Bio-based rheology modifying agents
Advances in construction technology increased the importance of sustainability and reinforce the use of biological admixtures. Using bio-based admixtures brings new horizons to the construction material science by improving concrete properties through a more environmentally friendly and cost-efficient approach. Generally, bio-based additives are used as viscosity modifyin agents (VMAs) in concrete mixes. Traditional bio-based VMAs are water-soluble bipolymers that can be produced from polysaccharide-based biopolymers obtained from cellulose, starch or bacterial fermentation. Through the literature, nopal mucilage, brown algae and bacterial cell walls were proposed as alternatives to these bio-based admixtures. However, these alternatives also require extra processing which results again with a higher unit cost compared to admixtures that could be directly obtained from nature, like the direct addition of cells.
The aim of this study is to improve the rheology of cement paste by incorporating Peanibacillus polymxa (P.polymxa) cells and biofilm collected from Bacillus amyloliquefaciens (EPI 60) as viscosity modifying agents (VMAs). To achieve this goal, the bacterial cells and biofilms were directly incorporated into the mix water and influence of cells on viscosity and yield strength was evaluated by rheological tests. The impact of fly ash and superplasticizer on performance of cells were also investigated. Our results showed that the apparent viscosity and yield stress of the cement-paste mix were increased with the addition of the bio-based additives. Biofilm obtained from EPI 60 cells were found to be more efficient in terms of improving rheological parameters. Moreover, both biological VMAs was found to be compatible with the use of fly ash and superplasticizers.