PURPOSES : The objective of this study is to present a practical application method for measuring the setting time of concrete in the field, considering different concrete blending and curing environments. METHODS : In the experimental environment of the concrete setting experiment, a mold was made in the laboratory, and the curing temperature was performed at laboratory room temperature (20-25 ℃), heater (30 ℃), and dryer (40 ℃). In the field, the experimental method was performed in summer and autumn, setting experiments on penetration resistance, ultrasonic pulse velocity, and semi-calorimeter. RESULTS : The result of the concrete setting time experiment was that the early setting time was achieved in the combination of filash and slag when the concrete was mixed, and the setting time in the curing environment was the same as the early setting time in the field. The setting time measurement method shows the correlation of the high crystal coefficient at UPV with 0.99 based on PR and the good ratio of 92 % to 107 % on average. In addition, the semi-calorimeter shows a good crystal coefficient of 0.96 to 0.99 and a good setting time of 88 % to 101 % on average. CONCLUSIONS : The analysis of the setting time of the concrete shows that the curing temperature is more affected than the mixture, and it is considered that the UPV test, which evaluates the reliability of the degree of purification, is easy to sampie among the three methods.

본 연구에서 10℃ 이하의 저온환경에서 콘크리트 강도 발현이 늦어지는 현상을 개선하기 위해 조강 시 멘트와 플라이애쉬, 고로슬래그 혼합시멘트로 강도 발현을 개선하기 위한 응결 특성에 대한 비교 실험을 수행하였다. 응결 특성 분석 실험은 표 1과 같이 6종 배합과 4~10℃ 온도 조건에서 실시하였다. 2성분계 혼합 시멘트의 응결 시간에 대한 분석 결과는 그림 1과 같다. 초결의 경우 전체적으로 살펴보 면 3종 시멘트를 사용한 경우의 응결 시간이 1종 시멘트를 사용한 배합보다 더 빨리 나타났다. 4℃ 온도 조건에서는 3종 시멘트를 사용한 경우, 광물성 혼화재들이 들어가지 않은 배합이 가장 빠른 초결이 나타 났으며, 다음으로 플라이애쉬, 그리고 슬래그 순으로 나타났다. 하지만 다른 온도조건(10℃, 15℃, 20℃) 에서는 슬래그와 플라이애쉬의 초결은 큰 차이가 없었다. 1종의 경우에서는 슬래그를 사용한 경우와 혼화 재를 사용하지 않은 배합이 유사하게 나타났으며, 플라이애쉬를 사용한 경우가 가장 늦었다. 이러한 경향 은 전 온도조건에서 유사하였다. 다음으로 종결에 대한 분석 결과, 시멘트 종류에 대한 경향은 초결과 유 사하였다. 1종 시멘트를 사용한 배합에서는 4℃에서 일반시멘트를 사용한 경우가 가장 빨랐으며, 다음으 로 슬래그, 그리고 플라이애쉬 순으로 나타났다. 전체적으로 보면 고속도로 콘크리트 포장 시공 시 사용 하는 1종-F2S0-6%의 배합보다 3종시멘트에 플라이애쉬나 슬래그를 사용한 배합의 초결 및 종결 모두 다 앞당겨지는 것을 확인하였다. 본 연구에서는 10℃ 이하의 저온환경에서 콘크리트 강도 발현을 개선하기 위해 혼합 시멘트에 대한 응 결 특성을 분석하였다. 저온 환경에서 플라이애쉬 또는 고로슬래그를 혼합하여 사용하는 경우 1종 시멘트 와 비교하여 3종 시멘트를 사용하였을 때 초결 및 종결이 조기에 달성되는 것을 확인하였다. 향후 3종 혼 합 시멘트 사용에 대한 특성 분석 연구를 추가적으로 수행할 예정이다.

본 연구는 촉진양생한 프리캐스트 콘크리트의 응결 시점 분석을 위하여 누설 표면파 기법과 성숙도법을 적용하였다. 누설 표면파 기법은 콘크리트 표면이나 내부에 센서를 설치하지 않고 비접촉 센싱을 통하여 응결을 정의할 수 있는 장점이 있으며, 성숙도법은 콘크리트 내부의 온도변화를 통하여 재령을 정량적으로 평가할 수 있는 기법이다. 촉진양생을 적용한 일반 콘크리트와 고강도 콘크리트를 대상으로 각 기법을 적용하여 실험적으로 그 결과를 분석하였다. 특히, 기존 응결 시험 방법인 관입저항침 시험법을 기반으로 비교 분석한 결과, 성숙도법을 통한 재령 평가법은 초결 시점과 누설 표면파의 계측은 종 결 시점과 각각 유사함을 확인할 수 있었다.

본 연구에서는 Durometer A타입으로 응결시간에 확실하게 차이를 나타낼 수 있는 플라이애시(이하 FA) 치환 콘크리트에서 프록터 관입저항 시험치와 경도치를 비교 분석하고자 하였다. 연구결과로 프록터 관입저항 시험치와 Durometer A타입의 경도치는 곡선의 형태로 높은 상관관계를 나타내었다. 표면 마감작업에 대하여 Durometer A타입의 경도치로 약 25 HD는 초결, 약 35 HD는 종결로 관리한다면 표면 마감작업시간 판정에 효과적일 것으로 사료된다.

As a result of this study, the testor penetration resistance and the hardness of the durometer are considered highly correlated and are thought to be effective when using the durometer to determine the setting time in the field structure.

Recently, high-performance and high-fluidity concrete have been studied and developed because high-rised build is constructed. An early-age properties of these concretes have been studied and developed bacause of comparing existed concrete. This study proposed non-destructive method as electrical resistivity measurement, which evaluates setting time of cement-based materials. An assessment of the effect on the setting time was studied on the addition of a superplasticizer to delay the setting time and the curing temperature to promote the setting time. 6th of samples prepared mortar according to adding superplasticizer(PNS) or curing temperature and measured the electrical resistivity during 24 h. As the results, mortars which curing higher temperature were promoted rising time which is setting time in the electrical resistivity, also mortars which adding superplasticizer were retard rising time.

In this study, the correlation between the durometer and the proctor penetration resistance tester, which is considered to be efficient in determining the setting time in a simple portability for soil and concrete utilizing organic lime (H) and Goto lime (G), is used. The results of the study show a high correlation between the portable hardness meter, the durometer and the proctor penetration resistance test period. Therefore, it is expected that the durometer will be useful for the measurement of setting time and the time limit.

In this study, the correlation with a proctor penetration resistance tester is analyzed for the purpose of judging the setting time of concrete by the convenient portability of the durometer which is a rubber hardness meter.The result of this study showed a high correlation between the value of the tilt of the durometer and the measured value of the proctor penetration resistance tester.

In the current study, retarding type and standard type admixture design of concrete have been proposed to control the generation of hydration heat for foundation members that use high strengths concrete. Finite element analysis also has been conducted to understand the rational placing heights of concrete. In addition, real-size structures have experimented and their results were compared to the analytical results to evaluate the reducing effect of thermal stress . For a large 6.5 m×6.5 m×3.5 m member with retarding and standard type horizontal partition placement of concrete showed the manageable possibility of temperature difference within 25-degree Celcius between the middle and surface portion while the maximum temperature was 77-degree Celcius. Also, temperature cracking index from the finite element analysis appeared to be 1.49 that predicts no formation of cracking due to the effects of temperature. Finally, it appeared that horizontal partition placement of retarding and standard type concrete has the significant effect of reducing the thermal stress that generated by the hydration heat in the high strengths mass concrete.

This study is based on developing a free-cement. The Setting time of 100% GGBS(Ground Granulated Blast furnace Slag) admixed alkali-activators is measured, the influence of cation of alkali-activators on setting time is assessed. As a result, in case of mixing KOH or NaOH, setting time is getting shorter, although, GGBS admixed Ca(OH)2 has similar setting times regardless of concentration of alkali-activators.

Set-controlling admixtures via granulation method may be secured the operation time by adjusting the response time. therefore, mortar with Set-controlling admixtures via granulation is measured setting-time. As a result, the possibility of initial reaction control confirmed and also was developed the required properties of setting-time.

Be constructed in the Middle East, recent overseas plant business mainly due to an increase in the amount of concrete in the construction sector is growing. When using plain concrete and concrete development of the initial expansion of the initial hydration, due to thermal stress that causes cracks in the concrete problems, and prevention of this by the use of the delay is expected to increase. In addition to the increase in domestic traffic produced in ready-mixed concrete plants and concrete due to high temperature during transportation upon arrival at the scene quickly if condensation begins to degrade due to the slump loss and workability after curing of cold joint and cause filling defects and the need for the measures . In the case of the powder that is currently on the market in order to obtain a uniform delay effects can be mixed, may be added, such as, wet, etc. Keep a less efficient storage, even if the delay has to be taken. This powder improves the delay and store it in a tablet, a delay effect to encourage the development of tablet, and the delay for compliance with basic properties was investigated.