• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.232-238
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• 1996

In this paper, the properties of high-strength concrete are described with respect to materials and mix conditions(water-cement ratio, chemical admixture, replacement of fly ash). As primary purposes of this study, the optimum mix design method of high-strength concrete to decrease unit cement contents is investigated, and the properties of fresh and hardened concretes are tested in terms of slump, air content and compressive strength. As results of this study, workability and strength development of the high-strength concrete depend on the water-cement ratio, replacement ratio of fly ash and dosage of the chemical admixture. The conditions which are proposed optimum mix design of the high-strength concrete show W/C 37%, S/A 42~45% and unit cement content 470~480kg/$\textrm{m}^3$. Based on the results, the applicability of high-strength concrete in site is clearly proved.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.60-65
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• 2015

In order to improve the strength of paper, mixing ratio of Sw-BKP and Hw-BKP and PVA (polyvinyl alcohol) fibers dosage were investigated. When the Sw-BKP fraction was increased, strength properties were increased because of average fibers length increased. When PVA fraction increased, paper strength was increased, but there was dissolution of PVA in water. The reason for improving handsheet strength that contained PVA was due to increased bonding action between the fibers by the PVA. The addition of PVA to kraft pulp would be helpful for packaging paper materials to increase strength and fracture toughness.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.237-242
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• 2000

Recently, the importation of overseas cement has been increasing and the spot materials of different quality from Japan have to be treated in overseas construction work for technical cooperation with neighboring countries. However, a study on the quality of those oversea materials has not yet been carried out systematically, especially cement among those materials. Accordingly, in this study the properties of high-strength concrete with oversea cement imported from four countries in East Asia and South-east Asia were investigated under normal and high temperature condition, including the carbonation of normal-strength concrete under normal temperature. As a result, it is found that the required of normal-strength concrete will be expected regardless of temperature condition when the flowability is ensured by selecting the appropriate superplaticizer and dosage of it, and the carbonation rate of normal-strength concrete with overseas cement is approximately the same as that with Japanese one under the condition of the same compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.23-28
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• 1998

In this paper, the compensation of the shrinkage in high performance concrete by applying CSA expansive additives are discussed. According to toe experimental results, fluidity and strength decrease with the increase of the dosage of expansive additives. When 5% of expansive additive are mixed, not only high fluidity and strength, but also the compensation of drying-shrinkage can be achieved.

• Resources Recycling
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• v.25 no.3
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• pp.20-28
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• 2016

Assessment on adequate dosage of superplasticizer in eco-friendly ultra-high performance concrete (UHPC) containing industrial by-products was carried out from the standpoint of workability. Various types of industrial by-products, including blast-furnace slag, coal bottom ash and rapid-cooled electric arc furnace oxidizing slag, were utilized, and the effects of dosage of superplasticizer on the workability and strength of UHPC containing the by-products were evaluated. By utilizing the by-products, the workability of UHPC was improved and required dosage of superplasticizer was reduced. In addition, the material cost for UHPC with by-products was decreased due to reduced dosage of superplasticizer.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.137-145
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• 2012

Strength model for blasted furnace slag mortar blended with sodium was investigated in this study. The main parameters of AAS (alkali activated slag) mortar were dosage of alkali activator, water to binder ratio (W/B), and aggregate to binder ratio (A/B). For evaluating the property related to the dosage of alkali activator, sodium carbonate ($Na_2CO_3$) of 4~8% was added to 4% dosage of sodium hydroxide (NaOH). W/B and A/B was varied 0.45~0.60 and 2.05~2.85, respectively. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide ($Na_2O$) in sodium hydroxide and sodium carbonate is proposed to assess the compressive strength of alkali activated mortars. Test results clearly showed that the compressive strength development of alkali-activated mortars were significantly dependent on the proposed alkali quality coefficient. Compressive strength development of AAS mortars were also estimated using the formula specified in the previous study, which was calibrated using the collected database. Predictions from the simplified equations showed good agreements with the test results.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.628-631
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• 2004

In this paper, mechanical properties of concrete incorporating CKD are discussed with W/B and fluidity. For setting properties, an increase in W/B retarded setting time greatly in $5^{\circ}C$, while accelerated in $20^{\circ}C$. For fluidity, an increase in slump delayed the setting time with dosage of SP agent. The presence of CKD has little influence on setting time compared with plain concrete. For compressive strength, an increase in maturity enhanced compressive strength. Fluidity had no relation to compressive strength. At low curing temperature, concrete with CKD has slight strength loss compared with plain concrete. However, remarkable strength loss at low curing temperature in early stage was not found, which can be applicable to low temperature environment concrete placing.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.383-386
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• 2005

This paper is to investigate the effect of W/B, blend ratio of crushed sand with sea sand on fluidity and strength properties of high strength concrete utilizing crushed sand. W/B set up 0.25, 0.30, 0.35 and the blend ratio of crushed sand with sea sand set up 0:100, 30:70, 50:50, 70:30, 100:0 The results of this study are summarized as the follows; 1) The increase of the blend rate of crushed sand, affected on the enhancement of flow, the increase of dosage of SP and water content, but the decrease S/a 2) Compressive strength is increased when crushed sand $30\~70\%$ was replaced with sea sand. 3) The optimal replacement percentage of crushed sand is $50\%$ with sea sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.710-713
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• 2000

The corrosion protection methods of reinforcing steel in concrete are the various methods such as increasing thickness of cover concrete, using of reinforcing bars coated with epoxy, dosage of corrosion inhibitor as concrete admixture, cathodic protection method and etc. The most economical method of them will be the corrosion protection method using corrosion inhibitor as concrete admixture. Therefore, the purpose of this research is to investigate the performance of corrosion protection of ordinary strength and high strength concrete using corrosion inhibitor, respectively. For this purpose, after manufacturing ordinary strength and high strength concrete with and without corrosion inhibitor, the accelerated corrosion tests for reinforcing steel were conducted according to the periodic cycles (140 day) of wetting ($65^{\circ}C$, 90% R.H.) and drying period ($15^{\circ}C$, 65% R.H.). As a result, th high strength concrete using corrosion inhibitor showed an excellent performance of corrosion protection.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.275-282
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• 2002

High fluidity concrete needs high dosage of superplasticizer to acquire sufficient fluidity and high contents of fine powder and viscosity agents to prevent segregation. But it requires high manufacturing cost and has difficult in quality control. Therefore, in this paper, determination of optimal mixture proportion of segregation type superplasticizer for high fluidity concrete and manufacturing high fluidity concrete by applying developed segregation reducing type superplasticizer are discussed using flowing concrete method. According to test results, as dosage of superplasticizer increases, it shows that fluidity and bleeding increase, while air contents and ratio of segregation resistance decrease. It also shows that adding viscosity agent into it reduce bleeding and improve segregation resistance. Dosage of AE agent into it containing viscosity agent recovers loss of air contents during flowing procedure. Combination of proper contents of superplasticizer, viscosity agent and AE agent make possible to develope segregation reducing type superplasticizer Compressive strength of high fluidity concrete applying flowing method with it is higher than that of base concrete. No differences of compressive strength between compacting methods are found.