beams. Flange welded shear studs are suggested. Based on the deformation coordination theory and superposition method, combined with the simplified modified compression field model and the Truss-arch model, Modified Deformation Coordination Truss-arch (M.D.C.T.) model was proposed. Compared with the shear capacity from YB9038-2006 and JGJ138-2016, the calculation results from M.D.C.T. model could provide reasonable predictions.

• 콘크리트학회논문집
• /
• 제28권5호
• /
• pp.519-525
• /
• 2016

본 논문에서는 혼화제에 따른 3성분계 그라우트에 대하여 자유수축 및 구속수축에 대하여 평가하였다. 본 연구에서 3성분계 그라우트는 플라이애쉬, 지르코늄 실리카퓸을 사용하였고, 팽창재(a, b)와 수축저감제 혼화제를 병용 사용하였다. 또한 유럽규정 EN 445에 따라 그라우트의 기본재료특성 실험을 수행하여 블리딩, 체적변화량, 유동성, 압축강도 실험을 수행하여 기본재료특성 거동도 분석하였다. 실험결과, 팽창재와 수축저감제 혼입률에 따라 유동성은 다소 영향은 없었으나, 우수한 블리딩 및 침하 저감성능과 압축강도를 나타났다. 자유수축 거동에서는 팽창재와 수축저감제를 혼입한 변수들은 0.0E-0.0R 변수보다 최소 29%의 수축저감성능을 보여 주었다. 특히 팽창재 a와 수축저감제를 병용 사용한 변수에서는 수축 저감의 효과가 더욱 우수한 것으로 나타났으며, 혼화제의 혼입률이 증가할수록 텐던 구속에 의한 수축균열은 뒤늦게 발생함을 알 수 있었다. 그러나 유독 팽창재 a 2.0%, 수축저감제 0.50%를 혼입한 변수에서는 우수한 수축저감성능으로 수축균열이 발생하지 않았다. 종합하여 볼 때, 본 연구의 실험 조건에서는 팽창재 a 2.0%, 수축저감제 0.50%인 조합이 PSC 교량용 고품질 3성분계 그라우트의 최적의 혼입률인 것으로 분석된다.

• Computers and Concrete
• /
• 제19권2호
• /
• pp.133-142
• /
• 2017

Two-stage concrete (TSC), also known as pre-placed aggregate concrete, is characterized by its unique placement technique, whereby the coarse aggregate is first placed in the formwork, then injected with a special grout. Despite its superior sustainability and technical features, TSC has remained a basic concrete technology without much use of modern chemical admixtures, new binders, fiber reinforcement or other emerging additions. In the present study, an experimental database for TSC was built. Different types of cementitious binders (single, binary, and ternary) comprising ordinary portland cement, fly ash, silica fume, and metakaolin were used to produce the various TSC mixtures. Different dosages of steel fibres having different lengths were also incorporated to enhance the mechanical properties of TSC. The database thus created was used to develop fuzzy logic models as predictive tools for the grout flowability and mechanical properties of TSC mixtures. The performance of the developed models was evaluated using statistical parameters and error analyses. The results indicate that the fuzzy logic models thus developed can be powerful tools for predicting the TSC grout flowability and mechanical properties and a useful aid for the design of TSC mixtures.

• 콘크리트학회논문집
• /
• 제22권3호
• /
• pp.419-426
• /
• 2010

이 논문에서는 포스트텐션 구조물에 적용되는 그라우팅 품질확보를 위한 재료개선 및 실험과정을 기술하였다. 그라우팅이란 강연선이 삽입된 덕트를 시멘트물질로 채우는 공정이다. 국내에서는 아직 그라우팅의 품질과 포스트텐션 구조물의 내구성에 대한 관계가 인식되지 않아 적절한 품질관리에 어려움이 있다. 국내표준시험법은 강연선에 의한 심지효과(wick effect)를 고려하지 않기 때문에 시공 시 발생할 수 있는 재료분리량을 평가하기 어렵다. 따라서 현 품질기준을 만족하는 그라우트를 사용하더라도, 시공 시 과다한 불리딩 수나 재료수축이 발생할 수 있다. 이 연구에서는 그라우트에 관련된 해외기준과 표준시험법을 조사하여 국내기준 및 표준시험법과 비교한 후 해외기준에 준하는 성능을 나타낼 수 있는 그라우트 구성성분비 및 혼화제를 제시하여 보았다. 개선된 그라우트의 성능을 해외표준시험법에 따라 일반적으로 적용되고 있는 그라우트재와 비교하였으며 PC빔의 덕트형상을 고려한 목업시험을 통하여 흐름유형(flow pattern) 및 충전성능을 관찰하였다. 이 실험을 통하여 그라우팅의 성능은 재료특성에 의하여 높은 영향을 받으며 적용 대상의 기하학적 형상에 따라 상이한 충전특성을 가진다는 것 알 수 있었다.

• Structural Engineering and Mechanics
• /
• 제82권3호
• /
• pp.313-323
• /
• 2022

Steel laminated elastomeric bearings are commonly used in bridge structures to control displacements and rotations and transfer forces from the superstructure to the substructure. Proper knowledge of design, fabrication and erection procedures is important to ensure stability and adequate structural performance during the lifetime of the bridge. Difference in elevations sometimes leads to large size gaps between the bearing and the girder which makes the grout thickness that is commonly used for leveling deviate beyond standards. This paper investigates the structural response of High Strength Fiber Reinforced Cementitious (HSFRC) thin plinths that are used to close gaps between bearing pads and precast girders. An experimental program was developed for this purpose where HSFRC plinths of different size were cast and tested under vertical loads that simulate bridge loading in service. The structural performance of the plinths was closely monitored during testing, mainly crack propagation, vertical reaction and displacement. Analytically, the HSFRC plinth was analyzed using the beam on elastic foundation theory as the supporting elastomeric bearing pads are highly compressible. Closed form solutions were derived for induced displacement and forces and comparisons were made between analytical and experimental results. Finally, recommendations were made to facilitate the practical use of HSFRC plinths in bridge construction based on its enhanced load carrying capacity in shear and flexure.