Laboratory characterization and field performance of hot in-place recycled mixtures

Hot in-place recycling;Flexibility Index;∆Tcritical;IRI;FWD;Delfection basin parameters

Singhvi, Punit ; Ozer, Hasan ; Al-Qadi ; Imad L.

关键词: Hot in-place recycling;    Flexibility Index;    ∆Tcritical;    IRI;    FWD;    Delfection basin parameters;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/90668/SINGHVI-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Hot in-place recycling (HIR) is one of the pavement preservation techniques. HIR can prove to be an economical as well as environmentally sustainable treatment as it recycles in-place aggregates and binder for the new application by adding small amounts of virgin materials (emulsion or virgin binder). The HIR treatments are commonly categorized into three types including surface recycling, repaving and remixing. The decision for choosing between different types of HIR treatments is made based on the severity of distress of the pavement and availability of equipment. The timing of treatment and the existing condition of the pavement are the deciding factors for the efficiency of HIR. The objective of this study is to characterize material properties and field performance of HIR treatments. Three field sites were evaluated as part of the study: Galesburg and Machesney in Illinois and Dyer in Indiana. Surface recycling followed by asphalt concrete (AC) overlay was used for all the three sites under investigation, where the top 38 mm to 50 mm thickness was milled and recycled with a rejuvenator followed by a 38 mm thick AC overlay. Field investigation comprised of Falling Weight Deflectometer (FWD), profiling for predicting International Roughness Index (IRI) and Condition Rating Survey (CRS). FWD was conducted at every 61 m for the evaluation of pavement structural capacity of existing pavement, post-HIR and post-overlay conditions. Smoothness measurements for existing and the post-HIR conditions was carried out to evaluate the effect on riding quality after HIR while CRS for existing pavement condition were performed as a part of field evaluation. Laboratory material characterization was conducted using field cores collected at every 244 m and loose mix samples from each site. The laboratory characterization program comprised of binder-level testing and mixture-level testing. Illinois Semi-circular Bending (IL-SCB) test and Hamburg Wheel Track Test (WTT) were performed to characterize cracking and rut resistance, respectively. On the other hand, dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests were conducted for binder level investigation. The binder level tests showed that binder grades varied from very soft grade of PG 40-46 (Machesney 15-16) to as stiff as PG 76-28 (Dyer) when evaluated assuming field aged condition. The modulus properties of recovered binder obtained from the sections varied significantly with respect to each other. Significant variability also existed in the materials collected from the same site from different lanes. According to the ∆Tcritical parameter, commonly used to evaluate brittleness of binder, showed that some of Machesney 17-18 section had the highest value of ∆Tcritical of 23.8°C indicating that binder recovered from this section is the most brittle and cracking susceptible. However, in general, binder recovered from Dyer had higher values of ∆Tcritical than that of other section. According to the mixture level tests, the IL-SCB test results showed that Dyer section to be the most susceptible one to cracking related damage. Cracking resistance of mixes were evaluated using fracture energy and flexibility index (FI) that were obtained from the IL-SCB test. The FI of Dyer section was less than 1.0 while Galesburg section outer lane mixes had FI values of of 8.2 in average. The WTT results showed Dyer being the most rut resistant mix while Galesburg outer lane being the least resistant to rutting. Both test results were combined in one parameter called balanced mix design to evaluate the overall mixture performance. The field evaluation concluded that condition of existing pavement prior to the treatment was considered as poor with high values of initial IRI and CRS values less than 4. A significant IRI reduction in the range of 30-100% from the initial value was observed after the treatment. The Falling Weight Deflectometer (FWD) results showed a decrease in the pavement structural capacity after HIR whereas an increase in capacity was seen after the overlay placement. The current study quantifies the effect of HIR treatment based on laboratory material characterization; existing, post HIR and post overlay field evaluation on overall pavement performance because of HIR treatment. The outcome of the study indicates that the initial pavement condition, timing, and the resulting mixture properties play a significant role in the performance of HIR. Therefore appropriate treatment design guidelines are required for the use of HIR as a pavement preservation technique.