• International Journal of Concrete Structures and Materials
• /
• v.10 no.1
• /
• pp.61-73
• /
• 2016

In predicating the probability distribution of chloride diffusion coefficient of recycled aggregate concrete ($D_{RAC}$), the morphological characteristics of three phases, i.e., the old attached mortar, the natural aggregate and the new mortar, should all be taken into account. The present paper attempts to develop a probability density evolution method (PDEM) to achieve this. After verifying the derived PDEM results with experimental results, the effects of old attached mortar to the $D_{RAC}$ are examined in a quantitative manner. It is found that (1) the variation of the attached mortar content is much sensitive to $D_{RAC}$; (2) given the probability distribution of the content and chloride diffusion coefficient of old mortar, the probability distribution of DRAC can be analysed based on the PDEM; and (3) the critical chloride diffusion coefficient at a certain assurance rate can be obtained by the PDEM. The analysis results of this investigation will be valuable to the durability design for RAC.

• Journal of the Korea Institute of Building Construction
• /
• v.12 no.5
• /
• pp.460-467
• /
• 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.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2009.11a
• /
• pp.65-68
• /
• 2009

Recycled aggregate by the recycling construction waste has a lot of advantage such as the developing the alternative resource and protecting of environment. However, recycled aggregate is used as the low quality grade, because the technic to remove old mortar from aggregate is low level. To use the recycled aggregate as high quality grade, it is important to develop the technic to produce the high quality recycled aggregate. To manufacture the high quality recycled aggregate, old mortar attached on the aggregates should remove efficiently. Therefore, in this study, we suggested the optimum condition to remove old mortar effectively using sulfuric acid and low speed wet rotary mill for high quality recycled fine aggregate. The results shows that the recycled aggregate satisfy on the standards of KS F 2573 in density, absorption and solid volume when, adequate condition of sulfuric mole ratio and aggregate ratio are make.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.2
• /
• pp.146-151
• /
• 2015

Recycled aggregate by the recycling construction waste has a lot of advantage such as the developing the alternative resource and protecting of environment. However, recycled aggregate is used as the low quality grade, because it is difficult to remove old mortar from aggregate. To use the recycled aggregate as high quality grade, it is important to develop the technology to produce the high quality recycled aggregate. To manufacture the high quality recycled aggregate, old mortar attached on the aggregates should be removed efficiently. Therefore, in this study, we suggested the optimum condition to remove old mortar effectively using sulfuric acid and low speed wet rotary mill for high quality recycled fine aggregate. The results shows that the recycled aggregate satisfy on the standards of KS F 2573 in density, absorption and solid volume, when adequate condition of sulfuric mole ratio and aggregate ratio are make.