116 4.17 Results of frequency inspection of binders for warm asphalt PMB with Sasobit 116 4.18 Results of frequency measurement of binders for warm asphalt CRMB with Sasobit117 4.19 Results of temperature measurement of binders for warm asphalt PMB with. 176 6.2 Modified results of Lottman's CRMB warm mix tests with Evotherm 176 6.3 RMS results of PMB warm mix test with Evotherm.
List of Tables
178 6.2 ANOVA results for RMS values for hot mixes containing Evotherm 180 6.3 ANOVA results for TSR values for hot mixes containing Sasobit. 200 7.5 ANOVA results for fracture life for hot mixes containing Evotherm 202 7.6 ANOVA results for MRat 5°C for hot mixes containing Sasobit.
List of Abbreviations
List of Symbols
Introduction
- General
- Problem Statement
- Objectives of the Study
- Organisation of Thesis
Under this perspective, this study evaluates the effect of WMA additives on rheological properties of modified asphalt binders as well as on performance. The study includes two WMA additives (Evotherm and Sasobit) each with different dosages, two modified binder types (VMV: polymer modified bitumen and CRMB: crumb rubber modified bitumen), and four reductions in mix production temperatures.
Review of Literature
Introduction
WMA: Historical Timeline
The original process for producing foamed bitumen consisted of injecting steam into hot bitumen. In 1995, Maccarone studied developments in cold asphalt with foamed bitumen and high binder emulsions (Maccarrone, 1995).
Classification of WMA Technologies
- Use of Foaming Technologies
In this WMA technology, small amounts of water are either injected into the hot binder or directly into the mixing chamber. Typically, water is added at a rate of 0.5% (by weight of binder) to hot bitumen just before mixing with aggregates (Zaumanis, 2010).
HOT MIX
Organic Additives
When these additives are added to the binder, a reduction in binder viscosity is observed at temperatures beyond their melting point. Organic additives can be added directly to either the asphalt binder or the asphalt mixture.
Chemical Additives
The water in the emulsion flashes as vapor when mixed with hot aggregates leaving residual asphalt and chemical additives (Hurley and Prowell, 2006; Kandhal, 2010; Bonaquist, 2011). This technology does not require plant modification and simply replaces liquid asphalt in the HMA design (Estakhri et al., 2010).
EVOTHERM DAT
However, some hot mix systems involving water addition appear to improve the low temperature properties of the mix. Lower mixing temperatures result in lower oxidative hardening of the asphalt in the actual mixing process.
The Rediset WMX concept
Benefits of WMA Technologies
Although beneficial in terms of long-term pavement life, the initial stiffness of both the bitumen and the pavement may be reduced compared to conventional hot mix (8). On the other hand, some wax-based additives can maintain or even enhance the stiffness of the asphalt mixture in normal pavement.
Effect of WMA Additives on Binder Rheology
The viscosity of the neat and CRM binders was reduced by the addition of WMA additives. It was found that the addition of WMA additives has no significant effect on the chemical properties of asphalt binders.
Effect of WMA Additives on Mixture Properties
For the preparation of WMA mixtures, a Sasobit H8 content of 1.5 wt% of the total binder was used. The air voids of WMA mixtures compacted at lower temperatures were similar to those of the HMA mixtures, as shown in Figure 2.12. The rut depth and susceptibility to fraying of WMA blends were greater than those of the control blend, except in the case of WMA-B (with fine gradation) prepared at 30°C.
The results of the elastic modulus test showed an increase in the temperature sensitivity of PMA mixtures with the addition of WMA additives. The moisture resistance of WMA mixtures increased with the addition of WMA additives even after the production temperatures were reduced by 35–40 °C. 2012) investigated the compactness and performance characteristics of warm mixes.
Summary
RSM results showed that the maximum TSR was achieved at medium aggregate grading, 0.1% Zycosoil content, 6.5% bitumen content, 1.5% Sasobit content and at mixing temperature of 120°C. Furthermore, interactions between different parameters showed that TSR values were more affected by Zycosoil content and gradation than bitumen content, Sasob content and mixing temperatures. Lowering production temperatures affects the aging characteristics of the binder and the workability of the mixtures, and therefore plays a major role in achieving the desired volumetric properties, performance and durability of asphalt mixtures.
However, it cannot be denied that the technology is quickly gaining widespread acceptance among highway agencies around the world. From this perspective, the current research effort considers a holistic investigation of two WMA additives (Evotherm and Sasobit), each at different dosages, on the properties of two modified binders (polymer and crumb rubber modified binders), and bituminous concrete mixtures made with combinations of these binders and additives at different reductions in production temperatures.
Materials and Experimental Programme
Introduction
Materials
- Bitumen
- Aggregates
- WMA Additives and Dosage Rates
In this study, the mixing and compaction temperatures for the modified binders presented in Table 3.4 were used based on the manufacturer's recommendations. The mean values adopted for the study are presented in Table 3.6 along with the recommended range as per IRC and MoRTH (2013) specifications. Sasobit used in the study was provided by KPL International Limited, India in the form of beads as shown in Figure 3.1.
Sasol wax recommends the Sasobit dosage in the range of 0.8% to 4% by weight of binder (Sasobit Product Information 124, 2017). Evotherm is a chemical hot mix additive developed in the USA by MeadWestvaco (MWV) Asphalt Innovations, Charleston, South Carolina.
Experimental Plan
- Task 1: Rheological Evaluation of Warm Asphalt Binders
- Preparation of Warm Asphalt Binders
- Operation Principle of Testing Instruments
- Test Procedures
- Task 2: Evaluation of Marshall Mix Design Parameters of Warm MixesWarm Mixes
- Design of Bituminous Concrete Mixes
- Preparation of Warm Mixes
- Task 3: Moisture Susceptibility Characteristics of Warm MixesMixes
- Test Procedures
- Task 4: Performance Characteristics of Warm Mixes
- Test Procedures
CoreLokTM equipment (manufactured by InstroTek Inc.) was used to determine maximum specific gravity of bituminous mixtures as shown in Figure 3.11 according to ASTM D6857/D6857M (2011). Marshall stability testing was performed using Matest 50 kN UTM II digitized Marshall stability testing machine shown in Figure 3.12 in accordance with ASTM D1559 (1989). The average values of bulk density, Marshall stability, flow, AV, VMA and VFB were plotted separately against the bitumen content as shown in Figures 3.13 and 3.14 for bituminous mixtures with PMB and CRMB binders respectively.
Two LVDTs were placed to monitor axial deformations of the test specimen throughout the test duration. In this study, indirect tensile fatigue testing (ITFT) was used to evaluate the fatigue properties of the hot mixes.
Summary
Rheological Characteristics of Warm Asphalt Binders
Introduction
Changes in the properties of asphalt binders under the influence of WBG additives can be understood from the study of rheology of binders containing these additives. In other words, binders can exhibit different properties (different performance) with different doses of WMA additives. Therefore, there is a need to evaluate the rheological properties of binders with different doses of WMA additives.
Viscosity of hot asphalt binders was also determined at 150°C using Brookfield rotational viscometer DV II Pro. Rheological properties of both VMV and CRMB binders with WBG addition Sasobit were also assessed under different short-term aging temperatures (163°C, 143°C and 123°C).
Effect of Evotherm on Rheological Properties of Modified Binders
Phase angle (δ), ° . Figure 4.8: Temperature test results of CRMB hot mixes with Evotherm s) for PMB and CRMB hot asphalt binders. There is a slight decrease in the compliance values of both PMB and CRMB binders with the addition of Evotherm. The compliance values of PMB and CRMB hot asphalt binders are shown in Figures 4.11 and 4.12, respectively.
Addition of Evotherm only leads to a slight increase in the compliance values for both PMB and CRMB binders. These results demonstrate that the addition of Evotherm had no appreciable effect on the rheological properties of either PMB or CRMB binders because this additive is designed to act at the aggregate-binder interface rather than altering the rheology of the binders. to influence.
Effect of Sasobit on Rheological Properties of Modified Binders
Figures 4.23 and 4.24 respectively show the results of repeated creep recovery tests conducted on PMB and CRMB hot asphalt binders. It is observed that addition of Sasobit reduces the compliance values of both hot asphalt binders. Hot asphalt binders with Sasobit and control binders (without Sasobit) were both briefly aged using an RTFO for 85 minutes according to ASTM D2872-12e1 (2012) at different temperatures.
It has been observed that a reduction in RTFO aging temperature reduces the AI values of hot asphalt binders. As expected, the short-term decrease in aging temperature reduces the failure temperature of both PMB and CRMB hot asphalt binders.
Summary
With the addition of Sasobit, viscosities of both PMB and CRMB binders at 150°C showed significant reductions. Frequency and temperature sweep results showed that addition of Sasobit had a positive effect on the elastic properties of both binders. Rheological aspects of Sasobit hot binders were further investigated under different short-term aging temperatures.
The viscosity, failure temperature, complex modulus, elastic modulus, and viscous modulus of both binders decreased as the aging temperature decreased. The addition of Sasobit compensated for the effects of reduced aging, as the rheological parameters of Sasobit warm binders aged at 143 °C and 123 °C compared well with control binders aged at the standard aging temperature (163 °C).
Volumetric and Marshall Parameters of Warm Mixes
Introduction
Mixing and compression temperatures for pure (unmodified) asphalt binders are determined at viscosities of 170±20 cSt and 280±30 cSt, respectively, according to Asphalt Institute Manual Series No.2 (Asphalt Institute, 1997) guidelines (also used in India). These viscosity ranges do not apply equally well to modified binders and often result in unreasonably high mixing and compaction temperatures (>190 °C), which can eventually lead to modifier damage, binder damage, structural problems, and smoke generation (Yildirim et al., 2000). ;. Tang and Haddock, 2006). Incorporating WMA technologies with modified binders should help reduce mixing and compaction temperatures, which are generally higher than unmodified binders, without sacrificing the volumetric and design parameters of bituminous mixtures.
Therefore, the volumetric and Marshall parameters of bituminous concrete (BC) mixtures with two WMA additives (Evotherm and Sasobit) are studied as a function of production temperature, dose/content of each WMA additive, and type of binder and the results are presented in this chapter. . Results of volumetric and Marshall parameters of hot mixes with Evotherm and Sasobit versus control mixes (without WBG additives) are presented and discussed in the chapter.
Marshall Mix Design Parameters of Warm Mixes with Evothermwith Evotherm
The effect of reducing production temperatures on the air void content of PMB and CRMB hot mixes are shown in Figures 5.3 and 5.4, respectively. The Marshall stability results of PMB and CRMB hot mixes produced at different production temperatures are illustrated in Figures 5.5 and 5.6, respectively. Marshall stability values of hot mixes are found to decrease with decreasing production temperature.
Results show that the main effects of all factors significantly affect the Marshall stability of hot mixtures. At 30°C and 40°C reduction in the production temperatures, both VMV and CRMB hot mixes can do this.
Marshall Mix Design Parameters of Warm Mixes with Sasobit
The bulk density of PMB and CRMB warm mixes with 2% and 3% Sasobit at a 20°C reduction in production temperature is greater than that of the control mixes at standard production temperature (0°C reduction). An air void content of 4% (as in control mixes) is achieved for warm mixes with 2% and 3% Sasobit to reduce production temperatures in the range of 20°C to 30°C. In general, it is observed that the Marshall stability of warm mixes increases with increasing Sasobit dosage and decreases with decreasing production temperatures.
Marshall stability of hot mixes with both binders is found to increase with increase in Sasobit dosage. Among all interactions, two-way interaction between binder type and RPT is found to have significant influence on Marshall stability of hot mixes.
Determination of Optimum Range for Reduction in Production Temperature for Warm Mixes
It is observed that increasing the content of the WMA additive allows greater reductions (up to 40 °C) in production temperatures and also meets the requirements for control mixes.
