The ingress of water into mortar and concrete is an ongoing problem which can reduce the lifetime of cementitious structures. Commonly used approaches that aim at preventing water ingress mainly employ an additional surface treatment after the casting process. Thus, they are time-consuming and make use of synthetic, nonsustainable additives. In contrast, it was shown recently that a biological material, i.e., a bacterial biofilm generated by B. subtilis 3610 bacteria, can be used as a bulk additive which leads to hybrid mortar with increased wetting resistance. Here, we demonstrate that a similar enhancement of the water resistance of mortar can be achieved by using different bacterial additives, i.e., wet biofilm, freeze-dried biofilm powder, and bacterial suspensions, each of which can be produced by one of three selected variants of B. subtilis bacteria. We characterize the mechanical properties of the different hybrid mortar variants regarding their setting behavior, tensile and compressive strength, and density. Our results imply that bacterial additives could be an eco-friendly and sustainable alternative to existing synthetic mortar additives.     «

The ingress of water into mortar and concrete is an ongoing problem which can reduce the lifetime of cementitious structures. Commonly used approaches that aim at preventing water ingress mainly employ an additional surface treatment after the casting process. Thus, they are time-consuming and make use of synthetic, nonsustainable additives. In contrast, it was shown recently that a biological material, i.e., a bacterial biofilm generated by B. subtilis 3610 bacteria, can be used as a bulk addit...     »