• 한국지반신소재학회논문집
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• 제11권3호
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• pp.37-42
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• 2012

국내에 시공되고 있는 매입말뚝의 충전재는 주로 시멘트 페이스트를 사용하고 있다. 시멘트 페이스트를 사용한 충전재는 현장 시공 시 실 주입량이 지나치게 커서 비효율적이며, 설계기준에 비해 지나친 강도를 발현하여 시멘트사용에 따른 환경성 문제를 지니고 있다. 이에 대한 대안으로 매입말뚝 시공 시 발생하는 굴착토사를 활용하여 적정 고화제를 혼합한 고화토를 충전함으로써 폐기물 처리비용 절약과 친환경적인 고화토 충전공법의 현장적용성을 검토하였다. 일축압축강도 시험과 현장 재하시험 결과를 토대로 고화토와 기존 시멘트 페이스트 주입재의 성능을 비교하고 설계기준에 적합한지 여부를 검토하였다. 그 결과 고화토 충전재는 시멘트 페이스트 충전재와 유사한 성능을 나타내며 설계기준에도 적합하여 매입말뚝 충전재로서 고화토의 적용성을 확인하였다.

• Computers and Concrete
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• 제8권3호
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• pp.279-292
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• 2011

The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.

• 토지주택연구
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• 제3권1호
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• pp.83-88
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• 2012

In this study, physical characteristics of cement and/or concrete materials that are typically used for energy-foundation (EF) structures have been studied. The thermal conductivity and structural integrity of the cement-based materials were examined, which are commonly encountered in backfilling a vertical ground heat exchangers, cast-in-place concrete piles and concrete lining in tunnel. For this purpose the thermal conductivity and unconfined compression strength of cement-based materials with various curing conditions were experimentally estimated and compared. Hydration heat generated from massive concrete in the cast-in-place concrete energy pile was observed for 4 weeks to estimate its dissipation time in the underground. The hydration heat may mask the in-situ thermal response test (TRT) result performed in the cast-in-place concrete energy pile. It is concluded that at least two weeks are needed to dissipate the hydration heat in this case. In addition, a series of numerical analysis was performed to compare the effect of thermal property of the concrete material on the cast-in-place pile.

• Computers and Concrete
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• 제10권4호
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• pp.391-407
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• 2012

Utilization of supplementary cementing materials (SCM) by the cement industry, as a highly promising solution of sustainable cement development aiming to reduce carbon dioxide emissions, necessitates a more thorough evaluation of these types of materials on concrete durability. In this study a comparative assessment of the effect of SCM on concrete durability, of every cement type as defined in the European Standard EN 197-1 is taking place, using a software tool, based on proven predictive models (according to performance-related methods for assessing durability) developed and wide-validated for the estimation of concrete service life when designing for durability under harsh environments. The effect of Type II additives (fly ash, silica fume) on CEM I type of cement, as well as the effect of every Portland-composite type of cement (and others) are evaluated in terms of their performance in carbonation and chloride exposure, for a service life of 50 years. The main aim is to portray a unified and comprehensive evaluation of the efficiency of SCM in order to create the basis for future consideration of more types of cement to enter the production line in industry.

• 한국세라믹학회지
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• 제37권2호
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• pp.145-151
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• 2000

In order to investigate the rheological properties of belite-rich cement(BRC) added polycarbonate-based superplasticizer and blastfurnace slags which have different blaines at 4500, 6000 and 8000$\textrm{cm}^2$/g, the change of minislumps and mortar slumps are measured with time. The rheological properties improve as specific surface area of added slag decreases or amount of polycarbonate-based superplasticizer increases. The slump loss can be controlled effectively by the steric hinderance effect of polycarbonate-based superplasticizer. According to the results, when mix proportion of the mortar is 1.5% mass content of superplasticizer and 30% mass addition of blastfurnace slag which blaine is 4500$\textrm{cm}^2$/g, the best mortar slump can be achieved without any significant segregation of materials.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.205-206
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• 2019

This study investigated the fluidity and compressive strength properties of blast furnace slag based non-cement paste containing ferronickel slag powder to evaluate the possibility of use in for cement replacement materials. As a result, the fluidity of non-cement paste showed a higher flow as the mixing ratio of ferronickel slag powder increased. The compressive strengths similar to those of the non-cement paste using only blast furnace slag powder were obtained when 5 and 10% of ferronickel slag powder were used.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.125-126
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• 2021

Fly ash, has been widely used as one of the main supplementary cementitious materials (SCMs) in the world, to replace part of cement to significantly save energy and reduce greenhouse emission. Via mechanical activation, fly ash can replace more cement without impairing early age compressive strength. This study focuses on the strength-based evaluation of carbon dioxide emission for blended cement composite containing mechanically activated fly ash. Results indicate that under similar compressive strength, a prominent drop has been witnessed in embodied energy of binary cement and CO2 emission of the composite containing mechanically activated fly ash compared with those containing ordinary fly ash.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.185-186
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• 2023

Recently, a lot of nano-scale material technology development and research have been conducted in construction fields to improve the compressive strength and durability of cement-based Composites. There are some studies that have confirmed the properties and application effects of cement-based complex using each nanomaterial, but development and research using both materials are relatively limited. This study sought to confirm the effect of multi-wall carbon nanotubes (MWCNT) and nanosilica, which are representative construction nanomaterials, on the compressive strength, voids, and microstructure formation of cement. The purpose was to produce a cement composite by changing the mixing rate of the two nanomaterials, and to find the optimal mixing amount considering its mechanical and rheological properties.

• Advances in concrete construction
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• 제11권5호
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• pp.419-428
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• 2021

The pH of cement-based materials (CBMs) is an important factor for their durability, sustainability, and long service life. Currently, the use of supplementary cementitious materials (SCMs) is becoming mandatory due to economic, environmental, and sustainable issues. There is a decreasing trend in pH of CBMs due to incorporation of SCMs. The determination of numerical values of pH is very important for various low and high volume SCMs blended cement mortars for the better understanding of different defects and durability issues during their service life. In addition, the effect of cement hydration and pozzolanic reaction of SCMs on the pH should be determined at initial and later ages. In this study, the effect of low and high-volume fly ash (FA) and ground granulated ballast furnace slag (GGBFS) cement mortars in different curing conditions on their pH values has been determined. Thermal gravimetric analysis (TGA) was carried out to support the findings from pH measurements. In addition, thermal conductivity (k-value) and strength activity indices of these cement mortars were discussed. The results showed that pH values of all blended cement mortars were less than ordinary Portland cement (OPC) mortar in all curing conditions used. There was a decreasing tendency in pH of all mortars with passage of time. In addition, the pH of cement mortars was not only dependent on the quantity of Ca(OH)₂. The effect of adding SCMs on the pH value of cement mortar should be monitored and measured for both short and long terms.

• Advances in concrete construction
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• 제11권5호
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• pp.409-417
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• 2021

The incorporation of non-biodegradable tyre waste in cement-based material has gained more interest towards sustainable construction these days. Crumb rubber (CR) from waste tyre is an alternative for sand replacement in low strength applications. Many researchers have studied CR cement-based materials produced by normal mixing (NM) method and reported a significant decrease in compressive strength due to CR. To compensate this strength loss, this research aims to study the innovative incorporation of CR in cement composite via the preplaced mixing (PM) method. In this investigation, cement composite was produced with NM and PM methods by replacing sand with 0%, 50%, and 100% CR by volume. The test results showed no significant difference in terms of densities of cement composite prepared with both mixing methods. However, cement composite prepared with PM method had lower strength reduction (about 10%) and lowered drying shrinkage (about 20%). In addition, the sound absorption coefficient and noise reduction coefficient of CR cement composite prepared by PM method were in similar range as those prepared with NM method. Overall, the results demonstrate that the PM method is promising, and the maximum replacement level of 50% is recommended for CR in the cement composite.