• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.69-74
• /
• 2003

This study evaluated durability through measurement of substituted test piece's pH degree and experiments of neutralization. Comparing and evaluating cared test piece's pH degrees which we got before the neutralization and after the neutralization. After evaluating neutralization depth through neutralization, evaluating neutralization properties by Fly Ash replacement ratio. pH degree was decreased by cement replacement ratio of Fly Ash. And in the case of substitution of the same amount of Fly Ash, fine aggregate replacement ratio was increased. When the test piece, which had been cared in high temperature, was promoted to neutralization, Among the test piece which was replaced with Fly Ash 40%, the test piece which has high rate of fine aggregate proved opposition of neutralization Through the test, Ⅰ summarized that the test piece cared in high temperature was mostly effected by compress strength, the test piece cared in low temperature was mostly effected by pH degree.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
• /
• pp.365-368
• /
• 2005

Waste concrete powder(WCP) has been estimated with a great value-added material as by-product of waste concrete manufactured to fine and coarse aggregate for concrete, because it is able to utilized for cement clinker and concrete admixture. Experimental tests were performed as such plastic viscosity of paste, flow and compressive strength of mortar by surface area of WCP. As a result, flow and 28days compressive strength of mortar was decreased according to increased replacement ratio of WCP as compared to control mortar. Also, plastic viscosity of paste used WCP1 and WCP2 was decreased with increasing replacement ratio, but WCP3 was increased with increasing replacement ratio.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
• /
• pp.209-210
• /
• 2019

Current international concerns are the energy crisis due to climate change and depletion of fossil fuels due to global warming. Korea has a very high dependency on energy imports 93%. In Korea, 63% of the country is forested, and a power plant using wood biomass is being built in Korea. Biomass fly ash, a by-product of biomass energy generation, is now being discarded. There is little research to utilize discarded biomass fly ash. Therefore, this study aims to solve the environmental problems, develop new mixed materials, improve the quality and utilize the biomass fly ash, which is a by-product of the industrial waste. As a result of the experiment, the flowability decreased as the replacement ratio of biomass fly ash increased. As the replacement ratio of biomass fly ash decreased, the amount of air content.

• 콘크리트학회논문집
• /
• 제24권5호
• /
• pp.597-604
• /
• 2012

이 연구에서는 2464개의 시멘트 콘크리트 배합과 776개의 혼화재가 치환된 혼합 시멘트 콘크리트 배합을 포함하는 실험 데이터베이스를 이용하여 콘크리트 압축강도 및 혼화재 치환율에 따른 콘크리트 $CO_2$ 배출량을 평가하였다. 국내 생애주기 데이터 목록에 기반한 콘크리트 $CO_2$ 평가에서 고려된 시스템은 요람에서 현장 콘크리트 타설 전까지로서 구성재료, 운반 및 생산단계를 포함하고 있다. 콘크리트의 성능 효율성 지표로서 결합재 지수와 $CO_2$ 지수가 분석되었으며, 콘크리트 $CO_2$ 배출량을 평가하기 위한 단순 식이 각 혼화재의 치환비 및 콘크리트 압축강도의 함수로서 제시되었다. 따라서 이 제안된 모델은 목표 압축강도 및 목표 시멘트 콘크리트 대비 $CO_2$ 배출 저감율을 만족하는 콘크리트 배합설계를 위하여 단위 결합재 양 및 혼화재 종류와 치환비를 결정하는 데 가이드 라인으로서 유용하게 이용될 수 있을 것으로 기대된다.

• 한국건설순환자원학회논문집
• /
• 제4권4호
• /
• pp.425-430
• /
• 2016

산업의 급격한 발달과 함께 사회 또한 급격한 발달을 이루면서 전 세계는 편리한 생활을 이룰 수 있게 되었다. 하지만 이러한 산업의 발달의 이면에는 환경오염으로 인한 지구온난화와 산업부산물 대량 발생 등의 문제가 발생하고 있는 실정이다. 이에 본 연구는 건축분야에서 $CO_2$ 배출 비율이 높은 시멘트의 사용량을 줄이고자 산업부산물인 고로슬래그와 순환 유동층 연소 플라이애시를 사용하였으며, 국내 염색공단에서 배출되고 있는 20만 톤 이상의 슬러지를 재활용하는 방안을 검토하기 위해 염색슬러지 탄화물을 활용한 무시멘트 경화체의 특성에 대한 기초자료를 제시하고자 하였다. 그 결과, 염색슬러지 탄화물의 치환율이 증가함에 따라 공기량은 증가하였고 플로어는 증가하였다. 또한 염색슬러지 탄화물 치환율이 증가함에 따라 휨강도 및 압축강도는 감소하는 경향을 보였다.

• Computers and Concrete
• /
• 제3권2_3호
• /
• pp.163-175
• /
• 2006

This research was conducted to determine effect of pumice aggregate ratio, cement dosage and slumps on freeze-thaw resistance, density, water absorption and elasticity of concrete. In the first batch, $300kg/m^3$ cement dosage were kept constant and pumice ratios were changed as 25%, 50%, 75% and 100% of replacement for normal aggregate by volume for $3{\pm}1cm$, $5{\pm}1cm$ and $7{\pm}1cm$ slumps. Other batches were prepared with $200kg/m^3$, $250kg/m^3$, $350kg/m^3$, $400kg/m^3$ and $500kg/m^3$ cement dosages and 25% pumice aggregate +75% normal aggregate at a constant slump. Test results showed that when pumice-aggregate ratio decreased the density and freeze-thaw resistance of concretes increased. With increasing of cement dosage in the mixtures, density of the concretes increased, however, freeze-thaw resistance of concretes decreased. Water absorption of the concrete decreased with increasing cement dosage but increased with the pumice ratio. Water absorption of the concrete also decreased after freeze-thaw cycles. Freeze-thaw resistance of concretes was decreased with increasing the slumps.

• Advances in concrete construction
• /
• 제5권1호
• /
• pp.31-48
• /
• 2017

Supplementary cementitious materials (SCM) have turned out to be a vital portion of extraordinary strength and performance concrete. Metakaolin (MK) is one of SCM material is acquired by calcinations of kaolinite. Universally utilised as pozzolanic material in concrete to enhance mechanical and durability properties. This study investigates the fresh and hardened properties of conventional concrete (CC) and self compacting concrete (SCC) by partially replacing cement with MK in diverse percentages. In CC and SCC, partial replacement of cement with MK varies from 5-20%. Fresh concrete properties of CC are conducted by slump test and compaction factor tests and for SCC, slump flow, T500, J-Ring, L-Box, V-Funnel and U-Box tests. Hardened concrete characteristics are investigated by compressive, split tensile and flexural strengths at age of 7, 28 and 90 days of curing under water. Carbonation depth, water absorption and density of MK based CC and SCC was also computed. Fresh concrete test results indicated that increase in MK replacement increases workability of concrete in a constant w/b ratio. Also, outcomes reveal that concrete integrating MK had greater compressive, flexural and split tensile strengths. Optimum replacement level of MK for cement was 10%, which increased mechanical properties and robustness properties of concrete.

• Advances in concrete construction
• /
• 제11권3호
• /
• pp.183-192
• /
• 2021

Due to economic and environmental benefits, increasing the substitution ratio of ordinary cement by industry by-products like fly ash (FA) is one of the best approaches to reduce the impact of the concrete industry on the environment. However, as the substitution rate of FA increases, it will have an adverse impact on the performance of cement-based materials, so the actual substitution rate of FA is limited to around 10-30%. Therefore, in order to increase the early-age strength of high replacement (30-70%) low-calcium ultrafine FA blended cement paste, sodium sulfate and calcium sulfate dihydrate were used to improve the reactivity of FA. The results show that sodium sulfate has a significant enhancement effect on the strength of the composite pastes in the early and late ages, while calcium sulfate dihydrate has only a slight effect in the late ages. The addition of sodium sulfate in the cement-FA blended system can enhance the gain rate of non-evaporation water, and can decrease the Ca(OH)2 content. In addition, when the sulfate chemical activators are added, the ettringite content increases, and the surface of the FA is dissolved and hydrated.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.616-619
• /
• 2004

This study has focused on the possibility for recycling of tailings from the Sangdong tungsten mine as powder. The experimental tests for entrapped water ratio were carried out in accordance with the specificed method by Okamura. The rheological measurements of cement paste were conducted by using a commerically digital Brookfield viscometer (Model LVDV-II+) equipped with cylindrical spindles. The results of this study, in case of cement paste mixed with tailings, entrapped water ratio was decreased with increasement of mixing ratio. Thickness of pseudo water film was increased, and mean plastic viscosity was decreased with increasing replacement.

• 한국건축시공학회지
• /
• 제7권1호
• /
• pp.91-98
• /
• 2007

In this study, the property and plastic cracking pattern of concrete were compared and analyzed with the replacement ratio of fly ash 0, 5, 10, 15, 20% by cement weight. And curing conditions of concrete were given variously such as indoors(with wind speed as 0, 300, 500m/min), outdoors and chamber. The hydration temperature had a tendency to decrease as the replacement ratio of fly ash increased, and in the case of the wind speed 0m/min, it was showed that the moment that the amount of evaporation of water from surface of reference concrete was more than the volume of bleeding was 90 min since casting concrete. The time that the crack initiated had a tendency to be more quickly as the replacement ratio of fly ash increased. The number, length, width and area of crack in the indoor curing, exposed outdoor curing, enclosed outdoor curing had a tendency to decrease as the replacement ratio of fly ash increased. The crack had a tendency to decrease in sequence of exposed outdoor, enclosed outdoor curing, indoors curing. The outbreak of cracking by the change of temperature and humidity was affected by relative humidity more than temperature and the cracking had a tendency to increase as relative humidity lowered.