슬럼프 고정 순환골재콘크리트의 물리적 특성 및 압축강도 추정에 관한 실험적 연구

김상헌,전찬수,이세현 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 논문집 Vol.22 No.2

This study was a basic research for actual production of recycled aggregate concrete, and experiments were carried out on the change of water cement ratio and physical properties of recycled aggregate concrete with fixed slump. Results were as follows. Concrete using recycled aggregate were required increased water to maintain the target slump, and the recycled fine aggregate are necessary more increased water more than the recycled coarse aggregate. The replacement ratio of recycled fine aggregate be less than 60%, would be possible to obtain the air content volume that did not deviate from the concrete quality specification. The compressive strength of concrete using recycled aggregate decreased with increasing the replacement of recycled aggregate, and compressive strength decreased by 25% when 100% recycled fine aggregate were replaced. As a result of analyzing the correlation of compressive strength according to the mixing factors of concrete, it was found that replacement of recycled fine aggregate> water cement ratio> air content volume were influenced in order. 본 연구는 콘크리트 산업에 있어 자원 고갈, 환경 문제 등을 대처할 수 있는 순환골재의 활용을 촉진하며 순환골재콘크리트의 레미콘 실생산을 위한 기초적 연구로서, 순환골재 사용량에 따른 슬럼프 고정 순환골재콘크리트의 물시멘트비 변화 및 물리적 특성을 실험하고 그 결과를 회귀분석하여 순환골재콘크리트의 압축강도 추정을 위한 단위시멘트량, 순환골재의 사용량, 물시멘트비 등 레미콘 생산 조건을 검토하여 다음과 같은 결론을 얻었다. 순환골재를 사용한 콘크리트는 목표 슬럼프를 유지하기 위해서는 단위수량 증가가 요구되며, 순환굵은골재보다 순환잔골재의 치환에 더 많은 단위수량의 증가가 필요하였다. 순환잔골재의 치환율은 60%이하는 레미콘 품질기준에 벗어나지 않는 공기량 확보가 가능하였다. 순환골재를 사용한 콘크리트의 압축강도는 순환골재의 치환율이 증가할수록 감소하는 것으로 나타났으며, 특히 순환잔골재를 100% 치환한 경우 압축강도는 25%정도 저하하였다. 순환골재를 사용한 콘크리트의 배합인자에 따른 압축강도의 상관관계를 분석한 결과, 순환잔골재>물시멘트비>공기량 순으로 영향을 미치는 것으로 나타났다.

Influence of the Quality of Recycled Aggregates on Microstructures and Strength Development of Concrete

Moon Dae-Joong,Moon Han-Young,Kim Yang-Bae Korea Concrete Institute 2004 콘크리트학회논문집 Vol.16 No.6

The quality of recycled aggregate is affected by original concrete strength and the manufacturing process of recycled aggregates. In this study, the porosity of old and new mortar, and the compressive strength of concrete were investigated to examine the influence of recycled aggregate on the concrete. Six kinds of recycled coarse aggregates were produced from concrete blocks of differing strength levels (A:60. 1MPa, B:41.7MPa, C:25.5MPa). Original concrete strength and the bond mortar of recycled aggregate influences the pore structures of both old and new mortar. The pore size distribution of old mortar was found to be greatly affected by age, and the reduction of the porosity of bond mortar on low strength recycled aggregate increased at a greater rate than that of bond mortar on high strength recycled aggregate. The pore size distribution of new mortar in recycled aggregate concrete changed in comparison with that of new mortar in virgin aggregate concrete. The total porosity of new mortar using B level recycled aggregates was smaller than that of new mortar with A, and C level recycled aggregates. Moreover, the compressive strength of recycled aggregate concrete was found to have been affected by original concrete strength. The compressive strength of concrete only changed slightly in the porosity of new mortar over $15\%$, but increased rapidly in the porosity of new mortar fewer than $15\%$.

Influence of the Quality of Recycled Aggregates on Microstructures and Strength Development of Concrete

문대중,문한영,김양배 한국콘크리트학회 2004 콘크리트학회논문집 Vol.16 No.6

The quality of recycled aggregate is affected by original concrete strength and the manufacturing process of recycled aggregates. In this study, the porosity of old and new mortar, and the compressive strength of concrete were investigated to examine the influence of recycled aggregate on the concrete. Six kinds of recycled coarse aggregates were produced from concrete blocks of differing strength levels (A:60.1MPa, B:41.7MPa, C:25.5MPa).Original concrete strength and the bond mortar of recycled aggregate influences the pore structures of both old and new mortar. The pore size distribution of old mortar was found to be greatly affected by age, and the reduction of the porosity of bond mortar on low strength recycled aggregate increased at a greater rate than that of bond mortar on high strength recycled aggregate. The pore size distribution of new mortar in recycled aggregate concrete changed in comparison with that of new mortar in virgin aggregate concrete. The total porosity of new mortar using B level recycled aggregates was smaller than that of new mortar with A, and C level recycled aggregates. Moreover, the compressive strength of recycled aggregate concrete was found to have been affected by original concrete strength. The compressive strength of concrete only changed slightly in the porosity of new mortar over 15%, but increased rapidly in the porosity of new mortar fewer than 15%.

재생골재를 콘크리트용 골재로 사용하기 위한 기초 물성 연구

공경록,강헌찬 東亞大學校 附設 環境問題硏究所 2004 硏究報告 Vol.26 No.-

This study research the method that it will be able to increase the demand of the quality of the construction waste and recycled aggregate. It includes a test for sieve analysis of aggregate, a test for specific gravity, a test for absorption, a test for impurity contents and crisis effect of cement paste of recycled aggregate. The grain size change of the 13~45mm recycled aggregate by the crusher when moving toward the 2nd cone crusher from the 2nd jaw crusher, the content change from 6.69% changed with 55.34%. The recycled aggregate of 13~45mm includes a standard grain size distribution. A test of impurity contents was resulted 1.49%. Density of the recycled aggregate of 13~45mm was 2.14g/㎤ and water absorption ratio was 7.74%. Content of the aggregate where the cement paste sticks below 50% changed 8.35% → 12.68% → 13.76% → 23.61% → 23.67% when first jaw crusher → second jaw crusher → first cone crusher → double screen → recycled aggregate of 13~45mm. The crisis of the recording aggregate which will be rough the crusher and the cement paste goes well. For the recycled aggregate production of quality the development of the system which separates the recycled aggregate is necessary.

저속습식 마쇄방법과 황산수를 이용한 고품질 순환잔골재 제조방법에 관한 실험적 연구

김진만,김하석,박선규,곽은구,선정수 大韓建築學會 2008 大韓建築學會論文集 : 構造系 Vol. No.

Recycled aggregate, produced by crushing waste concrete, can be used for many purposes. The use of recycled aggregate can save money for our society, create additional business opportunities, save energy when recycling is done on site, and conserve diminishing resources of urban aggregates. However the usage is limited to a lower value-add product such as the roadbed material. While the research and the development have been performed to produce the high quality recycled aggregate, recycled fine aggregate has low quality because it contains large amount of old mortar. To produce the high quality recycled aggregate, breaking and washing process must be added to the existing process to remove the ingredient of old mortar from aggregate. This paper is aim to develop the high quality recycled aggregate. The ingredient of cement paste is removed from recycled fine aggregate using both the low speed wet abrasional crusher as mechanical process and the acid treatment as chemical processes. Consequently, the optimum condition for this process is investigated for high quality recycled fine aggregate by using the design of experiments. For the result, recycled fine aggregate with dry density 2.51 and absorption ratio 2.3%, satisfying Korean standard for recycled fine aggregate, was made by this mechanical and chemical process.

Durability characteristics of recycled aggregate concrete

Palaniraj Saravanakumar,Govindasamy Dhinakaran 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

Durability characteristics of recycled aggregate concrete

Saravanakumar, Palaniraj,Dhinakaran, Govindasamy Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

싸이클론 건식공정으로 생산된 재생 잔골재가 콘크리트의 기초특성에 미치는 영향

이문환,이세현 대한건축학회 2005 大韓建築學會論文集 : 構造系 Vol.21 No.2

This study is intended for how to utilize the recycled fine aggregate which is produced by concrete wastes. It analyses the quality of the fine aggregate which is reproduced through a dry production process with cyclone, and comprehends the characteristics of mortar using the recycled fine aggregate to review whether it can be put to practical use for concrete. In: the experiment, recycled fine aggregate is substitute for natural fine aggregate the rate of 0, 25, 50, 75 and 100% each. The results of the study are as follows. 1) The air content is increased irregularly according to the substitutive ratio of recycled fine aggregate. 2) The slump and loss of slump with time since mixing are decreased irregularly according to the substitutive ratio of recycled fine aggregate. 3) The compressive strength of concrete using the wet recycled fine aggregate tends to be reduced with the increase of the mixing ratio of recycled fine aggregate, but the compressive strength of 25% substitution ratio is increased. Based on the above results, it is concluded that the recycled fine aggregate through the wet production process can be used as fine aggregate on condition that the substitution ration is under 25%.

저품질 순환골재를 활용한 콘크리트 성능 평가

이승태(Seung-Tae Lee),박광필(Kwang-Pil Park) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.11

본 연구에서는 콘크리트 적용 저품질 순환골재의 콘크리트 적용을 위하여 공학적 특성을 평가 하였다. 이를 위해서 저품질 순환골재의 세척유무에 따라서 골재 치환율을 30%, 60%, 100%로 콘크리트 제작하여 실험하였으며, 성능평가를 위하여 제작된 순환골재 사용 콘크리트의 압축강도, 흡수율, 표면전기저항, 초음파속도, 염소이온침투저항성 평가를 실시하였다. 세척한 저품질 순환골재의 경우 30% 치환시 천연골재와 유사한 결과를 모든 시험에서 나타내었다. 또한 60%를 치환한 콘크리트에서도 천연골재와 유사한 성능을 나타내는 것으로 확인되었다. 그러나 100%의 골재를 사용하는 것은 천연 골재 보다 다소 낮은 결과 값을 나타내었다. 반면 세척을 하지 않은 저품질 순환골재의 경우는 치환율에 관계없이 전체적으로 천연골재보다 좋지 않은 결과를 나타내었다. 특히 내구성 평가의 척도로 평가한 염소이온침투저항성 평가에서는 초기의 경우 매우 높음의 결과를 나타내었으며, 28일 재령에서도 보통 수준의 저항성을 나타내어 세척 순환골재와 약 2배 정도의 차이를 나타내었다. 따라서, 저품질 순환골재의 콘크리트 적용에 있어서 골재의 세척유무에 따라서 성능이 변화하는 것을 확인하였다. The purpose of this study was to evaluate the properties of recycled aggregate concrete (RAC) using low quality recycled aggregate with or without washing before usage. The recycled aggregate concrete evaluated in this study contained various amounts of low quality recycled aggregate, viz. 30%, 60% and 100%. To evaluate the performance of the recycled aggregate concrete, various test methods were employed to assess its compressive strength, absorption, surface resistance, ultrasound velocity, chloride ion resistance, etc. The properties of the RAC with 30% and 60% washed recycled aggregate were similar those of the natural aggregate. However, the properties of the RAC with 100% washed recycled aggregate were slightly lower than those of the other versions. Also, the RAC with the non-washed recycled aggregate exhibited lower performance results. The results showed that the RAC with washed recycled aggregate had similar properties to normal concrete (concrete using natural aggregate). This implies that the recycled aggregate should be washed to improve the RCA.

설계기준 강도별 순환골재 콘크리트의 탄산화 특성

이준(Jun Lee),이봉춘(Bong-Chun Lee),조영근(Young-Keun Cho),박광민(Kwang-Min Park),정상화(Sang-Hwa Jung) 한국건설순환자원학회 2017 한국건설순환자원학회 논문집 Vol.5 No.1

본 연구에서는 국내에서 생산되고 있는 콘크리트용 순환 굵은골재 및 순환잔골재를 사용하여 콘크리트의 설계기준 강도(21, 35, 50㎫) 및 순환골재의 혼입조건 변화가 콘크리트의 탄산화 거동에 미치는 영향을 분석하였다. 실험결과 순환 굵은골재의 혼입률 변화에 따른 콘크리트의 슬럼프는 순환골재를 혼입하지 않은 경우에 비해 동등하거나 양호한 유동성을 나타내는 것으로 나타났으며, 순환 잔골재를 혼입한 경우는 혼입률이 증가함에 따라 슬럼프가 감소되는 결과를 나타냈다. 또한, 순환 굵은골재 및 순환 잔골재의 혼입률이 증가할수록 콘크리트의 압축강도는 감소하는 것으로 나타났으며, 순환골재 혼입률이 50%를 초과할 경우 급격한 강도 감소 경향을 나타냈다. 그리고 탄산화 깊이는 모든 순환골재 종류에서 혼입률이 증가함에 따라 최대 40%까지 증가하는 결과를 나타냈으며 낮은 강도 수준의 콘크리트 일수록 순환골재 활용에 따른 탄산화 저항성 저하 정도가 큰 것으로 나타났다. 그리고 콘크리트의 압축강도가 증가할수록 순환골재 혼입에 따른 영향은 감소되어, 고강도 영역에서는 일반 콘크리트와 유사한 탄산화 특성을 발현하는 것으로 분석되었다. 따라서 순환골재를 콘크리트용 재료로 대량 활용하기 위해서는 콘크리트의 탄산화 저항성의 개선 위한 혼화재료의 적용 또는 배합설계상 조정을 통한 강도의 개선 등이 필요할 것으로 판단된다. This paper presents mechanical properties and carbonation behavior of the recycled aggregate concretes(RAC) in which natural aggregate was replaced by recycled coarse aggregate and fine aggregate by specified concrete strength levels(21, 35, 50㎫). A total of 18 RAC were produced and classified into six series, each of which included three mixes designed with three specified concrete strength levels of 21㎫, 35㎫ and 50㎫ and three recycled aggregate replacement ratios of 0, 50 and 100%. Physical and mechanical properties of RAC were tested for slump test, compressive strength, and carbonation depth. The test results indicated that the slump of RAC could be improved or same by recycled coarse aggregate replacement ratios, when compared with natural aggregate. But slump of RAC was decreased as the recycled fine aggregate replacement ratios increase. Also, the test results showed that the compressive strength was decreased as the recycled aggregate replacement ratios increased and it had a conspicuous tendency to decrease when the content of the recycled aggregate exceeded 50%. Furthermore, the result indicated that the measured carbonation depth increases by 40% with the increase of the recycled aggregate replacement. In the case of the concrete having low level compressive strength, the increase of carbonation depth tends to be higher when using the RCA. However, the trend of carbonation resistivity in high level compressive strength concrete is similar to that obtained in natural aggregate concrete. Therefore, an advance on the admixture application and mix ratio control are required to improve the carbonation resistivity when using the recycled aggregate in large scale.