Evaluation of Various Treatment Methods for Enhancing the Properties of Recycled Concrete Aggregate for Hot Mix Asphalt PDF Download

Author: Hanaa Al-Bayati
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Languages : en
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Book Description
The application of treated CRCA with heat treatment and short mechanical treatment leads to an increase in the rutting resistance, a decrease in the total rut depth, a slight increase in the stiffness modulus, and an increase in the rutting factor of asphalt mixtures depending on the type of CRCA. The application of treated CRCA with the pre-soaking method and short mechanical treatment results in an increase in the stiffness and rutting factor of mixtures, depending on the type of CRCA. The findings demonstrated that the mixtures that included untreated CRCA have much higher ITS values than the control mix, registering a significant increase of 68%, 70%, 85.6% and 86.7%, for the mixtures that included 30% untreated CRCA#1 and CRCA#2 in both unconditioned and conditioned samples, respectively. This is followed by the ITS values of the mixtures that included 60% untreated CRCA#1 and CRCA#2 for both unconditioned and conditioned samples with an increase of 41.4%, 49.0%, 71.5%, and 56.8%, respectively. Additionally, a reasonable improvement in the ITS values in both conditioned and unconditioned samples were recorded for the mixtures that included 30% treated CRCA with different treatment techniques compared to the mixture that included 30% untreated CRCA. Furthermore, all tensile strength ratio (TSR) values for mixtures that included untreated CRCA with different types and percentages are higher than the minimum required value of MTO specifications. This indicates a successful application for CRCA in these mixtures. The use of the combination technique of pre-soaking method with weak acid followed by a short mechanical treatment method was a highly successful method for enhancing moisture resistance of asphalt mixtures as compared to other combination methods. From TSRST test, the findings indicated that the fracture temperature is reduced due to the CRCA addition compared to the control mix. However, there is no significant influence for the RCA type on the thermal cracks at low temperatures. Additionally, the fracture stress of the mixtures that included different untreated CRCA types with various proportions is generally higher than the fracture stress of the control mix Furthermore, the application of the combination of various treatments leads to a significant reduction in the fracture temperature, indicating a successful application of treated CRCA in HMA mixtures in cold regions. However, the combination of heat at 300 °C and short mechanical treatment has a considerable impact on the fracture temperature of asphalt mixtures as compared to other combination techniques. The results of ANOVA statistical analysis showed that the type of CRCA had a significant effect on the stiffness and rutting, ITS, and the fracture temperature of asphalt mixtures. Additionally, the type of treatment method had a considerable effect on the stiffness, rutting, and fracture temperature of HMA mixtures. In contrast, both the type of treatment method and the type of CRCA have an insignificant effect on the fracture stress of asphalt mixtures. The results of cost analysis revealed that both heat and pre-soaking treatment is quite reasonable, referring to many economic benefits and indicating that these treatment methods could be applicable. In conclusion, the results of this study indicate that the application of different CRCA types in various forms: treated and untreated is very successful and can contribute greatly towards more RCA applications in the asphalt pavements.