TY - JOUR
T1 - Bacterial Self-Healing Performance of Coated Expanded Clay in Concrete
AU - Han, Sanghyun
AU - Jang, Indong
AU - Choi, Eun Kyung
AU - Park, Woojun
AU - Yi, Chongku
AU - Chung, Namhyun
N1 - Funding Information:
This study was supported by a Grant (19SCIP-B103706-05) from the Construction Technology Research Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government.
Publisher Copyright:
© 2020 American Society of Civil Engineers.
PY - 2020/7/1
Y1 - 2020/7/1
N2 - Concrete crack healing by microbial calcium carbonate producers has been intensively studied for the last 10 years. To overcome the harsh environments of concrete, various carriers have been tested for their ability to protect the healing bacteria. Using expanded clay (EC) as a carrier is attractive because it provides adequate bond strength to the cement composites as well as protection to the bacteria from harsh environments. In this study, self-healing performance by EC was examined using styrene-Acrylic emulsion coatings. First, the presence of bacteria (Lysinibacillus boronitolerans YS11) within EC was verified using electron microscopy after the bacteria were immobilized. Although coating has a negative effect on the preservation of bacterial density under normal conditions, the bacterial density was higher for coated EC [5.0×104 colony forming unit (CFU)/g of EC] than for uncoated EC (2.4×103 CFU/g of EC) when exposed to a harsh environment (60°C and pH 12) for 48 h. This suggests that coating the surface of EC was successful in protecting bacteria from the environmental stressors. Even though bacteria were within the EC, the bacterial survival rate quickly declined with time inside the mortar. However, the bacterial density was much higher for coated than for uncoated EC at day 28, suggesting that the coating provides the bacteria with excellent protection from the harsh environment within the mortar. The concrete healing rates were 70% for uncoated EC and 75% for coated EC, compared to the healing rate of 50% and 42% for plain mortar and mortar with empty EC, respectively. These results suggest that the healing rate has increased with EC containing bacteria.
AB - Concrete crack healing by microbial calcium carbonate producers has been intensively studied for the last 10 years. To overcome the harsh environments of concrete, various carriers have been tested for their ability to protect the healing bacteria. Using expanded clay (EC) as a carrier is attractive because it provides adequate bond strength to the cement composites as well as protection to the bacteria from harsh environments. In this study, self-healing performance by EC was examined using styrene-Acrylic emulsion coatings. First, the presence of bacteria (Lysinibacillus boronitolerans YS11) within EC was verified using electron microscopy after the bacteria were immobilized. Although coating has a negative effect on the preservation of bacterial density under normal conditions, the bacterial density was higher for coated EC [5.0×104 colony forming unit (CFU)/g of EC] than for uncoated EC (2.4×103 CFU/g of EC) when exposed to a harsh environment (60°C and pH 12) for 48 h. This suggests that coating the surface of EC was successful in protecting bacteria from the environmental stressors. Even though bacteria were within the EC, the bacterial survival rate quickly declined with time inside the mortar. However, the bacterial density was much higher for coated than for uncoated EC at day 28, suggesting that the coating provides the bacteria with excellent protection from the harsh environment within the mortar. The concrete healing rates were 70% for uncoated EC and 75% for coated EC, compared to the healing rate of 50% and 42% for plain mortar and mortar with empty EC, respectively. These results suggest that the healing rate has increased with EC containing bacteria.
KW - Bacterial biomineralization
KW - Coating
KW - Expanded clay
KW - Permeability experiment
KW - Self-healing concrete
UR - http://www.scopus.com/inward/record.url?scp=85087388262&partnerID=8YFLogxK
U2 - 10.1061/(ASCE)EE.1943-7870.0001713
DO - 10.1061/(ASCE)EE.1943-7870.0001713
M3 - Article
AN - SCOPUS:85087388262
SN - 0733-9372
VL - 146
JO - Journal of Environmental Engineering, ASCE
JF - Journal of Environmental Engineering, ASCE
IS - 7
M1 - 04020072
ER -