PURPOSES : The purpose of this study was to investigate the performance of additives that affect internal curing in order to reduce the damage occurring in concrete pavements. METHODS : SAP was used as an additive to reduce internal curing in concrete pavements. SAP is an additive that has a very high absorption rate which prevents concrete wrappers from externally draining water. To evaluate the internal curing performance according to the ratio of SAP, we identified the number of cracks and amount of abrasion reduction. RESULTS : Plastic shrinkage and durability of a concrete mixture with added SAP were evaluated. The following results were obtained: (1) SAP showed a tendency to reduce slumps due to absorption of the concrete mixture. (2) It was possible to verify that concrete condensation did not occur during the penetration resistance test and that the initial curing did not lead to reactions within the mixture. (3) Adding more than 0.6% of SAP for dry curing resulted in greater compressive strength at all ages than OPC, with the highest compression strength of 0.9% after 56 days. (4) Regarding abrasion resistance, it was found that adding SAP was 30~50% better than adding the OPC mixture, and at 0.9% compression strength, abrasion resistance showed the best performance. (5) In the chlorine ion immersion resistance experiment, the passing charge of the OPC mixture was rated “high,” but it was rated “normal” in SAP. The results showed that the addition of SAP improved the water density of concrete due to internal curing effects, and that it showed the greatest chlorine ion penetration resistance for a compressive strength of 0.9%. (6) Regarding plastic shrinkage resistance, cracks did not occur on the surface until the end of the experiment, but the plastic shrinkage rate upon addition of SAP was relatively low compared to that of the OPC mixture. CONCLUSIONS : Recent studies have shown that internal curing techniques can be applied using SAP to prevent shrinkage due to the loss of water and to decrease the effects of hydration. If internal curing effects are expressed using SAP, it is thought that contraction due to a loss of moisture and reduction in sign language reaction can be prevented.

The purpose of this study is to investigate the optimum conditions of dispersion and strength to maximize the mechanical properties of woody cellulose nano–crystal (CNC). As a dispersing method, ultrasonic dispersing machine and magnetic stirrer were used as the mechanical dispersion method. The mixing ratio of cellulose nano-crystals (CNCs) was 0.2% and the dispersion time was 10 minutes. Steam curing was carried out for 6, 24 and 48 hours. Based on the experimental results, we will propose source technology regarding CNC for construction materials.

In this study, prediction of later-age compressive strength of ultra-high strength concrete, based on the accelerated strength of concrete cured in hot water was investigated. Comparing other acceleration method, hot water curing method is relatively easy and intuitive to use in the real construction site. The amount of time for evaluation of the concrete strength using the hot water curing method in KS and JIS is too long to predict the strength of the ultra-high strength concrete that are used in the tall building structure. For that reason, curing temperature of 40, 50, 60℃ 3 levels were examined to shorten the amount of time for the evaluation of the strength. When curing in warm water, different strength characteristics are verified from the experiment. In case of F3 substituting 30% fly ash in combination, because of the curing temperature sensitivity of fly ash, differences of strength expression velocity was verified according to the curing temperature at the same age. In case of B4 substituting 40% ground granulated blast furnace slag, there were no big strength expression velocity differences of the specimen cured in 3 different level of curing temperature(40, 50, 60℃). The results show reliable accuracy by regression relation between 28day strength cured by standard curing method and accelerated strength of concrete cured in warm water.(y=1x-0.0002 R2=0.9866) As a result, the feasibility of 3day-prediction was confirmed using warm water curing method with accelerated strength of concrete cured for three days in warm water.

Because of building higher story and larger buildings, and because current concrete, a basic construction material, needs higher strength rather than normal strength, the use of high-strength concrete becomes more widely spread. High-strength concrete shows very high temperature increase due to inside heat of hydration different from normal-strength concrete, and because mass concrete under low temperature shows temperature stress due to temperature difference between inner and outer parts, it is known or reported that there is a significant difference between the compressive strength of srtucture and that of specimen for management, and between the compressivestrength of circular specimen made by standard underwater curing and structure concrete Therefore, in this research, an adiabatic curing box was manufactured which can provide hydration heat hysteresis of high strength mass concrete members and similar hydration heat hysteresis, using insulating materials, as a easy and exact method to manage compressive strength of rnass concrete member under low temperature, and the features of concrete member and those of specimen for management were compared.

본 연구에서는 플라이애시가 90 %만큼 다량치환된 모르타르에 알칼리 활성화를 통한 강도증진을 동일한 양생온도 조건 에서 양생방법 및 유지시간 변화에 따라 비교 분석하고자 하였다. 연구 결과로 플래이애시를 90 % 치환한 경우, 소생재 도 포 후 40℃로 24시간 기중양생시 가장 높은 압축강도를 발휘하였지만, OPC의 압축강도까지 발휘하는 것은 어려울 것으로 분석되었다.

본 연구에서는 플라이애시가 다량치환된 모르타르에 알칼리 활성화를 통한 강도증진을 양생온도 및 양생방법 변화에 따라 비교 분석하였다. 연구 결과로 플라이애시를 60 % 과다치환한 경우 소생재 도포 후 40℃의 온도로 48시간 기중양생을 실시한다면 OPC의 28일 압축강도에 근접하게 발휘되는 것이 얻어졌다.

콘크리트 구조물이 화재 손상을 입을 경우 노출온도 및 지속시간에 따라 구조물의 심각한 성능 저하를 야기하며, 콘크리트의 재료 물성 저하를 수반한다. 화재 손상을 입은 콘크리트 구조물의 재사용여부 및 보수보강 판단을 위해서는 손상 직후 및 재양생 조건에 따른 주요 손상 부위의 면밀한 손상 평가가 필요하다. 본 연구에서는 재양생 조건에 따른 화재 손상을 입은 콘크리트의 재료물성 회복에 관한 실험적 연구 를 수행하였다. 화재 손상을 입은 콘크리트 시편을 상대습도 및 재양생 기간을 달리한 재양생 조건을 적용하였으며, 충격공진기법을 도입하여 콘크리트 시편의 화재 손상 전후 및 재양생 이후의 동탄성계수를 측정하여 손상 정도를 평가하였다. 측정된 결과로부터 재양생 조건 중 높은 상 대습도 조건에서 지배적으로 재료물성의 회복이 발생하였다. 추가적으로 콘크리트 시편의 동탄성계수 및 인장강도의 직접적인 비교 및 선형 회귀분석을 수행하여 재양생 조건에 따른 영향을 분석하였으며, 이를 토대로 높은 습도 조건에서 동탄성계수의 회복이 인장강도에 비해 두드 러지게 나타남을 확인하였다.

Quality control of concrete during its curing process is crucial when it comes to reaching the ideal strength. This paper presents the basic study of optimizing concrete curing process by using Arduino platform based on the maturity method. The research has suggested a quality control of curing process by visualizing the curing temperature and its strength from web. The maturity method was coded into the web which allows managers to monitor regardless their locations.

섬유보강콘크리트의 균열발생 평가는 보통 인장강도나 휨강도가 지표가 되지만 시험체 제작 과정 시에 이루어지는 양생의 영향도 좌우된다. 일반적으로 콘크리트 시험체는 20±3°C의 온도에서 수중양생을 실시한 후 강도 평가를 수행하나 실구조물은 습윤양생을 소정의 기 간 동안 실시한 후 건조 상태로 된다. 이러한 기술적인 진보가 이루어지고 있는 경향과는 달리 양생방법의 차이가 균열발생 강도에 미치는 영향 은 아직 명확하지 않고 있는 실정이다. 따라서 본 연구에서는 섬유보강콘크리트의 역학적 특성, 특히 균열발생강도에 미치는 양생방법의 영향 에 대해서 검토하였다.

The study is compressive strength of 110MPa PHC pile using ground granulated blast furnace slag to NAC, AC curing method. In the result, 20% of ground granulated blast furnace slag could be substituted for cement in PHC pile concrete.

In experimental results, the prediction equation for 28 day-strength of GGBF slag concrete could be produced through the linear regression analysis of early strength and 28 day-strength. In order to acquire the reliability, all mixture were repeated as 3 times and each mixture order was carried out by random sampling. The prediction equation for 28 day-strength of GGBF slag concrete by 1 day strength won the good reliability.

In experimental results, the prediction equation for 28 day-strength of GGBF slag concrete could be produced through the linear regression analysis of early strength and 28 day-strength. In order to acquire the reliability, all mixture were repeated as 3 times and each mixture order was carried out by random sampling. The prediction equation for 28 day-strength of GGBF slag concrete by 1-day strength won the good reliability.

This study is to introduce the results of physical property test on the polyurea ultra rapid curing membrane according to the test method by the KS F 2622

Carbon dioxide generated from construction materials and construction material industry among the fields ofconstruction is approximately 67 million tons. It is about 30% of the carbon dioxide generated in the fields of construction.In order to reduce carbon dioxide in the fields of construction, it is necessary to control the use of fossil fuel consumedand decrease carbon emission by reducing the secondary and tertiary curing generating carbon dioxide in constructionmaterial industry. Therefore, this study manufactured mortar by having cement as the base and substituting three bindingmaterials up to 50% and then adopted different curing methods to analyze congelation and strength characteristics. According to the result of strength characteristics by the types of binding materials and replacement ratio, the specimensubstituting ESA (Early Strength Admixture) and FPC (Fine Particle Cement) showed active strength improvement. Inparticular, the specimen substituting ESA as 25% indicated the greatest strength improvement, and as the number of curingincreased, the strength grew higher, too. And when the binding material was used by substitution, it showed strengthcharacteristics similar to or higher than the specimen conducting tertiary autoclave curing as the secondary steam curing.

This study was carried out to evaluate effects of curing method and age on compressive behavior of steel fiber reinforced Alkali-Activated Slag(AAS) concrete. AAS and Steel Fiber Reinforced Concrete (SFRC) material with specific compressive strength of 30MPa was reinforced with 0% to 1% steel fibers at the volume fraction. Two types of curing methods were used: water curing and exposed curing. Curing time is 3, 7, 28 day. Experimental results indicated that compressive strength, elastic modulus, compression index.

When manufacturing secondary concrete products, steam and autoclave curing are practiced for the purpose of securing product performance at early phase. CO2 is generated by combustion of fossil fuel at the time of curing. This study is part of a research conducted to minimize curing process which generates CO2. Combination materials types, substitution ratio, strength property per different types of curing are compared and evaluated. Result of the experiment indicates that combination material with 40%　blast furnace slag　substitution and W/B which has gone through 30,40% steam curing are the most outstanding experiment bodies.

The purpose of this study is to evaluate the flexural performance of a SHCC (Strain Hardening Cementitious Composites) panel which was manufactured by steam curing method for precast slab system. From the bending test result, it was found that the SHCC panel showed approximately 7.32 MPa of maximum flexural strength, 58 mm of mid-span deflection appearing excellent strain hardening behavior and multiple micro cracks between bending moment section of the specimen.

버어리종 대말림시 백화엽발생을 방지하고 건조기간을 단축하기 위하여 시험을 수행하였던 바, 결과를 요약하면 다음과 같다. 1. 건조실내 온도는 흑색비닐피복구 및 환기창이용구가 관행구보다 3℃ 정도 높았으며, 탈수속도는 환기창이용구가 훨씬 빨랐다. 2. 백화엽발생율은 완전대말림구가 높았고, 지면을 30cm 판 처리가 낮았다. 3. 수량감소는 완전대말림구가 컸다. 4. 품질 및 대금은 환기창이용구 및 지면을 30cm판 구가 높았다. 5. 물리성은 줄말림용 차광막처리가 비교적 양호하였다. 6. 백화엽발생을 억제하기 위하여는 첫째, 본포에서 치마름엽과 과숙엽을 방지하고, 둘째, 하위엽은 1-2회 수확한 후 대베기를 실시하며, 셋째, 갈변후에는 건조기간을 단축시키기 위한 온습도관리에 유의해야 할 것으로 생각된다. 7. 버어리종 담배의 물리성을 향상시키면서 건조중 백화의 원인이 되는 산소 및 수분과의 반응을 억제시킬 수 있는 방법에 대하여는 앞으로 더욱 검토가 요구된다.