Self-healing mortar using different types, content, and concentrations of bacteria to repair cracks.

Abstract

The creation of cracks, which are the most common cause of structural failure, has a significant impact on the structure's strength and durability. As a result, effective repair and maintenance are vital and unavoidable for treating any of these issues. Self-healing mortar holds promising benefits for reducing the cost of repair as cracks are autonomously repaired without any human intervention. This study investigated the effect of bacteria type, bacteria content, bacteria concentration, and nutrient type on the properties of the self-healing mortar. Three types of bacteria, Bacillus sphaericus, Bacillus Megaterium, and Bacillus subtilis encapsulated in calcium alginate beads, were introduced into the mortar. Two concentrations of bacteria, 2× 108 and 2× 109 Colony Forming Units per milliliter, and different percentages of bacteria of cement weight were selected for the study. In addition, calcium lactate and calcium acetate were used at 0.5% of cement weight as nutrition for bacteria. Tests were performed for compressive strength, bending strength, SEM, EDX, and TGA/DTG. The results show a significant development in the mechanical behaviour of mortar, especially with Bacillus Megaterium using a 2.5% bacterial proportion with a concentration 2× 109 CFU/ml. This can be related to the filling of voids and cracks in microbial mortar by calcite, which was confirmed by SEM and EDX.

Self-healing concrete techniques and performance, A review

“…• Type of micro-organisms Different types of bacteria can be used in concrete, such as anaerobic and aerobic bacteria. For aerobic bacteria, using Bacillus subtilis improved compressive strength [1,6,10,26,[77][78][79][80][81][82][83][84]. Using Bacillus pasteruii improved the strength and permeability of concrete [29,[85][86][87][88][89][90].…”

Innovative Strategies for Enhanced Concrete Durability: A Comparative Analysis of Autogenous and Autonomous Self-healing Mechanisms

“…On the other hand, the autonomous technique can heal cracks by introducing healing agents, such as microorganisms or chemicals, into the concrete matrix (Elmahdy et al 2022;Nguyen et al 2019;Nodehi et al 2022). This technique enables long-term healing using microorganisms, such as bacteria, through a process known as microbiologically induced calcium carbonate precipitation (MICP) (Balam et al 2017a;Mostofinejad et al 2021a, b;Nodehi et al 2022;Tayebani et al, 2019a).…”

“…Bacteria can affect the mechanical and durability characteristics of concrete. For the mechanical characteristics, many researchers have indicated that Bacillus subtilis bacteria have improved concrete strength (Afifudin et al 2011;Elmahdy et al 2022;Feng et al 2021;Kalhori et al, 2017;Khaliq et al, 2016;Khushnood et al 2020;Manikandan et al, 2015;Meera et al, 2016;Mostofinejad, Karimi, et al, 2022;Nguyen et al 2019;Sahoo et al 2016;Saleem et al 2021;Zahran et al 2014). Also, Bacillus pasteruii enhanced the strength (Achal et al 2010;Babu et al, 2016;Chahal et al 2012;Goyal et al, 2015;Jagannathan 2018;Ramakrishnan et al 2005;Ravindranatha et al 2014).…”

Effects of Five Sources of Mixing Water on Durability of Concrete

“…That might be ne in a controlled lab (though low slump never is) but get it to site and the contractor can't place and compact it resulting in a non durable structure due to voids or possibly uncontrolled water addition [10]. Concrete mix design is successful only if it satis es all of its performance criteria like workability, cohesiveness, strength and durability [11]. If anyone among them is missed, it's not work.…”