순환골재가 함유된 철근콘크리트보 휨거동의 고찰

여진동,박태희,김우석,강현구,홍성걸,곽윤근,Yeo, Jin-Dong,Park, Tae-Hee,Kim, Woo-Suk,Kang, Thomas H.K.,Hong, Sung-Gul,Kwak, Yoon-Keun 대한건축학회 2011 대한건축학회논문집 Vol.27 No.9

Developed society is beginning to face an environmental crisis in that enormous quantities of demolished concrete are both damaging to the environment and wasteful to the economy. Conversely, most of the waste concrete can be one of the largest market values by recycling. The problem is that the demolished concrete is currently not recycled economically and efficiently, and is used worthlessly for landfill or road basement. In many cases, the demolished concrete remains as just waste concrete, which can cause a serious environmental problem. Up to now, the Korean architectural and civil engineering society has barely found the value of the recycled concrete that can be matched with that of high performance concrete, both of which are especially useful for the mega construction site. The result from this recycled concrete study is very important in these aspects. The RCA (recycled concrete aggregate) must be researched more in terms of mechanical properties and structural performance. The moment strength, cracking and steel yielding processes and failure mode are investigated for varying steel ratios and percentage of RCA. The normal strength concrete with a 24 MPa compressive strength is used. In recycled concrete aggregate (RCA), the compressive strength is particularly important, because the RCA requires more water than NCA (normal concrete aggregate) so that a lower strength can be produced. Therefore, more efforts are needed to gain the design strength. This experiment investigates the flexural performance and suggests the possible application of RCA for building structures. Furthermore, this research will play an important role toward the establishment of the structural design standard for recycled concrete.

순환골재가 함유된 철근콘크리트보 휨거동의 고찰

여진동(Yeo Jin-Dong),박태희(Park Tae-Hee),김우석(Kim Woo-Suk),강현구(Kang Thomas H.-K.),홍성걸(Hong Sung-Gul),곽윤근(Kwak Yoon-Keun) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.9

Developed society is beginning to face an environmental crisis in that enormous quantities of demolished concrete are both damaging to the environment and wasteful to the economy. Conversely, most of the waste concrete can be one of the largest market values by recycling. The problem is that the demolished concrete is currently not recycled economically and efficiently, and is used worthlessly for landfill or road basement. In many cases, the demolished concrete remains as just waste concrete, which can cause a serious environmental problem. Up to now, the Korean architectural and civil engineering society has barely found the value of the recycled concrete that can be matched with that of high performance concrete, both of which are especially useful for the mega construction site. The result from this recycled concrete study is very important in these aspects. The RCA (recycled concrete aggregate) must be researched more in terms of mechanical properties and structural performance. The moment strength, cracking and steel yielding processes and failure mode are investigated for varying steel ratios and percentage of RCA. The normal strength concrete with a 24 MPa compressive strength is used. In recycled concrete aggregate (RCA), the compressive strength is particularly important, because the RCA requires more water than NCA (normal concrete aggregate) so that a lower strength can be produced. Therefore, more efforts are needed to gain the design strength. This experiment investigates the flexural performance and suggests the possible application of RCA for building structures. Furthermore, this research will play an important role toward the establishment of the structural design standard for recycled concrete.

The Application of Recycled Concrete Aggregate (RCA) for Hot Mix Asphalt (HMA) base Layer Aggregate

조윤호,윤태영,김인태,최영락 대한토목학회 2011 KSCE Journal of Civil Engineering Vol.15 No.3

Recycled Concrete Aggregate (RCA) is different from natural aggregate because of RCA’s cement paste and contaminants that cause low density and high porosity. In many cases, these properties of RCA that lead to poor engineering qualities are the major reasons that RCA is not recommended as aggregate for Hot Mix Asphalt (HMA). In this research, the performance of HMA mixtures with RCA is quantitatively evaluated using various tests to verify the applicability of RCA as aggregate for HMA material. For this verification, the Indirect Tensile (IDT) strength test, Kim test, wheel tracking test, and tensile strength ratio test accompanied by fundamental material property tests were performed on asphalt mixtures with four types of aggregate blends. In addition, asphalt mixtures with RCA, whose binder contents were determined from the Superpave mix design method, were utilized and evaluated against Marshall design criteria in order to effectively reflect both field specifications and field compaction conditions in South Korea. As a result of this study, it is observed that the study asphalt mixtures with RCA (Mixes II and III) show good performance compared to the asphalt mixture with natural aggregate only (Mix I) in terms of indirect tensile strength ratio, deformation strength,rut depth, and IDT strength, whereas Mix IV, which consists of coarse and fine RCA, does not exhibit good performance. By evaluating the Marshall test properties of each mixture, it is also concluded that the dynamic loading in the Marshall test compaction method possibly causes friction in the RCA of the asphalt mixtures and, therefore, leads to an underestimation of the engineering properties of HMA with RCA.

순환굵은골재를 사용한 레디믹스트 콘크리트의 역학적 특성

전에스더(Jeon Esther),윤현도(Yun Hyun-Do),지상규(Ji Sang-Kyu),최기선(Choi Ki-Sun),유영찬(You Young-Chan),김긍환(Kim Keung-Hwan) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.8

In this study, the mechanical properties of ready-mixed concrete with recycled coarse aggregate(RCA) were discussed. The mixing types were composed of twelve series based on specified compressive strength(i.e 21, 27, and 40MPa) and replacement ratio of recycled coarse aggregates(i.e 0, 30, 60 and 100%). Recycled coarse aggregate utilized in the study consists of 71.43% high quality recycled coarse aggregate, 28.57% low quality recycled coarse aggregate by weight. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. The strength properties of the hardened concrete were measured by means of compressive strength, splitting strength and modulus of rupture. Also test result were compared with existing domestic Codes(KBC2005 and KCI2007). Test result indicated that the replacement ratio of recycled coarse aggregate had little effect on fresh properties, such as slump and air content, of RCA concrete. Compressive strength, splitting strength and modulus of rupture of concrete is little affected by the replacement ratio of recycled coarse aggregate. And elastic modulus, splitting strength and modulus of rupture show relatively low values compared with relevant provisions in KBC2005 and KCI2007. Therefore, some design coefficients or recommendations in existing design code for natural aggregate concrete need to be amended for recycled aggregate concrete.

순환골재를 사용한 고강도 철근콘크리트보의 휨거동에 관한 연구

김우석(Kim, Woo-Suk),여진동(Yeo, Jin-Dong),곽윤근(Kwak, Yoon-Keun),강현구(Kang, Thomas H.-K.),홍성걸(Hong, Sung-Gul) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.3

Currently, approximately 90% of waste concrete is being used solely for landfills. Of the total waste concrete only about 14% is made into aggregate and recycled. Such usage is a very low-efficiency method of recycling these materials, under-utilizing an important and valuable asset. Common engineering practice has thus far failed to promote the design of structural members using recycled aggregates. Moreover, appropriate structural design standards for such materials have not been established, despite the number of domestic research studies which have been, and are being, conducted. Such practices overlook the fact that the recycling of aggregate from demolished concrete structures is both structurally and economically beneficial. In making full use of recycled concrete aggregates (RCA) it is necessary to understand its mechanical properties such as compressive, tensile and flexural strengths, and bond strength, as well as its structural performance. The main objectives of this research study are the investigation of flexural performance and the evaluation of the potential applications of RCA on concrete structures. For this, flexural tests of 12 reinforced high-strength concrete beams with RCA were performed. The current test data were examined in terms of flexural strength, along with the data from previously tested reinforced concrete beams with RCA. It is anticipated that this research will play a role of establishing the structural design standards for concrete members with RCA.

순환골재를 사용한 고강도 철근콘크리트보의 휨거동에 관한 연구

김우석,여진동,곽윤근,강현구,홍성걸,Kim, Woo-Suk,Yeo, Jin-Dong,Kwak, Yoon-Keun,Kang, Thomas H.K.,Hong, Sung-Gul 대한건축학회 2012 대한건축학회논문집 Vol.28 No.3

Currently, approximately 90% of waste concrete is being used solely for landfills. Of the total waste concrete only about 14% is made into aggregate and recycled. Such usage is a very low-efficiency method of recycling these materials, under-utilizing an important and valuable asset. Common engineering practice has thus far failed to promote the design of structural members using recycled aggregates. Moreover, appropriate structural design standards for such materials have not been established, despite the number of domestic research studies which have been, and are being, conducted. Such practices overlook the fact that the recycling of aggregate from demolished concrete structures is both structurally and economically beneficial. In making full use of recycled concrete aggregates (RCA) it is necessary to understand its mechanical properties such as compressive, tensile and flexural strengths, and bond strength, as well as its structural performance. The main objectives of this research study are the investigation of flexural performance and the evaluation of the potential applications of RCA on concrete structures. For this, flexural tests of 12 reinforced high-strength concrete beams with RCA were performed. The current test data were examined in terms of flexural strength, along with the data from previously tested reinforced concrete beams with RCA. It is anticipated that this research will play a role of establishing the structural design standards for concrete members with RCA.

Bond strength prediction for deformed steel rebar embedded in recycled coarse aggregate concrete

Kim, S.W.,Yun, H.D.,Park, W.S.,Jang, Y.I. Scientific and Technical Press ; Elsevier Science 2015 Materials & Design Vol.83 No.-

This paper summarizes the results of an experimental investigation into the bond behavior between recycled aggregate concrete (RAC) and deformed steel rebars, with the main variables being the recycled coarse aggregate replacement ratio (RCAr) and water-to-cement ratio of the concrete mixture. The investigation into splitting cracking strength indicates that the degradation of the bond splitting tensile stress of the cover concrete was affected by not only the roundness of the coarse aggregate particles but also the weak interfacial transition zone (ITZ) between the cement paste and the RCA that has a more porous structure in the ITZ than normal concrete. In this study, a linear relationship between the bond strength and the density of the RCA was found, but the high compressive strength reduced the effects of the parameters. To predict the bond strength of RAC using the main parameters, a multivariable model was developed using nonlinear regression analysis. It can be inferred from this study that the degradation characteristic of the bond strength of RAC can be predicted well, whereas other empirical equations and code provisions are very conservative.

순환골재를 사용한 콘크리트부재의 최소철근비 검토

신명환,송건호,백승민,김우석,곽윤근 한국폐기물자원순환학회 2015 한국폐기물자원순환학회지 Vol.32 No.4

Recently, demand for construction aggregates is increasing due to the growth of construction site scale. As natural aggregate sources are becoming depleted due to high demand in construction field, the utilization of recycled aggregate (RA) as coarse aggregate in concrete is becoming more important. In this study, the authors analyze the mechanical properties of normal- and high-strength concrete beams using RA and investigate the usefulness of the minimum steal ratio for RA reinforced concrete beams. The experimental results show that application of the minimum steel ratio to RA reinforced concrete beams is possible.

Accelerated calcite precipitation (ACP) method for recycled concrete aggregate (RCA)

Nam, B.H.,An, J.,Youn, H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.125 No.-

Recycled concrete aggregate (RCA) is often used as a replacement of virgin aggregate in embankments, roadbed, asphalt and concrete pavements. The use of RCA in drainage systems as pipe backfill materials has not received a large attention due to clogging potential. Calcite precipitation is one of major causes of permittivity reduction in filter fabrics. The calcite formation is a long-term process; thus, a means to evaluate the potential of calcite precipitation in an accelerated manner is necessary. In this study, an accelerated calcite precipitation (ACP) procedure of RCA was developed, and its performance was evaluated. Two types of ACP methods were devised: short-term and long-term simulations. The long-term ACP procedure can be used to determine maximum lifetime calcite precipitation while the short-term ACP procedure can be used to evaluate the effect of test variables (e.g. aggregate type, fine content, etc.) on the calcite precipitation.

On Probability Distribution of Chloride Diffusion Coefficient for Recycled Aggregate Concrete

Jingwei Ying,Jianzhuang Xiao,Qiujiang Meng 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.1

In predicating the probability distribution of chloride diffusion coefficient of recycled aggregate concrete (DRAC), the morphological characteristics of three phases, i.e., the old attached mortar, the natural aggregate and the new mortar, should all be taken into account. The present paper attempts to develop a probability density evolution method (PDEM) to achieve this. After verifying the derived PDEM results with experimental results, the effects of old attached mortar to the DRAC are examined in a quantitative manner. It is found that (1) the variation of the attached mortar content is much sensitive to DRAC; (2) given the probability distribution of the content and chloride diffusion coefficient of old mortar, the probability distribution of DRAC can be analysed based on the PDEM; and (3) the critical chloride diffusion coefficient at a certain assurance rate can be obtained by the PDEM. The analysis results of this investigation will be valuable to the durability design for RAC.