• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.199-206
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• 2018

Due to the advantages of less raw materials and fossil fuel consumption, lower carbon footprint, and the capability of pavement performance improvement, the recycling technology of asphalt is developed and applied for road rehabilitation and construction in the western countries over the past two decades. Cold recycled asphalt mixtures are bituminous materials normally made by mixing recycled aggregate from wasted asphalt with an asphalt emulsion and water at room temperature. This paper aims at investigating the properties of cold recycled asphalt mixture with alkali-activated filler according to wasted asphalt aggregate content. As a result, as the content of wasted asphalt aggregate increased, the marshall stability of cold recycled asphalt mixture decreased and void ratio increased. Also, grading curves for cold recycled asphalt mixture as specified in GR criteria were satisfied in all aggregate mixing conditions regardless of the wasted asphalt aggregate content.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.27-33
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• 2018

PURPOSES : The purpose of this study is to estimate the optimum content of an inorganic additive for cold-recycled asphalt mixtures and evaluate its performance. METHODS : An indirect tensile test, a tensile-strength ratio test, and an indirect tensile-fatigue test were conducted on cold-recycling asphalt mixtures with various additives. RESULTS : The laboratory performance tests indicated that granulated blast-furnace slag mixed with inorganic and cement activators provided optimum performance. The performance results of the cold-recycled asphalt pavement were similar to the inorganic and cement activators' performance in terms of the indirect tensile strength, tensile strength ratio, and indirect tensile-fatigue test. CONCLUSIONS : Overall, the performance of a cold-recycled asphalt mixture using inorganic additives and emulsion asphalt was comparable to a warm-recycled asphalt mixture. However, more experiments aimed at improving its performance and studying the effect of the inorganic additives must be conducted.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.67-74
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• 2017

PURPOSES : The objective of this study is to ascertain the curing period of cementless cold central plant recycled asphalt base-layer, using mechanical analyses and specimen quality tests on the field. METHODS : Cold central plant recycled asphalt base-layer mixture was produced in the plant from reclaimed asphalt, natural aggregate, filler for the cold mix, and the modified emulsion AP using asphalt mix design and plant mix design. In order to examine the applicability of the curing period during the field test, the international standards for the possibility of core extraction and the degree of compaction and LFWD deflection were analyzed. Moreover, Marshall stability test, porosity test, and indirect tensile strength test were performed on the specimens of asphalt mix and plant mix design. RESULTS : The plant production process and compaction method of cementless cold central plant recycled asphalt base-layer were established, and the applicability of the optical moisture content for producing the mixture was verified through the field test. In addition, it was determined that the core extraction method of the conventional international curing standard was insufficient to ensure performance, and the LFWD test demonstrated that the deflection converges after a two-day curing. However, the back-calculation analysis reveals that a three-day curing is satisfactory, resulting in a general level of performance of dense asphalt base-layer. Moreover, from the result of the specimen quality test of the asphalt mix design and plant mix design according to the curing period, it was determined that the qualities satisfied both domestic and international standards, after a two-day curing. However, it was determined that the strength and stiffness after three-day curing are higher than those after a two-day curing by approximately 3.5 % and 20 %, respectively. CONCLUSIONS:A three-day curing period is proposed for the cementless cold central plant recycled asphalt base-layer; this curing period can be demonstrated to retain the modulus of asphalt-base layer in the field and ensure stable quality characteristics.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.137-142
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• 2017

PURPOSES :The objective of this study is to evaluate the performance of asphalt mixtures containing inorganic additive and a high content of reclaimed asphalt pavement (RAP). METHODS : The laboratory tests verified the superior laboratory performance of inorganic additive compared to cement, in cold recycled asphalt mixtures. To investigate the moisture susceptibility of the specimens, tensile strength ratio (TSR) tests were performed. In addition, dynamic modulus test was conducted to evaluate the performance of cold recycled asphalt mixture. RESULTS :It was determined that NaOH solution mixed with $Na_2SiO_3$ in the ratio 75:10 provides optimum performance. Compared to Type B and C counterparts, Type A mixtures consisting of an inorganic additive performed better in the Indirect tensile strength test, tensile strength ratio test, and dynamic modulus test. CONCLUSIONS : The use of inorganic additive enhances the indirect strength and dynamic modulus performance of the asphalt mixture. However, additional experiments are to be conducted to improve the reliability of the result with respect to the effect of inorganic additive.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.302-309
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• 2020

This paper is a basic study for applying the dried recycled sludge of waste sludge generated in construction waste intermediate treatment facility and the crushed recycled glass aggregate of waste glass bottles that cannot be recycled to the recycled cold asphalt mixtures. This paper reviewed the characteristics of recycled cold asphalt mixtures using recycled sludge and recycled glass aggregate. As a result, as contents of recycled sludge and recycled glass aggregate increased, the Marshall stability, indirect tensile strength, and tensile strength ratio of the recycled cold asphalt mixtures decreased, but flow and void ratio of that increased.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.50-57
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• 2021

In this study, the engineering charateristics of recycled cold asphalt mixtures using waste glass and red mud were examined as part of the development of low carbon road pavement materials using large amounts of waste. It also examined the satisfaction of the performance criteria specified in the standard. As a result of the study, it was found that RCA using waste glass were not met standard of GR since strain resistance reduced. Therefore, it has been shown that improvements in the composition of the mixture are needed. It has also been shown to significantly improve the performance of the mixture when adding red mud. In addition, it was found that the quality standards for stability, flow value, indirect tensile strength and tensile strength ratio as specified by GR are satisfied.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.135-143
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• 2006

This study evaluated the fatigue resistance characteristics of hot-mix recycled asphalt mixtures which were prepared by a new blending method. Since the binder of RAP shows higher viscosity without being rejuvenated in the ordinary recycled mixture, this new(modified) blending method was developed for obtaining more uniform level of binder viscosity in the recycled mixture. Cold-planned RAP was collected and mix design was performed using 15% RAP content for two virgin aggregate, gneiss and granite. Penetration grade of 60-80 asphalt was used in mixing recycled mixture together with a polymer modifier, LDPE. Indirect tensile fatigue tests were carried out to evaluate characteristics of fatigue resistance of performance of recycled asphalt mixtures. The recycled mixtures with LDPE 6% showed higher repeated loading fatigue life. Fatigue life ratio of new(N) mixing method mixtures was approximately 0.6-0.7 before aging and 0.8-1.0 after aging treatment of ordinary(O) mixing method mixture. This means the N mixture becomes stronger with aging process increase. If further aging is treated, N mixture may be showing stronger resistance than O mixture.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.409-413
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• 2014

This study was carried out to design the optimum mixing ratio of aggregate, cyclic aggregate, and binder (moisture, emulsified asphalt, and emulsion type additives) and produce recycling cold asphalt paving mixture satisfying site work standard. The cyclic aggregate satisfying KS F 2572 was collected from waste asphalt by adequate processing. As the moisture content increased, the shearing strength was decreased. The maximum marshall stability was shown at the 3.0 wt% moisture content. So the optimum moisture content was 3.0 wt%. The marshall stability and flow value with the amount of emulsified asphalt was satisfied in the range of 0.5~2.5 wt%, and the porosity was satisfied in the range of 0.7~2.5 wt%. So the optimum amount of emulsified asphalt was 1.6 wt%. The optimum amount of emulsion type additive was 0.1 wt% in the light of marshall stability and degree of saturation of recycling cold asphalt mixture.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.69-76
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• 2018

PURPOSES : This study determined the optimal usage rate of RAP (reclaimed asphalt pavement) using cold central-plant recycling (CCPR) on a road-surface layer. In addition, a mixture-aggregate gradation design and a curing method based on the proposed rate for the surface-layer mix design were proposed. METHODS : First, current research trends were investigated by analyzing the optimum moisture content, mix design, and quality standards for surface layers in Korea and abroad. To analyze the aggregate characteristics of the RAP, its aggregate-size characteristics were analyzed through the combustion asphalt content test and the aggregate sieve analysis test. Moreover, aggregate-segregation experiments were performed to examine the possibility of RAP aggregate segregation from field compaction and vehicle traffic. After confirming the RAP quality standards, coarse aggregate and fine aggregate, aggregate-gradation design and quality tests were conducted for mixtures with 40% and 50% RAP usage. The optimum moisture content of the surface-layer mixture containing RAP was tested, as was the evapotranspiration effect on the surface-layer mixture of the optimum moisture content. RESULTS : After analyzing the RAP recycled aggregate size and extraction aggregate size, 13-8mm aggregate was found to be mostly 8mm aggregate after combustion. After using surface-chipping and mixing methods to examine the possibility of RAP aggregate segregation, it was found that the mixing method contributed very little for 3.32%, and because the surface-chipping method applied compaction energy directly as the maximum assumption the separation ratio was 15.46%. However, the composite aggregate gradation did not change. Using a 40% RAP aggregate rate on the surface-layer mixture for cold central-plant recycling satisfied the Abroad quality standard. The optimum moisture content of the surface-layer mixture was found to be 7.9% using the modified Marshall compaction test. It was found that the mixture was over 90% cured after curing at $60^{\circ}C$ for two days. CONCLUSIONS : To use the cold central-plant recycling mixture on a road-surface layer, a mixture-aggregate gradation design was proposed as the RAP recycled aggregate size without considering aggregate segregation, and the RAP optimal usage rate was 40%. In addition, the modified Marshall compaction test was used to determine the optimum moisture content as a mix-design parameter, and the curing method was adapted using the method recommended by Asphalt Recycling & Reclaiming Association (ARRA).