Method for obtaining microbial samples from concrete and its effects on microbial community structure

The anticipated acceleration of labor shortages suggests that the maintenance and management of aging buildings may increasingly fall to custodians without specialized knowledge. The purpose of this study is to propose a method for detecting microorganisms on the surface and interior of concrete and to address relevant issues, with the aim of estimating the deterioration state of concrete materials based on the types, quantities and composition ratios of present microorganisms. This study includes a review of existing methods and findings on microbial community structures in the surface and interior layers of concrete. DNA extraction and high-throughput sequencing were conducted on samples obtained from raw concrete materials, hardened concrete, and concrete subjected to accelerated neutralization tests using various methods. Microbial community structures were found to differ among the raw materials (cement powder, gravel, sand and water). In the concrete samples, phyla such as Proteobacteria, Actinobacteria, and Cyanobacteria were detected, consistent with the previous studies. It was observed that the microbial community structures of the surface and interior, and those within the interior itself differed, indicating limited microbial movement between these regions. Although methods for investigating microbial communities of concrete are not yet well-established, understanding microbial compositions may provide insights into deterioration mechanisms and support the development of more effective maintenance strategies. • 16S rRNA sequencing analyzed microbes in raw materials and concrete (surface/interior). • Microbial communities in concrete differ between surface and interior regions. • Raw materials shaped concrete microbiota; hardened samples showed reduced diversity. • Core drilling heat had little effect on microbial community structure. • Dominant phyla in concrete included Proteobacteria and Actinobacteria.