• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.112-118
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• 2011

The recycled asphalt concrete has gotten increasing attention due to the environmental issues. The volume of reclaimed asphalt has increased significantly for last few years because of city remodeling, pavement maintenance, utility excavation, and road widening. Considering the value of reclaimed asphalt, it is rather used for the recycled asphalt concrete than it is used for fill and cover up material instead of soil. This research will be a supplements incomplete issues from existing research results and suggests the quality control guideline for recycled asphalt concrete and upcoming laws. As the first step of research, the trial construction of RAP(Recycled Asphalt Pavement) performed in expressway construction sites. These trial construction sites have been checked every years. And another construction sites studied and selected for more deeper performance check of RAP. For this checks, we used automatic pavement survey equipment and computerized analysis tools. Also, DSR(Dynamic Shear Rheometer) was used for the fatigue life calculation of binder blends(RAP and virgin binder). As a consequence of this research, the application of recycled asphalt provides good enough quality for highway construction. The preceeding literatures reviewed shows that the asphalt rejuvenator are used in many countries but that type of chemical agent are not used in Korea. By using the data of trial construction and mix design in Chongwon-Sangju construction lane, the surface and base courses consisted with the 10% and 30% rap mix asphalt section maintains good performance for up to 7 years. Through the performance check and laboratory tests(DSR), the quality control and mixture's low temperature prevention are the important factor and chemical agent necessary for increasing the fatigue life of RAP binder.

• Geomechanics and Engineering
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• v.6 no.3
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• pp.235-248
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• 2014

Population increase and economic developments can lead to construction as well as demolition of infrastructures such as buildings, bridges, roads, etc resulting in used concrete as a primary waste product. Recycling of waste concrete to obtain the recycled concrete aggregates (RCA) for base and/or sub-base materials in road construction is a foremost application to be promoted to gain economical and sustainability benefits. As the mortar, bricks, glass and reclaimed asphalt pavement (RAP) present as constituents in RCA, it exhibits inconsistent properties and performance. In this study, six different types of RCA samples were subjected classification tests such as particle size distribution, plasticity, compaction test, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. Results were compared with those of the standard road materials used in Queensland, Australia. It was found that material type 'RM1-100/RM3-0' and 'RM1-80/RM3-20' samples are in the margin of the minimum required specifications of base materials used for high volume unbound granular roads while others are lower than that the minimum requirement.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.6
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• pp.125-134
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• 2010

This study was performed to evaluate the workability, strengths and durability of polymer concrete using oyster shell that are reclaimed at public shore illegally or leaved on the surroundings of shore to prevent the environmental pollution. We investigated the effect of oyster shell powder (OSP) and $CaCO_3$. on the slump, compressive strength, flexural strength, acid sulfuric and freezing and thawing resistance as a filler of polymer concrete. Modified OSP obtained by crushing oyster shell (less than 0.15 mm size) consists of 60.47 wt% of $SiO_2$ and 39.5 wt% of $CaCO_3$. As a result of slump test by OSP and $CaCO_3$. contents, it is found that slump of specimen used OSP is lower than that used $CaCO_3$. and the more OSP contents are, its slump is increased. Compressive and flexural strength of polymer concrete using OSP are similar or slightly lower than that using $CaCO_3$. In acid sulfuric test for 5 % $H_2SO_4$ and freezing thawing test, regardless of kinds of fillers and contents are not found fatal defects in weight change, falling-off in surface and durability factor.

• International Journal of Highway Engineering
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• v.19 no.1
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• pp.37-44
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• 2017

PURPOSES : This study is primarily focused on evaluating the effects of the non-linear stress-strain behavior of RAP concrete on structural response characteristics as is applicable to concrete pavement. METHODS : A 3D FE model was developed by incorporating the actual stress-strain behavior of RAP concrete obtained via flexural strength testing as a material property model to evaluate the effects of the non-linear stress-strain behavior to failure on the maximum stresses in the concrete slab and potential performance prediction results. In addition, a typical linear elastic model was employed to analyze the structural responses for comparison purposes. The analytical results from the FE model incorporating the actual stress-strain behavior of RAP concrete were compared to the corresponding results from the linear elastic FE model. RESULTS : The results indicate that the linear elastic model tends to yield higher predicted maximum stresses in the concrete as compared to those obtained via the actual stress-strain model. Consequently, these higher predicted stresses lead to a difference in potential performance of the concrete pavement containing RAP. CONCLUSIONS : Analysis of the concrete pavement containing RAP demonstrated that an appropriate analytical model using the actual stress-strain characteristics should be employed to calculate the structural responses of RAP concrete pavement instead of simply assuming the concrete to be a linear elastic material.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.105-116
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• 1999

The Inchon International Airport site was formed by reclaimed soil from the sea. The average thickness of soft soil Is about 5 m and most of soft soils are normally consolidated or slightly over consolidated. There are many box culverts which are being constructed under the runways in the airfield. Sometimes, differential settlement can be occurred in the adjacent of box culvert or underground structures at the top layer of runway Soil compaction at very near to the structure is not easy all the time. Thus, one layer of geogrid was placed at the bottom of lean concrete layer for the concrete paved runway and at the middle of cement stabilized sub-base course layer for the asphalt paved runway. The length of geogrid reinforcement is 5m from the end of box culvert for both sides. The extended length of geogrid was 2m from the end of backfill soil in the box culvert. The tensile strength tests of geogrid were conducted for make sure the chemical compatibility with cement treated sub-base material. The location of geogrid placement for the concrete paved runway was evaluated. The construction damage to the geogrid could be occurred. Because the cement treated sub-base layer or lean concrete was spread by the finisher. The magnitude of tensile strength reduction was 1.16%~1.90% due to the construction damage and the ultimate tensile strength is maintained with the specification required. Total area of geogrid placement in this project is about 50,000 $m^2$.

• Journal of Environmental Science International
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• v.19 no.5
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• pp.639-646
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• 2010

Differently from fly ash, the bottom ash produced from incinerated urban solid waste has been treated as an industrial waste matter, and almost reclaimed a tract form the sea. If this waste material is applicable to foam concrete as an fine aggregate, however, it may be worthy of environmental preservation by recycling of waste material as well as reducing self-weight of high-rising structure and long-span bridge. This research has an objective of evaluating the effects of application of bottom ash on the mechanical properties of foam concrete. Thus, the ratio of bottom ash to cement was selected as a variable for experiment and the effect was tested by compression strength, flexural strength, absorption ratio, density, expansion factor. It can be observed from experiments that the application ratios have different effects on the material parameters considered in this experiment, thus major relationship between application ratio and each material parameter were finally introduced. The result of this study can be applied to decide a optimal mix design proportion of foam light-weight concrete while bottom ash is used as an fine aggregate of the concrete.

• Advances in concrete construction
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• v.10 no.6
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• pp.489-498
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• 2020

This paper investigates mechanical properties of roller compacted concrete (RCC) involving reclaimed asphalt pavement (RAP). In this way, a set of 276 cylindrical RCC specimens were prepared with different RAP sizes (i.e., fine, coarse & total) at various ratios (i.e., 10%, 20%, and 40%). Results reveal that incorporation of RAP decreases unconfined compressive strength (UCS), modulus of elasticity (E), and indirect tensile (IDT) strength of RCC. For each RAP size, a regression model was used to maximize RAP content while satisfying the UCS lower limit (27.6 Mpa) mentioned by ACI as a minimum requirement for RCC used in pavement construction. Moreover, UCS of RAP incorporated mixes, dissimilar to that of control mixes, was found to be sensitive and insensitive to the testing temperature and curing time after 7 days, respectively. The results also demonstrate that the higher amounts of RAP, the more flexibility in RCC is. This issue was also proved by the results of modulus of elasticity test. In addition, the toughness index (TI) shows that increase in RAP content leads to up to 43% increase in energy absorbance capacity of RCC.

• Computers and Concrete
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• v.33 no.5
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• pp.605-619
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• 2024

The increase of reclaimed asphalt pavement (RAP) content in recycled asphalt concrete (RAC) is accompanied by the degradation of low-temperature cracking resistance, which has become an obstacle to the development of RAC. This paper aims to reveal the meso-scale mechanisms of the low-temperature fracture behavior of RAC and provide a theoretical basis for the economical recycling of RAP. For this purpose, micromechanical heterogeneous peridynamic model of RAC was established and validated by comparing three-point bending (TPB) test results against corresponding numerical simulation results of RAC with 50% RAP content. Furthermore, the models with different aggregate shapes (i.e., average aggregates circularity (${\bar{C_r}}=1.00$, 0.75, and 0.50) and RAP content (i.e., 0%, 15%, 30%, 50%, 75%, and 100%) were constructed to investigate the effect of aggregate shape and RAP content on the low-temperature cracking resistance. The results show that peridynamic models can accurately simulate the low-temperature fracture behavior of RAC, with only 2.9% and 13.9% differences from the TPB test in flexural strength and failure strain, respectively. On the meso-scale, the damage in the RAC is mainly controlled by horizontal tensile stress and the stress concentration appears in the interface transition zone (ITZ). Aggregate shape has a significant effect on the low-temperature fracture resistance, i.e., higher aggregate circularity leads to better low-temperature performance. The large number of microcracks generated during the damage evolution process for the peridynamic model with circular aggregates contributes to slowing down the fracture, whereas the severe stress concentration at the corners leads to the fracture of the aggregates with low circularity under lower stress levels. The effect of RAP content below 30% or above 50% is not significant, but a substantial reduction (16.9% in flexural strength and 16.4% in failure strain) is observed between the RAP content of 30% and 50%. This reduction is mainly attributed to the fact that the damage in the ITZ region transfers significantly to the aggregates, especially the RAP aggregates, when the RAP content ranges from 30% to 50%.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.202-209
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• 2015

This study compared and analyzed the measurements of pullout load according to the depth of reclamation in the foundation, compaction ratio of soil, spiral diameter, and soil textures in an experiment with a model and reached the following conclusions: The comparison results of extreme pullout load between farm and reclaimed soil show that farmland soil recorded a score that was 1.2~3 times higher than that of reclaimed soil. The investigator measured pullout load in farmland and reclaimed soil and observed a tendency of rising extreme pullout load according to the increasing depth of reclamation and compaction ratio with a similar load-displacement curve between the two types of soil. Extreme pullout load made a greater increase by the rising size of diameter than the increasing depth of reclamation, also making a considerably bigger increase according to the rising compaction ratio than the other conditions. Therefore, the spirals bar is expected to be available in soft soil foundation, as well as farmland as increasing buried deep of foundations, compaction rate, diameter of the spiral, ect.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.173-179
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• 2014

This is an experimental study for recycling coal ash left over from coal use as a potential fine aggregate in concrete. Coal ash is generally divided into either fly ash or bottom ash. Fly ash has been utilized as a substitution material for cement in concrete mixes. On the other hand, bottom ash has the problem of low recycling rates, and thus it has been primarily reclaimed. This study partially substituted fine concrete aggregates with bottom ash to increase its application rate and therefore its recycling rate; its suitability for this purpose was confirmed. The concrete's workability dropped noticeably with increasing bottom ash content when a fixed water-cement ratio of concrete mix was used. Thus, concrete mixes with higher ratio levels are required. To address this problem, concrete was mixed using a polycarboxylate high-range water reducing agent. The fluidity and air entrainment immediately after mixing the concrete and 1 h after mixing were measured, thereby replicating the time concrete is placed in the field when produced either in a ready-mixed concrete or in a batch plant. As a result of this research, the workability and air entrainment were maintained 1 h after mixing for a concrete mixture with approximately 30% of its fine concrete aggregates substituted with the bottom ash. A slight drop in compression strength was seen; however, this confirmed that potential of using bottom ash as a fine aggregate in concrete.