• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.6
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• pp.97-103
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• 2009

This study was performed to evaluate the strength and durability properties of recycled polymer concrete using unsaturated polyester resin and recycled aggregates. Unsaturated polyester resin, natural and recycled aggregates and fly ash were used. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate sizes (5-10 and 5-25 mm) and unit binder contents (10% and 12%). Tests for the compressive and flexural strength, freezing and thawing and durability for 20% sulfuric solution were performed. The compressive and flexural strength of recycled polymer concrete were in the range of 85~97 MPa and 17.9~20.8 MPa, respectively. The strengths of recycled polymer concrete using recycled aggregate have similar or slightly decreased compared to polymer concrete using natural aggregate. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of recycled polymer concrete were in the range of 0.13~1.42% and 94~99, respectively.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.875-881
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• 2004

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 $15\%$.

• Advances in concrete construction
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• v.9 no.1
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• pp.9-22
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• 2020

The present work looks at the possibilities of recycling more than once demolished concrete as coarse aggregates, to produce new concrete. Different concrete mixes were made with substitutions of 50%, 75% and 100% of recycled concrete aggregates respectively as coarse aggregates. The physico-mechanical characterization tests carried out on the recycled concrete aggregates revealed that they are suitable for use in obtaining a structural concrete. The resulting concrete materials had rheological parameters, compressive strengths and tensile strengths very slightly lower than those of the original concrete even when 100% of two cycles recycled concrete aggregates were used. The durability of the recycled aggregates concrete was assessed through water permeability, water absorption and chemical attacks. The obtained concretes were thought fit for use as structural materials. A linear regression was developed between the strength of the material and the number of cycles of concrete recycling to anticipate the strength of the recycled aggregates concrete. From the results, it appear clear that recycling demolished concrete represents a valuable resource for aggregates supply to the concrete industry and a the same time plays a key role in meeting the challenge for a sustainable development.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.307-314
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• 2002

Utilization of demolished-concrete as recycled aggregate has been researched for the purpose of substituting for insufficient natural aggregate, saving resources and protecting environment. There, however, are some Problems not only the large difference of dualities in recycled aggregates but also a little deterioration of mechanical properties in recycled aggregate concrete in comparison with that of natural aggregate concrete. In this study, the test results of freez and thaw durability of concrete with demolished-concrete recycled aggregate(DRA) arc as follows. Improvement of crushing process is an important assignment because that adhered mortar on source-concrete recycled aggregate(SRA) and DRA highly affects thc qualifies of recycled aggregate. The compressive strength of recycled aggregate concrete was not highly different in comparison with that of control concrete. But the resistance to penetration of Cl in recycled aggregate concrete was shown smaller than that of control concrete because of adhered mortar on recycled aggregate. The resistance to frcezing and thawing of recycled aggregate concrete was highly different due to adhered mortar on recycled aggregate, and durability factor of concrete with NA-SRA and DRA was more decreased than that of control concrete. On the other hand, durability factor of concrete with AA-SRA was larger than that of control concrete. It, therefore, is necessarily required that recycled aggregate including adequate entrained air should be used for satisfying the freez and thaw durability of recycled aggregate concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.364-367
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• 2004

The purpose of this study is to investigate quality of recycled fine aggregate manufactured by drying manufacturing system which is the manufacture method of high quality recycled fine aggregate, and to analyze on the fresh, hardened and durability properties of recycled concrete using it. Therefore it is to present the fundamental data for structural application of recycled concrete. The results of this study are as follows; Quality of recycled fine aggregate by drying manufacturing system is improved, and compressive and tensile strength of recycled concrete using high quality recycled fine aggregate are similar to those of normal concrete. But, durability such as carbonation, salt damage and dry shrinkage show decreased somewhat.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.93-96
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• 2005

In this study, Mock-up was manufactured using recycled aggregate concrete and then analyzed with respect to physical properties. Finally, the applicability of recycled aggregates as constructional aggregates was reviewed by practically putting recycled aggregates concrete into construction. Right after mixing, the slump of recycled-aggregates concrete showed decreased slump as time goes by because the surface mortar of recycled aggregates absorbed the mix water with time passing. The air contents of recycled-aggregates concrete overall increase a little due to the effect of surface mortar of the aggregates. For strengths, the strengths of recycled aggregate concrete tended to decrease from the proportion of 30$\%$ to 100$\%$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.87-91
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• 2009

Recycling demolished concrete as an alternative source of coarse aggregates for the production of new concrete can help solve the growing waste disposal crisis and the problem of depleted natural aggregates. The purpose of this study is to investigate chloride migration of recycled aggregate concrete containing pozzolanic materials by chloride migration coefficient. The specimens were made with recycled coarse aggregate as various replacement ratio(10, 30, 50%) and metakaolin, blast furnace slag, fly ash is replaced for recycled concrete with mixing ratio 20%. The major results are as follows. 1) Compressive strength of recycled aggregate concrete containing pozzolanic materials increase as curing age and chloride migration decrease. 2) When the replacement ratio of recycled coarse aggregate is 30%, the chloride migration coefficient of recycled concrete containing blast furnace slag, metakaolin shows the similar or lower value than plain concrete at all ages.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.16-21
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• 1993

The study of recycled aggregate concrete in which demolition waste is utilized to produce aggregate for new concrete, can contribute to the solution of two problems. The first is the shortage of aggregate from river, and the second is the waste disposal problem. In comparison with natural aggregate concrete, recycled aggregate concrete shows reductions in compressive strength, tensile strength , vending strength, shear strength and increases in drying shrinkage and creep. Recycled aggregate concrete may also be less durable due to increase in porosity and permeability. Therefore, the purpose of this study is to analyze the applicability of recycled concrete in the influence of a substitute ratio of recycled sand gravel.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.373-376
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• 2008

The objective of this study is to investigate the properties of fresh concrete with recycled fine aggregates. Three different kinds of fine aggregate with natural, high and low quality recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled fine aggregate. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. Quality control method to maintain the constant total mixing water for recycled aggregate concrete was suggested. The all concrete mixtures were produced with approximately the same slump on the job site after an hour. Test results indicated that compressive strength of the concrete mixtures with constant slump is not affected by the replacement ratio of recycled fine aggregate. Therefore, the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.345-348
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• 2006

Along with recent improvement of recycling technique, the quality of the recycled concrete aggregate have become very competitive to the natural concrete aggregate. Therefore, a practical use of the recycled concrete aggregate may be possible for structural members. Majority studies about the recycled concrete aggregate was emphasized a limitation of fundamental study concerned with a strength characteristics and durability of the recycled aggregate concrete. Therefore, for the extension of application of recycled concrete aggregate, this investigation verifies the strength characteristics and structural performances of PHC piles used with coarce and fine recycled concrete aggregate.