Cement is one of the most essential building materials worldwide, especially because the global population grows constantly and the demand for new buildings and infrastructure increases. The production of cement is very energy intensive and causes high carbon dioxide emissions, making it very harmful to the environment. To make cement more sustainable, self-healing cement can be used. It works with additives, such as bacteria, that autonomously close cracks in the cement structures by producing calcium carbonate and therefore enhances the lifespan and durability of cement structures, which saves emissions and money. Bacteria such as Bacillus subtilis and Sporosarcina pasteurii can be used as additives in self-healing cement. To simplify the method of adding those bacteria to cement, a correlation between the optical density (OD600) and cell count of both Bacillus subtilis and Sporosarcina pasteurii was determined. This allows the measurement of a certain amount of bacteria using the OD600 instead of having to count the cells as before, which is much more efficient and less time-consuming. Another approach for an additive in self-healing cement involves coralline red algae, which naturally produces calcium carbonate as well. In order to further explore that method, the coralline red algae needs to be cultivated first, to have an abundance of material to work with. Cultivation of coralline red algae was monitored for two months to optimize growth conditions and recommendations for modification of the artificial seawater media were proposed. The comparison of the cultivation media to Provasoli’s Enriched Seawater and to suggestions from an aquarium website were used to determine further adjustments for better growing conditions.  To test the ability of coralline red algae to close cracks in cement, coralline red algae powder was added to both cement and mortar prisms in different concentrations and was then documented for three months to evaluate the formation and closing of cracks. Based on that data, no correlation between the coralline red algae concentration in prisms and the closing of cracks could be determined. To further examine this method, the prisms need to be documented over a longer time period and a larger number of cracks would be useful to be able to analyze a larger amount of data.. Suggestions were developed for inducing further cracks in the prisms in order to improve the documentation of coralline red algae in cement.To further investigate coralline red algae, a DNA extraction was performed. Since it didn’t deliver the hoped-for results due to impurities in the extracted DNA, suggestions for further purification of coralline red algae were researched to improve the DNA extraction method in the future.