The experimental investigation delves into assessing the influence of varying ratios of calcite (Cc) and sand on the mechanical and microstructural characteristics of self-healing concrete (SHC). This study employs Hay Bacillus as a catalyst for initiating calcite precipitation within the concrete matrix. The proportions of calcite under scrutiny encompass 5%, 10%, and 15% of the cement's weight. Additionally, two distinct types of sand, crushed stone sand (CSS) and river sand (RS) are juxtaposed for comparative analysis. The primary focus of this research is on evaluating the compressive and flexural strengths of the SHC, with particular emphasis on the utilization of a 10% bacterial solution. This proportion emerged as the optimal dosage for enhancing concrete strength. To gain a comprehensive understanding of the underlying mechanisms, the microstructure of the concrete is probed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. These tests allow elucidating the impact of varying calcite and sand ratios on the formation of calcium lactate, as well as the production of calcium silicate hydrate (CSH) gel and non-expanding ettringite within the concrete matrix. This investigation contributes valuable insights into the development of self-healing concrete with improved mechanical properties, underpinned by a deeper comprehension of its microstructural transformations.