• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.48-49
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• 2015

High-calcium fly ash (FH) is widely used as mineral admixtures in concrete industry. In this paper, a hydration model is proposed to describe the hydration of high-calcium fly ash blended-cement. This model takes into account the hydration reaction of cement, the chemical reaction of fly ash, and reaction of free CaO in fly ash. Using the proposed model, the development of compressive strength of FH blended concrete is predicted using the amount of calcium silicate hydrate (CSH). The agreement between simulation and experimental results proves that the new model is quite effective.

• Computers and Concrete
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• v.8 no.5
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• pp.583-595
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• 2011

This paper studied the cement efficiency factor (k factor) of high calcium Class F fly ash. This k factor represents a unit of fly ash with efficiency equivalent to k unit of cement. The high calcium Class F fly ash was used to replace cement in concrete. The modified Bolomey's law with linear relationship was used for the analysis of the result of compressive strength, cement to water ratio (c/w) and fly ash to water ratio (f/w) by using the multi-linear regression to determine the k factor and other constants in the equations. The results of analysis were compared with the results from other researcher and showed that the k factor of high calcium Class F fly ash depends on the fineness of fly ash, replacement level and curing age. While the amount of CaO content in Class F fly ash not evident. Furthermore, necessary criteria and variables for the determination of the k factor including the use of the k factor in concrete mix design containing fly ash were proposed.

• The Korean Journal of Community Living Science
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• v.13 no.2
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• pp.53-61
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• 2002

This study is to find out how the 4 types of calcium salt such as calcium carbonate, calcium phosphate, calcium lactate and calcium citrate in soy protein diet, the vegetable protein source, affect the calcium utilization in the body. To do so, calcium, phosphate and creatinine concentration and ALP activity in blood as well as the content of calcium and ash, the length, weight strength, and the calcium utilization in the bone were measured. Four groups of Sprague-Dawley male rats with the weight of around 180g were fed for 3 weeks with the experimental diet. Each group was fed with the isolated soy protein containing 14% of the diet and the above mentioned 4 types of calcium salt as the calcium source. The results are as follows; 1. There were no differences of the feed intake, weight gain, and feed efficiency among groups. 2. ALP activity in blood was sinificantly high in calcium lactate group(P<0.05), but there were no differences of concentration of calcium, phosphates, and creatinine in blood among groups. 3. The weight, calcium content, calcium ratio in ash and the strength of bone were low when calcium lactate was provided(P<0.05). 4. The content of calcium in the liver was high in calcium lactate group and calcium citrate group(P<.0.05). 5. The exceretion of feces was low in calcium lactate group(P<0.05) and the excretion of urine was also relatively low. In addition, the ratio of absorption and the retention of calcium were high(P<0.05). In summary, out of four types of calcium salt such as calcium carbontate, calcium phosphate, calcium lactate and calcium citrate when calcium lactate was provided the ALP activity in blood was high and the weight, calcium content, calcium ratio in ash and the strength of bone were low. In calcium utilization, the ratio of absorption and retention of calcium were high, however it has lower effect than 3 other calcium types in improving weight, the content of calcium and the strength of bone.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.171-176
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• 2000

The phosphatic calcium compounds such as calcium hydrogen phosphate, bone ash, hydroxyapatite and tricalcium phosphate were prepared using the high purity calcium hydroxide and calcium carbonate obtained from shell resources. Calcium hydrogen phosphate had been prepared using the high purity calcium hydroxide and phosphoric acid solution. Using the calcium hydrogen phosphate as a starting materials, bone ash have been prepared by solid state reaction method and hydroxyapatite could be obtained by hydrothermal treatment method, respectively. The tricalcium phosphate was prepared by the solid state reaction of a stoichiometic mixture of bone ash and high purity calcium carbonate. In this paper, the optimal preparation process and conditions of phosphatic calcium compounds were established.

• Advances in concrete construction
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• v.11 no.3
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• pp.183-192
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• 2021

Due to economic and environmental benefits, increasing the substitution ratio of ordinary cement by industry by-products like fly ash (FA) is one of the best approaches to reduce the impact of the concrete industry on the environment. However, as the substitution rate of FA increases, it will have an adverse impact on the performance of cement-based materials, so the actual substitution rate of FA is limited to around 10-30%. Therefore, in order to increase the early-age strength of high replacement (30-70%) low-calcium ultrafine FA blended cement paste, sodium sulfate and calcium sulfate dihydrate were used to improve the reactivity of FA. The results show that sodium sulfate has a significant enhancement effect on the strength of the composite pastes in the early and late ages, while calcium sulfate dihydrate has only a slight effect in the late ages. The addition of sodium sulfate in the cement-FA blended system can enhance the gain rate of non-evaporation water, and can decrease the Ca(OH)2 content. In addition, when the sulfate chemical activators are added, the ettringite content increases, and the surface of the FA is dissolved and hydrated.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.284-291
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• 2016

To evaluate the properties of inorganic composites using a great quantity of high-calcium fly ash generated in combined heat and power plants, high-calcium fly ash and F-class fly ash commonly used as concrete admixtures were substituted with binding materials to examine changes of fluidity and compressive strength depending on the substitution ratio for each curing temperature. According to the experimental result, CFA-mixed mortar showed a tendency to reduce its flow unlike FFA-mixed mortar as the substitution ratio was increased, but its flow loss showed smaller than FFA as time passed. As a result of examining compressive strength depending on mixing FA, FFA-mixed mortar had an optimum range within 50% when curing at ambient temperature, but it was found that the compressive strength is reduced when mixing CFA. When curing at high temperature, FFA did not relatively have a great effect on the substitution ratio, but CFA could expect a strength enhancement effect compared with 100% of OPC when using within 25% of binding materials.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.289-291
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• 2013

This study evaluated basic material properties of finishing mortar in ondol floor using NSB(Non-sinetering binder), and the binder for the purpose of the developing of high performance mortar and reducing crack problem without shrinkage-reduction agent.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.199-200
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• 2019

The purpose of the research is assessing the possibility of strength recovery for mortar added with accidently high amount of fly ash. For compressive strength at 28 day, the sample painted with sodium hydroxide showed higher compressive strength than the sample painted with calcium hydroxide. Regarding the curing conditions, the curing temperature 65℃ provided better conditions than the curing temperature 20℃ in aspect of solution penetration depth and reactivity of fly ash. In the case of drying after saturation, the case painted with sodium hydroxid 65℃ showed the clearest engrossing mark.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.27-34
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• 2020

In the industry, due to the carbon dioxide gas produced during cement production is increasing, research on recycling by-products has been actively conducted. In the industrial by-products, the high calcium fly ash(HCFA) produced by the blast-furnace in the circulating fluidized bed combustion method has a high ratio of CaO and CaSO4. In view of this, the purpose of this is to use high calcium fly ash(HCFA) as a stimulant in blast furnace slag powder and use it as a cement substitute. As a result, it is judged that the substitution ratio of HCFA should be 15% or less. In addition, although durability and strength are relatively lower than of OPC, it is considered that it can be utilized as an environmentally building material.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.31-32
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• 2013

ThThe purpose of this study is to investigate the compressive strength properties of fly ash using water eluted from recycled coarse aggregate. When fly ash come into contact with water, they have not a autonomously chemical reaction. But fly ash is a pozzolan reaction when fly ash come into contact with water and calcium hydroxide(Ca(OH)2) in alkaline environment. For that reason, if water eluted from recycled coarse aggregate use mixture water, fly ash is expected to reaction of pozzolan reaction property in early stage. According to the experimentation result, ICP-MS analysis showed water eluted from recycled coarse aggregate has a high alkali-ash value of pH of 12 and over. And mixing ratio 30% fly ash mortar using water eluted from recycled coarse aggregate showed a similar strength of plain mortar due to the pozzolan reaction. Also, poor strength in initial age, disadvantage of mortar using fly ash, can be improved as hydration in early age is expedited due to calcium hydroxide(Ca(OH)₂) and unhydrated cement component eluted from recycled aggregate mortar.