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Microscopic images (ranging in magnification from 24× to 28×) of control mortar samples before and after 14 and 35 days of healing: (a) mortar samples without microcapsules; (b) mortar samples with capsules with nutrients and without bacteria spores. Here, wi is the initial crack width; wt is the crack width after healing; Hc is the calculated healing ratio. The blue arrows indicate the location where the width of the gap was measured.
