• 한국농공학회논문집
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• 제48권1호
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• pp.51-60
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• 2006

This study was conducted to investigate experimentally the drying shrinkage and the strength properties of redispersible SBR and PAE powder-modified mortars. Polymer-cement ratio, content of shrinkage-reducing agent and antifoamer content were manipulated as the experimental variables. The peculiarity of this study is to obtain a high early-age strength by using the portland cement and alumina cement with the ratio of 8 : 2. Until 7 days of age, the drying shrinkage remarkably increased up to $1\~2\times10^{-4}$, while it tended to decrease as the ratio of polymer to cement ratio and the content of shrinkage-reducing agent increased. Polymer-cement ratio was effective in improving the flexural, tensile and adhesive strengths: As the ratio increased, the strengths correspondingly increased. The flexural strength was in the range of $7\~11$ MPa, the tensile strength was $3.5\~5$ MPa and the adhesive strength was $1.2\~3.9$ MPa. On the other hand, the compressive strength tended to decrease as the polymer-cement ratio increased, and it was in the range of $23\~39$ MPa. All strengths, flexural, tensile, adhesive and compressive strengths, decreased as the content of powder shrinkage-reducing agent increased. It turned out that the polymer-cement ratio influenced more on the behavior of drying shrinkage and the properties of strength than the powder shrinkage-reducing agent did.

• 한국세라믹학회지
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• 제44권9호
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• pp.477-482
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• 2007

The effect of the mixing ratio of compounds in a slag-OPC-Gypsum system on the physical properties of Slag cement is investigated in this study. $Na_2SO_4$ was used as an alkali activator. Blast furnace slag cement was prepared from a mixture of blast furnace slag, ordinary Portland cement and anhydride gypsum. The fluidity and the compressive strength according to the ratio of each mixture were analyzed in statistical analyses in order to discover the parameters influencing the fluidity and compressive strength. The results showed that the hydration of blast furnace slag took place with the addition of $Na_2SO_4$ and that column-crystalline ettringite was created as the main hydration product of the blast furnace slag. In addition, it was found that the compressive strength of blast furnace slag cement tends to increase when the ordinary Portland cement content is higher up to three days. However, it is known that the compressive strength tends to increase as the blast furnace slag content becomes higher with increases in the level of OPC after 28 days. As a result of this analysis, it is believed that the ordinary Portland cement content influences the initial compressive strength of blast furnace slag cement, and that in later days this is highly influenced by the slag content.

• 폴리머
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• 제37권2호
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• pp.148-155
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• 2013

본 연구는 시멘트 혼화용 폴리머를 스티렌과 부틸 아크릴레이트를 단량체로 이용하여 유화제의 첨가량을 달리하여 합성제조하고 제조된 폴리머를 시멘트 모르타르에 혼입하여 그 특성을 파악함으로써 시멘트 혼화용으로써의 사용가능성을 확인하고자 하는 기초적 실험이다. 유화제 첨가량과 단량체비를 달리하여 스티렌-부틸 아크릴레이트(styrene/butyl acrylate)계 폴리머 시멘트 모르타르의 특성은 물-시멘트 비, 공기량, 강도, 방수성 및 염화물 이온 침투저항성을 측정하여 그 특성을 파악하고자 하였다. 연구 결과 보통 시멘트 모르타르에 비해 유화제의 첨가량이 6%일 때, S/BA의 단량체비가 60:40일 때 우수한 강도특성을 나타냈으며, 방수성과 염화물 이온 침투 저항성에서는 유화제의 첨가량과 단량체비보다는 폴리머-시멘트 비에 의해 크게 개선되는 것을 알 수 있었다. 따라서 S/BA를 시멘트 혼화용으로 혼입한 폴리머 시멘트 모르타르의 현장적용이 가능할 것으로 판단되었다.

• Smart Structures and Systems
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• 제8권3호
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• pp.321-341
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• 2011

Acoustic emission (AE) monitoring was conducted for mortar specimens under three types of static loading patterns (cubic-splitting, direct-shear and pull-out). Each of the applied loading patterns was expected to produce a particular fracture process. Subsequently, the AEs generated by various fracture or damage processes carried specific information on temporal micro-crack behaviors of concrete for post analysis, which was represented in the form of detected AE signal characteristics. Among various available characteristics of acquired AE signals, frequency content was of great interest. In this study, cement-based piezoelectric sensor (as AE transducer) and home-programmed DEcLIN monitoring system were utilized for AE monitoring on mortar. The cement-based piezoelectric sensor demonstrated enhanced sensitivity and broad frequency domain response range after being embedded into mortar specimens. This broad band characteristic of cement-based piezoelectric sensor in frequency domain response benefited the analysis of frequency content of AE. Various evaluation methods were introduced and employed to clarify the variation characteristics of AE frequency content in each test. It was found that the variation behaviors of AE frequency content exhibited a close relationship with the applied loading processes during the tests.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.142-147
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• 2000

Durability characteristics of controlled low strength material(flowable fill) with high volume fly ash content was examined. The mix proportions used for flowable fill are selected to obtain low-strength material in the 10 to 15kgf/㎥ range. The optimized flowable fill was consisted of 60kgf/㎥ cement content, 280kgf/㎥ fly ash content, 1400kgf/㎥sand content, and 320kgf/㎥water content. Subsequently, durability tests including permeability warm water immersion, repeated wetting & drying, freezing & thawing for high volume fly ash-flowable fill are conducted The test results indicated that flowable fill has has acceptable durability characteristics.

• Computers and Concrete
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• 제16권6호
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• pp.847-864
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• 2015

This study aimed to develop models of sulfate diffusion and ettringite content profile in cement paste for the predication of the damage behavior in cement paste subject to external sulfate. In the models, multiphase reaction equilibrium between ions in pore solution and solid calcium aluminates phases and the microstructure changes in different positions of cement paste were taken into account. The distributions of expansive volume strain and expansion stress in cement paste were calculated based on the ettringite content profile model. In addition, more sulfate diffusion tests and SEM analyses were determined to verify the reliability and veracity of the models. As the results shown, there was a good correlation between the numerical simulation results and experimental evidences. The results indicated that the water to cement ratio (w/c) had a significant influence on the diffusion of sulfate ions, ettringite concentration profile and expansion properties in cement paste specimens. The cracking points caused by ettringite growth in cement paste specimens were predicted through numerical methods. According to the simulation results, the fracture of cement paste would be accelerated when the specimens were prepared with higher w/c or when they were exposed to sulfate solution with higher concentration.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.312-315
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• 2004

The effects of polymer-cement ratio, antifoamer content and shrinkage-reducing agent content on the strength of high-fluidity polymer-modified mortars using redispersible polymer powder are examined. As a result, the flexural and tensile strengths of the high-fluidity polymer-modified mortars using redispersible polymer powder tend to increase with increasing polymer-cement ratio, and tend to decrease with increasing shrinkage-reducing agent content, regardless of the antifoamer content. However, the compressive strength of the high-fluidity polymer-modified mortars using redispersible polymer powder decrease with increasing polymer-cement ratio and shrinkage-reducing agent content.

• 자원리싸이클링
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• 제25권6호
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• pp.58-64
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• 2016

제지산업은 다량의 산업부산물을 배출하고 있으며, 제지애쉬 발생량도 증가하고 있다. 본 연구에서는 제지애쉬를 시멘트 혼합재로 사용하기 위해서 수화수를 사용하여 전처리 하였다. 전처리 제지애쉬와 석고를 혼합하여 혼합재를 제조하였으며, 이후 시멘트를 대체하여 사용하였다. 제지애쉬 혼합시멘트는 제지애쉬 함량에 따라 물성이 변화하였으나, 10% 이하 사용시에는 기존 OPC와 동등 물성이 발현되었다. 이때 압축강도는 수화물 중 $Ca(OH)_2$의 생성량과도 일정 상관성을 나타내었으며, 3일 강도는 $Ca(OH)_2$ 함량이 증가할수록, 28일 강도는 감소할수록 압축강도가 증가하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.133-136
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• 2007

This study investigates mechanical properties of the concrete using fine particle cement which is manufactured by the pulverizing process. The variable factors are 3 types of W/C such as 40, 50, and 60%, 3 types of curing temperature such as 5, 20, and $35^{\circ}C$, and 5types of the replacement of the fine particle cement such as 0, 25, 50, 75, and 100%. The unit water content, S/a and amount of the SP and AE agents to secure the slump and air content is gradually increased in accordance with amount of replacement. It can be confirmed that the delay of the setting time depending on FC content is decreased corresponding to FC content, so the effect of the acceleration to the setting time is expected. The compressive strength corresponding to FC content is proportionally increased, and the growth is confirmed about $30{\sim}40%$ at a day in 50% of FC contents. However, the increase of the strength is gradually decreased in accordance with increasing age.

• Geomechanics and Engineering
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• 제19권4호
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• pp.307-314
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• 2019

Light construction waste (LCW) particles are pieces of light concrete or insulation wall with light quality and certain strength, containing rich isolated and disconnected pores. Mixing LCW particles with soil can be one of the alternative lightweight soils. It can lighten and stabilize the deep-thick soft soil in-situ. In this study, the unconfined compressive strength (UCS) and its mechanism of Construction Waste Stabilized Lightweight Soil (CWSLS) are investigated. According to the prescription design, totally 35 sets of specimens are tested for the index of dry density (DD) and unconfined compressive strength (UCS). The results show that the DD of CWSLS is mainly affected by LCW content, and it decreases obviously with the increase of LCW content, while increases slightly with the increase of cement content. The UCS of CWSLS first increases and then decreases with the increase of LCW content, existing a peak value. The UCS increases linearly with the increase of cement content, while the strength growth rate is dramatically affected by the different LCW contents. The UCS of CWSLS mainly comes from the skeleton impaction of LCW particles and the gelation of soil-cement composite slurry. According to the distribution of LCW particles and soil-cement composite slurry, CWSLS specimens are divided into three structures: "suspend-dense" structure, "framework-dense" structure and "framework-pore" structure.