• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.253-256
• /
• 2004

Recently, construction works of scale are getting larger with economic growth. Shotcreting is one of major processes in tunnels construction. Accelerator is used in tunnel and underground structures to ensure early strength of shotcrete. Silicate based accelerator and aluminate based accelerator is getting widely in the field. But these accelerators have many problems due to decesase of long-term strength and low quality of the hardened shotcrete. in order to solve these problems, recently developed powder types cement mineral accelerator. In this study, we tested chloride permeability, freezing and thawing and accelerated carbonation of shotcrete. As a result of the test, wet-mixed shotcrete with powder types cement mineral accelerator exhibited durability improvement compared to the conventional shotcrete accelerator.

• 대한치과기공학회지
• /
• 제19권1호
• /
• pp.43-54
• /
• 1997

This investigation is carried out of inqurie into the effects of the accelerator on the setting time and haedness when it is used with plaster products. Plaster($\beta$), dental hard stone($\alpha$), and limproved dental hard stone($M{\alpha}$) are selected as the objects of the investigation, since they are most common materials for dental plaster products. Setting time is gauged by means of Vicket Needle and Gilmore Needle, and hardness is gauged by means of Brinell and Vicket Hardness machines. Samples of each material are made in the standerd water powder ratio and with the accelerator repectively, Every material is tested five times each. The results of the tests are as fallow : 1) In each case the setting time is shortened when the accelerator is used. 2) Of the three materials the hardness of the plaster was lowest A($\beta$) < B($\alpha$) < C($M{\alpha}$)} 3) In each case the hardness of the samples made in the standard water powder ratio were higher than that of the sample made with the accelerator. A1 > A2 ; B1>B2 ; C1>C2 4) Final Conclusion : Higher quality cast is expected when it is made in the standard water powder ratio.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.609-617
• /
• 2003

The use of Shotcrete(Sprayed concrete) for the support of underground excavations was pioneered by the Civil engineering industry. Permanent shotcrete tunnel linings such as Single-shell, NMT(Norwegian Method of Tunnelling) have been constructed in many countries for reducing construction time and lowering construction costs instead of conventional in-situ concrete linings. Among essential technologies for successful application of Permanent Shotcrete Linings, high performance shotcrete having high strength, high durability, better pumpability has to be developed in advance. This paper presents the ideas and the first field test results of wet-mixed Steel Fiber Reinforced Shotcrete(SFRS) with powder types cement mineral accelerator. From the results, wet-mix SFRS with powdered accelerator exhibited good early strength improvement and less rebound ratio compared to the ordinary accelerator.

• 한국구조물진단유지관리공학회 논문집
• /
• 제24권2호
• /
• pp.86-93
• /
• 2020

숏크리트용 콘크리트는 일반적으로 1종 보통 포틀랜드시멘트(이하 OPC)를 100% 사용한 레미콘 제품에 현장에서 별도로 숏크리트용 급결제를 약 5% 혼합하는 방식으로 사용된다. 본 연구에서는 국내에서 사용률이 높은 시멘트 광물계 급결제(calcium aluminate)를 사용한 숏크리트용 결합재로서 기존 OPC에 슬래그분말(이하 SP), 석회석분말(이하 LSP)를 첨가하여 혼합시멘트를 사용할 때의 응결 및 압축강도, 페이스트 수화물 및 공극구조에 미치는 영향을 시험 및 분석하여 재령별 수화물의 생성량과 공극구조가 숏크리트의 모르타르 성능에 미치는 영향을 파악하였다. 향후 숏크리트용 결합재로서 최적화된 결합재를 제조하는데 활용할 수 있을 것으로 기대된다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.555-558
• /
• 2005

The purpose of this study is to evaluate the chemical resistance of polymer powder-modified mortars with special accelerator component. Polymer powder-modified mortars with the accelerator are prepared with various polymer-binder ratios, and tested for flexural and compressive strengths and mass change. Chemicals resistance was tested by dealing with $10\%$ HCl and $5\%\;H_2SO_4$ aqueous solution. As a result, the weight reduction ratio of the mortars decreased with increasing polymer-binder ratio. However, in the viewpoint of strength reduction by chemical attacks, the maximum chemical resistance of the mortars was shown at a polymer-binder ratio of $5\%$.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.731-734
• /
• 2004

Admixture compounds for reducing setting time and accelerating early strength development of redispersible polymer powder-modified mortars were made by mixing various inorganic accelerating inorganic materials. Redispersible polymer powder-modified mortars are prepared with various accelerator contents, and it was tested for setting time, flexural and compressive strengths. As a result, the accelerators contribute to strength development of the mortars in the early curing age of 12h or less. In the viewpoint of early strength development of redispersible polymer powder-modified mortars, an accelerator content of $20\%$ is recommended.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
• /
• pp.259-262
• /
• 2012

Recently, as the national policy of green growth is promoted, construction field also makes an effort to reduce CO₂ gas released when producing cement continuously. In other words, as the method solving environmental pollution and resources exhaustion, lots of mineral material compounds such as blast furnace slag powder which is industrial by-product, fly ash, red mud, etc. are examined to bo used as the substitute good of cement Therefore this study is to investigate the hardening characteristics of alumino-silicate inorganic binder using red-mud used as a accelerator of industrial by-product such as fly ash and blast furnace slag powder according to curing temperature. As a result, it is effective to use red-mud as the accelerator of inorganic binder with other additory accelerators.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.1162-1167
• /
• 2004

From the early 1980's, the New Austrian Tunnelling Method (NATM) has been developed as a one of the standard tunneling method in Korea. Owing to the results of many researches, the practical problems of shotcrete has been improved for a last decade. However, the excess amount of rebound still remains one of the critical problems in shotcrete technology. In order to improve for this rebound problem, recently developed cement mineral accelerator has been successfully applied to several NATM tunnels in Korea. An experimental investigation was carried out in order to verify the rebound characteristics of wet-mix Steel Fiber Reinforced Shotcrete (SFRS) with powder types cement mineral accelerator. Mortar setting test, SEM analysis, bonding test under spring water condition and rebound test were conducted. From the result, wet-mix SFRS with cement mineral acelerator exhibited excellent bonding characteristics even spring water condition and less rebound ratio compared to the conventional liquid accelerator.

• 한국농공학회지
• /
• 제42권5호
• /
• pp.125-132
• /
• 2000

This study was performed to evaluate the physical properties of reinforced soil mixture powder. Soil sample was prepared by passing into the standard sieve of No. 200 and reinforcement materials were calcium carbonate, quicklime and portland cement. Fineness, setting time, and compressive strength test for reinforced soil mixture powder were performed and analyzed to investigate their physical properties. The main results were summarized as follow. The compressive strength of soil mixture powder itself and most reinforced was reinforced according to increasing in the mixture rate of reinforcement and the rate of increase was remarkably higher in the cement reinforced soil moisture powder. It was appeared that the early compressive strength is considering higher in the cement reinforced soil moisture powder with 2% of moisture rate of accelerator.

• 한국건축시공학회지
• /
• 제15권3호
• /
• pp.265-271
• /
• 2015

본 연구는 재령 6시간에 압축강도 10MPa 이상을 만족하는 조강형 콘크리트를 개발함에 스팀양생 공정을 생략한 PC(Precast Concrete)부재를 생산하고자 하였으며, 거푸집의 회전율을 높임에 경제성을 확보하는데 목적이 있다. 이에, $C_3S$의 함유량이 높은 조강시멘트와 $C_3S$의 수화작용을 촉진시키는 분말형 경화촉진제를 사용하였으며, 경화촉진제 혼입율 0%, 1.2%, 1.6%, 2.0%에 따른 콘크리트의 특성을 평가하였다. 경화촉진제 혼입율에 따라 슬럼프 및 공기량 시험에는 큰 차이를 나타내지 않았으며, 1.6%이상을 혼입하였을 때, 재령 6시간에 10MPa를 만족하였다. 자기(건조)수축 길이변화 시험 및 소성수축 시험결과, 경화촉진제의 혼입으로 수화반응 속도에 따른 차이는 있지만, 균열 및 내구성에 대한 문제가 발생되지 않을 것으로 나타났으며, 동결융해 및 탄산화 침투에 대한 저항성도 우수한 것으로 나타났다.