• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.76-81
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• 1998

The physical properties of cement sludge treated with hydrofluosilicic acid were investigated. The compressive strength of cement mortar substituted cement sludge was decreased than that of OPC(ordinary portland cement) mortar. Cement sludge, for improving its physical properties, was treated with hydrofluosilicic acid. And compressive strength of cement mortar substituted TCS was greatly improved than that of OPC mortar. Particularly, cement mortar substituted TCS had the higher value in water-proofness than of OPC.

• 한국도로학회논문집
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• 제6권2호
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• pp.61-70
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• 2004

시멘트 안정처리는 우수한 강도발현, 내구성, 강성, 동상저항 등의 우수한 능력을 발휘하지만 건조수축으로 인해 표층부로의 반사균열을 발생시키는 단점을 가지고 친다. 이에 본 연구에서는 시멘트의 건조수축을 억제하여 표층부로의 반사균열을 억제할 수 있는 저수축 시멘트 안정처리기법에 대한 타당성을 연구하였다.

• Geomechanics and Engineering
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• 제35권1호
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• pp.95-108
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• 2023

Soft soil ground is a crucial factor limiting the development of the construction of transportation infrastructure in coastal areas. Soft soil is characterized by low strength, low permeability and high compressibility. However, the ordinary treatment method uses Portland cement to solidify the soft soil, which has low early strength and requires a long curing time. Microbially induced carbonate precipitation (MICP) is an emerging method to address geo-environmental problems associated with geotechnical materials. In this study, a method of bio-cementitious mortars consisting of MICP and cement was proposed to stabilize the soft soil. A series of laboratory tests were conducted on MICP-treated and cement-MICP-treated (C-MICP-treated) soft soils to improve mechanical properties. Microscale observations were also undertaken to reveal the underlying mechanism of cement-soil treated by MICP. The results showed that cohesion and internal friction angles of MICP-treated soft soil were greater than those of remolded soft soil. The UCS, elastic modulus and toughness of C-MICP-treated soft soil with high moisture content (50%, 60%, 70%, 80%) were improved compared to traditional cement-soil. A remarkable difference was observed that the MICP process mainly played a role in the early curing stage (i.e., within 14 days) while cement hydration continued during the whole process. Micro-characterization revealed that the calcium carbonate filling the pores enhanced the soft soil.

• 한국세라믹학회지
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• 제26권5호
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• pp.609-616
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• 1989

For the development of high durable portland cement, it was tested that the some physical properties of ordinary portland cements (OPC) treated with 0.3-1.5wt.% asphalt and 0.5-1.0wt.% carbon black. From the results, the contact angles of water against cements treated with more than 0.6wt.% asphalt were increased over 80 degrees, the initial and the final setting times of cement paste were delayed about 20min. according to the every 0.3wt.% increase of asphalt. The first and the second pick heights of the hydration curve of the cement were considerabely decreased and the induction period of that was increased. And so, the cumulative hydration heat of the cement which was treated with 0.6wt.% asphalt and 0.5wt.% carbon black was lower about 10cal/g than that of ordinary portland cement during 42 hydration times.

• Geomechanics and Engineering
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• 제12권6호
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• pp.935-948
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• 2017

An experimental program was conducted to investigate the effects of the static compaction pressure, cement content, water/cement ratio, and curing time on unconfined compressive strength (UCS) of the cement treated sand. UCS were conducted on samples prepared with 4 different cement/sand ratios and were compacted under the lowest and highest static pressures (8 MPa and 40 MPa). Each sample was cured for 7 and 28 days to observe the impact of curing time on UCS of cement treated samples. Results of the study showed the unconfined compressive strength of sand increased as the cement content (5% to 10%) of the cement-sand mixture and compaction pressure (8 MPa to 40 MPa) increased. UCS of sand soil increased 30% to 800% when cement content was increased from 2.5% to 10%. Impact of compaction pressure on UCS decreased with a reduction in cement contents. On the other hand, it was observed that as the water content the cement-sand mixture increased, the unconfined compressive strength showed tendency to decrease regardless of compaction pressure and cement content. When the curing time was extended from 7 days to 28 days, the unconfined compressive strengths of almost all the samples increased approximately by 2 or 3 times.

• 한국산학기술학회논문지
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• 제21권10호
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• pp.23-29
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• 2020

철도 공용에 따른 반복 동하중을 지속적으로 경험하는 흙 구조물은 지속적인 침하가 발생한다. 본 논문에서는 흙 구조물을 구성하는 세립분 함량 변화에 따른 시멘트 혼합토의 침하 및 강성 특성을 반복 동하중 시험을 실시하여 평가하였다. 흙의 세립분 함량, 시멘트 함량, 양생일 수을 변화시켜가면서 총 18 케이스의 시험을 실시하였다. 동 시험결과로부터 시멘트 혼합토는 침하 측면에서 시멘트 함량 3% 이상 사용 시 세립분 함량이 높은 흙에서도 침하 저감 가능성이 크다는 것을 확인할 수 있었다. 또한, 시멘트 함량이 0% 에서 3 ~ 4% 로 증가 시 탄성 침하량은 1/4 수준으로, 소성 침하량은 1/6 수준으로 감소하는 것을 확인할 수 있었다. 시멘트 혼합토는 강성 측면에서 시멘트 함량 증가에 따라 회복탄성계수가 증가하는 경향을 보였다. 시멘트 함량 3% 이상 사용 시에는 흙의 세립분 함량 40% 수준에서도 철도 상부노반 다짐 강성 품질기준인 80 MPa을 만족하는 것을 확인할 수 있었다.

• Geomechanics and Engineering
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• 제31권4호
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• pp.409-422
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• 2022

The use of calcium sulfoaluminate (CSA) cement as a rapid-hardening cement admixture or eco-friendly alternate for ordinary Portland cement (OPC) has been attempted over the years, but the cost of CSA cement and availability of suitable aluminium resource prevent its wide practical application. To propose an effective ground improvement design in sandy soil, this study aims at blending a certain percentage of CSA with OPC to find an optimum blend that would have fast-setting behavior with a lower carbon footprint than OPC without compromising the mechanical properties of the cemented sand. Compared to the 100% CSA case, initial speed of strength development of blended cement is relatively low as it is mixed with OPC. It is found that 80% OPC and 20% CSA blend has low initial strength but eventually produces equivalent ultimate strength (28 days curing) to that of CSA treated sand. The specific OPC-CSA blend (80:20) exhibits significantly higher strength gain than using pure OPC, thus allowing effective geotechnical designs for sustainable and controlled ground improvement. Further parametric studies were conducted for the blended cement under various curing conditions, cement contents, and curing times. Wet-cured cement treated sand had 33% lower strength than that of dry-cured samples, while the stiffness of wet-cured samples was 25% lower than that of dry-cured samples.

• Geomechanics and Engineering
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• 제33권1호
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• pp.41-51
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• 2023

Cementitious materials such as Ordinary Portland Cement (OPC), fly ash, lime, and bitumen have been employed for soil improvement over the years. However, due to the environmental concerns associated with the use of OPC, substituting OPC with calcium sulfoaluminate (CSA) cement offers good potential for ground improvement because it is more eco-friendly. Although earlier research has investigated the stabilizing effects of CSA cement-treated sand, no attempt has been made to examine soil behavior under high confining pressure. As a result, this study aimed to investigate the shear strength and mechanical behavior of CSA cement-treated sand using a consolidated drained (CD) triaxial test with high confining pressure. The microstructure of the examined sand samples was investigated using scanning electron microscopy. This study used sand with CSA cement contents of 3%, 5%, and 7% and confining pressures of 0.5, 1.0, and 1.5 MPa. It revealed that the confining pressures and CSA cement content significantly affected the stress-strain and volumetric change behavior of CSA cement-treated sand at high confining pressures.

• 한국지반공학회논문집
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• 제31권1호
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• pp.37-46
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• 2015

본 연구에서는 고로슬래그의 수화반응을 일으키는 극한미생물(Bacillus halodurans) 알칼리 활성화제를 사용하여 현장 지반을 고결시키는 연구를 수행하였다. 현장 토사를 고결시키기 위해 저가의 미생물 배양액을 대량으로 제조하였으며, 제조된 미생물 배양액에 대한 생장실험을 실시하여 기존 미생물 배양액과의 효율성을 비교하였다. 현장 적용은 고로슬래그와 미생물 배양액을 혼합한 알칼리 활성화제로 고결된 지반(미생물 고결토), 보통 포틀랜드 시멘트로 고결된 지반(시멘트 고결토), 그리고 무처리된 지반(무처리토)으로 나누어 시험 시공하였다. 현장 지반 3곳 모두 동일한 크기인 가로 2.6m, 세로 4m, 깊이 0.2m로 시공하였다. 현장 시공 후 28일에 코어를 채취하여 일축압축시험을 실시하였으며, 무처리토 지반은 토베인시험으로 지반의 강도를 평가하였다. 본 연구에서 개발한 미생물 고결토는 시멘트 고결토에 비해 약 1/5 정도 낮은 강도를 보였으나, 무처리토에 비해서는 약 6배 정도 높은 강도를 발휘하였다. 또한, 미생물 고결토의 pH는 10으로 11 이상인 시멘트 고결토보다 낮아 상대적으로 친환경적인 것으로 판단되었으며, SEM-EDS 분석을 통하여 고결도와 고결 물질인 C-S-H 수화물이 생성됨을 확인할 수 있었다.

• 한국지반공학회논문집
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• 제32권9호
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• pp.29-36
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• 2016

국내 철도교대 뒤채움재의 구조는 시멘트 안정처리된 골재, 일반 골재, 토사로 되어 있다. 시멘트 안정처리된 골재는 강도 증진효과로 인해 내부마찰각이 $40^{\circ}$이상 증가 된다. 그러나 실무에서는 교대설계 시 경험치인 $30{\sim}35^{\circ}$의 내부마찰각을 적용한다. 이는 과다설계의 원인이 될 수 있으므로 합리적인 물성치 값의 설정이 필요하다. 본 논문은 원형모형 실험과 CBR 실험을 통해 시멘트 안정처리된 골재의 시멘트 혼합 비율에 따른 강도 및 침하특성을 정량적으로 분석하였다. 시멘트 안정처리된 골재의 침하율은 반복재하 함에 따라 감소하였다. 또한 양생함에 따라 침하량이 감소하였다. 재령 28일 기준으로 일반골재 대비 시멘트 안정처리된 골재의 CBR 증가율은 13~16배 증가하였다.