Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria
Concrete structures placed in aggressive aqueous environments are vulnerable to degradation. Majority of studies have linked structural failures to the ingress of deleterious ions into the cement matrix. Some microbial activities may accelerate the penetration of harmful materials into the cement ma...
Saved in:
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2020-01-01
|
| Series: | Advances in Materials Science and Engineering |
| Online Access: | http://dx.doi.org/10.1155/2020/4191806 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832566496171130880 |
|---|---|
| author | Onesmus Mulwa Munyao Joseph Karanja Thiong’o Jackson Muthengia Wachira Daniel Karanja Mutitu Genson Murithi Romano Mwirichia |
| author_facet | Onesmus Mulwa Munyao Joseph Karanja Thiong’o Jackson Muthengia Wachira Daniel Karanja Mutitu Genson Murithi Romano Mwirichia |
| author_sort | Onesmus Mulwa Munyao |
| collection | DOAJ |
| description | Concrete structures placed in aggressive aqueous environments are vulnerable to degradation. Majority of studies have linked structural failures to the ingress of deleterious ions into the cement matrix. Some microbial activities may accelerate the penetration of harmful materials into the cement matrix and hence cause pronounced deterioration. This work reports a laboratory-simulated study carried out to determine the extent of chloride ingress in cement mortars exposed to Acidithiobacillus thiooxidans. Test prisms were cast from Portland pozzolana cement (PPC) and ordinary Portland cement (OPC) with water-to-cement ratio maintained at 0.5. Acidithiobacillus thiooxidans bacterial solution of concentration 1.0×107 cell/mL was used to prepare microbial mortar prisms, whereas distilled water was used to prepare the control mortar prisms. The test prisms were subjected to porosity and accelerated chloride ingress after 28th day of curing. Compressive strength was determined after the 2nd, 7th, 28th, and 56th days of curing. Apparent diffusion coefficients (Dapp) were estimated from the solutions to Fick’s second law of diffusion. After the 56th day of curing, the microbial-treated mortars exhibited a significant reduction in compressive strength. The resultant percentage decrease in compressive strength was 30.74% and 19.88% for OPC and PPC, respectively. Further, microbial-treated mortars demonstrated both high porosity and chloride ingress as compared to the control test mortars. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses showed the formation of new deleterious products in the microbial-exposed mortars. |
| format | Article |
| id | doaj-art-a08abd5c94954cc49efa5940673b4a1b |
| institution | Kabale University |
| issn | 1687-8434 1687-8442 |
| language | English |
| publishDate | 2020-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Advances in Materials Science and Engineering |
| spelling | doaj-art-a08abd5c94954cc49efa5940673b4a1b2025-02-03T01:03:57ZengWileyAdvances in Materials Science and Engineering1687-84341687-84422020-01-01202010.1155/2020/41918064191806Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans BacteriaOnesmus Mulwa Munyao0Joseph Karanja Thiong’o1Jackson Muthengia Wachira2Daniel Karanja Mutitu3Genson Murithi4Romano Mwirichia5Department of Chemistry, Kenyatta University, Nairobi, KenyaDepartment of Chemistry, Kenyatta University, Nairobi, KenyaDepartment of Physical Sciences, University of Embu, Embu, KenyaDepartment of Physical Sciences, University of Embu, Embu, KenyaDepartment of Physical Sciences, University of Embu, Embu, KenyaDepartment of Biological Sciences, University of Embu, Embu, KenyaConcrete structures placed in aggressive aqueous environments are vulnerable to degradation. Majority of studies have linked structural failures to the ingress of deleterious ions into the cement matrix. Some microbial activities may accelerate the penetration of harmful materials into the cement matrix and hence cause pronounced deterioration. This work reports a laboratory-simulated study carried out to determine the extent of chloride ingress in cement mortars exposed to Acidithiobacillus thiooxidans. Test prisms were cast from Portland pozzolana cement (PPC) and ordinary Portland cement (OPC) with water-to-cement ratio maintained at 0.5. Acidithiobacillus thiooxidans bacterial solution of concentration 1.0×107 cell/mL was used to prepare microbial mortar prisms, whereas distilled water was used to prepare the control mortar prisms. The test prisms were subjected to porosity and accelerated chloride ingress after 28th day of curing. Compressive strength was determined after the 2nd, 7th, 28th, and 56th days of curing. Apparent diffusion coefficients (Dapp) were estimated from the solutions to Fick’s second law of diffusion. After the 56th day of curing, the microbial-treated mortars exhibited a significant reduction in compressive strength. The resultant percentage decrease in compressive strength was 30.74% and 19.88% for OPC and PPC, respectively. Further, microbial-treated mortars demonstrated both high porosity and chloride ingress as compared to the control test mortars. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses showed the formation of new deleterious products in the microbial-exposed mortars.http://dx.doi.org/10.1155/2020/4191806 |
| spellingShingle | Onesmus Mulwa Munyao Joseph Karanja Thiong’o Jackson Muthengia Wachira Daniel Karanja Mutitu Genson Murithi Romano Mwirichia Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria Advances in Materials Science and Engineering |
| title | Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria |
| title_full | Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria |
| title_fullStr | Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria |
| title_full_unstemmed | Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria |
| title_short | Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria |
| title_sort | chloride ingress in cement mortars exposed to acidithiobacillus thiooxidans bacteria |
| url | http://dx.doi.org/10.1155/2020/4191806 |
| work_keys_str_mv | AT onesmusmulwamunyao chlorideingressincementmortarsexposedtoacidithiobacillusthiooxidansbacteria AT josephkaranjathiongo chlorideingressincementmortarsexposedtoacidithiobacillusthiooxidansbacteria AT jacksonmuthengiawachira chlorideingressincementmortarsexposedtoacidithiobacillusthiooxidansbacteria AT danielkaranjamutitu chlorideingressincementmortarsexposedtoacidithiobacillusthiooxidansbacteria AT gensonmurithi chlorideingressincementmortarsexposedtoacidithiobacillusthiooxidansbacteria AT romanomwirichia chlorideingressincementmortarsexposedtoacidithiobacillusthiooxidansbacteria |