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cure itself without human intervention.
CaCO3. It is therefore vital to understand the mechanisms for crack formation.
while formation of calcium results in sealing the micro cracks in carbonate is the most likely cause of self. The freshly composed micro- healing at later ages. enhance self-healing efficiency. concrete. self-healing processes within Self-healing using chemicals: One method concrete can be divided into two categories: for self-healing which comes under autogenic and autonomic.et. et. engineered additions that does not Bio concrete: Bio concrete is a product that conventionally added into cementitious will biologically produce limestone to heal materials. et. to produce new compounds which seal the healing approach (Jiaguang Zhang. Ongoing hydration is the main healing mechanism in young concrete due to its Self-healing using biological methods: Bio- relatively high content of unhydrated cement mineralization techniques give promising particles. 2017). obstructs the structural integrity and Many systems and techniques have been durability of material but also makes investigated to heal concrete cracks concrete particularly vulnerable to a autonomically such as modifying concrete by deleterious environment. autonomic self-healing in concrete is by the addition of chemicals. Alghamri. Specially selected types of the Page | 2 . The strength and the crack widths are restricted to be less of the Bacterial concrete will be more than than 100 𝜇m and preferably less than 50 𝜇m the normal concrete (Kunamineni Vijay. 2016). water is essential hydration process in concrete. al. occurs the shell of the capsule or the wall of to improve the strength and durability of the tube ruptures and the healing agent is concrete once cracks appear. crack and/or bond the crack faces (R. In addition. it can embedding microcapsules or hollow fibres lead into concrete deterioration and the with a suitable healing agent. Broadly. one way is to released and reacts in the region of damage implement automatic repair it is called self. Once the crack corrosion of steel reinforcement. Autonomic self-healing: It involves the use of al. These additions are added cracks that appear on the surface of concrete structures. For attaining effective cracks can be sealed up by perpetual autogenous self-healing.The presence of cracks results in the specifically to enhance self-healing reduction of the strength of concrete and capability. 2017). Therefore. Microfibers and Autogenic self-healing: It is the phenomenon superabsorbent polymers are some material where the material heals cracks using its own solution to restrict crack propagation and generic components and constituents. al.
These light weight If anaerobic bacteria like closely related aggregates are good carrier for bacteria. that can be used in concrete are: This can be used where light weight Anaerobic Bacteria structures are required.2015). Concrete being extremely phosphorus.) Concrete is a dry material and the pH value of cement and water when mixed is up to 13 Strength and durability of structural concrete which makes it confrontational as most of the can be increased by a biotechnological organisms cannot survive in an environment method based on calcite precipitation. They are present not cracks can heal with the calcite precipitation. and nitrogen and with bacteria. Jonkers. al. 2017).bacteria. the bacteria added should the concrete when it is being mixed. along with a calcium-based nutrient In suspension state. are added to the ingredients of alkaline in nature. Al. specie of shewanella are added to concrete. only on the surface but also beneath the The strength of bacterial lightweight mortar surface of the earth.  Bacillus halodurans  Bacillus massiliensis Page | 3 .Bacteria Used in Bio Concrete can be used in concrete are: Selection of bacteria is done based on its  Bacillus pasteurii high resistance against pH. 30% (Mohanadoss P. size more than 0. Crack having pH value higher than 10. concrete mix is added known as calcium lactate. The various bacteria was more than normal lightweight mortar. The added bacte- self-healing agents can lie dormant within the ria should be able to withstand the harsh concrete for up to 200 years. 2014) Materials The various types of aerobic bacteria that a.8mm is more difficult to be Types of Bacteria: Bacteria naturally occur in repaired however with the use of bacteria nature in various forms. et. (Dr Henk environmental conditions of concrete. et. These fit in some special norms. MATERIALS & MECHANISM Aerobic Bacteria (Soundharya S.al. Bacteria genus  Bacillus subtilis Bacillus were found to thrive in this high. et.  Bacillus cohnii alkaline environment and can synthesise  Bacillus pseudofirmus calcium carbonate. which increases the healing efficiency and the compressive strength increases from 25- structural durability (Kunamineni Vijay. temperature  Escherichia coli and lack of water content.
Hence. experimental work replacement of river sand used material for building materials by quarry waste (fineness modulus of industry. Graphite nanoplatelets hence the amount of chloride present is very emerged as good carrier compound less than the permissible limit.Graded Fine Aggregates centigrade at which temperature.b. and alkalis and has a water- Zhang. is exhibited significant proportion depending upon their purity and enhancement in compressive composition and burning them in a kiln at a strength of concrete. temperature of about 1300 – 1500 degree c. which can be found crushed sand equal to 3. 2017). Perlite:It is a valuable and worldwide. As per 2. soluble Chloride content of 140 mg/lit.Graded Coarse Aggregate subjected to heating above 870°C.72 was used as coarse absorption.Carrier generally used as fine aggregate. for short period healing. times its original one when it is d. mixing them intimately in certain aggregate. Cement weight aggregate depicted as good Ordinary Portland Cement: The cement is a carrier compound for long period binding material.75 mm size is material Cinter and partially fuses to form called fine aggregates. The grading Zone III of IS – 383 – 1970 was used volume of perlite will expand to 4–20 as fine aggregates. The water is free from reserves and low cost (Jiaguang oils.Water bacteria-carrier material because of Potable water has been used for casting its availability in large geological concrete specimens.2) conforming to extensively in volcanic rock. concrete incorporated with 2000-53 grade. Light weight aggregates (LWA): Light f. It consists of grinding the raw bacteria immobilized with light weight materials. considered as an attractive and ideal e. After this physical transformation. the Locally available well graded granite expanded perlite (EP) exhibits aggregates of normal size greater than 4. Natural sand is Page | 4 . In this 1. al. It conforming to IS456- healing.75 excellent characteristics associated mm and less than 16mm having fineness with high porosity and high-water modulus of 2. the The materials smaller than 4. Graphite Nano platelets (GNP): They IS 456 – 2000. et. it could be aggregates. 3. acids. the permissible limit for are nanoparticles made from chloride is 500 mg/lit for reinforced concrete. graphite.
2017). the bacteria draw cations from the Vijay. activating polymerization and safeguard the The cell wall of the bacteria is negatively closure of the near-by cracks (Kunamineni charged. et. Of all the materials that influence the behavior of concrete. urea by bacteria. with the aid of the bacterial Mechanism urease enzyme. The clinker is mechanism is called as Microbiologically cooled and ground to a fine powder with Induced Calcium Carbonate Precipitation addition of 2 to 3% of gypsum the product (MICP).1 Possible self-healing mechanisms for cementitious atmospheric action. cement is the most important constituent. formed by using this procedure Portland cement. al. Bacteria species gives urease. together with Ca2+. In the second method into carbonate (𝐶𝑂32− ) and ammonium lightweight aggregates are impregnated by (NH4+) is be as follows: bacteria solution encapsulated in a polymer 𝐶𝑂(𝑁𝐻2 )2 + 𝐻2 𝑂 → 𝑁𝐻2 𝐶𝑂𝑂𝐻 + 𝑁𝐻3 coating. Now the healing agent 𝐻𝐶𝑂 −3 + 𝐻 + + 2𝑁𝐻 4+ + 2𝑂𝐻 − ↔ 𝐶𝑂32− + 2𝑁𝐻 4+ + 2𝐻2 𝑂 associates with the embedded catalyst. As soon as the crack ruptures the 𝑁𝐻2 𝐶𝑂𝑂𝐻 + 𝐻2 𝑂 → 𝑁𝐻3 + 𝐻2𝐶𝑂3 embedded microcapsules. to deposit on their cell surface. The process of making concentration of bacteria for strength urease for the hydrolysis of urea𝐶𝑂(𝑁𝐻2 )2 purpose and the optimum concentration was 30x105cfu/ml. The Ca2+ ions react Self-Healing Approach: Bacteria act as a with the 𝐶𝑂32− prime to precipitation of long lasting healing agent and this Page | 5 . because it is 11 used to bind sand and aggregate and it resists Fig.modular chapped clinker. The hydrolyze to ammonia (𝑁𝐻 4+) and carbonic application of healing agent by the direct acid 𝐶𝑂32− that leads to the formation of method used for finding optimum calcium carbonate. that catalyzes urea to carbonate and Mechanism of applying the healing agents in ammonium that results in an increase of pH concrete: Direct application and and carbonate concentration in the bacterial Encapsulation are the two methods by which surroundings. These components further bacteria can be applied to the concrete. Portland cement is a materials general term used to describe hydraulic The mechanism involves decomposition of cement. environment. the healing agent 𝐻2𝐶𝑂3 ↔ 𝐻𝐶𝑂3− + 𝐻 + is released into the crack faces by using 2𝑁𝐻3 + 2𝐻2 𝑂 → 2𝑁𝐻 4+ + 2𝑂𝐻 − capillary movement.
Bio Effect of bacteria on properties of concrete mineralization is a biological precipitation in which organisms create a local micro 1 Hydration kinetics environment by providing chemical The addition of bacteria spore powder in precipitation of mineral phases concrete either accelerate or retard the extracellularly. photosynthesis and urea bacteria are supplied in the form of calcium hydrolysis end up in giving CaCO3 as there lactate. • Calcium concentration. and calcium formate.et concrete is known as microbial Induced al. bacterial cell wall. bacteria which Fig. 2015). Some usually occurring setting time of concrete depending on the metabolic processes including sulfate calcium source supplied. byproduct (Vekariya M. nitrate can accelerate the setting time of Calcium carbonate precipitation is mainly concrete (M.e. al. 2016). serves as a nucleation site. et al.2 shows the 2011). Fig. The nutrients to reduction. Various The addition of calcium lactate can retard the bacteria can precipitate calcium carbonate in setting time. calcium nitrate. The main mechanism behind making a self- healing concrete is that the bacteria should be able to convert the soluble organic nutrients into insoluble inorganic calcite crystals which seals the cracks. Calcium Carbonate Precipitation (MICCP) or RESULTS AND DISCUSSIONS Bio mineralization (Kavia K. et al. 𝐶𝑎2+ + Cell → Cell – 𝐶𝑎2+ • DIC (Dissolved Inorganic 2+ Cell –𝐶𝑎 + 𝐶𝑂32− → Cell –CaCO3 Carbon) concentration. calcium formate and calcium both natural and laboratory conditions. Luo.2008). The self- healing agent that is applied to the concrete consists of two components. 2013). Page | 6 .calcium carbonate at the cell surface that governed by following factors (Jonkers HM. the METHODOLGY mineral precursor which is converted to The method of using microbes in bacterial calcium carbonate minerals (Henk MJ.2 Calcium carbonates formation on bacterial cell wall acts as a catalyst and calcium lactate i. image of calcium carbonates precipitation on • pH value. • Nucleation sites. et.
higher grade concrete in all ages due to microbial precipitation of imparts more strength as compared to the calcium carbonate (W. Khaliq. et. 2001).al. calcite precipitates on surface of carbonate was present in the concrete (N. there is a possibility for strength of the bacteria added to silica fume bacterial cells to grow slowly in the initial concrete improved due to the precipitation of period and accustoms to high PH conditions CaCO3. But these cells were carbonate on cell surfaces of microorganism adapting to a new atmosphere. et. the grade concrete as compared to the lower compressive strength of concrete increased grade concrete so. SEM confirmed that calcium cell growth. The maximum The 28 days compressive strength increased development rate of strength for the highest when compared to control cement mortar by grade of 50 MPa concrete is as high 24% in Page | 7 . The compressive which may be due to the presence of various strength of concrete with Sparcina pasteurii ions in the media. 14% and 10%. et. Thus the behaviour of cell improved mortar compressive strength increased compressive strength with by 19%. The addition of precipitation of calcite was higher in higher Bacillus subtilis bacteria along with GNP. GNP acts Santhosh. Microstructure analysis of concrete in the curing period. Achal.al. Chahal. 2016).al. lower grade concrete. 2016). 2016). 20% method based on calcite precipitation. bacterial endospores. et. and 40% in mortar.al. 2012). et. During the process of using XRD. Cement was replaced with 10% of fly ash and the The strength of the structural concrete has inclusions of 10^5cells/ml Sparcious been improved by a Bio-technological pasteurii bacteria were included. as the cement which is due to the deposition of calcium mortar was permeable. specimens (V. compared to control microbial cells can be explained (K. The (2 X 10^9cells/ml) is 20% more than concrete flow of nutrients and oxygen to the bacterial without bacteria as observed for 28 days (F. Chahal. et. This results in less porosity accompanied with Bacillus subtilis bacteria and permeability of the cement mortar. 2012). 20%. crack healing efficiency. In due course. Cement was matrix are plugged at a time. Due to the (N.2 Compressive strength strength (R. 2011). et.al. replaced with different fly ash concentrations the cell either gets dead or turns into of 10%. The compressive high PH of cement. the cell and also in the cement mortar matrix. Andalib.al.al. cells gets stopped if many of the pores in the Nosouhian. during initial curing period. enhancement in compressive strength of Microbial cells attained good nourishment structural fly ash concrete was observed. By introducing as a good carrier compound for uniform Bacillus megaterium bacteria of distribution of bacteria resulting in maximum concentration 30 X 10^5 cfu/ml in concrete.
et. 2016 concrete compared to control with 10% dosage of RHA Compressive strength 35% more 5 Sporosarcina pasteurii 10^5 cells/ml N. et. Al. et.incorporating the reactive spore powder in Bacillus sp. Ghosh. et. Deposition of CaCO3 on the cell surfaces bacterial concentration and the values of and in the pores of cement-sand matrix plugs compressive strength. 2013 than the control concrete Maximum rate of strength development was 24% achieved 2 Bacillus megaterium 30 x 10^5 *cfu/ml R. Al. 2005 compared with the control mortar Table1. Al. The results of compressive conventional concrete showed an eloquent strength of bacterial concrete and difference. Achal. 2016 in highest grade of concrete 50 Mpa Improvement of 12% in compressive strength as 3 Bacillus subtilis compared to controlled concrete 2. Andalib. gives the details of bacteria used. Chahal. et. Bacteria used Best results Reference concentration Compressive strength 40% more 1 Bacillus sp.al. Al.al. Al. The table and charts given shows conventional concrete are given in Table 2 the clear information regarding compressive and Fig. Various types of bacteria and their compressive strength results. Luo. et. 2012 than the control concrete 10% increase in compressive 6 AKKR5 strength as compared to control 10^5 cells/ml R. CT-5 5x10^7 cells/mm3 V. Bacterial Sl.8 x 10^8 cells/ml W. et.4 The M20 bio concrete using different types of results of flexural strength of bacterial Page | 8 . Al. 2011). Siddique.8% in bacterial 4 Bacillus aerius 10^5 cells/ml R. these may vary the pores in the mortar and causes depending on the calcium source supplied to improvement in the compressive strength by the bacteria. 2011 & 7 Shewanella Species strength of cement mortar 10^5 cells/ml P. *Cfu – Colony forming unit Some other test results of bio concrete and bacteria15. Al. Siddique. Khaliq. et. 2016). Siddique. et. Achal. Table1. split tensile strength and flexural of bacterial concrete and conventional strength of M20 conventional concrete and concrete are given in Table 3 and Fig. 2016 specimens with light weight aggregates Increase in compressive strength by 11. CT-5 (V. 2016 concrete 25% increase in compressive R.No. et. Al.3 The results of split tensile strength strength. cement mortar (M.
35 1.99 Subtilis Bacillus 2 27. bacteria days days days days Bacillus 1 pasteurii 4.5 Comparison between flexural strength of bacterial Name of 7 28 7 28 concrete and conventional concrete.Comparison between compressive strength of concrete and conventional concrete.73 1.92 7.No Compressive Compressive strength strength (N/mm2) (N/mm2) Name of 7 28 7 28 bacteria days days days days Bacillus 1 22.concrete and conventional concrete are given in Table 4 and Fig.24 3.74 20.5.84 29.84 29. s Table3.26 Subtilis Bacillus Fig.708 3.85 3.6 7.26 concrete and conventional concrete.36 3. bacterial concrete and conventional concrete Bacterial Conventional concrete concrete S No Compressive Compressive strength strength (N/mm2) (N/mm2) Name of 7 28 7 28 bacteria days days days days Bacillus 1 2. Bacterial Conventional concrete concrete S.09 38.3 Comparison between compressive strength of bacterial Table2.Comparison between split tensile strength of bacterial concrete and conventional concrete Bacterial Conventional concrete concrete S.Comparison between flexural strength of bacterial concrete and conventional concrete 3 Water permeability The penetration of aggressive substances that are accountable for degradation of Page | 9 .99 sphaericus Fig.No Compressive Compressive strength strength (N/mm2) (N/mm2) Fig.98 20.06 Table4.4 Comparison between split tensile strength of bacterial 2 sphaericu 2.708 3.18 32.
Chahal. 2011). In bacterial concrete pores are filled with calcium carbonate precipitation by bacteria (N. decrease of water absorption and permeability of concrete specimens. Tri. Siddique. At 28 days. the particle size absorption of recycled aggregate (J. 2012) revealed that addition of S. et. all control cement determined by permeability and hence is bag house filter dust concrete specimens considered to be the fundamental property show high to moderate permeability but for portraying the durability of concrete. This AKKR5 bacterial (10^5 cells/ml) concrete depends on the features of pore network of specimens show high to low permeability cementitious materials quantified by due to pores filled with calcium carbonate (R. Achal. tortuosity. specific surface. size Siddique.al. and micro cracks. 2016). the age of hardened et. 2012). Water absorption was found to be reduced fourfold with a concentration of 10^5 cells/ml bacteria in concrete. Studies (N.al. microbial precipitation this will reduce water controlled by the (w/c) ratio.al. connectivity.al. The quality of the distribution. et. Pastteurii bacteria in fly ash concrete lead to a decrease in porosity and permeability of concrete. Page | 10 . results of different bacteria after 28 days of CaCO3 deposition in concrete resulted in a curing: shown in Table 4.al.al. recycled aggregate was improved due to These parameters are amongst others. Cubes cast with the addition of Bacillus Megaterium and its nutrients absorbed more than three times less water than control specimens due to microbial calcite deposition (V. et. The addition of Bacillus Aerius bacteria causes the reduction in water absorption and porosity due to calcite precipitation which in turn increases the durability of concrete structures (R. 2013). 2014). 2016). Qiu. cementitious materials and the intrusion of Compressive strength and water absorption aggressive substances (Q. Chahal. et.al.concrete under pressure gradient is et. et. distribution. porosity.
al (2011) concrete concrete sample N.R.al (2014) concrete sample concrete sample Nearly 40% 10-18% less than Baciillus increase than 6 controlled Kumar Jagdeesha et.al (2010) Nearly 35% 15% increase less than 5 Bacillus cohnii than controlled controlled Sierra –beltron et.al () 2 controlled subtilis controlled R. Compressive strength and water absorption results of different bacteria after 28 days of curing. Qian et. Muynck et.al (2008) concrete sample sample C.Bang et.I.Park et. Muynck et.al (2014) Pacheco et al.De.al (2010) 9 controlled species controlled V. Muhammad et. (scanning electron microscope). Water Compressive absorption Sl.Pei et. Due to this deposition.al (2011) 18% increase than controlled Navneet chahal et.al (2005) 4 than controlled pasteurii concrete De.al (2011) 1 than controlled Sphaericus concrete Jagdeesha et.al (2013) M.2% increase Bacillus controlled 3 than controlled Dhamia et.al (2012) magaterium concrete concrete sample sample Ramachandran et.S.Park et. 2011).Iyer et. et.Topc et. Manjunath et.al. Achal. Rod- microstructure of concrete by mineral shaped bacteria associated with calcite precipitation.muynck et.Achal et. The addition Calcite precipitation in mortar and concrete of bacteria into the concrete can improve the was visualized by SEM analysis.al (2010) 7 Bacillus cereus controlled concrete Maheshwaran et..Achal et.al (2013) flexus controlled concrete concrete sample sample 30-40% 50% less than increase than controlled W.al (2001) 2-4% increase Bacillus than controlled Ramakrishanan et. EDS the impermeability of the concrete is (Energy-dispersive X-ray spectroscopy) and improved as this deposition acts as a barrier Page | 11 .De.Chidara et.l (2011) sample Table4.al (2004) Y.al (2012) 8 S.al (2010) 80-85% less V.no Bacteria strength results References results 28 28 days days W.al (2009) Y.al (2008) 45-50% less W.Ghosh et.al (2014) Nearly 50% 12-17% Reddy et.park et.al (2013) R.al (2001) 50-70% less S.al (2009) less than Shewanella increase than Y.al (2014) sample 46% less than 24. This has been verified by SEM crystals were found.al (2010) 30-35% increase Bacillus than controlled V.al (2013) concrete concrete sample I.al (2013) less than Bacillus increase than Y. Pasteurii than controlled concrete Navneet chahal et.Park et.Achal et.al (2012) concrete sample sample R. muynck et.al (2012) concrete sample sample Kumar jagdeesha et.pei et.D. 4 Microstructure to harmful substances as that enter the sample (V.al (2014) concrete sample sample B.(2013) Nearly 50% 25-30 % S.
2016). and this was confirmed by using EDX and XRD analysis. strength of RHA concrete was improved by the addition of bacteria. 2016). This paper has reviewed voids are filled calcite (R. Fig. Siddique.XRD (X-ray powder diffraction) analysis. et. et. et. 2012).5 SEM Images (a) control concrete (b) Bacterial calcite precipitation in 10% silica fume concrete.5 shows the SEM images of control concrete and bacterial concrete. chloride penetration and chloride ion permeability. Hung. Luo. Thus with the increase of compressive strength of concrete. The SEM analysis showed the different calcite crystals embedded with Fig.al. This study has also identified that confirmed by the results obtained using bacteria has a positive effect on the microstructures.al). It was observed that calcite is present in the form of calcium carbonate as the high amounts of calcium were found in the sample. the water absorption. the use of urease producing shows the SEM images of normal concrete bacteria isolates.al. due to the deposition CONCLUSION of calcium carbonate in pores and this was The significance of this work is to confirmed by using SEM images. The signal transmission rate of ultrasonic pulse advantage of using bacteria decreases water velocity. bacteria.al. different types of bacteria that can be used 2016). The permeability and acid ingress are decreased researcher stated that an addition of 30 X (C. such as Bacillus subtilis. Chahal. These images can conform the calcite crystals in bacterial Fig. et. It could be bacillus pasteuri species in healing of cracks clearly seen that in bacterial concrete the in concrete. 10^5cfu/ml concentration of Bacillus Megaterium bacteria had (38.C.76%) maximum weight of calcium compared with other proportions of bacteria and in absence of bacteria in concrete (R.6 understand. It can increase the durability of concrete (M. The concrete (BR0) (c) 5% of RHA Concrete (R5) (d) Bacterial concrete with 5% RHA (BR5). The deposition of calcium carbonate for healing cracks and increase durability of within the cracks of the test samples was concrete. et. and bacterial RHA concrete. Andalib. The present study results recommend that Page | 12 .6 SEM images of (a) Normal concrete (R0) (b) Bacterial concrete (N.al. Fig.
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