• 콘크리트학회논문집
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• 제16권6호
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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 $15\%$.

• 한국도로학회논문집
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• 제17권4호
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• pp.19-24
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• 2015

PURPOSES : The objective of this study is to evaluate the effect of the residual mortar of recycled concrete aggregate on the expansion behavior during alkali silica reaction (ASR). METHODS: In order to evaluate the net effect of residual mortar on ASR expansion behavior, two aggregate samples with the same original virgin aggregate source but different residual mortar volumes were used. ASTM C1260 test was used to evaluate the ASR expansion behavior of these two aggregates and the original virgin aggregate. RESULTS: The greater the amount of residual mortar in recycled concrete aggregates, the less is the induced ASR expansion. Depending on the amount of residual mortar in recycled concrete aggregate, the ASR expansion of recycled concrete aggregate may be less than half of that of the original virgin aggregate. CONCLUSIONS: The residual mortar of recycled concrete aggregate may lead to the under estimation of the ASR expansion behavior of the original virgin aggregate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.392-397
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• 1998

In this paper, the properties of cement mortar used recycled aggregate are analyzed and compared with river and crushed sand mortar. Recycled aggregates are made by crushing wasted concrete had various compressive strength, and test items are the properties of fresh mortar, hardened mortar and durability. According to the experimental results, flow, unitweight, strength and durability of cement mortar used recycled aggregates decrease compared with those of river and crushed sand mortar.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.179-182
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• 2009

Concrete containing styrene-butadiene latex is widely used, nowadays, as a protective system for bridge. Latex modification mortar have taken advantage of latex modification concrete advantage that is used in existing, Also, when repair, protection and sticking performance of concrete overlay waterproof agent were known as that are good. Replace and experimented from fine aggregate to recycled aggregate to secure economic performance than existing latex modification concrete. Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. This study is purposed to improve the performance of mortar made of recycled fine aggregate. For this, recycled aggregate mortar was produced with latex, and fluidity, strength were examined. Test result indicate that mortar using recycled fine aggregate is higher compressive and flexural strength than mortar using river sand.

• 한국건설순환자원학회논문집
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• 제4권1호
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• pp.96-100
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• 2009

모재콘크리트의 품질이 각기 다른 순환잔골재의 특성을 모르타르 시험에 의해 비교 고찰하였다. 모재콘크리트 강도가 클수록 밀도가 컸으며, 부착 시멘트페이스트의 공극량이 감소하므로 흡수율은 작게 나타났다. 순환잔골재를 사용한 모르타르의 압축강도 및 휨강도 특성은 신모르타르의 계면영역과 순환잔골재에 부착된 모르타르의 강도에 의해 지배적인 영향을 받으며, 모재콘크리트의 강도가 작을수록 다공성 재료가 되므로 강도발현이 작게 나타났다. 재령 180일에서 순환잔골재를 사용한 모르타르의 건조수축은 약 $1800{\sim}2000{\mu}m/m$ 정도로 천연잔골재를 사용한 모르타르보다 1.5배 정도 크게 나타났는데 이것은 순환잔골재에 부착된 모르타르가 다공성으로 흡수율이 크기 때문에 나타난 결과로 판단된다. 그러나 동결융해시험에서 순환잔골재를 사용한 모르타르의 내구성은 천연골재와 비슷한 수준으로 모재콘크리트의 강도에 의한 영향은 크지 않은 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.103-107
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• 2008

This study was to execute the experiment for analyzing the quality characteristics of mortar by type of recycled sand by using the recycled sand produced by the manufacturing system by wet gravity separation in order to develop the removal device of impurities for the production of high-quality recycled sand. As a result, this study has sown that the mortar using the high-quality recycled sand through the manufacturing system by wet gravity separation in the fluidity property, strength property, and shrinkage property largely, compared with the mortar using low-quality recycled sand that not passed the device of sand flux. There was a tendency similar to the plane mortar. In conclusion, it was considered as various quality performances of the recycled sand were improved through the production stage of prototype.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.81-84
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• 2006

This study is intended for how to utilize the recycled fine aggregate which is produced by concrete wastes. It analyzes the quality of the fine aggregate which is reproduced through the acid treatment process, and comprehends the characteristics of mortar using the recycled fine aggregate to review whether it can be put to practical use for concrete. The conclusion of the study are as follows 1. The recycled fine aggregate through the acid treat shows the low rate of absorption and high density. 2. Compared to the mortar made from acid liquid precipitated recycled fine aggregate, using nature water precipitated one reduces the flow. 3. The compressive strength of mortar using recycled fine aggregate tends to be reduced according to the kind of precipitated water. Based on the above results, the recycled fine aggregate through the acid treatment process satisfies the quality standards of the first-grade recycled fine aggregate of KS F 2573 (recycled fine aggregate for concrete) but it is concluded that the recycled fine aggregate through the acid treatment process can not used as fine aggregate used concrete because it has destructive characteristics when the mortar is produced

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.501-504
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• 2006

Recycled aggregate mortar contains plenty of calcium hydroxide to improve the strength of blast furnace slag, although the surface mortar made of recycled aggregate deteriorates adhesion to cement paste and blast furnace slag has a low initial strength. Therefore, this study assumes that the combination with both recycled aggregate and blast furnace slag will produce a better performance. The results of the experiment show that dry mortar made of recycled aggregate provides with higher strength than wet mortar does at the 3-day and 7-day age, while lower at the 28-day age. It indicates that a large amount of cement mortar made of dry recycled aggregate has deteriorated adhesion strength. The mixes with 30% and 50% of blast furnace slag and 50% and 75% of recycled aggregate provide with much better strength at the 7-day age, although they usually have latent hydraulic property at the 28-day age. It indicates that calcium hydroxide($Ca(OH){_2}$) in recycled aggregate has affected ground granulated blast furnace slag.

• 한국건축시공학회지
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• 제12권5호
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• pp.460-467
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• 2012

When recycled aggregate with old mortar and particles is used in concrete mixing, such aggregates can affect hydration reaction by promoting or inhibiting it. In this study, the possibility of hydration reaction on old mortar and particle was analyzed. Hydration reaction was carried out in old mortar that is finely crushed by an impact machine in the production of recycled aggregates, and it was found that this did have an impact on the strength development of concrete. Unlike in old cement, the hydration reaction did not progress in the particles, and it had high amounts of silica powder and calcium carbonate. In conclusion, the old mortar can have the influence of improving compressive strength, but the particles can delay the setting time of recycled aggregate concrete.

• 한국건축시공학회지
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• 제12권1호
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• pp.73-86
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• 2012

In this research, the possible applicability of mixture blended with natural, crushed, and recycled fine aggregate are discussed. The fresh and hardened properties of mortar using blended fine aggregates are monitored depending on various blending ratio of fine aggregates. Newly developed ternary diagram was also utilized for better interpretation of the data. It was found that air content increased and unit weight decreased as recycled fine aggregate content increased. With moisture type processing of recycled fine aggregate, the mortar flow was not negatively affected by increase in the recycled fine aggregate content. The ternary diagram is found to be an effective graphical presentation tool that can be used for the quality evaluation of mortar using blended fine aggregate.