research article achievement of early compressive strength in...

Research ArticleAchievement of Early Compressive Strength in Concrete UsingSporosarcina pasteurii Bacteria as an Admixture

Rakesh Chidara1 Rahul Nagulagama2 and Smitha Yadav1

1 National Institute of Construction Management and Research (NICMAR) Pune 411045 India2Manipal Institute of Technology HNo 1-3-72 Janda galli Banswada Nizamabad Telangana 503187 India

Correspondence should be addressed to Smitha Yadav smiyad01gmailcom

Received 21 February 2014 Revised 6 August 2014 Accepted 20 August 2014 Published 11 September 2014

Academic Editor Andreas Kappos

Copyright copy 2014 Rakesh Chidara et alThis is an open access article distributed under the Creative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Often it is observed attainment of early compressive strength in concrete is a challenge Researchers have tried various admixturesto achieve the objective This work addresses the issue of achieving early compressive strength in concrete using a bacteriumcalled Sporosarcina pasteurii The bacterium is characterised with the ability to precipitate calcium carbonate in the presence ofany carbonate source and is known for its resistive capacity in extreme temperature and pressure zones To establish the objectiveof gain in early strength around 192 concrete cubes were tested at 3 7 14 and 28 days and the results compared with controlledconcreteThe bacteriumwas used in combination of chemicals and the dosage proportions were altered to achieve the desiredM20compressive strength at 28 days

1 Introduction

The compressive strength achieved in concrete is one ofthe most important and desirable properties of concreteMany admixtures have been tried by experts to achieve thedesired compressive strength This paper aims at achievingcompressive strength in concrete however the authors ofthe paper have tried to use a nutrition medium containinga bacterium named Sporosarcina pasteurii as an admixturein concrete The focus of the work has been to decrease thetime taken by the cement to hydrate and achieve maximumstrength at early ages Early strength gain in normal concreteismainly associated to thewatercement ratioMixeswith lowwater cement ratio gain strengthmore rapidly than thosewithhigher water cement ratio This is because the cement grainsare closer to one another and a continuous system of gel isestablished more rapidly

There are actually many different types of acceleratorspresent in the market but the common problems posedby the accelerators are low slump low initial setting timeand thus reduced workability These adverse properties ofaccelerators refrain most of the experts from using thesame in concrete The use of blended cements presently

has also been on rise in construction industry blendedcements with a defined amount of cement replaced withflyash are commonly being used The addition of flyash tocement however has little disadvantage that is for flyashto hydrolyse and form into a strong component like cementit needs Ca(OH)

2 The Ca(OH)

2is a biproduct of cement

hydration process hence for the flyash to form the C-S-H gelit requires calcium hydroxide in adequate quantity and thiscan occur only if adequate cement hydrolisation takes placeIf calcium carbonate is present in cement the hydrolisationprocess takes place quickly and inturn provides Ca(OH)

2in

requisite quantity for flyash to hydrolyse and give the desiredcompressive strength

Sporosarcina pasteurii formerly known as Bacillus pas-teurii is a bacterium with the ability to precipitate calciumcarbonate in the presence of any carbonate source Thismicroorganism is well known for its resistive propertiesto resist the harsh conditions of sea water and very hightemperatures whichare generally found in shallowwaters andin Sahara desert This bacterium is used in the present workfor checking the improvement in the compressive strength ofconcrete Sporosarcina pasteurii secretes calcium carbonateThis calcium carbonate inturn acts as a positive catalyst for

Hindawi Publishing CorporationAdvances in Civil EngineeringVolume 2014 Article ID 435948 7 pageshttpdxdoiorg1011552014435948

2 Advances in Civil Engineering

the cement hydration process as discussed by Ramachandran[1] Pera et el [2] and Kakali et al [3] It was found thatthe Sporosarcina pasteurii bacteria attain their maximumactivity rate at 16 hours and maintain this till the timethe nutrition medium is consumed Thus the secretion ofmaximum amount of calcium carbonate takes place only16 hours after the concrete has been mixed thus providingenough workable time for concrete Also it has been seen thatthis nutritional medium neither allows for the loss in slumpnor causes immediate setting of the concrete

In the present work the bacterial admixture has beenadded in different compositions and concentrations alongwith other products like urea sodium carbonate calciumchloride and so forth in differing proportions to study itsimpact on compressive strength at 3 7 14 and 28 days ofcuring The compressive strength obtained of bioconcretethat is with Sporosarcina pasteurii bacteria is compared withthe strength gained by controlled concrete at 3 7 14 and 28days respectively

The work also tries to examine the use of sodium carbon-ate along with the nutrient medium in concrete and simulatethe chemical reaction which is the major contribution of theauthors to the research wherein earlier only urea had beentried by experts The below chemical reactions (1) and (2)depict the formation of calcium carbonate that acts like acatalyst for the formation of C-S-H gel which is required forthe hydrolization of cement

Using urea

CO(NH2)2+H2O 997904rArr NH

2COOH + NH

3

NH2COOH +H

2O 997904rArr NH

3+H2CO3

H2CO3997904rArr 2H+ + CO

3

2minus

2NH3+ 2H2O 997904rArr 2NH

4

+ + 2OHminus

HCO3minus +H+ + 2OHminus 997904rArr CO3

2minus + 2H2O

Ca2+ + CO3

2minus 997904rArr CaCO3

(1)

(Kashyap and Radhakrishna [4])Using sodium carbonate

Na2CO3997904rArr 2Na+ + CO

3

2minus

CO3

2minus +H2O 997904rArr HCO

3

minus +OHminus

Na+ +OHminus 997904rArr NaOH (increasing pH)

HCO3

minus 997904rArr CO3

2minus +H+

Ca2+ + CO3


(2)

(experimental work)

2 Literature Review

A novel technique for the remediation of damaged struc-tural formation has been developed by Arunachalam et al[5] by employing a selective microbial plugging process

0 25 50 75 100 125 150 175

Time (hr)

0

1

2

3

4

5

6

Wat

er ab

sorb

ed (k

gm

2)

Control

Bacillus sp CT-5

Figure 1 Water absorption experiment on Bacillus sp CT-5 [7]

In this process the microbial metabolic activities promoteprecipitation of calcium carbonate in the form of calcite Themicrobial sealant CaCO

3 exhibits positive potential to selec-

tively consolidate simulated fractures and surface fissures ingranites and sand plugging as reported by Arunachalam etal [5] Previous studies with aerobic microorganism (Bacilluspasteurii and Pseudomonas aeruginosa) showed a significantimprovement (about 18) in compressive strength of cementmortar as shown by Ramakrishnan et al [6] The researchdone by Achal et al [7] illustrates a 3615 improvementin the compressive strength of mortar specimens at 28 daysprepared with bacterial cells It is significantly noted thatamong the controlled concrete specimens prepared withoutthe inclusion of bacterial cells the concrete cubes cured inmicrobial growth medium were stronger than those curedin water although there was not much significant variationResearch has also showed that the ionic strength of mediumcontaining urea-CaCl

2appeared to enhance the compressive

strength of the concreteThe improvement in compressive strength by Bacillus

sp CT-5 is probably due to deposition of CaCO3on the

microorganism cell surfaces and within the pores of cement-sand matrix which plug the pores within the mortar asdiscussed by Supratao [8] They also found that once thepores in the matrix were plugged the flow of the nutrientsand oxygen to the bacterial cells stopped eventually the cellseither died or turned into endospores and acted as an organicfiber increasing the compressive strength of the concrete

The decrease in permeability of mortar specimens treatedwith bacteria could also be seen from the water absorptionexperiment Figure 1 shows a decrease in thewater absorptionby a CT-5 cube in comparison to control cube Thus it can beinterpreted that the permeability also reduces which is a verydesirable property in concrete This also limits the ingress ofharmful substances as reported by Achal et al [7] From theexperiment it is clear that the presence of a layer of carbonatecrystals on the surface by bacterial isolate has the potentialto improve the resistance of cementitious materials towardsdegradation processes

Advances in Civil Engineering 3

Table 1 Composition of chemicals used in bioconcrete

Sr number Concrete mix Description1 CC Normal mix proportions (control concrete)2 Set 1 Mix proportions + urea 50mL + nutrient media3 Set 2 Mix proportions + sodium carbonate 50mL + nutrient media4 Set 3 Mix proportions + sodium carbonate 100mL + nutrient media5 Set 4 Mix proportions + urea 50mL + 20 gms of CaCl21 ltr + nutrient media6 Set 5 Mix proportions + urea 10mL + 20 gms of CaCl21 ltr + nutrient media7 Set 6 Mix proportions + sodium carbonate 50mL + 20 gms of CaCl21 ltr + nutrient media8 Set 7 Mix proportions + sodium carbonate 15mL + 20 gms of CaCl21 ltr + nutrient media

In 2010-2011 Chahal et al [9] studied the bacterial isolateson the basis of their calcite precipitation and survival athigher pH They concluded that the bacterial isolates whichshowed increased urease activity calcite precipitation andsurvival at higher pH could be used in the remediation ofcracks in building materials Thus it was summarised thatSporosarcina pasteurii can be used to make concrete withadequate strength and also sustain high temperature andpressures

3 Materials and Compositions Used

31 Mix Compositions The bacterial admixture has beenadded in the concrete mix with different chemical composi-tions like urea sodium carbonate calcium chloride and soforth with varying concentrations as defined in Set 1 to Set 7to study its impact on compressive strength at 3 7 14 and 28days of curing as shown in Table 1

32 Nutrient Media The nutrient media were prepared byusing a composition of beef extract yeast NaCl and so forthas shown inTable 2However the composition of the nutrientmedium was changed for different proportions of chemicalsadded to the concrete mix Table 2 shows the composition ofthe nutrientmediumwith differing chemical compositions tostudy the effect on the compressive strength of concrete

33 Mother Liquor The composition of the nutrient mediawas mixed in mother liquor solution The process to preparethe mother liquor in the present work consisted of thefollowing steps

(1) Themicrobe sample (Sporosarcina pasteurii) obtainedfrom the microbial bank is broken and mixed with10mL of distilled water

(2) The distilled water sample is then stored in sterilizedconditions

(3) 50mL of nutrient medium is prepared and sterilized

(4) 5mL of the microbial distilled water is then trans-ferred into the nutrientmediumwhich is then kept ona stirrer at 120 rpm for 24 hours in room temperature

(5) The microbe starts to grow in the nutrient mediumand the nutrient medium is stored in a cold storageroom at 4∘C for future use

34 Cement The cement used was UltraTech cement 43grade ordinary Portland cement (OPC) confirming to IS8112-1989 [10] with characteristics as depicted in Table 3

35 Aggregates The fine aggregates used in the test werenatural river sand having a fineness modulus of 2856 Thespecific gravity of the same was 260 The coarse aggregatesfor the present work were obtained from local quarry nearManipal having a specific gravity of 260 with a finenessmodulus of 7389 Given below in Table 4 is the sieve analysisof coarse and fine aggregates used in the present work Fromthe sieve analysis it is seen that the sand belonged to zone IIas per IS 383-1970 [11]

36 Concrete Bioconcrete was prepared using the ingredi-ents listed above and adopting the IS 10262-1982 mix designprocedure [12]

4 Test Programme

The test programme consisted of testing concrete cubes ofsize 150 times 150 times 150mm at 3 7 14 and 28 days usingvarious combinations of nutrient and chemical compositionsas depicted in Table 1 The concrete was designed for mildexposure as per the IS mix design methodThe water cementratio adopted for the mix was 044 and a slump of 25ndash50mm was achieved for all the experiments on slump coneapparatus

24 cubes of control concrete cubes without the nutrientmedia were prepared as per IS mix design and 6 cubes eachwere tested for the compressive strength at 3 7 14 and 28days respectively

The bioconcrete cubes were cast using the nutrientmedium in differing proportions and also the changing of thechemical constituent for example urea or sodium carbonateWith each chemical constituent added to the concrete forstudying its impact on compressive strength 24 numbers ofspecimen cubes were cast and tested at 3 7 14 and 28 daysage of curing The details of the test programme are shownin Table 5 In all around 192 cubes were tested under thementioned experimental work

5 Experimental Procedure

The work consisted of testing concrete at 3 7 14 and 28 daysfor achieving 20MPa compressive strength using admixture


Table 2 Composition of nutrient media

Composition of nutrient media per 1 litreSr number Desc (1) (gm) (2) (gm) (3) (gm) (4) (gm) (5) (gm) (6) (mL) (7) (gm) (8) (gm) (9) (gm) (10) (mL)1 CC 0 0 0 0 0 0 0 0 0 0mL of mother liquor2 Set 1 1 2 5 5 15 1000 4 0 0 20mL of mother liquor3 Set 2 1 2 5 5 15 1000 0 4 0 20mL of mother liquor4 Set 3 1 2 5 5 15 1000 0 4 0 20mL of mother liquor5 Set 4 1 2 5 5 15 1000 4 0 20 20mL of mother liquor6 Set 5 1 2 5 5 15 1000 4 0 20 20mL of mother liquor7 Set 6 1 2 5 5 15 1000 0 4 20 20mL of mother liquor8 Set 7 1 2 5 5 15 1000 0 4 20 20mL of mother liquor(1) Beef extract (2) Yeast extract (3) Peptone (4)NaCl (5) Agar (6)Distilledwater (7)Urea (8) Sodium carbonate (9) Calcium chloride (10) Bacteria solution

Table 3 Properties of cement

Sr number Fineness m2kg (min) Setting time in minutes Soundness Compressive strength in MPaInitial (min) Final (max) Le Chatelier (mm) Autoclave () 3 days 7 days 28 days

1 225 30 600 10 08 232 332 4342 225 30 600 10 08 231 328 4313 225 30 600 10 08 227 331 432

Table 4 Sieve analysis of coarse aggregates

IS sieve size Wt retained(gm)

Cumulative Wtretained (gm)

Cumulative Wtpassing ()

Wt retained(gm)



60mm 0 0 10040mm 0 0 10020mm 900 900 5510mm 987 1887 565 0 0 0475mm 104 1991 045 25 25 975236mm 9 2000 0 27 52 948118mm 0 2000 0 209 261 739600 120583 0 2000 0 292 553 447300 120583 0 2000 0 412 965 35150 120583 0 2000 0 35 1000 0

Table 5 Test programme

Composition of concrete per every 1 cube of concrete

Sr number Set Nutrientmedia (lts) Mix design Cement (kg) Fine agg (kg) Course agg

(kg) Water (lts) Total number ofcubes tested

1 CC 0 1 15 3 1422 2133 4267 0625 242 Set 1 005 1 15 3 1422 2133 4267 0575 243 Set 2 005 1 15 3 1422 2133 4267 0575 244 Set 3 01 1 15 3 1422 2133 4267 0525 245 Set 4 005 1 15 3 1422 2133 4267 0575 246 Set 5 001 1 15 3 1422 2133 4267 0615 247 Set 6 005 1 15 3 1422 2133 4267 0575 248 Set 7 0015 1 15 3 1422 2133 4267 061 24


of nutrient medium made up of bacterium Sporosarcinapasteurii Since admixtures require calcium carbonate inadequate quantity for the hydrolisation process the samewas supplemented by using urea which was already tried byresearchers However supplementation of calcium carbonaterequired for hydrolisation can also be done by additionof sodium carbonate and calcium chloride The work thusconsisted of adding these chemical components in variouscompositions Initially the compressive strength with 50mLurea was found out and the same repeated with sodiumcarbonate with compositions 50mL and 100mL Further20 gm of calcium chloride was also tried along with urea10mL and 50mL urea and the same repeated with 15mLand 50mL sodium carbonateThe results of the experimentalwork are discussed below

6 Results and Discussions

(1) Concrete was prepared by using a combination of thebacterial admixture along with 50mL of urea (Set 1) and alsothe admixture along with 50mL of sodium carbonate (Set 2)Urea and sodium carbonate were added to the nutrientmediato simulate the reactions as represented in (1) and (2) Thecompressive strength results in MPa of CC Set 1 and Set 2 at3 7 14 and 28 days of curing are shown in Figure 1

From Figure 2 it is evident that an increase in compres-sive strength is observed to the extent of 766 at the end of 3days with 50mL urea that is Set 1 However the compressivestrength of Set 1 at 28 days is at parwith control concrete (CC)From the above figure it is also seen that this combinationshowed a gain in strength up to 14 days of curing beyondwhich a decrease in strength is noted

The result with sodium carbonate (Set 2) also representeda similar trend as with urea (Set 1) though in this case theincrease in strength was gradual from 3 to 28 days Set 2mixes though provided a higher strength at 3 7 and 14 dayshowever strength at 28 days was comparable to controlledconcrete The strength however was marginally (5) lowerthan the mix with urea that is Set 1 Since this did notcontribute to a rise in compressive strength a slight increasein the percentage of sodium carbonate was tried(2) Concrete was prepared by using a combination of the

bacterial admixture along with 100mL of sodium carbonateSodium carbonate was added to the nutrient media in higheramount to provide the necessary calcium hydroxide requiredfor the hydrolisation process The test results of CC Set 3 at3 7 14 and 28 days of curing in MPa are shown in Figure 3

From the observation of results attained by adding100mL sodium carbonate to the nutrient medium to prepareconcrete that is Set 3 it is observed that there is increasein compressive strength up to 144 at 3 days and around43 at 7 days However this rise beyond 7 days is foundto be moreover constant till the 28 days of curing It isnoticed that these compositions of Set 3 showed a slightdecrease in compressive strength around 26 in comparisonto that of the control concrete at 28 days of curing Sincethis composition also did not give any substantial change incompressive strength the formulation of the nutrient media

0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 1

SET 2

Figure 2 Comparison of control concrete with Set 1 and Set 2

0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

ControlSET 3

Figure 3 Comparison of control concrete with Set 3

was further altered by addition of calcium chloride to thenutrient media along with urea or sodium carbonate(3) In the next set of workCaCl

2was added to the nutrient

media as was also carried out by researchers VarenyamAchal et al [7] The amount of nutrient media added was50mLcube and this was tried with both the nutrient mediabases that is urea and sodium carbonate and the resultsobtained are shown in Figure 4

It is observed from Figure 4 that when nutrient mediabased on urea (Set 4) were used there was an increase incompressive strength up to 14 days however the compressivestrength observed at 28 days was less than that of the 28 daysstrength of controlled concrete

The above figure also shows that when nutrient mediabased on sodium carbonate (Set 6) were used then there wasan increase in strength up to 3374 at 3 days 259 at 7 daysand 1853 at 14 days when compared to control however thestrength obtained at the end of 28 days was similar to that ofcontrol(4) As the results obtained by adding the nutrient media

consisting of CaCl2gave some positive results the same


0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 4

SET 6


0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 5

SET 7


amount of CaCl2was added again to the concrete however

the amount of urea was decreased to 10mLcube (Set 5) andsodium carbonate taken as 15mLcube (Set 7) The trend ofcompressive strengths gained by the concrete by the change isrepresented in Figure 5 It is observed from the above figurethat there was slight increase in the compressive strengthwith Set 5 but the gain at 28 days was comparable to thatof controlled concrete Figure 5 also shows that there wasincrease in strength when Set 7 combination was used inconcrete There was an increase in strength up to 758 at3 days 396 at 7 days 2624 at 14 days and 935 at theend of the 28 days when compared to that of control concreteThis gain of strength has been attributed to the Sporosarcinapasteurii bacteria as this secretes calcium ions which in turnreact with the carbonate ions and form calcium carbonate asshown in (2) This calcium carbonate does not directly reactwith the cement particles (C

3S C2S C3A and C

4AF) but

instead it acts like a catalyst for the cement hydration reaction

as shown in (3) thereby fastening the process of hydration andincreasing the strength of concrete thus produced

C3SC2SC3AC4AF +H

2O 997888rarr C-S-H gel + Ca(OH)

2

(3)

This calcium carbonate if added manually actually more-over acts like an accelerator which actually decreases thesetting time of concrete and thus may not be acceptableIn the present work the calcium carbonate is produced inadequate quantity after the bacteria reach their maximumactivity that is 16 hrs allowing enough working time Thusit can be summarised that Sporosarcina pasteurii bacteriawhen added to concrete in proper proportions results in earlystrength gain of concrete without affecting the initial settingtime

7 Conclusions

(1) It can be concluded that the use of Sporosarcinapasteurii bacteria leads to early strength gain and alsoleads to overall increase in the compressive strengthof concrete

(2) The results obtained by both sodium carbonate andurea were found to be almost similar and thus sodiumcarbonate can also be used as a substitute to enhancestrength in concrete

(3) The highest gain in compressive strength wasobtained when admixture which constitutes ofsodium carbonate and calcium chloride was addedto the concrete mix

(4) The addition of the admixture consisting ofSporosarcina pasteurii bacteria affected neitherthe slump nor the initial setting time of concrete

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] V S Ramachandran Thermal Analyses of Cement ComponentsHydrated in the Presence of Calcium Carbonate Building Mate-rials Section Thermochimica Acta Institute for Research inConstruction National Research Council Ontario Canada1988

[2] J Pera S Husson and B Guilhot ldquoInfluence of finely groundlimestone on cement hydrationrdquoCement and Concrete Compos-ites vol 21 no 2 pp 99ndash105 1999

[3] G Kakali S Tsivilis E Aggeli and M Bati ldquoHydrationproducts of C

3A C3S and Portland cement in the presence of

CaCO3rdquo Cement and Concrete Research vol 30 no 7 pp 1073ndash

1077 2000[4] V N Kashyap and Radhakrishna ldquoA study on effect of bacteria

on cement compositesrdquo International Journal of Research InEngineering and Technology pp 356ndash360 2013

[5] K D Arunachalam K S Sathyanarayanan B S Darshanand R B Raja ldquoStudies on the characterisation of biosealant


oroperties of Bacillus Sphaericusrdquo International Journal ofEngineering Science and Technology vol 2 no 3 pp 270ndash2772010

[6] V Ramakrishnan S S Bang and K S Deo ldquoA novel tech-nique for repairing cracks in high performance concrete usingbacteriardquo in Proceedings of the International Conference onHigh Performance High Strength Concrete pp 597ndash618 PerthAustralia 1998

[7] V Achal A Mukherjee and M Sudhakara Reddy ldquoMicrobialconcrete a way to enhance durability of building structuresrdquo inProceedings of the 2nd International Conference on SustainableConstruction Materials and Technologies Ancona Italy June2010

[8] Y H Supratao Application of microbiology to improve themechanical properties of soil and concrete [MS thesis] Univer-sity of Indonesia 2011

[9] N Chahal R Siddique and A Rajor ldquoInfluence of bacteria onthe compressive strength water absorption and rapid chloridepermeability of fly ash concreterdquo Construction and BuildingMaterials vol 28 no 1 pp 351ndash356 2012

[10] IS 8112 ldquo43 Grade Ordinary Portland CementmdashSpecificationrdquo1989

[11] IS 383-1970 ldquoSpecification for Coarse and Fine Aggregatesfrom Natural Sources for Concreterdquo

[12] IS 10262-1984 ldquoIndian Standard Recommended Guidelines forConcrete mix designrdquo

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Propagation




Navigation and Observation



DistributedSensor Networks



the cement hydration process as discussed by Ramachandran[1] Pera et el [2] and Kakali et al [3] It was found thatthe Sporosarcina pasteurii bacteria attain their maximumactivity rate at 16 hours and maintain this till the timethe nutrition medium is consumed Thus the secretion ofmaximum amount of calcium carbonate takes place only16 hours after the concrete has been mixed thus providingenough workable time for concrete Also it has been seen thatthis nutritional medium neither allows for the loss in slumpnor causes immediate setting of the concrete

In the present work the bacterial admixture has beenadded in different compositions and concentrations alongwith other products like urea sodium carbonate calciumchloride and so forth in differing proportions to study itsimpact on compressive strength at 3 7 14 and 28 days ofcuring The compressive strength obtained of bioconcretethat is with Sporosarcina pasteurii bacteria is compared withthe strength gained by controlled concrete at 3 7 14 and 28days respectively

The work also tries to examine the use of sodium carbon-ate along with the nutrient medium in concrete and simulatethe chemical reaction which is the major contribution of theauthors to the research wherein earlier only urea had beentried by experts The below chemical reactions (1) and (2)depict the formation of calcium carbonate that acts like acatalyst for the formation of C-S-H gel which is required forthe hydrolization of cement

Using urea

CO(NH2)2+H2O 997904rArr NH

2COOH + NH

3

NH2COOH +H

2O 997904rArr NH

3+H2CO3

H2CO3997904rArr 2H+ + CO

3

2minus

2NH3+ 2H2O 997904rArr 2NH

4

+ + 2OHminus

HCO3minus +H+ + 2OHminus 997904rArr CO3

2minus + 2H2O

Ca2+ + CO3


(1)

(Kashyap and Radhakrishna [4])Using sodium carbonate

Na2CO3997904rArr 2Na+ + CO

3

2minus

CO3

2minus +H2O 997904rArr HCO

3

minus +OHminus

Na+ +OHminus 997904rArr NaOH (increasing pH)

HCO3

minus 997904rArr CO3

2minus +H+

Ca2+ + CO3


(2)

(experimental work)

2 Literature Review

A novel technique for the remediation of damaged struc-tural formation has been developed by Arunachalam et al[5] by employing a selective microbial plugging process

0 25 50 75 100 125 150 175

Time (hr)

0

1

2

3

4

5

6

Wat

er ab

sorb

ed (k

gm

2)

Control

Bacillus sp CT-5

Figure 1 Water absorption experiment on Bacillus sp CT-5 [7]

In this process the microbial metabolic activities promoteprecipitation of calcium carbonate in the form of calcite Themicrobial sealant CaCO

3 exhibits positive potential to selec-

tively consolidate simulated fractures and surface fissures ingranites and sand plugging as reported by Arunachalam etal [5] Previous studies with aerobic microorganism (Bacilluspasteurii and Pseudomonas aeruginosa) showed a significantimprovement (about 18) in compressive strength of cementmortar as shown by Ramakrishnan et al [6] The researchdone by Achal et al [7] illustrates a 3615 improvementin the compressive strength of mortar specimens at 28 daysprepared with bacterial cells It is significantly noted thatamong the controlled concrete specimens prepared withoutthe inclusion of bacterial cells the concrete cubes cured inmicrobial growth medium were stronger than those curedin water although there was not much significant variationResearch has also showed that the ionic strength of mediumcontaining urea-CaCl

2appeared to enhance the compressive

strength of the concreteThe improvement in compressive strength by Bacillus

sp CT-5 is probably due to deposition of CaCO3on the

microorganism cell surfaces and within the pores of cement-sand matrix which plug the pores within the mortar asdiscussed by Supratao [8] They also found that once thepores in the matrix were plugged the flow of the nutrientsand oxygen to the bacterial cells stopped eventually the cellseither died or turned into endospores and acted as an organicfiber increasing the compressive strength of the concrete

The decrease in permeability of mortar specimens treatedwith bacteria could also be seen from the water absorptionexperiment Figure 1 shows a decrease in thewater absorptionby a CT-5 cube in comparison to control cube Thus it can beinterpreted that the permeability also reduces which is a verydesirable property in concrete This also limits the ingress ofharmful substances as reported by Achal et al [7] From theexperiment it is clear that the presence of a layer of carbonatecrystals on the surface by bacterial isolate has the potentialto improve the resistance of cementitious materials towardsdegradation processes

















4 Test Programme











1 225 30 600 10 08 232 332 4342 225 30 600 10 08 231 328 4313 225 30 600 10 08 227 331 432





Wt retained(gm)



60mm 0 0 10040mm 0 0 10020mm 900 900 5510mm 987 1887 565 0 0 0475mm 104 1991 045 25 25 975236mm 9 2000 0 27 52 948118mm 0 2000 0 209 261 739600 120583 0 2000 0 292 553 447300 120583 0 2000 0 412 965 35150 120583 0 2000 0 35 1000 0














0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 1

SET 2


0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

ControlSET 3









0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 4

SET 6


0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 5

SET 7




3S C2S C3A and C

4AF) but



C3SC2SC3AC4AF +H


2

(3)


7 Conclusions







References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation

























4 Test Programme











1 225 30 600 10 08 232 332 4342 225 30 600 10 08 231 328 4313 225 30 600 10 08 227 331 432





Wt retained(gm)



60mm 0 0 10040mm 0 0 10020mm 900 900 5510mm 987 1887 565 0 0 0475mm 104 1991 045 25 25 975236mm 9 2000 0 27 52 948118mm 0 2000 0 209 261 739600 120583 0 2000 0 292 553 447300 120583 0 2000 0 412 965 35150 120583 0 2000 0 35 1000 0














0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 1

SET 2


0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

ControlSET 3









0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 4

SET 6


0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 5

SET 7




3S C2S C3A and C

4AF) but



C3SC2SC3AC4AF +H


2

(3)


7 Conclusions







References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














1 225 30 600 10 08 232 332 4342 225 30 600 10 08 231 328 4313 225 30 600 10 08 227 331 432





Wt retained(gm)



60mm 0 0 10040mm 0 0 10020mm 900 900 5510mm 987 1887 565 0 0 0475mm 104 1991 045 25 25 975236mm 9 2000 0 27 52 948118mm 0 2000 0 209 261 739600 120583 0 2000 0 292 553 447300 120583 0 2000 0 412 965 35150 120583 0 2000 0 35 1000 0














0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 1

SET 2


0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

ControlSET 3









0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 4

SET 6


0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 5

SET 7




3S C2S C3A and C

4AF) but



C3SC2SC3AC4AF +H


2

(3)


7 Conclusions







References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation

















0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 1

SET 2


0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

ControlSET 3









0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 4

SET 6


0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 5

SET 7




3S C2S C3A and C

4AF) but



C3SC2SC3AC4AF +H


2

(3)


7 Conclusions







References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0 5 10 15 20 25 30

35

40

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 4

SET 6


0 5 10 15 20 25 30

35

40

45

0

5

10

15

20

25

30

Com

pres

sive s

treng

th

Days

CCSET 5

SET 7




3S C2S C3A and C

4AF) but



C3SC2SC3AC4AF +H


2

(3)


7 Conclusions







References




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









research article achievement of early compressive strength in...

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