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.

Currently, in Korea, the frequent damage of aged concrete pavements causes route blockages due to maintenance and repair works. Ultra-rapid cement has been used as a measure to solve the economic losses which result from traffic delays, accidents, and civil complaints due to blocked routes. However, now, it couldn’t be used except for urgent constructions because the price is expensive and its onsite application is complicated, hence, fast hardening admixtures are being used in ordinary cement to solve the problem with ultra-rapid cement. In this research, it is intended to develop a material which enables early opening of the road being constructed and cured within 24 hours of closure, to secure durability characteristics of early strength concrete by incorporating admixtures (silica fume, latex, polymer powder), and to find optimal mixing ratio and select the optimal variable for each material.

This document gives a result of experiments on concrete using admixture Sikament® R4 combine with Sikacrete PP1. In developing countries, the development guides to build and set up a new infrastructure. In this case, the schedule of works is very important, which depends on the setting time of concrete structure. Specially, in tropical monsoon climate country, we need to use admixtures to increase the life time of constructions, especially concrete structures. Today, there are thousands of building, roads and bridges will be made. By using admixture, it not only helps to save the waiting time on the work site, but also increase quality of concrete structure. By using these good effects of admixtures, it’s necessary to find an optimal ratio of them in the mix design ingredient of concrete. The concrete strength can be controlled by changing a range of variety ratio of admixture in the mix design. This topic will find out the role of admixture and its relationship with the compressive strength of concrete.

일반적으로 UFFA(Ultra Fine Fly Ash)는 일반 플라이 애시보다 워커빌리티를 더 좋게 하고 포졸란 반응을 더 크게 활성화시키는 특성을 가지고 있으며, 이와 같은 특성이 콘크리트의 내구성을 더욱 향상시키는 것으로 보고되고 있다. 본 연구에서는 이러한 UFFA의 특성을 활용하여 초속경시멘트에 UFFA를 첨가한 콘크리트 혼합물이 조기교통개방용 콘크리트포장 보수재료로서 활용이 가능한지 여부를 판단하고자 하였다. 기 연구에서는 초속경시멘트에 UFFA만을 첨가할 경우, 포졸란 반응이 크게 활성화되지 못하여 내구성 증진에 큰 효과가 나타나지 않았다. 이에 본 연구에서는 초속경시멘트와 UFFA에 수산화칼슘을 추가로 첨가하여 제조된 콘크리트 혼합물의 포졸란 반응 발생여부를 판단하고, 이것이 콘크리트 물성에 어떠한 영향을 미치는지를 분석하였다. 본 연구결과, 초속경시멘트에 UFFA를 첨가할 경우 W/C비를 크게 낮출 수 있어 콘크리트의 조기강도 저감부분을 충분히 상쇄시킬 수 있는 것으로 나타났다. 또한 X-선회절분석과 염소이온침투저항성 실험결과를 볼 때 수산화칼슘 첨가에 따른 UFFA초속경 콘크리트의 포졸란반응이 첨가하지 않은 것에 비하여 더 크게 활성화되는 것으로 나타났으며, 특히 수산화칼슘 첨가량이 증가함에 따라 UFFA 초속경 콘크리트의 투수저항성이 전반적으로 증진됨을 알 수 있었다.

최근 새로운 교면포장 재료로 사용되고 있는 라텍스 개질 콘크리트(LMC; Later Modified Concrete)는 부착강도 및 휨 강도가 우수하고 염분 및 수분침투에 방수효과가 있어 점차 활용이 증가될 전망이다. 또한, 초속경시멘트를 사용한 라텍스 개질 콘크리트(RSLMC; Rapid-Setting Latex Modified Concrete)는 3시간에 실용강도를 발휘하여 긴급을 요하는 공사나 보수재료로서 적합하나, 염화물의 침투 및 동결융해로 인한 내구성능 저하 등의 문제가 검증되지 않아 이에 대한 연구가 필요한 실정이다. 따라서, 본 연구에서는 RSLMC의 내구특성을 평가하기 위해 염소이온 투과실험 및 동결융해 저항성 실험을 수행하여 투수특성과 동결융해 저항성을 분석하였다. 실험은 ASTM 규정과 KS 규정에 따라 실시하였으며, 실험변수는 라텍스 혼입률 0, 5, 10, 15, 20%와 소포제 혼입률 0, 1.6, 3.2, 4.8, 6.4%로 수행하였다. 실험결과 RSLMC는 라텍스 혼입률 15%에서 소포제 혼입량에 상관없이 모두 100이하의 전하량을 나타내어 매우 낮은 투수특성을 보였다. 또한, 소포제의 혼입률 3.2% 이상인 경우 동결융해 300 싸이클까지 상대동탄성계수가 90% 이상을 유지하여 소포제의 사용이 동결융해 저항성에 효과가 있는 것으로 나타났다.

최근 새로운 교면포장 재료로 사용되고 있는 라텍스 개질 콘크리트(LMC; Later Modified Concrete)는 부착강도 및 휨 강도가 우수하고 염분 및 수분침투에 방수효과가 있어 점차 활용이 증가될 전망이다. 또한, 초속경시멘트를 사용한 라텍스 개질 콘크리트(RSLMC; Rapid-Setting Latex Modified Concrete)는 3시간에 실용강도를 발휘하여 긴급을 요하는 공사나 보수재료로서 적합하나, 염화물의 침투 및 동결융해로 인한 내구성능 저하 등의 문제가 검증되지 않아 이에 대한 연구가 필요한 실정이다. 따라서, 본 연구에서는 RSLMC의 내구특성을 평가하기 위해 염소이온 투과실험 및 동결융해 저항성 실험을 수행하여 투수특성과 동결융해 저항성을 분석하였다. 실험은 ASTM 규정과 KS 규정에 따라 실시하였으며, 실험변수는 라텍스 혼입률 0, 5, 10, 15, 20%와 소포제 혼입률 0, 1.6, 3.2, 4.8, 6.4%로 수행하였다. 실험결과 RSLMC는 라텍스 혼입률 15%에서 소포제 혼입량에 상관없이 모두 100이하의 전하량을 나타내어 매우 낮은 투수특성을 보였다. 또한, 소포제의 혼입률 3.2% 이상인 경우 동결융해 300 싸이클까지 상대동탄성계수가 90% 이상을 유지하여 소포제의 사용이 동결융해 저항성에 효과가 있는 것으로 나타났다.

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.

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.

This paper presents the findings of the study conducted to evaluate workability and compressive strength characteristics of rapid-setting concrete containing metakaolin. The experimental variable selected was the rate of cement replacement with metakaolin at 0, 5, 10, and 15 percent. The findings are summarized as follows: compared with the control specimens with no replacement rate, the workability and compressive strength of the concrete with 5% of cement replaced with metakaolin were comparable to those of control specimens at 4hours; however, at 72 hours, the compressive strength of the concrete with the same replacement rate was larger than the strength of the control specimens by 4.1%, while no increase in strength was observed at higher replacement rates, implying that the optimum replacement rate of cement with metakaolin is 5%.

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 paper describes the findings of the study conducted to evaluate early-age strength characteristics of rapid-setting concrete containing waste pottery powder. The experimental variables selected were 5, 10, and 15 percent replacements of cement with waste pottery powder. The findings are summarized as follows: (1) slump of the concrete decreased as the replacement rate of cement with waste pottery powder increased, and (2) compared with the strength of the control specimens with no replacement rate, compressive strength of concrete increased at 5% replacement rate, and was comparable to the control at 10% replacement rate; however, at 15% replacement rate, compressive strength actually decreased.

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.

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.