Cleaning of concrete fouled by lichens with the aid of Thiobacilli

Title: Cleaning of concrete fouled by lichens with the aid of Thiobacilli
Author(s): B. De Graef, W. De Windt, J. Dick, W. Verstraete, N. De Belie
Paper category : journal
Serial title: Materials and Structures
Abreviated Serial title: Mater. Struct.
ISSN: 1359-5997
Publisher: RILEM Publications SARL
Volume: 38
Issue: 284
Issue date: 2005-12-01
Publication year: 2005
Pages: 875 - 882
Total Pages: 8
Nb references: 39
Language: English

Abstract: Concrete specimens weathered for over a decade in the moderate Belgian climate, showing a black organic outer layer that mainly consisted of lichens, were cleaned with a new biological technique.
In this technique, a mixture of sulphur oxidising bacteria of the genus Thiobacillus supplemented with an appropriate nutrient is applied to a fouled concrete surface, either by sprinkling or by submersion.
The aim of the cleaning technique was to remove the fouled layer in such a way that the surface is uniformly cleaned.
The general effect of the technique was evaluated by colorimetry and microscopy.
Two sets of weathered concrete samples, containing blast furnace slag cement or ordinary portland cement, were investigated.
The effectiveness of the technique depended on the cement type of the concrete samples.
The effect on the ordinary portland cement concrete samples was in some cases up to 100% stronger than the result on the blast furnace slag cement samples.
The sprinkling treatment was about 50% as effective as the submersion treatment.
A side effect was the formation of a gypsum layer on some of the specimens, resulting in a whiter colour.

Online publication: 2005-06-06
Classification: Scientific Reports
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/14254