Grumbein, S. et al. Hydrophobic Properties of Biofilm-Enriched Hybrid Mortar. Adv. Mater. 28, 8138–8143 (2016) [http://doi.org/10.1002/adma.201602123]
Purpose: A mortar hybrid material is presented in which biomineralization processes are stimulated by adding a biological component, i.e., bacterial biofilm, to standard mortar.
Wetting resistance of biofilm-enriched mortar samples. a) Hybrid mortar samples of different compositions are compared. At wc = 0.5, the contact angle is the highest when 2.5% (w/w) of biofilm is added. When wc is increased, the wetting resistance slightly decreases. A high wetting resistance of the hybrid mortar is also observed toward wetting with saltwater droplets (600 mM NaCl). When lyophilized biofilm is used, the wetting resistance of the hybrid samples is even higher because now larger amounts of biofilm can be added without compromising the integrity of the samples. The blue dashed line denotes the contact angle of a water droplet on polytetraflourethylen (PTFE). b) The high wetting resistance of the hybrid mortar persists over time, and for selected samples the measured contact angle remains above that measured for PTFE. The slight decrease in the measured contact angle is probably due to water evaporation from the droplets. c) Differential X-ray dark-field radiographs at time 5 s and 24 h (the radiograph obtained at time 0 was subtracted from each image) for both the unmodified and hybrid mortar during capillary uptake. The water-front moves from the bottom to the top in the unmodified mortar as indicated by the darker pixel values. Due to the increasing water content the scattering decreases in the unmodified sample. d) Quantitative analysis of the time dependence of the water uprise. The average dark-field signal per sample is shown for unmodified and hybrid mortar.