Influence of Lysinibacillus sphaericus on compressive strength and water sorptivity in microbial cement mortar

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.

Study on the effect of Thiobacillus intermedius bacteria on the physico-mechanical properties of mortars of ordinary portland cement

“…The test samples were exposed in bacteria solution for a period of 28 days. These SEM micrographs compared very well with other researcher's works already published [25,26,27,28].…”

Investigating mechanical properties and biocement application of CaCO3 precipitated by a newly-isolated Lysinibacillus sp. WH using artificial neural networks

“…Recently, an increase in cement strength of 17% was reported when using Lysinibacillus sphaericus grown with calcium acetate 54 . We remark that when using calcium acetate, strain WH could promote the compressive strength of Portland cement as high as 26.1%.…”

“…The AFt can fill in the gap of biocement and help increase the compactness of the cement 52 . Note that the peaks of biogenic CaCO 3 crystals could not be seen clearly from the XRD spectra of cement because less than 5% by weight is added in the biocement samples which is the standard amount usually used in previous literature 53 , 54 . This, however, could be beneficial in terms of saving the cost of biocement production and minimizing the effects of bacteria themselves on the biocement.…”

Bioremediation of mortar made from Ordinary Portland Cement degraded by Thiobacillus thioparus using Bacillus flexus

“…Presence of micro-cracks/voids provides a pathway for ingress of the degrading agents, such cracks can be sealed using biological methods. The metabolic conversion of calcium acetate using Bacilli bacteria has given promising results [ 1 , 2 , 3 ]. This metabolism involves the conversion of organic salt via microbial respiration to deposit calcium carbonate.…”

“…Remediation of cement based material by way of bacteria (bioremediation) has not been reported. However, the use of Microbiologically Induced Calcite Precipitation (MICP) in improving compressive strength has been reported [ 3 , 25 ], though the use of the same in bioremediation has not been documented This paper reports the use of the same in bioremediating biodegraded mortar.…”