Evaluation of durability of an ECC(Engineered Cementitious Composite) designed with ground granulated blast furnace slag

This paper presents the experimental results for durability of an ECC designed with ground granulated blast furnace slag (BFS) through the test method of chloride ion resistance and freezing-thawing resistance. In order to compare with ECC, normal mortar was also tested. Test results showed that BFS ECC exhibited higher durability performance than ordinary mortar. These results suggest that by adding BFS in ECC, its matrix density is increased which results in decreased of deterioration and it also adds to the fiber bridging that contributes in control of cracking

Hysteretic Behavior of Reinforced High-Strength Concrete Sections

국내에서도 건축물의 설계시에 내진설계를 요구함에 따라 지진하중을 받는 초고층 철근콘크리트 건축물의 해석 및 설계를 위하여 고강도콘크리트를 사용한 부재 및 구조물의 이력거동 및 내진성능 평가를 위한 연구가 시갑한 실정이며, 특히 초고층 철근콘크리트 건축물이 지진하중과 같은 심한 반복 주기하중을 받을 경우에 구조 부재의 성능을 정확히 파악하는 것을 매우 중요하다. 따라서 본 연구에서는 고강도 철근콘크리트 부재 단면의 내진성능을 평가하기 위하여 반복 주기하중을 받는 철근과 콘크리트의 재료 모델에 관한 기존의 연구결과를 분석하여 합리적인 재료 모델을 선정하고, 이를 토대로 모멘트-곡률 관계의 해석적 연구를 위한 프로그램을 개발하였다. 그리고 이 해석적 방법을 적용하여 고강도 철근콘크리트 부재 단면의 내진성능에 영향을 미치는 변수, 즉 콘크리트 압축강도, 인장 철근비, 압축 철근비, 축하중, 철근의 항복강도, 철근의 지배정도 및 구속 효과등의 영향을 평가하여 고강도콘크리트를 사용한 구조물의 설계시 기초자료로 활용할 수 있도록 하였다

Hysteretic behavior and seismic resistant capacity of reinforced high-strength concrete beam-column joints

학위논문(박사) - 한국과학기술원 : 토목공학과, 1993, [ x, 158 p. ]한국과학기술원 : 토목공학과

Processibility of High Ductile Fiber-Reinforced ECCs (Engineered Cementitious Composites)

In the recent design of high ductile fiber-reinforced cementitious composite ECC, which exhibits tensile strain-hardening behavior in the hardened state, optimizing both processing mechanical properties for specific applications is critical. This study introduced a method to develop useful ECCs in field, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or spray processing). Control of rheological modulation was regarded as a key factor to allow the performance of the desired processing, while retaining the ductile material properties. To control the rheological properties of the composite, we first determined basic ECC compositon, which is based on micromechanics and steady-state cracking theory. The stability and consequent viscosity of suspensions were, then, mediated by optimizing dosages of chemical and mineral admixtures. The rheological properties altered by this approach were revealed to be effective in obtaining ECC hardened properties, allowing us to readily achieve the desired function of the fresh ECC

Effects of water-cement ratio on fiber-matrix interface characteristics and matrix fracture toughness

This paper presents an experimental investigation examining water-cement ratio effects on fiber-matrix interface properties and on matrix fracture properties, which are used for designing mix proportion suitable for achieving strain-hardening behavior at a composite level. A single fiber pullout test and a wedge splitting test were employed to measure the bond properties in a matrix and the fracture toughness of mortar matrix, respectively. Test results showed that the properties tended to increase with decreasing water-cement ratio. Composite design using these test results will be discussed in the follow-up paper

Influence of ECC ductility on the diagonal tension behavior (shear capacity) of shear-wall panel

This paper presents a preliminary study on the influence of material ductility on diagonal tension behavior of shear-wall panels. There have been a number of previous studies, which suggest that the use of high ductile material such as ECC (Engineered Cementitious Composite) significantly enhanced shear capacity of structural elements even without shear reinforcements involved. The present study emphasizes increased shear capacity of shear-wall panels by employing a unique strain-hardening ECC reinforced with poly(vinyl alcohol) (PVA) short random fibers. Normal concrete was adopted as the reference material. Experimental investigation was performed to assess the failure mode of shear-wall panels subjected to knife-edge loading. The results from experiments show that ECC panels exhibit a more ductile failure mode and higher shear capacity when compared to ordinary concrete panels. The superior ductility of ECC was clearly reflected by micro-crack development, suppressing the localized drastic fracture typically observed in concrete specimen. This enhanced structural performance indicates that the application of ECC for a in-filled frame panel can be effective in enhancing seismic resistance of an existing frame in service

Mechanical properties of ductile fiber-reinforced mortar designed based on micromechanics

The objective of this study is to examine mechanical properties of ductile fiber-reinforced mortar designed based on micromechanics. This mortar was produced by employing raw materials commercially available in Korea. To verify property level of this material in uniaxial tension, a series of direct tensile tests were performed with varying water cement ratio. In addition to this, flexural tests as well as compressive tests were carried out. Experiments revealed that the fiber reinforced mortar exhibited high ductility represented by strain hardening behavior in uniaxial tension. Significant enhancements of ductility, in terms of strain at peak stress and post-peak behavior, were also observed during the tests in compression and in bending

Uniaxial tension behavior of high ductile fiber reinforced mortar designed based on micromechanics

A high ductile fiber reinforced mortar has been developed by employing micromechanics-based design procedure. Micromechanical analysis was initially performed to properly select water-cement ratio, and then optimal mixture proportion was determined based on workability considerations, including desirable fiber dispersion without segregation. Subsequent direct tensile tests revealed that the fiber reinforced mortar exhibited high ductile uniaxial tension property, represented by strain capacity, which is around 100 times the strain capacity of normal concrete

Development of Rerofitting System for the Remodeling of Reinforced Concrete Frame Using High Ductile Fiber Composite Mortar PC Panel

초록 Three reinforced concrete rigid frames and infilled rigid frames with new retrofitting system were tested under both vertical and cyclic loadings, Experimental programs were carried out to evaluate and improve the seismic performance of such test specimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. under load reversals. All the specimens were modeled in one-third scale size. For specimens(RFHPC, RFAR) designed by the improving of seismic performance of the rigid frame using the high ductile fiber composite PC panel and ALC panel system, load-carrying capacities were increased $1.45{\sim}2.28$ times, and hysteretic behavior was very stable during the final tests in comparison with the standard specimen(SRF)