USE OF MICROORGANISMS TO IMPROVE RHEOLOGY OF CEMENT-BASED MATERIALS

Author(s): Mahzad Azima, Arda Sepetçi, Şeyma Gürel and Zeynep Basaran Bundur
Paper category: Proceedings
Book title: Proceedings of the Final Conference of RILEM 253-MCI Microorganisms-Cementitious Materials Interactions Volume II
Editor(s): Alexandra Bertron and Henk Jonkers
ISBN: 978-2-35158-207-7 (Set)
ISBN: 978-2-35158-210-7 (Volume 2)
e-ISBN: 978-2-35158-206-0
Publisher: RILEM Publications SARL
Publication year: 2018
Pages: 551-558
Total Pages: 308
Language : English

Abstract: Recent development in concrete technology enabled the design of concrete or mortar mixes having high flowability and improved workability. These flowable mixes require incorporation of fine materials or viscosity modifying agents (VMA) to reduce the possible segregation and bleeding due to the use of high range water reducers. The VMAs used in concrete production are generally produced from acrylic polymers and polysaccharide-based biopolymers obtained from cellulose, starch or bacterial fermentation. Biological polysaccharides obtained by fermentation of genetically modified bacteria or using plant cell walls can also be used as VMAs. Advances in construction technology and risen importance of sustainability initiatives reinforce the use of biological admixtures; however, their relatively high costs can be a major drawback in practical applications. Through the literature, nopal mucilage, brown algae, and bacterial cell walls were proposed as alternatives to these bacterial fermentation products. However, these alternatives also require extra processing, which results in a higher unit even compared to bacterial fermentation products. In this study, the microorganisms were incorporated into the cement-based mix as VMAs without any extra intervention. Sporosarcina pasteurii and Paenibacillus polymyxa were grown in specified nutrient media and then collected from the inoculum by centrifuging. Then, these cells were suspended in mixing water separately and their influence on the rheology of cement paste was evaluated. In addition, the influence of water to cement ration, the number of cells added were tested along with the impacts of superplasticizers and fly ash on the bacterial VMA. Our results showed that the apparent viscosity and yield stress of the cement-paste mix were increased with the addition of the microorganisms regardless of w/c. Moreover, the provided biological VMA was found to be compatible with the use of fly ash and superplasticizers.

Online publication : 2018
Publication type : full_text
Public price (Euros) : 0.00