• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.43-49
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• 2015

The objective of this paper is to investigate experimentally the effect of the substitution of recycled aggregates under 13mm on the properties of the concrete using coarse aggregate with size of 13~25mm. Recycled aggregate under 13mm were substituted to the concrete ranged from 10% to 100%. To compare the properties with the case of recycled aggregate, crushed stone with smaller than 13mm was also substituted to the concrete by 20% and 40%. Test results showed that increase of recycled aggregate under 13mm resulted in the increase of slump and compressive strength compared with plain mixture, which was made with only aggregate with 13~25mm size. This is due to the dense gradation of aggregate in association with addition of relatively small particle. It is thought that the use of recycled aggregate under 13mm along with 30% contributes to the quality improvement of the concrete made with only 13~25mm aggregate.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.55-61
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• 2017

This paper is to investigate experimentally the effect of substitution of recycled coarse aggregate(RCA) under 13mm on the engineering properties of the concrete using gap graded coarse aggregates. Concretes with 0.4 of water to cement ratio(W/C) were fabricated to achieve 30MPa of design strength with coarse aggregate over 13mm in size with the maximum size of 25mm. RCA was substituted for coarse aggregate over 13mm from 10% to 50% and crushed coarse aggregate under 13mm was also substituted for coarse aggregate over 13mm from 20% to 40%, respectively. Test results indicated that the replacement of RCA up to 20% resulted in an increase of fluidity and strength. It also caused a decrease in the drying shrinkage due to dense packing effect by achieving continuous grading of mixed aggregates. For practical application of RCA, when properly substituted, the use of RCA enabled the concrete to reduce water contents and sand to aggregate ratio in mixing design stage of the concrete. And, it can also enhance the compressive strength of the concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.59-67
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• 2017

The objective of this paper is to investigate experimentally the effect of replacement of recycled coarse aggregates with 5~13mm in size on a field applicability of concretes through Mock-up test. Seven different mock-up specimens were prepared with the size of $1200{\times}800{\times}800mm$ simulating column and wall. For the concrete mixtures, 24MPa, 27MPa and 40MPa of nominal strength were adopted with 30% and 70%(only for 24MPa) of 5~13mm recycled coarse aggregate (RCA) replacement and without 5~13mm RCA(Plain). For test items, slump, slump flow, compressive strength with different curing conditions, core drilling, rebound numbers and drying shrinkage were measured. Test results indicated that 30% of 5~13 mm RCA replacement resulted in increase in slump, slump flow and resistance against segregation, while air contents decreased compared to those of plain mixture. Compressive strength of concrete with 30% of 5~13mm RCA was shown to be higher than that of plain mixture due to optimum packing effect associated with presence of well graded aggregates. Rebound number of the mock-up specimen with 30% of 5~13mm RCA had lower fluctuation according to hitting location than that of plain mock-up specimen. It is believed from the results of the study that replacement of 30% of 5~13mm RCA brings desirable improvement in various aspect of concrete performance due to associated dense packing effect.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.169-175
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• 2011

Strength is one of the very important factors to evaluate the physical properties of concrete. Aggregate forms the most parts in concrete. Cement as a binder in concrete is also closely related to strength. This experiment was tested to understand the effect of the characteristics of aggregate and cement on the relationship between concrete compressive strength and Shear Wave velocity. It was experimented by the different types of cement and maximum coarse aggregate sizes. Type I cement and rapid setting cement was used. Aggregates from three different regions were used. Aggregate of 19mm and 13mm maximum coarse aggregate sizes was used for grading. The relationship between compressive strength and Shear Wave velocity was tested under the condition of same mixture. LA wear test was used to quantify the characteristics of aggregate. As a result, the relationship between concrete compressive strength and Shear Wave velocity was affected by the types of cement, but regular relationship was appeared regardless of types of aggregate, grading and abrasion ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.63-72
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• 2012

The high-flowing concrete requires additionally or excessively more expensive admixture than conventional concrete. So, the concrete has not to be widely used in practical field due to the increase of production price, need of additional facilities, and excessive development of concrete strength in associate with addition of too much cementitious material even though it has more significant advantages than conventional concrete. Thus, this study aims at developing high-flowing concrete with general strength unlike high strength which has been carried out in conventional study. To observe the role of aggregate in the concrete quantitatively and to increase the performance of high-flowing concrete effectively, parametric studies were carried out such as W/C, s/a, fineness modulus of aggregate, contribution degree of particle sizes, and the effect of 13mm aggregate and fine stone powder as a partial replacement of aggregates. And the effect of these factors on performance of the concrete was evaluated by measuring slump-flow and gap of penetration height in U-typed instrument. As a result, it was found that flowability of high-flowing concrete depends upon grading of fine aggregate more significantly than that of coarse aggregate and is enhanced greatly as fineness modulus of fine aggregate decreases and the value of s/a increases. In addition, the application of 13mm aggregate and fine stone powder are expected as a partial replacement of aggregate in order to increase the performance of high-flowing concrete more effectively.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.21-29
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• 2016

In this study, recycled aggregates crushed from waste concrete were sorted into three groups, 10-13 mm, 13-20 mm, and 20-25 mm. They were treated in different ways and then their crushability was evaluated for each treatment. Coffee waste was used for reducing their pH level. The pH of recycled aggregate was almost 11, regardless of aggregate sizes. The pH of coffee waste was nearly 5 and 10, 30, or 50 g of coffee waste was mixed with 1000 ml of distilled water and recycled aggregates. The lowest pH was about 6.2 when 50 g of coffee waste was mixed. Aggregates were treated with microwave or soaked for 1 day in vinegar (pH = 2) for neutralization reaction. Microwave treated and neutralized aggregates showed 3.3% and 6.2% higher crushing values compared to non-treated one, respectively. Neutralized treatment was more effective for crushing. In crushing tests, a sample height of 120 mm was tried, which gave 6.3% higher crushing value. A four stepped loading with each 100 kN gave 7.1% higher crushing value, compared to standard 100 mm height and 400 kN continuous loading.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.137-138
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• 2014

The aim of this research is suggesting the method of obtaining well-graded aggregates for concrete replacing the recycled aggregate which size range is from 5 to 13 mm to currently used gap-graded natural aggregates which size range is only 13 to 25 mm. according to the tests results, the workability of concrete was improved with replacing the aggregates of 5 to 13 mm of size range because of compensating gap-grading. Furthermore, there was an improvement in compressive strength when the aggregates of 5 to 13 mm of size range was replaced because obtained well-graded aggregates contributed on increasing adhesiveness and filling internal pore system. Comparing replacing recycled aggregate to natural aggregate, there was no significant difference on the performances.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.19-20
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• 2013

Consider about aggregate's price, coarse aggregates from 13 to 25mm were widely used in ready mixed concrete company. But if only use 13 to 25mm aggregates in the concrete, gap grading problem would be occurred. When recycled aggregates from 13 to 25mm was used, continuous grading would increase the durability and strength for the concrete, meanwhile the construction waste materials would also be reused. In this paper, 5-13mm recycled aggregates was utilized, to analyse the fundamental properties for concrete, strength has been tested to evaluate the quality and reusing effect of the recycled materials.

• Journal of the Society of Disaster Information
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• v.9 no.1
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• pp.56-64
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• 2013

The study examines the quiet pavement using fine-size aggregates and warm-mix technique to reduce traffic noise. In order to evaluate the quality of pavement, mix design and laboratory tests were carried out. Test results showed that using 10mm aggregates can reduce the cantabro loss compared with 13mm aggregates due to increase contact area between aggregates. Mixing and compaction temperatures of warm mix quiet pavement should be determined by gyratory compactor test because it is used high viscosity asphalt binder. Using warm-mix additive could reduce compaction temperature by about $15^{\circ}C$. Noise measurement and permeability tests were conducted at the test road for evaluation of the field performance. All of quiet pavements meet the standard of permeability and have sufficient porosity. Noise reduction of the quiet pavement using fine-size aggregates is more effective than that using 13mm aggregates. In particular, the effect of noise reduction was noticeable at low speeds.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.47-55
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• 2008

This study was carried out to investigate and analyse the influence of maximum size of coarse aggregate and quality control of aggregate on the properties of shotcrete through the laboratory and field test. From the results of the test, as the maximum size of coarse aggregate decreased from 13 mm to 8 mm, plasticity property declined and compressive strength and dynamic modulus of elasticity of hardened concrete increased remarkably, so it was found that the aggregate size 8 mm was superior to 13, 10 mm in fluidity, constructability and durability. Therefore, it was advisable for well maximum size of coarse aggregate to apply to the 8mm aggregates through the Ready-mixed Method for quality control and minimum segregation.