Cement is widely used as a construction material in the construction industry. However, there are challenges affecting its durability efficacy. Cement mortar/concrete is subject to degradation by aggressive ions such as sulphates and chlorides. Sulphates can be introduced into the concrete or mortar by Sulphur producing bacteria of the species
Thiobacilli.
Microbiologically induced CaCO
3
precipitation (MICP) has found its application in bioremediating cement based materials. It has been found to be environmental friendly. However, no work has been reported on bioremediation of biodegraded cement based materials. This paper presents findings of possible bioremediation of mortars after undergoing biodegradation.
Bacillus flexus,
a beneficial bacterium was used. The control mortars were prepared using Ordinary Portland Cement (OPC). The test mortars were prepared and cured in a solution of
Thiobacillus thioparus,
a Sulphur oxidizing bacteria, deleterious bacterium for 14, 28, 56 and 90 days. Compressive strength analysis was conducted on the 14
th
, 28
th
, 56
th
and 90
th
day of curing. Results showed that the lowest compressive strength was recorded on the 90
th
day as 31.02 MPa. This was a 34.17 % loss in compressive strength. Another category of mortar cured in
Thiobacillus thioparus
for 28 days was bioremediated for 28 days using
Bacillus flexus
solution. Compressive strength and Scanning Electron Microscopy (SEM) analyses were then done. The results show a compressive strength of 45.83 MPa at the 56
th
day. This represents a 99.91 % strength recovery from biodeterioration. The SEM analysis results revealed a denser material. This was due to massive precipitation of calcium carbonate in the mortar matrix and pores/voids for bioremediated mortars as opposed to the biodegraded mortars. The results further revealed reduced ettringite crystals on the bioremediated mortars.
Bacillus flexus
could perhaps be used in restoring lost compressive strength as well as in sealing voids in degraded concrete in sewer lines and other cement based materials. This could improve on its efficacy with minimal repair.