Self-Maintenance Property of Asphalt Concrete through Modification and Crack Healing Process

Abstract: The Asphalt cement binder usually practices ageing throughout its service life due to the environment and loss of volatiles of the binder. The asphalt cement binder will lose the required flexibility, cohesion, and its adhesion to the aggregate’s properties. Modification with additives can enhance the quality of the binder by providing the self-maintenance property through the crack healing and extend its useful service life. In the present work, slab samples of dense graded asphalt concrete were prepared using roller compaction. Two types of additives (coal fly ash, and silica fumes) have been implemented as modifiers for asphalt binder with the aid of wet process. Beam specimens were obtained from slab samples. Testing was performed under controlled strain at 20°C in an environmental chamber using dynamic flexural stresses until 50% of the stiffness was retained. The loading was applied through 0.1second followed by 0.9 second of rest periods. Damage accumulation in the specimens was monitored through the changes of stiffness and deformation. Beam specimens were stored for healing in an oven for two hours at 85° C, cooled to 20° C, then subjected to another cycles of load repetitions. Crack healing rate was determined in terms of the recovered stiffness, deformation, and increment in fatigue life. Steric hardening appeared to play a significant role in a mixture’s response during the loading and healing portions of laboratory tests. Recovered stiffness and increment in fatigue life appear to be an adequate measure of healing. It was concluded that the percent increase in fatigue life due to healing was (26, 401, and 268) % for control, silica fumes modified, and fly ash modified mixtures respectively as compared with the case before healing. The permanent deformation of asphalt concrete decline by (0.4, and 30) % for control and silica fumes treated mix respectively while the fly ash treated mixture exhibit no significant variation after healing. The flexural stiffness of asphalt concrete after 100 repetitions increases by (5.2, 4.13, and 1.38) folds after healing for (control, silica fumes treated, and fly ash treated) asphalt concrete mixtures respectively. The flexural stiffness at failure increases by (5.02, 4.9, and 0.5) folds after healing for (control, silica fumes treated, and fly ash treated) asphalt concrete respectively.