Use of Bacteria Externally for Repairing Cracks and Improving Properties of Concrete Exposed to High Temperatures

Crystals

Bijan Samali¹  Saied Jalil Hosseini²  Milad Nimafar³  Alireza Akhlaghi⁴ 

[1] Centre for Infrastructure Engineering, School of Engineering, Design and Built Environment, Western Sydney University, Sydney 47360263, Australia;Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad 8514143131, Iran;Department of Engineering, Shahid Ashrafi Esfahani University, Isfahan 8179949999, Iran;Postdoctoral Fellow, Department of Civil Engineering, Isfahan University of Technology (IUT), Isfahan 8415683111, Iran;

关键词: concrete;    heat;    crack repairing;    bacteria;    compressive strength;   

DOI  :  10.3390/cryst11121503

来源: DOAJ

【 摘 要 】

The current paper presents the results of an experimental study on the application of calcium carbonate precipitation bacteria as a new approach to repairing damaged concrete when exposed to high temperatures. To do so, cylindrical and cubic concrete specimens were initially exposed to heat in a furnace for 1 h, after reaching two different temperatures of 600 and 800 °C. A heat rate of 5.5 °C per minute was used to achieve the target temperatures. Then, two types of bacteria, namely Sporosarcina pasteurii and Bacillus sphaericus, with cell concentration of 10⁷ cells/mL, were utilized externally, to repair the thermal cracks, enhancing the mechanical properties and durability of the damaged concrete. The efficiency of the bacterial remediation technique was then evaluated through compressive strength, ultrasonic pulse velocity (UPV), and electrical conductivity tests on the control specimens (unexposed to heat), and those exposed to high temperature with or without bacterial healing. The experimental results demonstrate that the compressive strength of the test specimens exposed to temperatures of 600 and 800 °C decreased by about 31–44% compared with the control ones. However, compared to those damaged at 600 and 800 °C, the compressive strength of specimens repaired by the S. pasteurii and the B. sphaericus showed increases of 31–93%. This increase is associated with the precipitation of calcium carbonate in the deep and superficial cracks and pores of the damaged specimens. Furthermore, the ultrasonic pulse velocity of the specimens subjected to bacterial remediation had a significant increase of about 1.65–3.47 times compared with the damaged ones. In addition, the electrical conductivity of repaired specimens decreased by 22–36% compared with the damaged specimens.

【 授权许可】

Unknown