Urban structure degradation caused by growth of plants and microbial activity

E Mejía,J I Tobón,W Osorio

doi:10.3989/mc.2019.09517

Abstract

The purpose of this study was to isolate microorganisms associated to surface-affected concrete structures and to measure the in vitro dissolution of concrete based on the release of elements such as calcium and silicon. Although many microorganisms were detected only a fungus was capable of significantly decreasing the culture medium pH and releasing both elements. The molecular characterization allowed to identify the microorganism as Aspergillus carbonaurius, a citric-acid producing fungus that dissolved concrete in the in vitro test. After seven days of incubation, the soluble calcium concentration in the uninoculated culture medium containing concrete was 172.3 mg/L, while in the inoculated medium it was 525.0 mg/L. The soluble silicon concentration in the uninoculated medium was 10.3 mg/L, while in the inoculated medium it was 50.1 mg/L. These findings showed that plants and microorganisms rendered a synergistic effect accelerating the biodeterioration of concrete.

Highlights

The purpose of this study was to isolate microorganisms associated to surface-affected concrete structures and to measure the in vitro dissolution of concrete based on the release of elements such as calcium and silicon
This work helps to understand the combined role of Aspergillus carbonarius and higher plants, established in urban structures, on the concrete dissolution
From all the isolated microorganisms in urban structures, only one was capable of acidification, and this was identified as Aspergillus carbonarius which can colonize urban structures, and induce deterioration by producing organic acid

Summary

Introduction

The purpose of this study was to isolate microorganisms associated to surface-affected concrete structures and to measure the in vitro dissolution of concrete based on the release of elements such as calcium and silicon. The soluble silicon concentration in the uninoculated medium was 10.3 mg/L, while in the inoculated medium it was 50.1 mg/L These findings showed that plants and microorganisms rendered a synergistic effect accelerating the biodeterioration of concrete. These factors play an important role in mass loss processes, discoloration, and structural cracking [5] In this way, it is important to know that microorganisms are considered the oldest forms of life, capable of living in hostile environments [6], and they may influence weathering processes [7] by catalyzing various reactions [8] as secretion of enzymes and corrosive metabolites e.g., acids that can react with the binding material of concrete surface [9]. The protons react with cementitious material resulting in further functional or structural problems [1, 17]

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