In the last decade, biological additives have gained increased attention as admixtures to cement based materials. One example are bacterial additives, which can improve the wetting resistance and/or the mechanical properties of cementitious materials. However, the production process of most bacterial additives investigated so far is typically time consuming and comparably expensive. Here, we investigate six different commercially available bacterial spores as an alternative bacterial additive to mortar and characterize the wetting resistance, capillary water uptake, and mechanical properties of the resulting hybrid mortar formulations. Our results imply that selected bacterial spores are indeed able to enhance the water-resistance of mortar; however, compared to other bacterial additives such as biofilm, the overall performance of the resulting hybrid material is decent but still inferior. © 2021 Elsevier Ltd     «

In the last decade, biological additives have gained increased attention as admixtures to cement based materials. One example are bacterial additives, which can improve the wetting resistance and/or the mechanical properties of cementitious materials. However, the production process of most bacterial additives investigated so far is typically time consuming and comparably expensive. Here, we investigate six different commercially available bacterial spores as an alternative bacterial additive to...     »