• Journal of the Korea Concrete Institute
• /
• v.14 no.5
• /
• pp.789-795
• /
• 2002

To evaluate the bind rate and behavior of two types chloride ion-one is the chloride ion added in mixture when un-washed sea sand is used as fine aggregate, one is the chloride ion admitted in the new version of concrete standard specification, pore solution extracted in cement paste were analyzed. The results are follow. 1 As passing the time, the chloride concentration in the pore solution decreases with the Increase in the chloride content absorbed by the hydrate products. As compared with chloride contents in mixing water, the bound ratio of chloride at 49 days is 64∼90％. 2. The bound ratio of chloride in cement paste considering evaporable water as pore solution is obtained. In case of Pl∼P3(added chloride content wt of cement 0.046∼0.16 ％), the bound ratio of chloride is 91.8∼93.5 ％. P4(added chloride wt of cement 0.3％) is 89.1％, but P5(added chloride wt of cement 0.617％) bound is only 77％. 3. The bound ratio of chloride to wt of cement is 0.015∼0.475％ with adding chloride. In case chloride added over 0.091 ％ wt of cement, the bound chloride content increases 1.7∼1.8 times in spite of added chloride increase twice. The bound ratio of chloride to wt of cement decreased with the increase in the chloride content. 4. The more increase added chloride content, the more increase the bound ration of chloride. But the absolute value of chloride content in pore solution increased.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.153-158
• /
• 2001

The effects of polymer-cement ratio and shrinkage-reducing agent content on the durability characteristics of ultrarapid-hardening polymer-modified mortars using redispersible polymer powder are examined. As a result, the flexural and tensile strengths of the ultrarapid-hardening polymer-modified mortars using redispersible polymer powder tend to increase with increasing polymer-cement ratio, and tend to decrease with increasing shrinkage-reducing agent content. However, the compressive strength of the ultrarapid-hardening polymer-modified mortars using redispersible polymer powder decrease with increasing polymer-cement ratio and shrinkage-reducing agent content. And, water absorption and mass change of chemicals resistance of ultrarapid-hardening polymer-modified mortars using redispersible polymer powder tend to decrease with increasing polymer-cement ratio.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.209-214
• /
• 1999

Strength provisions in Korea Concrete Institute code are more conservative that those in ACI code by increasing load factors and decreasing capacity reduction factors. Cement content of mix design in construction field is usually higher than the modified for standard deviation because of rigorous inspection. Higher cement content increases not only strengths but also heat of hydration, shrinkage and brittleness which are not beneficial. To reduce and optimize the cement content in current mix design of Korean Highway Corporation, properties of fresh and hardened concrete for 16 different mix proportions have been investigated. It is found that the chemical admixture and cement of current mix proportions for highway construction are somewhat higher than the optimum amount. Therefore, the optimum mix design for 16 different purposes has been proposed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1992.04a
• /
• pp.41-46
• /
• 1992

A potential use of superplasticizing admixture is to produce structural concrete of High-strength concrete,. By using a superplasticizer, more workable mixes can be achieved while permitting a high cement content and a low water/cement ratio both of which are necessary to obtain high strength by conventional manufacturing technique. In this study, therefore, high strength concrete having a 28-day strength in excess of 650kg/$\textrm{cm}^2$ can be obtained using a superplasticzer. However, before such a high strength concrete is recommended for use, engineering properties have to be assessed. This study is aimed to analyze and investigate the engineering properties, such as strength, elasticity, ultrasonic pulse velocity, rebound value of superplasticized concrete having a various cement content.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2007.11a
• /
• pp.45-48
• /
• 2007

This study investigates mechanical properties of the concrete using coarse particle cement which is manufactured by the classifying process. The variable factors are 3 types of W/C such as 40, 50, and 60% and 5types of the replacement of the coarse particle cement such as 0, 25, 50, 75, and 100%. As the results, amount of SP agent to secure the target fluidity is gradually declined in accordance with increasing CC replacement. There is no special tendency for target air content, but setting time is delayed according to increasing CC content. The peak of the simple adiabatic temperature rise is gradually decreased in accordance with increasing CC content, and approach time to peak is slightly delayed. The compressive strength is comparatively delayed.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2019.05a
• /
• pp.231-232
• /
• 2019

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.11a
• /
• pp.107-108
• /
• 2021

In the global trend of countries around the world announcing the declaration of carbon neutrality, the development of low-carbon cement in the cement industry can be seen as a very important issue that can determine the future development of the cement industry in the future. Therefore, this study evaluated the strength characteristics of limestone cement paste with limestone powder of CaCO3 and refinery desulfurization waste catalyst of high Al₂O₃ content, and using a Minitab mixture design to optimize a limestone cement content. As a resuls it was confirmed that limestone cement paste with 5-10% of limestone powder and 1.25-2.5% of the waste catalyst exhibits similar compressive strength to that of OPC.

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.7
• /
• pp.31-38
• /
• 2014

For analysis of mechanics properties of soil cement, unconfined compressive strength has been proposed by existing case studies. In this study, mechanical changes with water content of silt, curing time and cement content were analyzed through unconfined compressive strength test. In addition, the changes for B factor by Abrams were compared with existing case studies after the prediction equations could be proposed about the unconfined compressive strength of admixed cement soil. Especially, the B constant factor was changed with soil characteristics and curing time. For analysis results of appropriateness status and unconfined compressive strength, consideration of variable form was titrated. The prediction equations at low plasticity silt admixed using the uniaxial compressive strength with applying Abrams's equation and considering cement content, curing time is proposed.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.3
• /
• pp.218-225
• /
• 2023

In this study, we examine the feasibility of using chlorine in clinker as an early-strength cement by the effect of accelerating the cement hydration reaction of chlorine. Clinker with a chlorine content of 200-1,000 ppm was prepared using actual cement kilns, and 46 cement samples were prepared by adding gypsum and admixtures(GGBFs and limestone). We measured consistency, setting, 1-28 days compressive strength and analyzed them statistically. Test results indicated that an increase of the chlorine content resulted in shortening of initial and final setting time and the improvement of 1 day compressive strength. But the 28 days compressive strength was decreased. Specifically, when the chlorine content was increased from 230 to 965 ppm, the 1 day compressive strength increased up to 4.6 MPa, improvement effect was superior to that of increasing Blaine in the range of 3,400-3,970 cm²/g.

• The Journal of Engineering Geology
• /
• v.26 no.1
• /
• pp.101-115
• /
• 2016

We carried out laboratory material tests on two cements (KS-1 ordinary Portland and Class G) with changing W/S (Water/Solid) and the content of fly ash in order to evaluate their physical and mechanical properties. The specimens of KS-1 ordinary Portland cement were prepared with varying W/S (Solid=cement) in weight, while those of Class G cement were prepared with changing the content of fly ash in volume but maintaining W/S (Solid=cement+fly ash). The results of the material tests show that as the W/S in KS-1 ordinary Portland cement and the content of fly ash in Class G cement increase, the properties (density, sonic wave velocity, elastic constants, compressive and tensile strengths, thermal conductivity) decrease, but porosity and specific heat increase. In addition, an increase in confining pressure and in the content of fly ash leads to plastic failure behavior of the cements. The laboratory data were then used in a stability analysis of cement sheath for which an analytical solution for computing the stress distribution induced around a cased, cemented well was employed. The analysis was carried out with varying the injection well parameters such as thickness of casing and cement, injection pressure, dip and dip direction of injection well, and depth of injection well. The analysis results show that cement sheath is stable in the cases of relatively lower injection pressures and inclined and horizontal wells. However, in the other cases, it is damaged by mainly tensile failure.