Criteria for assessing bioconcrete recovery after repeated crack opening

The object of research is the recovery of bacterial cementitious materials after repeated crack opening. This work aims to develop an assessment procedure that combines crack-width measurements, sequential forecast validation, and functional indicators. Method. Three published second-loading crack-width series were normalised by their initial openings and analysed using local exponential fitting and expanding-window validation. Five recovery indicators from a separate mortar study were compared at matched observation times. Results. Crack-width reduction at 21 days after second loading was 89.47, 83.33 and 82.22%. The fitted rate constants ranged from 0.8 745 to 0.10 595 d-1, with R² values of 0.9425−0.9765. Nine next-observation forecasts yielded normalised mean absolute and root mean square errors of 0.6 934 and 0.7 712, equivalent to 0.5 116 and 0.5 799 mm. In the separate functional block, surface closure and ultrasonic recovery at 28 days were 96.0636 and 67.7680%, respectively, with a difference of 28.2956 percentage points. The proposed procedure records a new baseline for each cracking cycle, estimates local kinetics, checks the next observation, and assigns functional tests according to the intended performance of concrete products.

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