In this work, ultra-fine calcium oxide (CaO) powder derived from eggshells is used as the starting material to synthesize mineral trioxide aggregate (MTA). The prepared CaO powder is confirmed to have an average particle size of 500 nm. MTAs are synthesized with three types of fine CaO-based powders, namely, tricalcium silicate (C3S), dicalcium silicate (C2S), and tricalcium aluminate (C3A). The synthesis behavior of C3S, C2S and C3A with ultra-fine CaO powder and the effects of C3A content and curing time on the properties of MTA are investigated. The characteristics of the synthesized MTA powders are examined by X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), and a universal testing machine (UTM). The microstructure and compressive strength characteristics of the synthesized MTA powders are strongly dependent on the C3A wt.% and curing time. Furthermore, MTA with 5 wt.% C3A is found to increase the compressive strength and shorten the curing time.

This study was performed in order to obtain the effect of the compressive strength of the cured product with manufacturing conditions (amounts of fine aggregate and different types of alkali activator). Material which is the basis of the cured product was used for the blast furnace slag, which has a latent hydraulic activity. Consequently, when using sodium hydroxide as the alkali activator, it is possible to obtain a higher compressive strength than using the calcium hydroxide. And also, it can be added a 10% of fine aggregate with blast furnace slag to improve the compressive strength.

고로슬래그는 유동성 장기강도 및 내구성이 좋고 수화열을 낮아 경화체를 제조함에 따른 적용성이 우수하지만, 몇 가지 문제점을 갖는다. 시공시간이 증가하고 회전속도가 늦고 초기강도가 낮다. 본 연구에서는 알칼리활성화를 이용한 경화체 제조에 있어 필요한 알칼리 수용액을 해수담수화 과정에서 발생하는 농축수의 전기분해를 통하여 공급하였으며. 알칼리 수용액을 이용하여 고로슬래그와 경화체를 제작하였다. 결과는 다음과 같이 요약할 수 있다 : 모르타르의 압축강도는 NaOH 2%이하일 때는 감소하고, 6% 이하까지는 증가한다. 그리고 NaOCl의 함량이 증가할수록 압축강도도 증가한다. 그러나 NaCl이 모르타르에 존재하면 초기강도보다 재령 28일차 강도는 감소하게 된다.

본 논문에서는 ASTM C 1260을 이용하여 국내산 골재를 대상으로 알칼리-실리카 반응 판정 결과 반응성으로 판정된 골재를 대상으로 알칼리-실리카 반응 억제효과를 고찰하기 위하여 플라이애시와 질산리튬을 사용한 시멘트 경화체의 ASTM C 1260 적용성을 평가하였다. 알칼리-실리카 반응에 의한 팽창현상이 발생하는 지역에서 CaO 함량이 낮은 플라이애시를 시멘트 중량의 10, 20, 30%를 대체하는 경우 ASTM C 1260으로 알칼리-실리카 반응 억제효과를 확인할 수 있었다. 그러나 질산리튬을 사용할 경우는 ASTM C 1260은 시편을 1N NaOH 수용액에 수침하여 80℃의 온도로 길이변화를 유도하므로 시편내에 혼입된 질산리튬 성분이 외부로 용출될 수 있기 때문에 알칼리-실리카 반응 억제효과를 도출하지 못하였다. 따라서 질산리듐의 ASR 억제효과를 확인하기 위해서는 다른 시험방법을 고려해야 한다.

Carbonized concrete structure becomes superannuated gradually and its accelerated subsequent deterioration process leads to corrosion of steel while it ages. Recently economical and environmental concern about remodeling such superannuated concrete, including the basic structure of concrete, has been rapidly growing. Alkali restorative, which restores alkalinity in carbonized concrete structure, is used in the field of remodeling in order to improve the property of concrete structure. There have been many different kinds of materials which restore alkalinity in carbonized concrete. They can be classified according to their structural elements. This study focuses on the alkali restorative which mainly consists of silicic lithium metallic salt while examining the durable effectiveness of the factors (such as water permeation, surface erosion, elution of alkali, etc.), which will continuously affect concrete as deteriorating factors even after the restoration of alkali. The result shows that the alkali restorative consisting mainly of silicic lithium contributes to water-resistance, surface strength, and long term durability of alkali due to water permeation in carbonized concrete.

In this study, to analyze the change of mass of concrete structure subjected to fire damage, cement paste was exposed at high temperature to maintenance time and analyzed mass change characteristics by TGA analysis. As a result of analysis, the mass reduction rate of cement paste decreased with increasing heating time after heating at high temperature.

In this research is underway to determine the exact damage level of concrete structures damaged by fire. Cement paste hardened at 700℃ was characterized by TGA. As the depth increased, the mass reduction rate increased and the mass reduction rate decreased as the retention time increased.

In this study, the chemical deformation of cement pastes was determined by chemical analysis. X-ray diffraction equipment was used to investigate the chemical transformation. The decrease of ettringite and the collapse of gypsum were confirmed and then the calcium hydroxide gradually decreased.

The purpose of this study is to corroborate hydration and porosity of cement paste by the low water-cement ratio specimen. The test results show that calcium hydroxide was increased as the moisture was supplied from the outside and the porosity was lowered with a rapid manner.

In this study, the chemical deformation of cement pastes was determined by chemical analysis. The specimen for FT-IR analysis was prepared in the form of fine powder by grinding before heating. As the temperature increased, the hydrates inside the cement paste tended to decrease.

Recently, a method of using blast furnace slag to reduce the amount of cement which generates a large amount of carbon dioxide during the manufacturing process has been studied. Blast furnace slag is a latent hydraulic property material and requires the use of alkali activator. However, alkali activator is expensive and have problems in use. Therefore, in this study, an alkali aqueous solution was used instead of an alkali activator. The alkaline aqueous solution used in this study was obtained by electrolysis of pure water and has strong alkalinity of pH12. As a result, we found that the use of alkali aqueous solution is effective in improving the reactivity of blast furnace slag.

This study investigates the effect of elevated temperatures on the pore structure of cement paste which, in turn, can provides information to evaluate the damage level of concrete structures due to fire. Mercury intrusion porosimetry (MIP) test was conducted for this investigation. Test results showed that the higher the temperature, the higher is the pore volume of cement paste and the wider is the pore distribution.

This is an experimental study on manufacturing of non-cement matrix. Materials like cement and blowing agent in foamed concrete is replaced by by-products from blast furnace slag and paper ash. Sample Plain with density showed lowest. The compressive strength test result, showed a similar trend with density. And it showed that compressive strength of the 4:6 was highest.

This is an experimental study on manufacturing of non-cement matrix. Materials like cement and blowing agent in foamed concrete is replaced by by-products from blast furnace slag and paper ash. Further, the experiment was performed by replacing alkali with natural gypsum by (0, 5, 15, 20, 25, 35, 45) of weight of alkali (wt.%) in order to reduce the amount of expensive alkali activator. Sample NG-0.15 with density showed lowest. After this point, density increases as replacement ratio increases. The compressive strength test result, showed a similar trend with density. And it showed that compressive strength of the NG-0.45 was highest.

본 연구는 시멘트 경화체로부터의 알칼리 침출에 의한 pH 증가와 알칼리 침출속도에 관하여 수행되었다. 배합, 물-시멘트 비, 결합재에따른 영향을 평가하기 위해 각각을 변수로 하여 시험체를 제작하였다. 시험체는 정사각형 수조형태로 내부에 물을 저장하여 이온이 해리되어 침출될 수 있도록 하였다. 또한 시험체 내부 용액의 대기접촉으로 인한 예기치 못한 화학적 반응을 방지하기 위해 폴리에틸렌 수지로포장했다. 침투능과 침투속도를 결정하기 위해 용액의 pH는 더 이상 변화가 없을 때까지 시간 경과에 따라 측정하였다. 알칼리 침출에 의한 용액의 pH 변화에 있어서 물-시멘트 비의 영향은 거의 없는 것으로 나타났으며, 반면에 결합재에 따른 영향은 큰 것으로 나타났다. 결합재로 OPC 만을 사용한 경우에 알칼리 침출이 높았으며, 30% PFA와 60% GGBS의 경우에 알칼리 침출이 낮았다. pH 측정이 종료된후, 시험체 내부 표면으로부터 깊이 1.0 mm 간격으로 채취한 시료를 증류수로 현탁시켜 현탁액의 pH를 측정하였다. OPC의 경우에는 약7-8 mm 깊이까지 침출의 영향을 받고, 30% PFA와 60% GGBS의 경우에는 침출 영향을 받는 깊이가 더 깊어짐을 알 수 있었다.

산업 부산물인 고로슬래그 미분말은 잠재 수경성을 가지고 있어 Non-CO₂ 시멘트를 대표하는 물질로 평가받고 있다. 콘크리트 구조물의 균열은 콘크리트 자체의 자기수축 및 건조 수축에 기인한다. 이러한 균열은 수분과 공극의 이동 통로로 작용하여 콘크리트의 내구성을 저하시키는 주요 요인으로 작용한다. 본 연구는 2, 3종 고로 슬래그 미분말을 활용하여 공극 구조를 개선하고자 한 것으로 분말도 4,000 cm²/g과, 7,000 cm²/g을 사용하여 페이스트를 제작하고 이에 따른 공극 비교를 실시하였다. 슬래그 미분말의 치환량은 20, 40, 70%를 실시하였다. 팽창에 의한 수축 보상을 위하여 CSA를 일정 부분 치환하여 실험을 실시하였으며, 슬래그 분말도 증가에 따라 비표면적이 증가하고 이에 따른 작업성이 변동도 하기 때문에 이를 고유동화제를 사용하여 동일한 물배합비를 유지하였다. 슬래그 미분말 증가에 따른 총 공극량은 동일한 수준을 유지하였으나 0.02 ㎛ 이하의 공긍량은 증가하는 것으로 나타났으며 특히, 0.05~0.1 ㎛ 이하의 공극감소가 치환량 70%에서 높은 것을 알 수 있었다. 결과적으로 시멘트 페이스트 경화체 조직이 치밀해져 수밀한 콘크리트의 제조가 가능할 것으로 판단되었다.

This study is the basic experiment for manufacturing non-cement matrix of lightweight based on blast furnace slag. Consequently, the decrease ratio of the density of matrix about the density of mix showed Ca(OH)2 up to be the highest when adding 2.5%. And the compressive strength increased as the addition ratio of Ca(OH)2 was increased.

Concrete is generally accepted to have good fire resistance. It mainly relies on the assumption that concrete has low heat-transfer characteristic and spalling does not occur during the course of a fire. However, the significant numbers of fire accidents have shown in recent years that incidence of spalling has caused sever damages to many structures. This research has investigated a series of catastrophic tunnel fires and tested on the behaviour properties of concrete in association with loading in fire. This paper present that the theoretical consideration and experimental results are used the information of concrete spalling.

본 연구에서는 황토에 시멘트나 유기계 접착제를 첨가하지 않은 천연재료 황토결합재를 사용하여 황토경화체를 제작하고, 배합조건에 따른 강도성상을 평가하였다. 황토와 석회의 결합재에 천연재료를 첨가할 경우 사용한 천연재료는 모두 물리적 성능을 개선하는 효과가 있었다. 천연재료 중에서 석회는 황토경화체의 물성을 증가시키는데 가장 큰 영향을 미치고 있다. 황토경화체의 물리적 특성은 적용한 배합비 중에서 W/B 45%, 단위수량 285kg/m3, 석회첨가율 60%일 때 가장 우수하게 나타나고 있다.