• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.1231-1238
• /
• 2010

Recently, the utilization of recycled aggregates for backfilling a power transmission pipeline trench has been increasing due to the issues of eco-friendly construction and shortage of natural aggregate resource. It is important to investigate the physical and thermal properties of the recycled aggregates that can be used as a backfill material. This study presents the thermal properties of two types of recycled aggregates with various particle size distributions. The thermal properties of the recycled aggregate were measured using the transient hot wire method and the probe method after performing the standard compaction test using an automatic compactor. Similar to silica sand, the thermal resistivity of the recycled aggregates decreased when the water content increased. This study shows that the recycled aggregate can be a promising backfill material substituting for natural aggregate when backfilling the power transmission pipeline trench.

• Journal of the Korean Society of Safety
• /
• v.26 no.5
• /
• pp.65-72
• /
• 2011

The use of waste concrete can resolve the environmental pollution and shortage of natural aggregate. However, recycled aggregate includes substantial amount of cement paste. So, these aggregates are more porous, and less resistant to mechanical actions than natural aggregates. So, recently, the new manufacture processes of high quality recycled aggregates were suggested such as heating and solving to acid liquid. But the method of solving to acid liquid is not economical and produces additional environmental pollution. In this paper, for the purpose of manufacture of high quality recycled aggregates, the heating processes was added to the existing process of recycled aggregates. To find the optimum process, the experiment was performed by using the method of statistical experiment design, and the heating temperatures(4 levels : 300, 450, 600 and $750^{\circ}C$) and heating times(4 levels : 5, 20, 40, 60 minute) were main experimental variables. By the test results, the optimum manufacturing condition of coarse recycled aggregate was $600^{\circ}C$ and 40 minute, and for the fine recycled aggregate, a little heating made a satisfaction to the KS standard quality code.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.6
• /
• pp.527-534
• /
• 2017

Accordingly, this study, in order to use powder of recycled aggregate from production of recycled aggregate as an activator of ground granulated blast furnace slag, the influence of added recycled aggregate powder on physical properties of concrete induced ground granulated blast furnace slag were analyzed by hydration stages. The results of the study are summarized as follows: Except for samples eluted powder of recycled aggregate 1%, all the samples were high alkali suspensions with higher than pH 12.0. In particular, when eluted time was 5 hours, the sample eluted powder of recycled aggregate 3% showed about 15 mg/l of calcium hydroxide that was not different from the amount of calcium hydroxide in the mixing water eluted powder of recycled aggregate 5%. Hence, from this results, it can be considered that optimal eluted powder of recycled aggregate was 3% in this study. When using mixing water eluted with powder of recycled aggregate, compared to use of ordinary mixing water, it showed greater compressive strength in the entire ages, and in the sample replaced with ground granulated blast furnace slag by 50%, its compressive strength was greater than that of the OPC. As use of mixing water eluted with powder of recycled aggregate in concrete used with large amount of ground granulated blast furnace slag was more effective for improving compressive strength than ordinary mixing water, it is verified that powder of recycled aggregate had an effect of activator.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.675-680
• /
• 2003

In this study, various tests are performed for the durability of the concrete using domestic recycled coarse aggregate including drying shrinkage, permeability, freezing-thawing resistance and $CO_2$ diffusivity. Tests of freezing-thawing resistance, chloride ion permeability and $CO_2$ diffusivity of recycled concrete show favorable results. But, the maximum drying shrinkage ratio to normal concrete is increased 24% with increasing substitution ratio of recycled aggregate. Therefore, for the use of recycled concrete in structures, the preventive measures of drying shrinkage is necessary in mix design and the adequate substitution ratio of recycled aggregate should be proposed.

• Computers and Concrete
• /
• v.21 no.3
• /
• pp.249-259
• /
• 2018

The use of recycled aggregate in concrete is gaining much attention due to the growing need for sustainability in construction. In the present study, Self Compacting Concrete (SCC) is made using both natural and recycled aggregate (crushed recycled concrete aggregate from building demolished waste) and performance of recycled aggregate based SCC for the bond behaviour of reinforcement is evaluated. The major factors that influence the bond like concrete compressive strength (Mix-A, B and C), diameter of bar ($D_b=10$, 12 and 16 mm) and embedment length of bar ($L_d=2.5Db$, $5D_b$ and full depth of specimen) are the parameters considered in the present study in addition to type of aggregates (natural and recycled aggregates). The mix proportions of Natural Aggregate SCC (NASCC) are arrived based on the specifications of IS 10262. The mix proportions also satisfy the guidelines of EFNARC. In case of Recycled Aggregate SCC (RASCC), both the natural coarse and fine aggregates are replaced 100% by volume with that of recycled aggregates. These mixes are also evaluated for fresh properties as per EFNARC. The hardened properties like compressive strength, split tensile strength and flexural strength are also determined. The pull-out test is conducted as per the specifications of IS 2770 (Part-1) for determining the bond strength of reinforcement. Bond stress versus slip curves were plotted and a typical comparison of RASCC is made with NASCC. The fracture energy i.e., area under the bond stress slip curve is determined. With the use of recycled aggregates, reduction in maximum bond stress is noticed whereas, the normalised maximum bond stress is higher in case of recycled aggregates. Based on the experimental results, regression analysis is conducted and an equation is proposed to predict the maximum bond stress of RASCC. The equation is in good agreement with the experimental results. The available models in the literature are made use to predict the maximum bond stress and compare the present results.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.4
• /
• pp.366-373
• /
• 2015

Construction waste is recycled and used for the efficient and eco-friendly disposal of construction waste increasing due to reconstruction and redevelopment project and so on. There is recycled aggregate as a typical case. And this recycled aggregate shows strong alkalinity due to calcium hydroxide, and causes many environmental problems. Therefore, this is a study on reduction in the strong alkalinity of recycled aggregate by using sodium phosphate based ammonium in order to reduce the pH of recycled aggregate. Besides, a possibility that a pH reducing agent of recycled aggregate could be applied to a site was evaluated. As a result, it was possible to verify that pH decreased as the percentage of pH reducing agent increased. It is thought that the pH reducing agent can be applied to a site by methods such as immersion and spray using the pH reducing agent in the process of producing recycled aggregates.

• International Journal of Highway Engineering
• /
• v.6 no.1 s.19
• /
• pp.37-45
• /
• 2004

The characteristics of concrete strength and fracture parameters of recycled aggregate concrete were investigated to apply to the concrete pavements. As the results, the early strength of recycled aggregate concrete showed to be lower than that of natural coarse aggregate concrete, whereas strength at 28 days showed to be similar. Young's modulus of recycled aggregate concrete was lower than that of natural coarse aggregate concrete due to the difference of aggregate strength. And recycled aggregate concrete contained with ground granulated blast furnace slag seemed to have an effect of strength increasing. The critical stress intensity factor of recycled aggregate concrete at the early age was increased, and converged to be similar, compared to natural aggregate concrete at later age. The reliability of two-parameter fracture model was identified by the good correlation between the theoretical value computed by P-CMOD relationship and experimental results for Young's modulus and tensile strength.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.47 no.4
• /
• pp.25-32
• /
• 2005

This study was performed to evaluate the strength properties of polymer concrete using recycled aggre-gate. The compressive strength, splitting tensile strength, flexural strength and pulse velocity of polymer concrete were decreased with increasing the content of recycled aggregate. At the curing age of 7days, the compressive strength was $80.5\~88.3$ MPa, the splitting tensile strength was $9.1\~10.6$ MPa, the flexural strength was $19.2\~21.5$ MPa and the pulse velocity was $3,931\~4,041$ m/s, respectively. Also, the compressive strength, splitting tensile strength, flexural strength and pulse velocity of concrete using recycled fine aggregate were higher than that of the silica sand. Therefore, these recycled aggregate polymer concretes were estimated for high strength concrete without major problem.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2003.10a
• /
• pp.415-418
• /
• 2003

This study is performed to examine properties of polymer permeability concrete using recycled coarse aggregate and blast furnace slag for application of structures needed permeability. Tests for compressive strength, flexural strength and pulse velocity with replacement ratio of recycled coarse aggregate are performed. As a result, compressive strength, flexural strength and coefficient of permeability of polymer permeability concrete containing recycled coarse aggregate are in the range of $180{\sim}200kgf/cm^2,\;58{\sim}64kgf/cm^2\;and\;4.6{\times}10^{-2}{\sim}6.9{\times}10^{-2}cm/s$, respectively. Compressive strength, flexural strength and pulse velocity of polymer concrete containing crushed stone only are $192kgf/cm^2,\;65kgf/cm^2\;and\;6.1{\times}10^{-2}cm/s$, respectively. Accordingly, recycled coarse aggregate is expected that can be utilizing as an aggregate of polymer permeability concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2011.11a
• /
• pp.215-216
• /
• 2011

This study investigates the effect of partial replacement with cement on the properties of blast furnace slag-based mortar. Recycled fine aggregate with various contents was used to activate the hydration of blast furnace slag in the mortar and compared its effect on strength development. Results showed that increasing cement and recycled fine aggregate increased the strength of mortar specimens. However, this study found that the mortar made with partial replacement of river sand with recycled fine aggregate of 20% developed a similar strength to the strength that cement with 10% can achieved.