• International Journal of Highway Engineering
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• 제15권3호
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• pp.1-8
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• 2013

PURPOSES : This study is to evaluate the feasibility of using the alkali activated cement concrete for application of partial-depth repair in pavement. METHODS : This study analyzes the compressive strength of alkali activated cement mortar based on the changes in the amount/type/composition of binder(portland cement, fly ash, slag) and activator(NaOH, $Na_2SiO_3$, $Na_2CO_3$, $Na_2SO_4$). The mixture design is divided in case I of adding one kind-activator and case II of adding two kind-activators. RESULTS : The results of case I show that $Na_2SO_4$ based mixture has superior the long-term strength when compared to other mixtures, and that $Na_2CO_3$ based mixture has superior the early strength when compared to other mixtures. But the mixtures of case I is difficult to apply in the material for early-opening-to-traffic, because the strength of all mixtures isn't meet the criterion of traffic-opening. The results of case II show that NaOH-$Na_2SiO_3$ based mixtures has superior the early/long-term strength when compared to NaOH-$Na_2SiO_3$ based mixtures. In particular, the NaOH-$Na_2SiO_3$ based some mixtures turned out to pass the reference strength(1-day) of 21MPa as required for traffic-opening. CONCLUSIONS : With these results, it could be concluded that NaOH-$Na_2SiO_3$ based mixtures can be used as the material of pavement repair.

• Journal of the Korea institute for structural maintenance and inspection
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• 제9권3호
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• pp.120-128
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• 2005

In the construction industry, due to the cost rise of raw material for concrete, we have looked into recycling by-products which came from foundry. When using the Ground Granulated Blast-Furnace Slag(SG), it is good for enhancing the qualities of concrete such as reducing hydration heat, increasing fluidity, long-term strength and durability, but it has some problems : construction time is increased or the rotation rate of form is decreased due to low development of early strength. In this study, therefore, to enhance the early strength of SG mortar, we used some alkali activators(KOH, NaOH, $Na_2CO_3$, $Na_2SO_4$, water glass, $Ca(OH)_2$, alum. This paper deals with reacted products, setting time, heat evolution rate, flow and the strength development of SG cement mortar activated by alkali activators. From the results, if alkali activators were selected and added properly, SG is good for using as the materials of mortar and concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• 제6권3호
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• pp.182-189
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• 2018

Controlled low strength material(CLSM), known as flowable fill is used sewer. This paper evaluates flowability, segregation, early strength and excavatability of CLSM made using standard soils such as SM, ML, CL, CH. Also, various mix proportions of CLSM containing kaolinite, red soil, Joomun Jin standard soil were developed and the mixing ratio optimized. It was considered as the flowability and early strength were severly affected by W/B, S/B, and early strength and flowability depend on standard soils which means the satisfaction conditions of CLSM were variety of standard soil conditions. Finally, not only optimal mixing proportions were deducted according to standard soil condition but confirmed effectiveness of bleeding and excavatability.

• Journal of the Korean Society for Railway
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• 제17권5호
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• pp.365-372
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• 2014

Technologies for rapid concrete curing using elevated temperature are important for saving cost and time when constricting concrete structures. Recently, a microwave heating form was developed. In this study the early strength of concrete cured by the developed form was experimentally investigated. Large scale mock up tests were conducted six times, and the results were analyzed based on the maturity theory. Logarithmic correlation curves were generated based on the measured strength and estimated maturity. It was confirmed that the strength development of the concrete cured by microwave heating form can be estimated by the equivalent age theory usually applied to steam-curing technology. By using the microwave heating form, one day at most is enough to get the required strength for the safe removal of forms, even in cold weather.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.53-58
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• 2003

Many researchers have rigorously studied the nonlinear behavior of stress-strain relationship of concrete using mathematical curves. Most of model equations for stress-strain relationship, however, have been focused on old age concrete, and were not able to adequately represent the behavior of concrete at an early age. A wide understanding on the behavior of concrete from early age to old age is very important in evaluating the durability and service life of concrete structures. In previous study by authors of this paper, a stress-strain model equation for low- and medium-strength concretes was suggested. In this paper, to extend the application region of compressive stress-strain curve to high-strength concrete, an analytical research was performed. An analytical expression of stress-strain curve with strength and age was developed using regression analyses on the experimental results. For the verification of the proposed model equation, it was compared to the experimental data. The result showed that the proposed model equation was not only compatible with the experimental data quite satisfactorily but also describing well the effect of strength and age on stress-strain curve.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2003년도 학술.기술논문 발표회
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• pp.23-26
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• 2003

This study is intended to investigate the properties of early strength development by application of TEA to the field. According to the results, when TEA is added, fluidity is almost same to base concrete, and increases upto aimed slump after field flowing. Setting time does not differ in the case of base and TEA, but retarded after flowing. The time when compressive strength gains 5 MPa, which side form can be removed, is 23 hours, and so the removal time is shortened by I hours in comparison with plain concrete. But compressive strength is almost same to that of plain concrete at 28 days. The rebound value of P type schmidt hammer show similar tendency to compressive strength, and the rebound value of structure is higher than that of standard curing specimen due to heat capacity effect and drying by the air outside. Therefore, it is thought that if the rebound value of P type schmidt hammer is controled. by about 26 in consideration of open air environment, it is very effective to determine the removal time of side forms.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.23.1-26
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• 2003

This study is intended to investigate the properties of early strength development by application of TEA to the field. According to the results, when TEA is added, fluidity is almost same to base concrete, and increases upto aimed slump after field flowing. Setting time does not differ in the case of base and TEA, but is retarded after flowing. The time when compressive strength gains 5 MPa, which side form can be removed, is 23 hours, and so the removal time is shortened by 1hours in comparison with plain concrete. But compressive strength is almost same to that of plain concrete at 28 days. The rebound value of P type schmidt hammer show similar tendency to compressive strength, and the rebound value of structure is higher than that of standard curing specimen due to heat capacity effect and drying by the air outside. Therefore, it is thought that if the rebound value of P type schmidt hammer is controled. by about 26 in consideration of open air environment, it is very effective to determine the removal time of side forms.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.453-456
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• 2006

In this study, the experiment was carried out to investigate and analyze the influence of fineness of blast furnace slag powder on the properties of high strength concrete. The main experimental variables were water/binder ratio 27.5, 31.5, 35.5(%) water content $165kg/m^3$ and mineral admixtures such as blast furnace slag powder. Even in a case where the ratio of blast furnace slag powder is 70%, using a fineness of 8000 grade afforded a higher strength development than using a plain concrete, which indicates the potential of high utilization in the future. Although it has been pointed out that the concrete using blast furnace slag powder has a problem of yielding relatively low rate of strength development in the early age, it is demonstrated that this can be resolved by using a powder with fineness greater than 6000 grade. It is considered necessary that powder fineness should be upgraded for the applications such as high performance concrete to be used in high strength required areas by considering hydration heat control and early strength requirements in the future.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.269-273
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• 1997

Chemical composition of cement powder influences the setting time and early compressive strength development. The setting time increases as the amounts of zinc oxide and magnesium oxide are increased. For one day compressive strength development, a cement powder with a composition 90% ZnO, 8% MgO and 2% silica resulted in the highest strength (greater than 1, 090 kg/$\textrm{cm}^2$). Cement-forming liquids also need to be buffered, with both aluminum and zinc ions, for a good consistency and a higher strength of the zinc phosphate cement. These liquids control the setting reactions.

• 레미콘
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• 9호통권17호
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• pp.47-59
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• 1988