Self-Healing Analysis of Half-Warm Asphalt Mixes Containing Electric Arc Furnace (EAF) Slag and Reclaimed Asphalt Pavement (RAP) using a Novel Thermomechanical Healing Treatment.

José Manuel Lizárraga,Juan Gallego

doi:10.3390/ma13112502

Abstract

Nowadays, the self-healing of asphalt pavements promoted by microwave radiation heating energy is gaining attention and strength in the scientific community. However, most of these studies are only conceptual and, thus, remain shrouded in uncertainty regarding technology development, economy, and application effect. Therefore, there are several efforts underway to offer more effective assisted healing treatments that are capable of overcoming such uncertainties. This paper aims to assess and quantify the healing performance rates (HR) of half-warm recycled asphalt (HWRA) mixtures containing electric arc furnace (EAF) slag and total recycled asphalt pavement (RAP) rates. To this end, a novel assisted thermomechanical healing treatment (i.e., a recompaction-based technique and microwave heating energy) was put forward to promote the potential healing effect of this treatment on the mechanical properties of the asphalt mixtures. In order to do this, three microwave heating temperatures (25 °C, 60 °C, and 80 °C) and three mechanical recompaction levels (0, 25, and 50 gyrations) were selected. After that, the healing performance rates (%, HR) of the asphalt mixtures were calculated by repeated indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM). The results indicated that the 8% EAF slag mixture was found to provide significant microwave heating energy savings by up to 69% compared with the benchmark 100% RAP mixture, and, at the same time, it experienced a remarkable stiffness recovery response of 140% of the initial mechanical properties. These findings encourage greater confidence in promoting this innovative thermomechanical-based healing treatment for in-situ surface course asphalt mixtures of road pavements.

Highlights

Asphalt concrete (AC) mixtures are typically exposed to repeated heavy traffic loading cycles and premature fracture failures caused by thermomechanical surface distress that triggers the appearance of different ways of cracking, causing a significant decrease in the mechanical properties and durability of the asphalt mixtures over time [1,2,3]
One can say that the average internal cohesion values shown by the steel slag and recycled mixtures were found to meet the minimum in-dry indirect tensile strength (ITSdry > 1.7 MPa) values stipulated by the Spanish technical specifications, according to Art. 20 of PG-4 “Cold in-place recycling of bituminous mixtures with bitumen emulsion” [79]
A novel assisted healing treatment was launched and put into practice to quantify the healing performance rates arising from the mechanical performance properties of half-warm recycled asphalt (HWRA) mixtures containing three electric arc furnace (EAF) steel slag contents

Summary

Introduction

Asphalt concrete (AC) mixtures are typically exposed to repeated heavy traffic loading cycles and premature fracture failures caused by thermomechanical surface distress that triggers the appearance of different ways of cracking, causing a significant decrease in the mechanical properties and durability of the asphalt mixtures over time [1,2,3]. Some examples of self-healing asphalt pavement technologies commonly mentioned in the literature review that possess the potential to reverse the fracture failure process and restore the loss in the mechanical performance properties (e.g., stiffness and strength) and functionality suffered by the asphalt pavements during their service life include (but are not limited to these solutions): (1) Encapsulated chemical products containing rejuvenator oil agents to repair broken bonds due to the accumulated micro-crack damage caused by the fatigue cracking process [15,16,17]; (2) magnetic induction heating technique in combination with conductive materials (e.g., steel wool, steel fibers, metal particles, carbon black, and graphite) to speed up the asphalt healing process [18,19,20,21,22,23]; (3) infrared heating technique [24,25,26]; (4) microwave radiation heating energy in combination with ferrous particle aggregates (EAF slag) in order to accelerate the heating and healing capability of the asphalt mixtures [27,28,29,30]; (5) the addition of Nanomaterials into the asphalt mixture design, such as carbon nanotubes (CNTs), carbon black nanoparticles (CBNPs), and graphene nanoplatelets (GNPs); the GNPs nanoparticles especially improve the resistance to permanent deformation, moisture damage, skid resistance [31], flexural strength at low temperatures, and increase the cohesion recovery ratios of the mixtures [32]; and (6) industrial microwave heating applications through a mobile microwave power unit for pavement maintenance works [33,34], with emphasis being placed on recycling techniques for surface layers [35]

Objectives

Results

Conclusion