<p>Concrete’s inherent self-healing is limited by water availability and unhydrated particles. This study developed a novel self-healing system that overcomes this limitation through the synergistic combination of magnesium oxide expansive agent (MEA) and superabsorbent polymer (SAP). This study investigated the mechanical and self-healing properties of pre-damaged concrete with the addition of MEA and SAP. The effects of different dosages of MEA (0%, 4%, 8%, 12%) and SAP (0%, 0.5%) on the mechanical properties of the concrete were investigated by compressive strength tests and flexural strength tests. The self-healing effects and mechanisms of the concretes pre-damaged by various percentages of their peak strength were systematically analyzed by capillary water absorption experiments, ultrasonic pulse velocity (UPV) experiments, and microscopic observations. It was found that the compounded concrete had better mechanical properties compared with that mixed with MEA alone, whose 28d compressive strength and flexural strength were improved by 18.2% and 13.4%, respectively. Moreover, the compound concrete demonstrated enhanced cracking self-healing ability although it is related to the degree of pre-damage. The self-healing ability of the compounded concrete pre-damaged by 60% of its peak strength was the best, whose recovery rate of 14d and 28d compressive strengths reached 81.98% and 95.37%, respectively, whose capillary water absorption rate was close to that of undamaged concrete, and whose UPV recovery rate increased by up to 59.43%. Microstructural analysis revealed that the synergy enabled the formation of dense, well-bonded CaCO₃, magnesium carbonate hydrate, and calcium-magnesium complexes in cracks. This research demonstrates that the MEA-SAP combination provides an effective self-healing capability for resilient concrete infrastructure.</p>