• Journal of Construction Engineering and Project Management
• /
• 제3권1호
• /
• pp.28-34
• /
• 2013

Use of recycled aggregates in portland cement concrete (PCC) construction can offer benefits associated with both economy and sustainability. Testing performed to date indicates that recycled brick masonry aggregate (RBMA) can be used as a 100% replacement for conventional coarse aggregate in concrete that exhibits acceptable mechanical properties for use in structural and pavement elements, including satisfactory performance in some durability tests. Recycled brick masonry aggregate concrete (RBMAC) is currently not used in any type of construction in the United States. However, use of RBMAC could become a viable construction strategy as sustainable building practices become the norm. This paper explores the feasibility of use of RBMAC in several types of sustainable construction initiatives, based upon the findings of previous work with RBMAC that incorporates RBMA produced from construction and demolition waste from a case study site. A summary of material properties of RBMAC that will be useful to construction professionals are presented, along with a discussion of advantages and impediments to use. Several quality assurance and quality control techniques that could be incorporated into specifications are identified.

• 한국건축시공학회지
• /
• 제13권6호
• /
• pp.602-608
• /
• 2013

본 연구에서는 BS다량 치환 콘크리트의 알칼리자극제로서 순환골재 및 고분말도의 FC를 복합 사용한 콘크리트의 제반 공학적 특성 및 미시적 분석을 실시하였다. FC 치환에 따른 슬럼프 및 공기량은 큰 차이가 없었으며, 응결시간은 FC 치환에 따라 비례적으로 단축되는 것으로 나타났다. FC 치환에 따른 압축강도는 고분말도의 FC가 치환됨에 따라 촉진된 수화반응 및 순환골재의 미수화 시멘트의 알칼리 용출로 인해 BS의 잠재수경성 반응을 촉진시켜 초기 및 28일 재령에서의 Plain 대비 강도저하를 상당부분 회복할 수 있었으며, 특히 향후 재령이 경과함에 따라 포졸란 반응의 활성화로 추가적인 강도향상이 기대된다. 탄산화 저항성의 경우 큰 차이가 없으며, 세공분포의 경우 FC 치환률이 증가함에 따라 $0.1{\mu}m$이하의 미세 공극분포가 급격히 증가하는 경향을 보였고, SEM 측정결과 FC 치환에 따른 7일 및 28일에서의 C-S-H 및 $Ca(OH)_2$의 생성을 확인하여 FC가 BS 다량치환 순환골재 콘크리트의 알칼리 자극에 기여함을 확인 할 수 있었다.

• 농업과학연구
• /
• 제37권2호
• /
• pp.277-283
• /
• 2010

Research on permeable pavement like asphalt and concrete pavement with porous structure has been increasing due to environmental and functional need such as reduction of run off and flood. This study was performed to evaluate void ratio, permeability coefficient, and compressive strength of permeable polymer concrete (PPC) using crushed and recycled coarse aggregate that is obtained from waste concrete. Also, 6 mm length of polypropylene fiber was used to increase toughness and interlocking between aggregate and aggregate surrounded by binder. Binder and filler used were unsaturated polyester resin and CaCO3, respectively. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate sizes 5~10 mm. In the test results, regardless of kinds of aggregates and fiber contents, the void ratio, permeability coefficient and compressive strength of all types of PPC showed the higher than the criterion of porous concrete that is used in permeable pavement in Korea. Also, strengths of PPC with increase polypropylene fiber volume fraction showed slightly increased tendency due to increase binder with increase of fiber volume fraction. Accordingly, polypropylene fiber and recycled coarse aggregate can be used for permeable pavement.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.380-383
• /
• 2004

The coarse and fine aggregates that make up the majority of concrete are resources. But, the raw naturals that make up concrete are our earth's resources and there is not a replenishable stock. Also industrial waste and life waste leaped into a pollution source. Therefore, as construction continue, quarries are exhausted and new sources must be discovered. The purpose of this paper is to investigate an application of recycled coal ash plastics in the construction field. The study examined the physical and mechanical properties of recycled coal ash plastics aggregate. In the results, although the absorption and specific gravity of SLAs increases slightly as the fly ash content increases, the compressive strength and modulus of elastic of concrete made with SLAs remains relatively constant when mortar type and volume fraction are also held constant. These values are always lower than natural-weight aggregate concretes.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
• /
• pp.37-38
• /
• 2013

The fine powder obtained from the manufacturing process of recycled coarse aggregate contains unhydareted cement particles on their surface. It is believed that the alkalinity of the powder (11.0-12.5) is enough to active the slag-based composites. In this paper, the obtained powder was sieved and divided into two sizes, i.e., 0.08 mm and 0.3 mm, and added to the slag-based mortar. Results showed that the fine powder had an effect on the slump and the compressive strength of slag-based composites. With the different pH values of the powder, it could be seen that the distance between the two level powders. And found the peak 28 days compressive strength as the replacement ratio of the recycled aggregate powder changed. The findings from this study provide an indication that with achieved compressive strength, the fine powder can be used in a light weight concrete.

• 한국구조물진단유지관리공학회 논문집
• /
• 제15권1호
• /
• pp.103-111
• /
• 2011

이 연구에서는 나선철근으로 횡구속된 순환골재 콘크리트의 구조적 거동을 평가하였다. 주요 실험변수는 골재의 종류와 나선철근의 철근비로 계획하였다. 총 18체의 실험체를 제작하였으며, 실험체의 직경과 높이는 각각 150mm와 300mm이었다. 실험체는 사용된 굵은 골재의 종류에 따라 2가지로 구분할 수 있으며, 나선철근의 철근비는 0%에서 1.75%까지 변화하도록 계획하였다. 실험체의 축방향 및 횡방향 변형을 측정하기 위하여, 6개의 LVDT를 실험체에 부착하였다. 또한 나선철근의 변형률을 측정하기 위하여 스트레인 게이지를 120도 간격으로 나선철근에 부착하였다. 실험결과로부터, 나선철근으로 횡구속된 순환 골재 콘크리트의 구조 성능은 나선철근의 철근비와 관계없이 천연골재 콘크리트와 서로 유사함을 확인하였다.

• Steel and Composite Structures
• /
• 제49권4호
• /
• pp.457-471
• /
• 2023

To make up for the performance weaknesses of recycled aggregate concrete (RAC), expand the application range of RAC, and alleviate the environmental problems caused by excessive exploitation of natural coarse aggregates (NCA), this study proposes a basalt fiber-reinforced recycled aggregate concrete (BFRRAC)-filled square steel tubular columns that combines two modification methods of steel tube and fiber, which may greatly enhance the mechanical properties of RAC. The axial compression performance for BFRRAC-filled square steel tubular columns was reported during this study. Seven specimens with different replacement ratios of recycled coarse aggregate (RCA), length-diameter ratios, along with basalt fiber (BF) contents were designed as well as fabricated for performing axial compression test. For each specimen, the whole failure process as well as mode of specimen were discovered, subsequently the load-axial displacement curve has obtained, after which the mechanical properties was explained. A finite element analysis model for specimens under axial compression was then established. Subsequently, based on this model, the factors affecting axial compression performance for BFRRAC-filled square steel tubes were extended and analyzed, after which the corresponding design suggestion was proposed. The results show that in the columns with length-diameter ratios of 5 and 8, bulging failure was presented, and the RAC was severely crushed at the bulging area of the specimen. The replacement ratio of RCA as well as BF content little affected specimen's peak load (less than 5%). As the content of BF enhanced from 0 kg/m³ to 4 kg/m³, the dissipation factor and ductility coefficients increased by 10.2% and 5.6%, respectively, with a wide range.

• 한국건설순환자원학회논문집
• /
• 제1권1호
• /
• pp.72-80
• /
• 2005

건설폐기물 발생량이 급증함에 따라, 폐콘크피트를 파쇄가공한 순환골재를 구조체 콘크리트용으로 사용할 필요성이 증대하고 있다. 그러나 순환골재에는 콘크리트의 물리적 특성에 악영향을 미치는 각종 이물질이 포함되어 있어, 사전에 이물질 함유량을 적절히 판단하기 위한 시험방법이 요구된다. 본 연구에서는 순환잔골재와 순환굵은골재에 포함되어 있는 각종 이물질 함유량을 육안관찰에 의하여 선별하기 위한 시험방법을 개발하였으며, 그 결과는 다음과 같다. 1. 현행 KS F 2576(재생골재의 이물질 함유량 시험방법)은 시험대상 순환골재의 종류, 용어의 정의, 시료량, 시험방법 등의 전반적인 개정이 필요하다. 2. 순환골재에 포함된 이물질은 시료의 입경이 1.2mm 이상이면 육안선별이 가능하며, 입경이 클수록 측정 소요시간이 크게 단축된다. 3. 육안선별 방법에 의한 이물질 함유량 시험을 위하여 순환잔골재는 입경 2.5~5mm의 시료 30g, 순환굵은골재는 입경 5mm 이상의 시료 1kg을 대상으로 하면 시험의 용이성 및 정밀도 확보가 가능하다.

• 콘크리트학회지
• /
• 제7권2호
• /
• pp.136-145
• /
• 1995

본 연구는 천연 굵은 골재 50%를 재생골재로 대치시켜 제조한 재생콘크리트를 일반 구조물에 사용할 수 있도록 성능을 향상시키기 위한 연구의 일환으로 수행되었다. 쇄석골재 사용시의 배합설계 방법으로 콘크리트를 제조하였고 일반적인 수중양생으로 공시체를 야생하였다. 재생콘크리트의 성능향상을 목적으로 유동화제와 플라이애쉬를 첨가하였다. 압축강도 등 각종 강도와 파괴인성 등을 측정하여 이를 일반콘크리트와 비교한 결과 재생콘크리트는 강도와 탄성계수가 낮고 변형율이 크며 파괴인성도 낮았다. 그러나 유동화제의 사용으로 물-시멘트비를 35%까지 낮추므로써 슬럼프 $16{\pm}2$cm에서 일반 구조물에 소요 압축강도보다 높은$225kg/cm^2$이상의 압축강도를 얻었다. 하지만 재생콘크리트를 일반 구조물에 사용을 위해서는 탄성계수와 변형율에 대한 향상이 필요하다. 또한 플라이애쉬의 사용은 장기 강도 증진 효과를 보이는 반면 강도 저하를 유발했다.

• Steel and Composite Structures
• /
• 제43권2호
• /
• pp.257-270
• /
• 2022

Recycled aggregate concrete (RAC) is rarely used in load-carrying structural members. To widen its structural application, the compressive behavior of a promising type of composite column, steel-fiber reinforced polymer (FRP) double-tube confined RAC column, has been experimentally and analytically investigated in this study. The objectives are the different performance of such columns from their counterparts using natural aggregate concrete (NAC) and the different mechanisms of the double-tube and single-tube confined concrete. The single-tube confined concrete refers to that in concrete-filled steel tubular (CFST) columns and concrete-filled FRP tubular (CFFT) columns. The test results showed that the use of recycled coarse aggregates (RCA) affected the axial load-strain response in terms of deformation capacity but such effect could be eliminated with the increasing confinement. The composite effect can be triggered by the double confinement of the steel and carbon FRP (CFRP) tubes but not by the steel and polyethylene terephthalate (PET) FRP tubes. The proposed analysis-oriented stress-strain model is capable to capture the load-deformation history of such steel-FRP double-tube confined concrete columns under axial compression.