The Physical Properties of Granite Microfines and the Workability of Mortar with Granite Microfines

Koehler, Eric,Hahn, Michael De Moya,Trachet, Alison,Rached, Marc,Choi, Jae Jin,Fowler, David Korean Recycled Construction Resources Institute 2009 한국건설순환자원학회지 Vol.4 No.3

This paper summarizes the analysis of granite microfines from California for use in portland cement concrete. For reference, the granite microfines were compared to microfines used in previous International Center for Aggregates Research(ICAR) projects. The particle shape characteristics, based on the packing density results, were assessed and apparent clay content, based on the methylene blue value test, was evaluated. Also, the physical properties of the microfines were confirmed in self-consolidating mortar mixtures.

Improved Durability Performances in Cement Mortar with Rice Husk Ash

Saraswathy, Velu,Karthick, Subbiah,Kwon, Seung-Jun Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.1

Currently many researches have been performed for enhancing durability of concrete. Rice husk ash has several advantages like early strength of concrete and dense pore structure. A calcium silicate hydrate (CSH) gel around the cement particles due to pozzolanic reaction of rice husk can increase the strength of concrete against cracking. Very limitedly a systematic and detailed investigation on the corrosion performance of rice husk ash and silica fume blended concrete is performed. A realistic approach has been made through compressive strength, bond strength, and split tensile strength etc. Corrosion performance was also evaluated rapid chloride ion penetration test (RCPT) and impressed voltage test, and the results were discussed in the paper.

Durability Enhancement in Nano-Silica Admixed Reinforced Mortar

Saraswathy, Velu,Karthick, Subbiah,Kwon, Seung-Jun Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.4

Recently nano-materials are gaining more importance in the construction industry due to its enhanced energy efficiency, durability, economy, and sustainability. Nano-silica addition to cement based materials can control the degradation of the fundamental calcium-silicate-hydrate reaction of concrete caused by calcium leaching in water as well as block water penetration and therefore lead to improvements in durability. In this paper, the influence of synthesized nano silica from locally available rice husk on the mechanical properties and corrosion resistant properties of OPC (Ordinary Portland Cement) has been studied by conducting various experimental investigations. Micro structural properties have been assessed by conducting Scanning Electron Microscopy, Thermo gravimetry and Differential Thermal Analysis, X-Ray Diffraction analysis, and FTIR studies. The experimental results revealed that NS reacted with calcium hydroxide crystals in the cement paste and produces Calcium Silicate Hydrate gel which enhanced the strength and acts as a filler which filled the nano pores present in concrete. Hence the strength and corrosion resistant properties were enhanced than the control.

A Ground Penetrating Radar Detection of Buried Cavities and Pipes and Development of an Image Processing Program

이현호,Lee, Hyun-Ho Korean Recycled Construction Resources Institute 2017 한국건설순환자원학회 논문집 Vol.1 No.3

최근 한국에서는 많은 지반 침하 사고가 발생하고 있는데, 이는 상하수의 누수 및 손상된 하수관에 기인한 것이다. 본 연구는 지반 침하에 대한 GPR 탐지 데이터의 실증적 자료를 구축하는 것을 목표로 한다. 이러한 목적으로 테스트 베드가 제작되었으며, 제작 변수는 주철관 및 EPS의 매입 깊이 및 수평 거리이다. 탐사결과, 1.5m의 깊이로 매립된 EPS는 검출하기 어려웠으며, 0.5m 거리 내에서 주철관에 밀접하게 매설 된 EPS는 매우 강한 주철관 신호로 탐지가 불가능했다. 또한 본 연구에서는 GPR 탐사 이미지 결과를 처리하기 위해 GPR 이미지 처리 프로그램 (GPRiPP)을 개발했다. 그 주요 기능은 위글파 신호를 증폭시키는 게인 기능이며, 기존 프로그램과 GPRiPP의 이미지 처리 기능은 매우 유사함을 확인하였다. Many ground subsidence accidents have happened in Korea. The accident was caused by the subsidence and leakage of the deteriorated sewage pipe. This study aims to establish the empirical data of the ground penetration radar(GPR) detection for ground subsidence. A test bed was also manufactured for the same purpose. The GPR detection variables are embedment depth and horizontal distance of embedded cast iron pipe and expanded polystyrene(EPS). From the detection results, the EPS embedded by a depth of 1.5m was difficult for detection. The EPS closely embedded to the cast iron pipe within a 0.5m distance had a very strong cast iron pipe signal. Therefore, the detection was impossible. This study developed an image processing program, called the GPR image processing program(GPRiPP), to process the GPR detection results. Its major function is the gain function, which amplifies the wiggle wave signal. Compared to the existing programs, the GPRiPP is capable of showing a similar image processing performance.

Effect of Reinforcing Bar on Rayleigh Wave Propagation on Concrete Structures

Kim, Jae-Hong,Lee, Kang-Wook Korean Recycled Construction Resources Institute 2015 한국건설순환자원학회 논문집 Vol.3 No.2

This paper presents results on a study of the Rayleigh wave scattering in concrete with a steel bar using transient elastic waves. To study the characteristics of the scattered waves induced by a steel bar in concrete, a three-dimensional finite element method was adopted. A case for elastic wave propagation parallel to the steel bar is discussed. The effect of the cover thickness and steel bar diameter on the Rayleigh wave was studied. To confirm the numerical investigations, a concrete specimen containing a steel bar was made, and corresponding transient elastic wave experiments were conducted. It is believed that the result of this study can serve as an important reference in a nondestructive evaluation of concrete with a steel bar.

Studies on the Performance of Self Healing of Plastic Cracks Using Natural Fibers in Concrete

Saraswathy, Velu,Kwon, Seung-Jun,Karthick, Subbiah Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.2

Addition of fibers in cement or cement concrete may be of current interest, but this is not a new idea or concept. Fibers of any material and shape play an important role in improving the strength and deformation characteristics of the cement matrix in which they are incorporated. The new concept and technology reveal that the engineering advantages of adding fibers in concrete may improve the fracture toughness, fatigue resistance, impact resistance, flexural strength, compressive strength, thermal crack resistance, rebound loss, and so on. The magnitude of the improvement depends upon both the amount and the type of fibers used. In this paper, locally available waste fibers such as coir fibers, sisal fibers and polypropylene fibers have incorporated in concrete with varying percentages and l/d ratio and their effect on compressive, split, flexural, bond and impact resistance have been reported.

Tensile and Compressive Creep Behaviors of Amorphous Steel Fiber-Reinforced Concrete

Truong, Gia Toai,Choi, Kyoung-Kyu,Choi, Oan-Chul Korean Recycled Construction Resources Institute 2013 한국건설순환자원학회 논문집 Vol.1 No.3

In this study, the creep behaviors of amorphous steel fiber-reinforced concrete were investigated. Two different types of tests were carried out to evaluate the effect of amorphous steel fibers on the creep of concrete: compressive creep test and tensile creep test. Fiber volume fractions used in the test were 0.2% and 0.4% for tensile specimens, and 0.2% and 0.3% for compressive specimens. Based on the test results, the addition of fiber volume fraction of 0.2% into concrete could significantly reduce both compressive and tensile creep.

Recent Advances in Ultra-high Performance Concrete

Kim, Yail J. Korean Recycled Construction Resources Institute 2013 한국건설순환자원학회 논문집 Vol.1 No.3

This paper presents a comprehensive review of recent advances in ultra-high performance concrete (UHPC). Fundamental characteristics of UHPC are elaborated with focus on its material constituents, mixing, and formulation procedures. Use of state-of-the-art materials such as carbon nanotubes or nano-silica is discussed as well, whose inclusion may enhance the performance of UHPC. The review evaluates supplementary treatment methods (e.g., pressuring curing) and identifies applicable standard test methods for determining the properties and behavior of UHPC. Site implementation is provided to link laboratory research with full-scale application. Research needs are suggested to further develop UHPC technologies from technical and socio-economical perspectives.

Modeling of Environmental Response for Concrete Durability

윤인석,Yoon, In-Seok Korean Recycled Construction Resources Institute 2012 한국건설순환자원학회지 Vol.7 No.3

콘크리트의 열화는 현재 전세계적인 관심 분야로서 가장 보편적인 열화원인은 염해이다. 이를 고려한 내구수명 예측기법의 개발은 토목건설 기술에 매우 중요한 부분을 차지하고 있으나, 대부분의 기존의 연구는 수명예측에 대한 기법에 집중되어 왔을 뿐, 콘크리트 표면의 미세 기후조건을 고려한 환경 분석은 매우 드문 실정이다. 그러나 콘크리트의 내구성은 표면의 특성에 의해 지배되므로, 실질적으로 표면상태에 대응한 미세 기후조건을 연구하여 환경대응 인자로 정립할 필요가 있다. 본 연구는 현장 기후조건을 계측하여 콘크리트의 미세기후조건을 해석할 수 있는 방법을 제안하였다. 이 결과는 염소이온 확산계수와 같은 재료 매개변수에 반영하여 더욱 정밀한 수치 해를 얻는데 이용되었다. 본 연구는 콘크리트의 내구성 설계기법을 개발하기 위하여, 환경인자에 대응한 매개변수를 도출하는데 이용될 수 있을 것으로 기대된다. The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the durability of concrete have been accomplished, however, it is not easy to review literatures about environmental analysis. Since the durability of concrete depends on the properties of the surface concrete. micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The effect of degree of saturation on chloride diffusivity of concrete is also examined. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete.

Durability Evaluation of Concrete Using Fine Sand of Nakdong-River

Kwon, Soon-Oh,Bae, Su-Ho,Lee, Hyun-Jin Korean Recycled Construction Resources Institute 2014 한국건설순환자원학회 논문집 Vol.2 No.3

It is strongly needed to investigate the fine sand as an alternative fine aggregate of well-graded river sand because the fine sand which is being enormously distributed in the midstream and downstream of Nakdong-River in Korea has a poor grading but good quality as a fine aggregate for concrete. Thus, the purpose of this experimental research is to evaluate the durability of concrete using the fine sand to utilize it actively as a fine aggregate. For this purpose, the concrete specimens using different fine sand were made for the specified concrete strength of 35MPa, and then their durability such as the resistance to freezing and thawing and carbonation, and drying shrinkage were evaluated. It was observed from the test results that the resistance to freezing and thawing and carbonation of concrete using the fine sand was similar to that of concrete using reference sand, but the drying shrinkage of concrete using the fine sand with small fineness was comparatively lager than that of concrete using reference sand.