 Concrete mix has been reinforced with SiO 2 microcapsules to seal concrete cracks.  Great Self-healing capacity of concrete that contain SiO 2 microcapsules.  Crack of concrete with SiO 2 microcapsules was self-healed in 28 days. Cracks are a fundamental problem in concrete, so this research investigates an experimental study of the effect of adding SiO2 on the self-healing behaviour of concrete. The study is done by studying the physical properties, microstructure, and mechanical

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... of concrete. Microcapsules were prepared to contain (cement and nano SiO 2 ) in a (palettization (fluidize bed coating) method) with (5,10, and 15) % of cement weight. The ratio of the prepared concrete mixture was (1: 2: 4) and the ratio of water to cement (W / C) 0.45 by the weight of cement was also added as 0.6% Superplasticizer to all concrete mixtures. SiO2 MC is added with (2.5) % of the cement weight in the concrete mixture. In this study, porosity, density, and water absorption tests were performed to study the physical properties, compressive and bending strength to study mechanical properties. So, referring to the results, (SiO 2 MC) was used as an effective effect in the self-healing cracking mechanism, and in improving the bending strength and compressive strength. Also, 10 % wt. was recorded as the best addition because it has a positive effect on properties to be applied in construction.