Influence of Properties of Residual Mortar of Original Concrete on Quality of Recycled Aggregate Concrete

The developments of recycled aggregate concrete pressing hard in construction activities; however, the limitations on their applications had never being ended. The focus of this paper is: i) investigating the waste management strategy in construction; ii) proposing the two-stage mixing approach (TSMA) to improve the quality of RAC; and iii) experimenting the TSMA and assessing the benefits possibly gained. It proposes a new approach in mixing concrete, namely, the two-stage mixing method, to improve compressive strength of RAC and lower its strength variability. The replacement ratio from zero to thirty is under experiment on their compressive strength. Based upon the experimental results, improvements of 31 % in strength at 28 days with 30 % RA substitute was achieved. The effect can be attributably to the porous nature of the RA and the pre-mix process which can make some pores filled up resulting in a denser concrete and thus leading to higher strength when compared with the traditional mixing approach. Therefore, two-stage mixing approach can open up a wider application of recycled aggregate concrete.

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A Study on the Properties of Recycled Aggregate Concrete and Its Production Facilities

Applied Sciences ◽

10.3390/app9091935 ◽

2019 ◽

Vol 9 (9) ◽

pp. 1935 ◽

Cited By ~ 5

Author(s):

Jung-Ho Kim ◽

Jong-Hyun Sung ◽

Chan-Soo Jeon ◽

Sae-Hyun Lee ◽

Han-Soo Kim

Keyword(s):

Drying Shrinkage ◽

Quality Standards ◽

Poor Quality ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Freezing And Thawing ◽

Construction Waste ◽

Aggregate Concrete ◽

Air Volume

In recent years, the amount of construction waste and recycled aggregate has been increasing every year in Korea. However, as the recycled aggregate is poor quality, it is not used for concrete, and the Korean government has strengthened the quality standards for recycled aggregate for concrete. In this study, research was conducted on the mechanical and durability characteristics of concrete using recycled aggregate, after developing equipment to improve the quality of recycled aggregate to increase the use of recycled aggregate for environmental improvements. The results illustrated improvements in the air volume, slump, compressive strength, freezing and thawing resistance, and drying shrinkage. Furthermore, this study is expected to contribute to the increased use of recycled aggregate in the future.

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Development and Subjects of Recycled Aggregate Concrete in Japan

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.302-303.288 ◽

2006 ◽

Vol 302-303 ◽

pp. 288-300 ◽

Cited By ~ 4

Author(s):

Yoshio Kasai

Keyword(s):

Processing Method ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

General Character ◽

Aggregate Concrete

The quality of RCA is influenced by the processing method and quality of original concrete. The general character of RCA, RCA and TR A 0006-2000(concrete using recycled aggregate) are introduced. The execution of RAC work, examples of real constructions with RAC, recycling of concrete powder originated from production of RAC and barriers of using RAC are discussed.

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Development of Performance Optimization of Recycled Aggregate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.811.254 ◽

2013 ◽

Vol 811 ◽

pp. 254-257

Author(s):

Wei Li ◽

Ying Li ◽

Hai Ying Zhang

Keyword(s):

Performance Optimization ◽

Absorption Rate ◽

Cement Mortar ◽

Treatment Approach ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Interfacial Zone ◽

Cement Slurry ◽

Aggregate Concrete

Recycled aggregate concrete (RAC) differ from natural aggregate concrete in mechanical and durability properties. The poorer qualities of recycled aggregate (RA) limit utilization of RAC in engineering. Cement mortar attached on the surface of recycled aggregate result in higher water absorption rate. Also, interfacial zone between recycled aggregate and new mortar consist of loose and porous hydrates. Investigation is devoted to effects of different approaches on improving performance of RA to compensate the lower quality of RA. The pre-soaking treatment approach reduces the old cement mortar and removes the weaker link in interfacial zone. Moreover, The two-stage mixing approach (TSMA) is adopted, leads to the formation of a thin layer of cement slurry on the surface of RA which permeates into the porous old cement mortar, filling up the old cracks and voids for increasing compressive strength. Correlations in methods have been obtained and discussed.

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Application of Molten Slag Fine Aggregate Concrete Using Superplasticizer

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.302-303.329 ◽

2006 ◽

Vol 302-303 ◽

pp. 329-338

Author(s):

Shuzo Otsuka ◽

Yoshihisa Nakata ◽

Takeshi Saito ◽

Hiroki Takahashi ◽

Keishi Tobinai ◽

...

Keyword(s):

Molten Slag ◽

Full Scale ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Hardened Concrete ◽

Fine Aggregate ◽

Aggregate Concrete ◽

Significant Difference

With increasing number of melting-solidification plants for the domestic wastes and incineration ashes, the resulting molten slag is now expected as a recycled aggregate for concrete in Japan, while application examples until now are limited to non-loadbearing pre-cast concrete and concrete secondary products. This study deals with a full-scale application of molten slag recycled fine aggregate. Starting with the inspection of monthly variations in quality of molten slag fine aggregate in a plant, construction of a full-scale structure was attempted using the recycled aggregate concrete with a superplasticizer. During construction, pumpability of the recycled concrete was examined and the quality of hardened concrete in the structure was evaluated. It was shown that quality variation of the molten slag fine aggregate during eight months was sufficiently small, and pumpability as well as concrete quality in structure showed no significant difference with those of the ordinary concrete.

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