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 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.

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.

This research proposed MPC (Magnesia Phosphate Composite) mortar as a rapid repair material. But because this rapid reactivity inherently has issues related to microcracking caused by expansion and reaction heat, retarder and fibers are proposed to be used to control the hardening rate and cracking.

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 research proposed MPC (Magnesia Phosphate Composite) mortar as a rapid repair material. But because this rapid reactivity inherently has issues related to microcracking caused by expansion and reaction heat, retarder and fibers are proposed to be used to control the hardening rate and cracking

This study was aimed to investigate the effect of blending cement with crushed aggregate powder on the setting time. crushed aggregate powder was incorporated with the ratio of 0~30 wt.% of cement. The experimental results presented that there was little influence on the intial setting time, whereas the final setting time decreased by blending with higher amount of crushed aggregate powder.

The evolution of the electro-mechanical impedance (EMI) of piezoelectricity (PZT) sensor was investigated to determine the setting times of fiber reinforced cementitious materials in this study. Penetration resistance test was also conducted to validate the EMI sensing technique. As a result, the setting times of fiber reinforced cementitious materials can be effectively monitored through the EMI sensing technique using an embedded PZT sensor.

Even though high performance concrete was developed according to becoming bigger and higher of reinforced concrete building, the rheological evaluation is not enough to use as input data to accomplish the numerical analysis of construction design. Consistency curves were measured by the viscometer as hydration reaction time passed. There are a sudden change of viscosity and yield stress around initial setting in case of low W/B. The increase of workability by the change of free water in cement paste was offset by the coating effect of impermeable layer in case of W/B 40%.

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.

This study examined the setting time of Free-cement concrete and Ordinary Portland Cement(OPC). Alkali Activators(NaOH, KOH, CaOH2) were mixed when free-cement concrete was cast. Five different concentration levels of Alkali activator was used, ranging from 0.5%, 1.0%, 1.5%, 2.0%, and 3.0% by weight of binder.