• International Journal of Concrete Structures and Materials
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• 제6권4호
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• pp.239-246
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• 2012

Pervious concrete is a tailored-property concrete with high water permeability which allow the passage of water to flow through easily through the existing interconnected large pore structure. This paper reports the results of an experimental investigation into the development of pervious concrete with reduced cement content and recycled concrete aggregate for sustainable permeable pavement construction. High fineness ground granulated blast furnace slag was used to replace up to 70 % cement by weight. The properties of the pervious concrete were evaluated by determining the compressive strength at 7 and 28 days, void content and water permeability under falling head. The compressive strength of pervious concrete increased with a reduction in the maximum aggregate size from 20 to 13 mm. The relationship between 28-day compressive strength and porosity for pervious concrete was adversely affected by the use of recycled concrete aggregate instead of natural aggregate. However, the binder materials type, age, aggregate size and test specimen shape had marginal effect on the strength-porosity relationship. The results also showed that the water permeability of pervious concrete is primarily influenced by the porosity and not affected by the use of recycled concrete aggregate in place of natural aggregate. The empirical inter-relationships developed among porosity, compressive strength and water permeability could be used in the mix design of pervious concrete with either natural or recycled concrete aggregates to meet the specification requirements of compressive strength and water permeability.

• 한국도로학회논문집
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• 제20권1호
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• pp.69-76
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• 2018

PURPOSES : This study determined the optimal usage rate of RAP (reclaimed asphalt pavement) using cold central-plant recycling (CCPR) on a road-surface layer. In addition, a mixture-aggregate gradation design and a curing method based on the proposed rate for the surface-layer mix design were proposed. METHODS : First, current research trends were investigated by analyzing the optimum moisture content, mix design, and quality standards for surface layers in Korea and abroad. To analyze the aggregate characteristics of the RAP, its aggregate-size characteristics were analyzed through the combustion asphalt content test and the aggregate sieve analysis test. Moreover, aggregate-segregation experiments were performed to examine the possibility of RAP aggregate segregation from field compaction and vehicle traffic. After confirming the RAP quality standards, coarse aggregate and fine aggregate, aggregate-gradation design and quality tests were conducted for mixtures with 40% and 50% RAP usage. The optimum moisture content of the surface-layer mixture containing RAP was tested, as was the evapotranspiration effect on the surface-layer mixture of the optimum moisture content. RESULTS : After analyzing the RAP recycled aggregate size and extraction aggregate size, 13-8mm aggregate was found to be mostly 8mm aggregate after combustion. After using surface-chipping and mixing methods to examine the possibility of RAP aggregate segregation, it was found that the mixing method contributed very little for 3.32%, and because the surface-chipping method applied compaction energy directly as the maximum assumption the separation ratio was 15.46%. However, the composite aggregate gradation did not change. Using a 40% RAP aggregate rate on the surface-layer mixture for cold central-plant recycling satisfied the Abroad quality standard. The optimum moisture content of the surface-layer mixture was found to be 7.9% using the modified Marshall compaction test. It was found that the mixture was over 90% cured after curing at $60^{\circ}C$ for two days. CONCLUSIONS : To use the cold central-plant recycling mixture on a road-surface layer, a mixture-aggregate gradation design was proposed as the RAP recycled aggregate size without considering aggregate segregation, and the RAP optimal usage rate was 40%. In addition, the modified Marshall compaction test was used to determine the optimum moisture content as a mix-design parameter, and the curing method was adapted using the method recommended by Asphalt Recycling & Reclaiming Association (ARRA).

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2004년도 학술대회지
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• pp.15-19
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• 2004

The production of waste concrete is increased continuously by urban renewal, reconstruction, remodeling, and so on. So the positive use of recycled aggregate concrete is needed. Research for recycled aggregate concrete that use recycled aggregate from the mid-80s to solve environmental problem of aggregate insufficiency and waste concrete is consisting vigorously. However, specifications and mix design about waste concrete's use are evading use of recycled aggregate concrete yet in spot being not taken a triangular position. Therefore. it analyze existing research data for recycled aggregate concrete collection to develop strength estimate program in this research. Recycled aggregate concrete's strength estimate program if specifications and mix design about recycled aggregate concrete are taken a triangular position to foundation recycled aggregate concrete's practical use to increase judge.

• 한국도로학회논문집
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• 제11권2호
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• pp.1-15
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• 2009

골재노출콘크리트포장은 콘크리트 타설 직후 포장표면에 응결지연제를 살포하여 표면으로부터 깊이 2$\sim$3mm 정도의 모르타르 경화를 늦추게 한 후 표면의 모르타르 제거를 통해 굵은골재를 포장표면에 노출시키는 공법이다. 골재노출콘크리트포장의 타이어-노면 소음이 일반 콘크리트포장보다 작으면서도 적정한 미끄럼저항을 장기간 유지한다는 장점을 가지고 있다. 특히 굵은골재가 소입경일수록 소음저감효과가 우수한 것으로 알려져 있다. 성공적인 소입경 골재노출콘크리트포장의 건설을 위해서는 굵은골재의 최대입경이 적정하여야 하며, 적정량의 굵은골재를 포장표면에 균일하게 노출하도록 해야 하며 이를 위한 적절한 배합과 노출기법의 도출이 요구된다. 일반적인 콘크리트포장의 배합기준은 강도설계로 이루어지지만 소입경 골재노출콘크리트포장의 경우 강도뿐만 아니라 소음저감효과, 미끄럼저항을 적절히 발현시킬 수 있는 배합설계를 실시하기 위해서는 강도실험 외에도 노면의 미끄럼저항, 소음을 고려할 필요가 있다. 본 연구에서는 소입경 골재노출콘크리트포장에 대하여 적정 강도를 유지하며 포장표면조직의 소음 저감효과 및 적정 미끄럼저항성을 동시에 만족시킬 수 있도록 표면조직을 형성할 수 있는 최적배합에 대해 제시하였다. 또한 콘크리트포장은 온도, 습도 및 대기환경에 의해 모르타르의 경화속도가 달라지므로 콘크리트의 물리적 성질을 정량적으로 고려한 최적 노출기법이 제시되었다.

• 한국산학기술학회논문지
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• 제13권10호
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• pp.4832-4836
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• 2012

일반적으로 아스팔트 혼합물 배합설계는 많은 시간과 실험이 필요하다. 또한, 정밀한 배합설계 결과는 실험하는 사람의 숙련도와 밀접한 상관관계가 있다. 이러한 문제점을 해결하기 위하여 Bailey는 아스팔트 혼합물용 골재입도에 대한 연구를 통해 골재입도곡선에서 특정한 크기의 골재의 입도 및 통과중량비가 중요함을 제시하였다. 본 연구에서는 Bailey가 제안한 방법을 이용하여 19mm 밀입도 아스팔트 혼합물 및 미연방도로국의 배수성포장(PA 20mm) 혼합물에 대한 배합설계를 시행하였다. Bailey 방법을 이용한 아스팔트 혼합물용 골재입도 결정방법은 기존에 시행착오를 통합 배합설계방법에 비해 좀더 짧은 시간에 최적배합설계를 수행할 수 있음을 확인하였다. 19mm 밀입도 아스팔트 혼합물의 CA, $FA_c$, $FA_f$는 0.724, 0.440 및 0.455로 기준값을 만족하였다. PA 20mm 아스팔트 혼합물의 계산된 CA, $FA_c$, $FA_f$는 0.646, 0.476 및 0.450으로 기준값을 만족하였다.

• Computers and Concrete
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• 제23권1호
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• pp.37-47
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• 2019

In view of the increasing utility of concrete as a construction material, the major challenge is to improve the quality of construction. Nowadays the common problem faced by many of the concrete plants is the shortage of river sand as fine aggregate material. This led to the utilization of locally available materials from quarries as fine aggregate. With the percentage of fines present in Crushed Rock Fines (CRF)or crushed sand is more compared to river sand, it shows a better performance in terms of fresh properties. The present study deals with the formulation of SCC mix design based on the chosen plastic viscosity of the mix and the measured plastic viscosity of cement pastes incorporating supplementary cementitious materials with CRF and river sand as a fine aggregate. Four different combinations including two binary and one ternary mix are adopted for the current study. Influence of plastic viscosity of the mix on the fresh and hardened properties are investigated for SCC mixes with varying water to cement ratios. It is observed that for an increasing plastic viscosity of the mix, slump flow, T500 and J-ring spread increased but V-funnel and L-box decreased. Compressive, split tensile and flexural strengths decreased with the increase in plastic viscosity.

• 한국해양공학회지
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• 제17권4호
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• pp.16-22
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• 2003

The mechanical characteristics of newly recycled aggregate concrete on the basis of the proposed mix design model have been studied to develop the precast artificial fishing reefs. In the first task, the experimental test for the recycled aggregates taken from Jeju Island has been carried out to verify the material properties in terms of specific gravity, percentage of solids, absorption and abrasion of coarse aggregates. In the second task, the experimental parameters of newly recycled aggregate concrete are investigated to meet with the requirements of guidelines with respect to slump, unit weight, pH, ultrasonic velocity, void ratio, and compressive strength which are made of sea-shore sand ad slag cement. The natural aggregate and polypropylene fiber are added to newly recycled aggregate concrete to improve the compressive strength and quality. The optimal mix proportions for compressive strength are W/C=30％, S/a=15％, NA/G=50％ in porous concrete case, W/C=40％, S/a=45％ in plain concrete case, and W/C=40％, S/a-45％, PF=1.0kg/㎥ in fiber reinforced concrete case.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.525-528
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• 2005

This study determines the best composite grade to minimize the void of aggregate mixture based on the maximum density theory in an attempt to suggest a mix proportion method design for asphalt mixtures. Study results show that the grading curve with the maximum mass per unit capacity of each aggregate mixture satisfied the KS standards and the optimum AP content to meet the optimal asphalt mixture void rate of 4$\%$ was 5.7$\%$, less than the optimum AP content of 6.5$\%$ suggested in the Marshal mix proportion method design. At the same time, the asphalt mixture produced based upon the suggested mix proportion method had a flow value 17$\%$ lower than that of asphalt mixture produced according to the Marshal method, while its density was greater by 0.06$\～$0.09. This suggests that the introduced mix proportion method design helps to improve the shape flexibility and crack-resistance of asphalt concrete.

• 한국도로학회논문집
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• 제10권3호
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• pp.11-18
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• 2008

최근 국내외에서 역학적-경험적 설계법의 개발 및 이의 활용을 위한 각종 연구가 매우 활발하게 진행중에 있다. 미국의 경우 AASHTO 2002 설계법, 우리나라의 경우 한국형 도로포장설계법의 개발이 진행 중에 있고, 개발되는 설계법에 도로포장재료의 역학적 물성치 평가가 상당히 중요한 역할을 하도록 구성되어 있다. 따라서 설계법에 이용될 국내 아스팔트 혼합물의 재료물성의 평가가 매우 시급한 실정이다. 설계법에 이용되는 재료 물성을 평가하는 방법 중 최근에 많이 적용되는 방법이 동탄성계수 실험이다. 동탄성계수는 다양한 온도조건, 하중, 속도를 이용하여 다양한 교통조건을 반영할 수 있다. 사용된 골재의 입도, 아스팔트 바인더에 따라서 변화하며, 특히 아스팔트 혼합물의 점탄성적인 특성을 잘 묘사할 수 있는 물성치 평가방법이라고 할 수 있다. 본 연구에서는 아스팔트 혼합물에 사용되는 골재의 공칭최대치수 및 입도분포와 동탄성계수와의 상관관계를 규명하는 것이다. 국내의 실험장비 조건을 고려할 때, 시편의 직경 및 높이는 100mm 및 150mm를 이용하는 것이 바람직하다. 또한, 골재의 공칭최대치수가 커짐에 따라 동탄성계수가 증가하는 경향을 나타내었다.

• KCI Concrete Journal
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• 제14권3호
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• pp.121-129
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• 2002

This study investigates experimentally into the design factors and quality variations having an effect on the properties of the combined high flowing concrete to be poured in the slurry wall of Inchon LNG in-ground receiving terminal. Especially, high belite cement and lime stone powder as cementitious materials and viscosity agent in order to improve self-compaction and hydration heat are used in this study. Water-cement ratio(W/C), fine aggregate volume ratio(Sr) and coarse aggregate volume ratio(Gv) as design factors of the combined high flowing concrete are applied to determine the optimum mix design proportion. Also quality variations for sensitivity test are selected items as followings. (1)Surface moisture(5cases) and (2)Fineness modulus of fine aggregate(5cases), (3)Concrete temperature(3cases), (4)Specific surface(3cases) and particle size of lime stone powder. As experimental results, water-cement ratio, fine and coarse aggregate volume ratio are shown as the optimum range 51%, 43% and 53% separately considering site condition of slurry wall. Also quality factors by sensitivity test should be controlled in the following ranges. (1) Surface moisture :to.67% and (2)Fineness modulus 2.6$\pm$0.2 of fine aggregate, (3)Concrete temperature l0-20t, (4) Specific surface 6,000$\textrm{cm}^2$/g and particle size 9.7$\pm$1.0${\mu}{\textrm}{m}$ of lime stone powder. Based on the results of this study, the optimum mix design proportion of the combined high flowing concrete are selected and poured successfully in the slurry wall of LNG in-ground tank.