Identifiability of environmental coefficients in a crack healing model for bioconcrete

The object of research is the estimation of environmental coefficients for predicting crack closure in bacteria-modified cementitious materials. This work aims to determine which published measurements support temperature, humidity and pH coefficients without mixing different healing metrics. Method. Five temperature-dosage series and three humidity intervals were reanalysed with an exponential residual-state model. Local rate constants were separated from reference-based environmental multipliers; a Gaussian temperature response was assessed within the observed range. Results. For four series with the same reported bacterial dosage, normalised temperature coefficients were 1.000, 0.585, 0.222 and 0.255 at 24, 0, -16 and -24 °C, respectively. The fitted response width was 24.77 °C, with a normalised residual root mean square of 0.0695. The response was nonmonotonic at the two lowest temperatures. Lower-bound humidity surrogates were 0.383, 0.785 and 1.000, but their area-based definition and dependence on cracking age precluded transfer to crack-width kinetics. No transferable pH coefficient was established. Results. Environmental factors require a documented calibration metric, a reference regime and an independent validation series. The results support bounded secondary-data interpretation rather than a universal temperature-humidity-pH law.

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