• Journal of the Korea Institute of Building Construction
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• v.8 no.4
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• pp.79-85
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• 2008

The purpose of this study is to evaluate the mix design of pH reducing cement concrete which can be used for environment-friendly concrete. Cement pastes and concretes are prepared with water-binder ratios and various admixtures such as blast-furnace slag, fly ash and recycled cement, and tested for compressive strength and pH. pH is measured through pore solution expressed from hydrated cement paste by special apparatus. From the test results, regardless of water-binder ratio, The pH of expressed pore solution from hydrated cement paste which is made of ordinary portland cement with blast-furnace slag, fly ash is decreased with increasing of admixtures content, and compressive strength is also slightly improved. The compressive strength of cement paste made of recycled cement which is burnt at $1000^{\circ}C$, for 2 hours is considerably increased compared with that of none-burnt recycled cement due to restoration of hydraulic property, but pH is a little higher. Porous concrete with ordinary portland cement has high pH in the range of 12.22 to 12.59, however, that is reduced to the range of 8.95 to 10.39 by carbonation at the surface of porous concrete. The pH reduction of porous concrete is possible by various admixture addition, however their degrees are very slight. Therefore, to reduce the pH considerably, carbonation method of porous concrete is better in pH reduction methods for plant survival condition of pH of 9.0 or less. In this study, it is apparent that pH for the environment-friendly porous concrete products used in the construction field can be suppressed by this carbonation method and various admixtures addition.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.2
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• pp.104-110
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• 1999

This study was performed to evaluate the properties of permeable polymer concrete with fly ash and CaCO3. The following conclusions are drawn. The static modulusof elasticity is in the range of 1.19 $\times$105 ~1.49$\times$105 kgf/$\textrm{cm}^2$, which is approximately 53 ~56% of that of the normal cement concrete. The oission's number of permeable polymer concrete is in the range of 3.95 ~6.53, which is less than that of the normal cement concrete. The dynamic modulus of elasticity is in the range of 1.29$\times$105 ~1.59$\times$105 kgf/$\textrm{cm}^2$, which is approximately less compared to that of the normal cement of the static modulus . Fly ash 50% and CaCO3 50% filled permeable polymer concrete has showed higher dynamic modulus. The water permeability is in therange of 3.971 ~4.393$\ell$ /$\textrm{cm}^2$/h, and it is largely dependent upon the mix design. These concrete can be used to the structures which need water permeability.

• Advances in concrete construction
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• v.4 no.2
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• pp.107-121
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• 2016

This concrete is one of the most versatile construction material widely used for almost a century now. It was considered to be very durable material and required a little or no maintenance since long time. The assumption is very true, except when it is subjected to highly aggressive environments. The deterioration of concrete structures day by day due to aggressive environment is compelling engineers to assess the loss in advance so that proper preventive measure can be taken to achieve required durability to concrete structures. The compounds present in cement concrete are attacked by many salt solutions and acids. These chemicals are encountered by almost all concrete structures. The present study has been undertaken to investigate the effect of attack of chlorides and sulphates with varying severity on compressive strength of ground granulated blast furnace slag (GGBFS) concrete after immersion in salt solution for 28 days. The results indicate that the durability of GGBFS concrete increases with the increase in percentage replacement of cement by GGBFS for 20% and then gradually decreases with increases in percentage of GGBFS with cement (as in the study for 40% and 60%). Also there is increase in strength of GGBFS concrete with increase in age. Thus the durability of concrete improves when GGBFS is added as partial replacement of cement. In this study the strength of GGBFS concrete is less affected by chemicals as compared to conventional concrete when exposed to aggressive environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.41-49
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• 2020

To improve the problem of strength reduction of unary and binary blended non-cement concrete that occur at room temperature, comparative analysis was conducted based on the slump and compressive strength properties of ternary blended non-cement concrete in which cement was replaced with silica fume, fly ash, and blast furnace slag, and the following conclusions were drawn. The ternary blended non-cement concrete showed higher compressive strength than binary binder concrete, and the slump reduction was less when 10% silica fume was mixed. In addition, the appropriate composition ratio range of each by-product was suggested according to slump and compressive strength level based on ternary diagram.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.261-264
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• 2003

Cold weather can lead to many problems in mixing, placing, setting time, and curing of concrete that can have harmful effects on its properties and service life. Korean Concrete Institute (KCI) defines cold weather as a period when the average daily air temperature is less $4^{\circ}C$ and recommends to cast concrete with special care such as shielding, heating and so on. The use of high early strength cements may improve the rate of hardening characteristics of concrete in cold weather by making it possible to achieve faster setting time and evolving more hydration heat than ordinary Portland cement. Higher early strength can be achieved using Type III cement especially during the first 7 days. The strength increase property of Type III cement at low temperature was studied. As a conclusion the heat or heat insulation curing period can be reduced to 50~75%. So, it can be used for cold weather concreting to reduce construction cost and extend the construction season.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.324-329
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• 1999

This study is performed to evaluate an elastic properties of rice straw ash concrete . The following conclusions are drawn ; The ultrasonic pulse velocity is in the range of 4.084 ∼4.336㎧, which has showed abuot the same compared to that of the normal cement concrete. The highest ultrasonic pulse velocity is showed by 5% rice straw ash filled reice straw ash concrete. The dynamic and static modulus of elasticity i sin the range of 294 ${\times}$103 ∼ 347 ${\times}$103 and 266${\times}$ 103 ∼347${\times}$ 103 kgf/$\textrm{cm}^2$ , respectively. It is showed about the same compared to that of the normla cement concrete. The poisson's number of rice straw ash concrete is less than that of the normal cement concrete . The stress-strain curve of concrete which is contained rice straw ash within 10% appear slowly and over 10% appear almost straightly.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.463-473
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• 2015

Three full-scale instrumented test slabs were constructed and tested using a heavy vehicle simulator (HVS) to evaluate the structural behavior of internally cured concrete (ICC) for use in pavements under Florida condition. Three mix designs selected from a previous laboratory testing program include the standard mixture with 0.40 water-cement ratio, the ICC with 0.32 water-cement ratio, and the ICC mixture with 0.40 water-cement ratio. Concrete samples were prepared and laboratory tests were performed to measure strength, elastic modulus, coefficient of thermal expansion and shrinkage properties. The environmental responses were measured using strain gages, thermocouples, and linear variable differential transformers instrumented in full-scale concrete slabs. A 3-D finite element model was developed and calibrated using strain data measured from the full-scale tests using the HVS. The results indicate that the ICC slabs were less susceptible to the change of environmental conditions and appear to have better potential performance based on the critical stress analysis.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.685-694
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• 2010

As a eco-friendly material, Hwangtoh (red clay) has been studied for complete or partial replacement of portland cement. Most of existing studies focused on the material properties of the Hwangtoh concrete including the compressive strength, drying shringkage, and creep. In the present study, the shear strength of the beams made with the Hwangtoh concrete was tested. Further, bond strength of tension re-bars embedded in the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated. Hwangtoh replacing all the cement. The beam specimens were tested under two point static loading. The test result showed that the shear strength of activated Hwangtoh concrete beams replacing 20% and 100% of cement was equivalent to that of the ordinary portland cement concrete beam. However, the bond strength of activated Hwangtoh concrete replacing 100% of the cement was less than that of the ordinary portland cement concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.19-22
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• 2006

The quantity of Recycled concrete powder is increased, because it hal been ever so often crushing for production of a good quality recycled aggregates This Study is on the Development of Concrete-Product by Using Recycled Concrete Powder and alto for know performance of concrete-producted having low water contents and it is to know for all of performance of concrete-producted having low water contents The conclusions of this study are following. The use of replacement cement is not effective, because it has strengh of less than 10MPa But It is possible to develop high strength concrete-producted having 39MPa above compressive strength by using recycled concrete powder. Because strength enhancement effects by recycled concrete powder are responsible to optimum grading. The conclusions of this study are following. The use of replacement cement is not effective, because it has strengh of less than 10MPa. It is possible to develop high strength concrete-producted having 39MPa above compressive strength by using recycled concrete powder. Because strength enhancement effects by recycled concrete powder are responsible to optimum grading.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.797-807
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• 2008

For this study, the semi-adiabatic temperature rising test is accomplished by using ternary system cement (OPC, BFS, FA) reducing temperature crack. Two tests are conducted; one is for the paste test, and the other is for the concrete test. As the results of paste tests, using fly ash is better to reduce hydration temperature than doing blast furnace slag. In the case of the paste mixed ternary system cement, the more fly ash is mixed and the less blast furnace slag is used, the lower the temperature is. The less the mixture ratio of blast furnace slag is and the more the mixture ratio of fly ash is, the later the temperature rising velocity and descending velocity are. Besides, the temperature is lower if water/binder ratio is high. The use of ternary system cement has the retardation effect of temperature rising because the time to reach the maximum temperature is in the order of OPC100, binary system cement, and ternary system cement. From the test, the maximum temperature of concrete used ternary system cement is $8{\sim}11^{\circ}C$ lower than that of concrete used OPC100. Moreover, temperatures rising velocity and descending velocity of ternary system cement range $47{\sim}51%$ and $37{\sim}42%$ compared with OPC100. The specimen of concrete shows remarkable low internal temperature and slow temperature rising velocity and descending velocity compared with the specimen of paste because it is that temperature loss of concrete is much more than paste specimen according to aggregates.