• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.609-612
• /
• 2006

The quality of the concrete compression strength can be determined after the passage of 28 days, but if any defect is found the quality of concrete after that length of time, there can be serious problems in dismantling and repair. Thus, in response to the use of concrete using non sintering cement (NSC), the present study purposed to propose a method of managing the strength of high strength concrete using NSC in comparison with high strength concrete using ordinary Portland cement (OPC) through early strength estimation using microwave, which enables the quick estimation of the strength of high strength concrete using NSC.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2013.05a
• /
• pp.56-58
• /
• 2013

In order to develop concrete generating compressive strength of 15MPa~30MPa aging for 6~12 hours in the room temperature curing, Hardening accelerator containing Ca²⁺ mixed with rapid hardening portland cement containing C₃S in quantity. The result was that the more addictive contents of Hardening accelerator is, the more greatly early compressive strength was improved. That s because the composition of Ca(OH)₂ was mass-produced at early-ages.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2004.05a
• /
• pp.1-4
• /
• 2004

In this paper. applicability of high early strength type AE water reducing agent(HESAEWA) developed by the authors is discussed by applying Mock-up test. For fresh concrete properties, concrete using existing AE water reducing agent(EAEWRA) and HESAEW A meets the target slump and air content at jobsite. Setting time of concrete using HESAEWA is shorter than that using EAEWRA. Remarkable variance of bleeding and settlement is not observed with type of AE water reducing agent. For hardened concrete properties, use of HESAEW A results in higher strength development compared with that of EAEWRA at standard curing and in field curing condition. Reaching time to accomplish 5MPa of compressive strength. which is possible to remove side form. is taken using HESAEWA earlier than that of EAEWRA by 1day. Therefore, it is confirmed that use of HESAEWA can meet the requirements of general quality of concrete and achieve high early strength development as well as has a desirable field applicability.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2013.05a
• /
• pp.115-116
• /
• 2013

Property of the compressive strength of high strength concrete was investigated in adiabatic temperature history considering hot-weather conditions. As a result, compressive strength of specimens subjected to high temperature history showed more than 120% at 3days of age compare to standard cured specimens. But, at 91days of age showed the incidence of strength less than 100%.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.05a
• /
• pp.254-255
• /
• 2014

This study is a part of development to improve early-age compressive strength of concrete by using industrial by-products. It tried to investigate the characteristics of early-age compressive strength according to curing temperature and industrial by-product replacement ratio 10, 20, and 30 %. As a result, regardless of industrial by-product replacement ratio and age, early-age compressive strength of concrete was found to be high compared to Plain using 100 % cement.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.573-576
• /
• 2003

We have developed and applied the super high early strength concrete overlay pavements for repairing asphalts pavements within 24hours. This pavements repairing method by the super high early strength concrete have already applied in U.S.A, japan, England, etc. The super high early strength concrete developed by Ssangyong cement co. for repairing pavements speedily have replaced at No. 2, 17 pavements in managing by Sunchoen national pavements management office. In the results, all of works have finished within 16~24hours after intercepting traffics and all of traffics was opened to be hamonious. In present, this pavements is sound and strong

• Journal of Industrial Technology
• /
• v.25 no.B
• /
• pp.73-80
• /
• 2005

Durability of concrete structures is seriously compromised by cracking at early-age concretes, particularly in high-strength or high-performance concrete structures. Since early-age cracking is influenced by various factors that affect the hydration process, early-age shrinkage and stress/strain development, the behavior at early-age is highly complex and no rational methodologies for its control have yet been established. Concrete structures often present volumetrical changes particularly due to thermal and moisture related shrinkages. Volumetric instability is detrimental to the performance and durability of concrete structures because structural elements are usually restrained. These restrained shrinkages develope tensile stresses which often results in cracking in combination with the low fracture resistance of concrete. Early-age defects in high-performance concrete due to thermal and autogenous deformation shorten the life cycle of concrete structures. Thus, it is necessary to examine the behavior of early-age concrete at the stages of design and construction. The purpose of this study was to propose a shrinkage models of VES-LMC (very-early strength latex-modified concrete) at early-age considering thermal deformation and autogenous shrinkage.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.607-612
• /
• 2002

In road pavements, it is known that cement concrete pavement has superior durability, safety compared. But in repairing pavement, cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixed concrete because of rapid setting time, high slump loss and other restrictions. We developed special cement developing 1 day strength of over 30.0N/mm$^2$ to open the road within 1 day and workable time is maintained over 1 hour so that it can be used as ready mixed concrete. We performed experimental overlay construction with the cement and evaluated the mechanical property and the durability. At curing temperature of 8-l8$^{\circ}C$,the flexural strength was 6.4N/mm$^2$at 1 day, so that the road can be open to traffic within 1 day. In durability test, the hardened concrete showed higher durability than Portland cement concrete.

• Journal of the Korea Concrete Institute
• /
• v.23 no.6
• /
• pp.757-763
• /
• 2011

In order to secure the effective high early age strength of the concrete, the study was carried out with a goal of functional improvement of cement. This study was carried out as a follow up for the previous study, which analyzed the high early age strength and durability of concrete mixed with fine particle cement (FC) during cement production. The experimental results showed that the target range for each mix was satisfied at fresh state of concrete. Also, when mixed with fine particles cement, the setting time improved. Additionally, compressive strength and heat of hydration increased and remained same, respectively. Especially, the durability remained same even when mixed with fine particle cement.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.5
• /
• pp.459-470
• /
• 2014

Now-a-days, the trend in constructing tunnels is to build more deeper, more longer tunnels of greater cross-sections. That's why, the demand of "Early-high-strength shotcrete" is very high because of their advantage of attaining higher strength immediately after excavation, which controls the ground subsidence. So, this study reveals the supporting phenomena of early-high-strength shotcrete, using three-dimensional numerical analysis. The crux of this study can be applied practically in construction sites also. Support Performance of two different qualities of shotcrete was checked out, by keeping the general shotcrete's thickness constant and comparing it with early-high-strength shotcrete's thickness decreasing it gradually in five steps, and analysing/comparing the support performance in all cases. Effect of using early-high-strength shotcrete was analysed to save the cost of steel sets, which are widely used for supporting the ground before the hardening of general shotcrete. The results of numerical analysis on the performance of early-high-strength shotcrete show that, it behaves more effectively under worse ground conditions and it can support the ground more conveniently than steel sets, before the shotcrete is hardened.