Yi, Chong Ku

Cracking of concrete over time, is a natural phenomenon. Longer service life of concrete structures is desirable. Self-healing concrete using bacteria, which could form CaCO 3 crystals for crack sealing, has promised benefits to reduce cost for concrete maintenance, because cracks could be autonomously repaired without human intervention. However, because of harsh concrete internal environment render the effectiveness depending on the bacteria viability within concrete. In this study, expanded c

The objective of this study was to investigate the potential use of sand washing waste as filler for epoxy resin mortar. The mechanical properties of four series of mortars containing epoxy binder at 10, 15, 20, and 25 wt. % mixed with sand blended with sand washing waste filler in the range of 0-20 wt. % were examined. The compressive and flexural strength increased with the increase in epoxy and filler content; however, above epoxy 20 wt. %, slight change was seen in strength due to increase i

Concrete crack healing by microbial calcium carbonate producers has been intensively studied for the last 10 years. To overcome the harsh environments of concrete, various carriers have been tested for their ability to protect the healing bacteria. Using expanded clay (EC) as a carrier is attractive because it provides adequate bond strength to the cement composites as well as protection to the bacteria from harsh environments. In this study, self-healing performance by EC was examined using sty

Bio-concrete using bacterially produced calcium carbonate can repair microcracks but is still relatively expensive due to the addition of bacteria, nutrients, and calcium sources. Agricultural by-products and oyster shells were used to produce economical bio-concrete. Sesame meal was the optimal agricultural by-product for low-cost spore production of the alkaliphilic Bacillus miscanthi strain AK13. Transcriptomic dataset was utilized to compare the gene expressions of AK13 strain under neutral

The main objective of this investigation was to study the effect of stress states on the flexural fatigue behaviour of concrete. The fatigue behaviours obtained from different test methods were compared, including the recently developed biaxial flexure test, ASTM C 1550 and four-point bending test. Fourteen specimens were cast and tested for each test method, under both monotonic and repeated loadings. The fatigue strength was compared with those recommended by existing design codes. Test result

The biaxial flexural strength of a concrete panel can be evaluated by two different methods: the centrally loaded round panel test (ASTM C 1150) and the recently proposed biaxial flexure test (BFT). Twenty-six tests, with 13 specimens for each test method, were performed to verify the effect of the different test methods on the biaxial flexural strength of concrete. A finite-element analysis of the specimens of two test methods showed that the biaxial flexure test set-up allows a larger area wit

이 연구는 친환경적인 콘크리트 결합재로서 천연황토의 적용 가능성을 알아보기 위해 지오폴리머 반응법(geopolymerization)으로 얻어진 천연황토 경화체의 특성을 분석하였다. 이를 위해 천연황토와 알칼리 용액을 1 : 0.55 비율로 혼합하여 천연황토 페이스트를 제조하고 60℃와 20℃에서 양생시켜 재령에 따른 압축강도와 중량변화를 측정하였다. 또한, X-ray 회절분석(XRD)을 통해 반응 생성물을 확인하고 그 형상을 주사전자현미경(SEM)으로 촬영하였으며 수은압입법으로 경화체의 공극률을 분석하였다. 그 결과, 지오폴리머 반응법으로 얻어진 천연황토 경화체는 액상 규산나트륨(Na₂SiO₃)와 8 M 수산화나트륨(NaOH) 수용액을 1:4.5비율로 제조한 알칼리 용액을 사용하고 60℃에서 7일간 양생하였을 때 압축강도 29.1 MPa을 발현하는 천연황토 페이스트의 제조가 가능하였다. 또한, 개별 양생온도(20℃, 60℃)에서 압축강도 발현은 수분증발 비율에 따라 유사한 경향을 나

In Korea, attempts have been made to develop high strength concrete for the safety and design life improvement of nuclear power plants. In this study, the cracking potentials of nuclear power plant-high strength concretes (NPP-HSCs) containing industrial by-products with W/B 0.34 and W/B 0.28, which are being reviewed for their application in the construction of containment structures, were evaluated through autogenous shrinkage, unrestrained drying shrinkage, and restrained drying shrinkage exp