DEVELOPMENT OF SELF-HEALING MECHANISMS FOR ASPHALT PAVEMENTS

Evaluation of the self-healing microcapsules showed that the mixtures containing the produced microcapsules had a lower healing efficiency in both environmental curing conditions. The self-healing experiment conducted to evaluate the strength recovery of the produced fibers showed an improvement both at room and at high temperature of the mixtures prepared with unmodified binder containing recycled materials with the addition of fibers.

INTRODUCTION

Problem Statement
Objectives
Scope
Research Approach
References

The evaluation of the prepared HMA mixtures at high temperature will be characterized using a loaded wheel tracking test (LWT). Samples for each of the asphalt mixtures evaluated will be exposed to different dry temperature conditions.

LITERATURE REVIEW

Introduction

In addition, the expected service life of asphalt roads can be achieved by carrying out the appropriate design and construction process, as well as maintenance and rehabilitation treatments. According to the World Bank Pavement Deterioration Model, the cost of rehabilitating a new road can be four times the cost of maintaining the road in good condition if an asphalt road is allowed to deteriorate [2].

Asphalt Binder

Cutback asphalt is liquid asphalt produced by adding a petroleum solvent to lower the viscosity of the asphalt cement. The maltene component of the asphalt binder is divided into nitrogen bases as follows: first acidiffins, second acidiffins and paraffins.

Figure 0.2. Composition of Crude Oil [9]

Asphalt Mixture Performance Tests

The consequence of the reduction of pavement properties is the influence of the oxidation process on the binder, as the binder becomes more rigid and brittle [18]. The viscosity and elastic properties of binders are affected by changes in the composition of the binder that occur during the oxidation process [19].

Figure 0.3. Stress-Strain Relationship under Sinusoidal Load 2.3.2 Loaded Wheel Tracking (LWT) Test

Sustainable Pavement Technology

The performance parameters evaluated in the study consisted of rutting resistance, fatigue and thermal cracking. The rut performance of the evaluated mixtures was determined using an asphalt pavement analyzer (APA).

Table 0.1. Quality Acceptance Summary of Four Section [52]

Asphalt Rejuvenation

However, the rut depth of the WMA mixture with the foam technology was still acceptable according to the APA test. The purpose of the study was to determine whether these rejuvenators had the ability to restore the aged binder properties.

Self-Healing Technology in Asphalt Pavement

Studies have shown that the self-healing efficiency of asphalt concrete is dependent on temperature. The study concluded that as a result, an increase in the fatigue life extension ratio was observed due to the induction heating of the samples.

Table 0.3. Biomimetic Self-Healing Inspiration in Novel Self-Healing Materials [69]

Microcapsules Synthesis

The choice of microencapsulation procedure depends on the type of base material and the physical properties of the microcapsules. Also, the shell material, morphology and particle size will influence the selection of the microencapsulation procedure [89].

Figure 0.17. Schematic of Microcapsule [89]

Fibers Synthesis

However, the viscosity of the alginate solution increases with higher molecular weight, which makes it difficult to dissolve a high concentration of alginate. As mentioned in the previous section, the viscosity of the alginate solution increases with increasing concentration.

Figure 0.22. Schematic Diagram of Wet Spinning Procedure [110]

Wagner, "Use of Recycled Asphalt Pressure in Hot Mix Asphalt Superpave," Journal of the Transportation Research Board 1681, 1999. Lynn, "Evaluation of Roofing Shingles in Hot Mix Asphalt," Journal of Materials in Civil Engineering, p.

PERFORMANCE OF ASPHALT REJUVENATORS IN HOT MIX ASPHALT

Introduction

As a result, the use of RAS is not permitted in all US states. Another issue related to the use of RAS involves the variability and inconsistency of resources [14].

Objectives

To address the issues related to aging of the recycled material such as RAS, the use of rejuvenations has been proposed. Rejuvenator's application was used as a maintenance activity on the upper layer of the pavement to revive the oxidized upper part [13].

Background

The inclusion of a rejuvenator increased the recycled binder ratio, but also showed a detrimental effect on the intermediate and low-temperature performances of the mixture [21]. The results showed that sunflower oil partially restored the original properties of the aged binder, while the synthetic oil did not perform well [24].

Experimental Program

Experimental Test Matrix

The second blend was an HMA containing 5 wt% PCWS of the total blend, 70PG5P. Test Method for Quantitative Recovery of Asphalt Binder from Hot Mix Asphalt HMA – Method A.” AASHTO R 59, “Standard Practice for Recovery of Asphalt Binder from Solution by Abson Method,” which governed the process of distilling the solvent, was also performed.

Results and Analysis

In addition, the percentage of asphaltenes and maltenes in the extracted binders from the evaluated mixtures was determined to assess the effectiveness of the asphalt rejuvenators. In addition to the PG rating of the extracted binder mixtures, the useful temperature interval (UTI) is shown in Table 3.5.

Figure 0.2. Master Curve of Asphalt Mixtures

Conclusions

This study evaluated asphalt molecular weight distributions of extracted binder mixtures by performing HP-GPC. The addition of the commercial product Cargill 1253 restored the asphaltene/maltene ratio compared to the 70CO blend.

The characterization was performed in conventional HMA mixtures, mixtures containing 5% RAS, and asphalt mixtures containing 5% RAS with 5% asphalt rejuvenation products. Sustainable Materials for Pavement Infrastructure: Design and Performance of Asphalt Mixtures Containing Recycled Asphalt Shingles.

LABORATORY TESTING OF SELF-HEALING MICROCAPSULES IN

Introduction

Negulescu, “Laboratory Testing of Self-Healing Microcapsules in Asphalt Mixtures Prepared with Recycled Asphalt Shingles,” Journal of Materials in Civil Engineering, 2017, is reprinted here by permission of the American Society of Civil Engineers. Self-healing mechanisms would also improve the use of recycled materials such as RAS by restoring the properties of the aged binder.

Objectives

However, one of the difficulties in using a rejuvenator is that the agent must penetrate the asphalt layer to reverse the aging process of the binder [5]. Therefore, research is looking for an innovative approach to disperse the rejuvenator into the asphalt mixture, such as e.g.

Background

The results showed that the product will positively affect the high and low temperatures of the tested connectors. The study showed that vegetable oil had a positive influence on both high and low temperature degrees of aged binder.

Experimental Program

The experimental program considered the use of 5% PCWS by weight of the total mix and 5% Rejuvn8 by weight of RAS for the 70PG5Rej8 mix. In addition, the ratio of injured to healed stiffness was evaluated to determine stiffness recovery at the end of the healing period.

Results and Analysis

The analysis of the images showed that the cracks in the samples started to heal already one day after the healing period. The study performed a similar analysis for the healing state at high temperatures to assess the healing efficiency of the studied mixtures.

Figure 0.3. Double-Walled Microcapsules Containing an Asphalt Rejuvenator: (a) Undamaged Microcapsules; (b) Microcapsules After 2 H at 136°C; (c) Microcapsules After Mixing

Summary and Conclusions

The healing efficiency of the evaluated mixtures at room temperature reflected a higher healing efficiency for all mixtures than at high temperature. Furthermore, future research should evaluate the self-healing efficiency of the developed microcapsules in a full-scale asphalt pavement exposed to real traffic and environmental loads.

EVALUATION OF HOLLOW-FIBERS ENCAPSULATING A

Introduction

The proposed self-healing mechanism is promising as it will allow an asphalt pavement to resist the initiation and propagation of cracks caused by vehicular and environmental loading. Furthermore, the restoration of aged binder properties can be accomplished, resulting in an improvement in pavement performance.

Objectives

The development of polymer fibers containing a rejuvenating product will promote the use of recycled materials by restoring the properties of the aged binder and improving the properties of HMA.

Background

The use of alginate as a shell material in fibers is promising as the materials offer properties such as (1) water solubility, (2) rapid coagulation in the presence of divalent ions; and (3) adequate. Alginate has been investigated as a shell material for the production of hollow fibers containing fluid-filled vacuoles [16].

Experimental Program

The study used a scanning electron microscope (SEM-FEI QUANTA 3D FEG DUAL HAZARD SEM/FIB) to evaluate the morphology of the produced fibers. The purpose of this phase of the study was to evaluate the effects of adding sodium alginate fibers to asphalt binder mixtures containing RAS.

Table 0.1. Test Matrix for Fiber’s Optimization

Results and Analysis

The addition of 5% fibers to the asphalt binder mixtures prepared with PG 64-22 resulted in the lowest fatigue factor at 25ºC (i.e. 2,405 kPa), indicating a decrease in the susceptibility to fatigue cracking of the new binder (PG 64-22). However, Figure 5.8(a) shows that the addition of 5% fiber resulted in a reduction in the ICO index compared to Blend2.

Table 0.3. Optimization Test Results of Sodium-Alginate Fibers

Summary and Conclusions

However, an increase in the ICO index was observed in mixtures prepared with binder PG 70-22. The effect on volumetric and compaction requirements in asphalt mixtures containing the fibers will be evaluated in future studies.

With the addition of fibers in the PG 64-22 binder, a decrease in the ICO index was observed, which could be explained by the rejuvenating efficiency of the fiber core. In addition, a self-healing experiment should be performed to evaluate the healing ability and strength recovery ability of the developed fibers in the asphalt mixtures.

LABORATORY TESTING OF SELF-HEALING FIBERS IN ASPHALT

Introduction

Objectives

Background

The study concluded that the healing effectiveness of the microcapsules was dependent on the rupture of the capsules and thus the release of the core material to soften the binder around the crack. However, the study determined that the 4-point bending test was the most suitable test to evaluate the healing efficiency, since microcracks can be induced since the test is load-controlled.

Experimental Program

The results of the three-point bending test were used to calculate the strength for three main conditions (undamaged, damaged and healed conditions). After curing, a third three-point bending test was performed to evaluate the cured strength.

Results and Analysis

In contrast, Figure 6.3(b) shows that the addition of sodium alginate fibers improved the strength recovery for the asphalt mixture prepared with the unmodified asphalt. Nevertheless, Figure 6.6(b) shows that the improvement in strength recovery of the mixtures was not significantly different.

Figure 0.2. Fibers with Optimum Parameters (a) SEM Picture with 65x Magnification, (b) TGA Test Results, (c) Tensile Test Setup, and (d) UTS Test Results

Summary and Conclusions

The results of the TSRST test showed that the addition of fibers improved the load capacity of mixes containing recycled materials compared to conventional mixes. It is recommended to test the fibers developed with other types of binders and other RAP and RAS sources to evaluate their effects on the rheological properties of the binders and the improvement of the mechanical and healing properties of the mixtures.

Elseifi, "Laboratory Performance of Asphalt Mixtures Containing Recycled Asphalt Shingles," Journal of the Transportation Research Board, vol. Schlangen, "An Evaluation of the Efficacy of Split Alginate Fibers Encapsulating a Regenerant as an Asphalt Pavement Healing System," Applied Science, vol.