Bio-inspired self-healing cementitious mortar using Bacillus subtilis immobilized on nano-/micro-additives

2018 ◽  
Vol 30 (1) ◽  
pp. 3-15 ◽  
Author(s):  
Rao Arsalan Khushnood ◽  
Siraj ud din ◽  
Nafeesa Shaheen ◽  
Sajjad Ahmad ◽  
Filza Zarrar
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Iron Oxide ◽  
Cement Mortar ◽  
Healing Process ◽  
Main Concern ◽  
Scanning Electron Micrographs ◽  
Self Healing ◽  
Micro Cracks ◽  
Cracked Specimens

Bio-inspired self-healing strategies are much innovative and potentially viable for the production of healable cement mortar matrix. The present research explores the feasibility of gram-positive “Bacillus subtilis” microorganisms in the effective healing of nano-/micro-scale-induced structural and non-structural cracks. The main concern related to the survival of such microorganisms in cementitious environment has been successfully addressed by devising proficient immobilization scheme coherently. The investigated immobilizing media includes iron oxide nano-sized particles, micro-sized limestone particles, and milli-sized siliceous sand. The effect of induced B. subtilis microorganisms immobilized on nano-micro-additives was analyzed by the quantification of average compressive resistance of specimens (ASTM C109) and healing evaluation. The healing process was mechanically gauged by compressive strength regain of pre-cracked specimens after the healing period of 28 days. The pre-cracking load was affixed at 80% of ultimate compressive stress “[Formula: see text]” while the age of pre-cracking was kept variable as 3, 7, 14, and 28 days to precisely correlate healing effectiveness as the function of cracking period. The healing mechanism was further explored by examining the healed micro-crack using field emission scanning electron micrographs, energy dispersive x-ray spectrographs, and thermogravimetry. The results revealed that B. subtilis microorganisms contribute extremely well in the improvement of compressive strength and efficient healing process of pre-cracked cement mortar formulations. The iron oxide nano-sized particles were found to be the most effective immobilizer for preserving B. subtilis microbes till the generation of cracks followed by siliceous sand and limestone particles. The micro-graphical and chemical investigations endorsed the mechanical measurements by evidencing calcite precipitation in the induced nano-/micro-cracks as a result of microbial activity.

scholarly journals Bacillus Subtilis as Self-Healing Agent in Cement Mortar: The Effect of Curing Time and Amount of Calcium Lactate on Strength

2021 ◽  
Vol 40 (4) ◽  
pp. 889-897
Author(s):  
Sohail Muhammad ◽  
Humair Ahmed Siddiqui
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Calcium Carbonate ◽  
Cement Mortar ◽  
Calcium Lactate ◽  
Self Healing ◽  
Curing Time ◽  
Healing Agent ◽  
Cause Of Failure ◽  
The Cost

Crack growth is a major cause of failure in structures that are made using cement and concrete. Healing of these cracks can increase the life span of structures. In the present study micro-organism based self-healing of structures is studied. A commonly occurring micro-organism bacterium called Bacillus Subtilis, is used in the manufacturing of cement mortar blocks as a self-healing agent for cement mortar blocks, with the use of Calcium Lactate as feed for bacteria. In the first step, colonies of Bacillus Subtilis were grown and added with calcium lactate to produce a solution. The solution was then kept for one week to observe the metabolic product of Bacillus Subtilis. It was found that the bacterial product was composed of CaCO3 and thus the bacteria is suitable to be used as self-healing agent. Self-healing cement mortar blocks were made by adding Bacteria and Calcium Lactate with usual ingredients of cement mortar, i.e. cement, sand and water. It was found that the bacteria were also effective in converting Calcium Lactate to Calcium Carbonate, when mixed in cement mortar blocks. It was observed that the pores of cement mortar blocks were filled by Calcium Carbonate and that cracks get healed by the deposition of Calcium Carbonate in the cracks. Cement mortar blocks, with and without healing agent, were made to compare the effect of curing time. The samples were tested after seven, fourteen and twenty-eight days to compare the effect of healing agent. All the samples with the healing agent showed a higher compressive strength in comparison with the samples that were made without healing agent. Different percentages of Calcium Lactate, ranging from 1-7% were also used to find the best composition for future use. It was found that the compressive strength was increasing up to 5% while above 5% the increase was marginal thus it is proposed that Calcium Lactate should be used in between 5-7 % to reduce the cost of self-healing cement in construction industry.

scholarly journals Bacillus Subtilis as Self-Healing Agent in Cement Mortar: Combined and the Separate Effect of Bacteria and Calcium Lactate on Self-Healing Behavior in Cement Mortar

2021 ◽  
Vol 40 (2) ◽  
pp. 426-434
Author(s):  
Sohail Muhammad ◽  
Humair Ahmed Siddiqui ◽  
Muhammad Ishaque Abro ◽  
Adil Usmani ◽  
Muhammad Amjad Anwar Malik
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Cement Mortar ◽  
Surface Characteristics ◽  
Calcium Lactate ◽  
Sand Sample ◽  
Self Healing ◽  
Cement Sample ◽  
Remarkable Change ◽  
Surface Appearance

Cement mortar, which is one of the most useful materials for construction applications, can deteriorate its performance by developing cracks. In order to cope with this issue, the materials’ scientist came forward with a unique biogeochemical phenomenon in which cement mortar can selfheal its crack autonomously using calcium carbonate precipitating bacteria and their feed. In this research, it was intended to study the separate and combined effect of Bacillus Subtilis (bacteria) and Calcium Lactate (feed) on the properties of conventional mortar. Cement mortars were made using conventional method and cast in the form of cylinders. Four types of samples were taken. Sample-N contains only cement and sand, Sample-B was made by addition of bacteria Bacillus Subtilis with sand and cement, Sample-C contains Calcium Lactate which is usually used as feed for Bacteria while the last sample ‘BC’ have both Bacteria as well as Calcium Lactate. The samples were observed up to 44 days for their surface characteristics and compressive strength. The Sample-N and B did not show any remarkable change in their surface appearance with respect to curing time. Sample-C and BC did show the precipitation of CaCO3 but the Sample-C precipitation was stopped soon while for Sample-BC, the precipitation was continued for a longer time. The Sample-BC showed the highest compressive strength (approximately 17.57 MPa), followed by Sample-N (approximately 13.32 MPa), Sample-B (approximately 11.04 MPa) while Sample-C displayed lowest strength (approximately 2.75 MPa). This gives an idea that Calcium Lactate which acts as feed for bacteria has the negative effect on the strength if not consumed and converted into CaCO3.

scholarly journals Compressive strength of bacterial concrete by varying concentrations of E.Coli and JC3 bacteria for Self-Healing Concrete

2019 ◽  
Vol 9 (1) ◽  
pp. 3659-3661
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Cell Concentration ◽  
Self Healing ◽  
E Coli ◽  
Strength And Durability ◽  
Bacterial Concrete

This paper focuses on how the bacterium produces calcite to repair cracks and thereby increases the strength and durability of the concrete. The bacterial concrete can be made by embedding bacteria in the concrete to make it constantly precipitate calcite. Bacillus E Coli and Bacillus Subtilis JC3 are used for this purpose. Bacillus E coli and Bacillus Subtilis JC3 induced at cell concentration 10^5 cells/ml improves properties of concrete. This paper campaigns for the induction of bacteria in concrete for the promotion of self-healing cracks.

scholarly journals Self-healing bacterial cementitious concrete composites: development and performance evaluation

2021 ◽  
Author(s):  
Sini Bhaskar
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Statistical Modelling ◽  
Energy Dispersive Spectrum ◽  
Ultrasonic Pulse Velocity ◽  
Pulse Velocity ◽  
Self Healing ◽  
Chloride Permeability ◽  
Sporosarcina Pasteurii ◽  
Subtilis Subsp

The principal objective of the research is to contribute towards attaining the goal of developing self-healing cementitious concrete composites by incorporating bacteria as healing agent. Since the root cause of the majority of structural failure is attributed to concrete cracking, there is a compelling economic incentive to develop a concrete that can treat and repair the damage all by itself. Even though some research has been carried out in this area, a major breakthrough in identifying the types of bacteria, modes to protect this bacteria from high pH concrete environment and nutrients for effective healing are yet to materialise. For the present study, three different bacteria namely, Sporosarcina ureae, Sporosarcina pasteurii and Bacillus subtilis subsp. spizizenii and two protective vehicles such as zeolite and pumice were selected to determine the best combination among them for self-healing. Normal and fibre reinforced mortar and engineered cementitious composite (ECC) specimens were employed for the study. In order to develop self-healing bacterial concrete based materials, it is crucial to understand whether the introduction of mineral producing bacteria and nutrients adversely affect the properties. Thus, various concentrations of bacteria and nutrients were tested to determine the best possible combinations without sacrificing concrete properies. Evaluation of healing effect was determined by comparing compressive strength, sorptivity and rapid chloride permeability (RCPT), four point bending and ultrasonic pulse velocity (UPV) properties of sound and damaged specimens at different ages. Healing associated with crack closure was visualised and analysed using scanning electronmicroscopy (SEM), Energy Dispersive Spectrum Energy (EDS) and X-ray diffraction (XRD) studies. Finally, an attempt was made to employ statistical models for parameter optimization of self-healing characteristics in terms of compressive strength, sorptivity, RCPT and UPV by design and analysis of experiments. Evaluation of results to determine self-healing efficiency indicated that a significant amount of self-healing was achieved by all three selected bacteria, out of which Sporosarcina pasteurii and Bacillus subtilis subsp. spizizenii found to be promising choices. Both zeolite and pumice turned out to be effective protective vehicles. Statistical modelling of the experiment proved to be the ideal choice for modelling self-healing characteristics.

Self-Healing Microbial Concrete - A Review

2020 ◽  
Vol 990 ◽  
pp. 8-12
Author(s):  
Sasan Farhadi ◽  
Shervin Ziadloo
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Concrete Structure ◽  
Concrete Durability ◽  
Self Healing ◽  
Bacillus Pasteurii ◽  
Structure Degradation ◽  
Healing Agent

The cracks naturally exist in concrete and make it weak to the deleterious environment, ending with structure degradation. According to this fact, concrete requires to be improved and remediated. Self-healing methods are considered as a helpful way to mitigate the propagation and development of the cracks in the concrete. Bio-mineralization methods can heal the concrete by using bacteria suchlike Bacillus subtilis and Bacillus pasteurii, which can seal the cracks by CaCO3 precipitation. The literature represents the MICP method of using bacteria in concrete, which can improve the concrete durability by increasing the compressive strength. Furthermore, the different kinds of bacteria used in the concrete structure and the methods of employing as a self-healing agent review. Moreover, it illustrates B. Pasteurii and B. Sphaericus has more efficient results between other bacteria due to increasing the compressive strength and lifespan of the concrete.

scholarly journals Durability of self-healing concrete

2019 ◽  
Vol 289 ◽  
pp. 01003 ◽  
Author(s):  
Nele De Belie ◽  
Bjorn Van Belleghem ◽  
Yusuf Çağatay Erşan ◽  
Kim Van Tittelboom
Keyword(s):  
Corrosion Behaviour ◽  
Healing Process ◽  
Chloride Ingress ◽  
Self Healing ◽  
Crack Healing ◽  
Nacl Solution ◽  
Visual Damage ◽  
Chloride Profiles ◽  
Cracked Specimens ◽  
Concrete Matrix

Application of self-healing concrete reduces the need for expensive maintenance and repair actions. However, the durability of self-healing concrete has only been scarcely investigated. Here, recent results are presented regarding the resistance of self-healing concrete to chloride ingress. For self-healing concrete with macro-encapsulated polyurethane, chloride profiles and electron probe microanalysis indicated that this mechanism was efficient to reduce the chloride penetration into the crack and from the crack into the concrete matrix [1]. Furthermore, the corrosion behaviour of reinforced concrete specimens subjected to cyclic exposure with a NaCl solution was studied [2]. The electrochemical measurements indicated that autonomous crack healing could significantly reduce the corrosion in the propagation stage. No visual damage could be detected on the rebars after 44 weeks of exposure. On the contrary, cracked specimens without integrated self-healing mechanism, reached a state of active corrosion after 10 weeks of exposure and after 26 weeks clear pitting damage was observed on the rebars. While self-healing by encapsulated polyurethane is complete after one day, bacteria-based products take several weeks to heal a 300 µm crack. Bacterial granules containing denitrifying cultures released nitrite as an intermediate metabolic product which protected the reinforcement during the crack healing process [3].

scholarly journals AN INVESTIGATION ON THE USE OF BACILLUS SUBTILIS HU58 IN CEMENT MORTAR

2017 ◽  
Vol 7 (2) ◽  
pp. 1-8
Author(s):  
Nguyen Ngoc Tri Huynh ◽  
Nguyen Khanh Son
Keyword(s):  
Bacillus Subtilis ◽  
Calcium Carbonate ◽  
Portland Cement ◽  
Cement Mortar ◽  
Cement Matrix ◽  
Self Healing ◽  
Curing Time ◽  
Mortar Sample ◽  
New Type ◽  
Compressive And Flexural Strengths

Literature studies reveal the fact that incorporating bacteria into cement matrix could generate the formation of precipitated product of calcium carbonate. In this work, a new type of microorganism Bacillus subtilis HU58 was used as mixing component in formulating mortar sample of Portland cement and the effectiveness of self-healing character after 1 year of curing time was observed. Results showed the consequence in the enhancement of both compressive and flexural strengths of bacteria-modified mortar while comparing to a controlled mortar: 60MPa>56MPa (in compression) and 11MPa >9MPa (in flexion). Furthermore, those pre-existing artificial cracks 1mm in width of the prismatic mortar 40x40x160mm filled up partially (self-healing) by mineral glue.

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