Title: Evaluation of Mechanical Properties of Bacteria- Containing Mortar in Seawater Environment
Author(s): Davood Mostofinejad, Farzaneh Nosouhian, and Bahareh Tayebani
Publication: Materials Journal
Appears on pages(s): 35-43
Keywords: compressive and flexural strengths; microbial carbonate precipitation; mortar; seawater; tensile strength
Microbial carbonate precipitation (or biodeposition) has been widely studied for use in characteristics improvement and selfhealing of concrete and mortar of cementitious materials. The presence of a calcium source contributes to the formation of calcite (CaCO3), which is a key component in the biode-position process. The current study is aimed at benefiting from the available calcium ion in seawater as a calcium source in the biode-position of marine structures. To this end, four different bacteria strains were cultured and added to the mortar mixture for making bacteria-containing mortar specimens. The specimens consisted of six groups of 50 x 50 x 50 mm mortar cubes, 40 x 40 x 160 mm (1.57 x 1.57 x 6.3 in.) mortar prisms, and conventional mortar briquettes, all of which were cured in seawater. The effects of the exposure to seawater were mechanically investigated at different mortar ages in terms of their compressive, flexural, and tensile strengths and compared with control specimens made with no bacteria and cured in water. The experimental results represented an increase of 97% and 101%, respectively, in compressive and flexural strengths of mortar specimens containing Bacillus subtilis and cured in seawater at 28 days. It was found that the specimens cast and treated with Bacillus sphaericus exhibit a rise of approximately 72% in tensile strength. Therefore, it was concluded that treated mortar with bacteria and cured in seawater may enhance the mechanical properties of mortar, which can be a beneficial development in marine structures. The use of such bacteria strains in concrete technology, specifically in inshore structures, can eliminate the destructive effects of the coastal environment.