Assessment of the Self-Maintenance Property of Asphalt Concrete Pavement through the 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. Implication of 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 (hydrated lime, and coal fly ash) have been implemented as partial replacement of mineral filler, while silica fumes were used as additive to asphalt binder. 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 using 0.1second have sine loads followed by 0.9 second of rest periods. Damage accumulation in the specimens was monitored through the changes of stiffness and deformation. Testing was performed to cause micro damage to the specimens, and the load was terminated before macro cracking began. Beam specimens were subjected to load repetitions at 20° C. then beams were stored 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, 16.5, 401, and 268) % for control, lime-modified, silica fumes modified, and fly ash modified mixtures respectively as compared with the case before healing. The permanent deformation of asphalt concrete decline by (30, and 38) % for silica fumes treated mix and lime treated mix respectively after healing. The flexural stiffness of asphalt concrete after 100 repetitions increases by (5.2, 7.16, 4.13, and 1.38) folds after healing for (control, lime treated, silica fumes treated, and fly ash treated) asphalt concrete mixtures respectively. The flexural stiffness at failure increases by (5.02, 1.8, 4.9, and 0.5) folds after healing for (control, lime treated, silica fumes treated, and fly ash treated) asphalt concrete respectively. Keywords: asphalt concrete; flexural stiffness, crack healing; deformation; fatigue life; load repetitions.