Introduction. The use of biocides in primary and secondary protection ensures prolonged biological resistance of building materials. However, assessing their potential in cement systems requires a comprehensive analysis, taking into account the alkalinity of the environment, chemical compatibility with binder components, and the selection of an effective concentration. This article presents a comparative analysis of the resistance of biocides, conserving agents, and auxiliary components to Aspergillus niger micromycete to justify their applicability for protecting cement composites from biocorrosion. Materials and methods of research. The efficiency of biocides (alaminol, polyhexamethylene guanidine hydrochloride (PHMG), food conserving agents (sodium propionate, nisin), and additional components (butylene glycol, hydroxypropyl methylcellulose (HPMC)) against the micromycete Aspergillus niger, which is highly resistant to adverse conditions, was analyzed. A series of aqueous solutions of the additives studied were used at the dosages recommended by the manufacturers. Fungicidal and fungistatic activity were assessed based on the mycelial growth inhibition zone and fungal growth rate. Results and discussion. PHMG demonstrated the highest biocidal effictiveness against Aspergillus niger, providing complete suppression of test culture growth across the entire concentration range. The growth of the inhibition zone from 4 to 7 mm correlated with an increase in the biocide dosage from 1% to 5%. Modification of the samples with alaminol at concentrations of 5% and 8% resulted in the formation of an inhibition zone of 3-4 mm and the absence of visible mycelial growth. The remaining additives studied (sodium propionate, nisin, HPMC, and butylene glycol) did not exhibit any independent fungicidal activity under these conditions. Conclusion. The study conducted gives grounds for the perspective of using polyhexamethylene guanidine hydrochloride as an effective bioprotective agent for cement composites.