Abstract:
Cement structures are subject to degradation either by aggressive media or development of micro/macro cracks
which create external substance ingress pathways. Microbiocementation can be employed as a self-intelligent
solution to this deterioration process. This paper presents study results on the effects of Lysinibacillus sphaericus
microbiocementation on Ordinary Portland cement (OPC), normal consistency, setting time, soundness,
compressive strength and water sorptivity. Microbial solutions with a concentration of 1.0 107 cells/ml were
mixed with OPC to make prisms at a water/cement ratio of 0.5. Mortar prisms of 160 mm 40 mm x 40mm were
used in this study. A maximum compressive strength gain of 17% and 19.8% was observed on the microbial prism
at the 28th and 56th day of curing respectively. A minimum of 0.0190 and a maximum of 0.0355 water sorptivity
coefficient was observed on the OPC microbial prism and OPC control prism, after 28th day of curing respectively.
Scanning electron microscope images taken after the 28th day of curing showed formation of vast calcium silicate
hydrates and more calcite deposits on microbial mortars. Statistical findings of this study indicate that Lysinibacillus
sphaericus significantly retarded both the setting time and normal consistency, but has no influence on the
mortar soundness.
