Urban structures are naturally degraded by climatic activity, saline environments and microorganisms.The last of these accelerates dissolution processes, thus generating pathologies such as the darkening of concrete and the loss of mass.The purpose of this study was to isolate microorganisms from concrete structures where these types of pathologies were evident and to measure in vitro dissolution of concrete based on the liberation of elements such as calcium.With the objective of confirming microbial effects on concrete, a bioacidulation process was performed with Aspergillus niger, which has been previously found in materials exhibiting these pathologies.After seven days of incubation, it was found that the concentration of calcium in the uninoculated culture mediums was 172.3 mg L-1, while in the inoculated mediums it was 525.0 mg L-1.These findings are important because they confirm that microbial activity is a determining factor in the degradation of urban structures.This should be taken into consideration in maintenance and protection programs for these structures.