icise 2015 full paper -papr id 151

8/20/2019 ICISE 2015 Full Paper -Papr ID 151

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MATHEMATICAL MODELING FOR DURABILITY

CHARACTERISTICS OF BACTERIAL CONCRETE

1Dr V Srinivasa Reddy1, Dr M V Seshagiri Rao2, S Sushma3

SYNOPSIS: This paper presents the results obtained from the mathematical modeling for thedurability characteristics of bacterial concrete ! mathematical model is employed to predict the"ater absorption capacity, porosity, permeability, sorpitivity and acid resistance of the concreteembedded "ith bacteria #acillus Subtilis $%3 of 1&' bacterial cells ( ml This model is valid for various grades of bacterial concrete considered The mathematical model developed predict thefor "ater absorption capacity, the rate of permeability, sorpitivity and porosity of different gradesand at various ages These parameters in concrete structure determine the durability and performance of concrete This statistical analysis assures reasonable response prediction "hencompared "ith the e)perimental results

KEYWORDS: #acterial %oncrete* #acillus Subtilis $%3* mathematical modeling* durability*self+healing

INTRODUCTION

Durability of concrete can be defined as the capability to perform satisfactorily in the e)posurecondition to "hich it is subected over an intended period of time "ith minimum of maintenance"hile maintaining its preferred engineering properties %hemical attac- by aggressive "ater isone of the factors responsible for damage to concrete %oncrete can also be subected to attac- byvarious mineral acids such as sulphuric acid, nitric acid, hydrochloric acid and phosphoric acid.n natural ground "ater, only sulphuric acid is li-ely to be found as a result of the o)idation of

sulphide minerals such as pyrites and marcasite /hen concrete comes in contact "ith suchacidic "aters, the calcium hydro)ide reacts "ith the sulphuric acid to form gypsum, "hich can bereadily "ashed a"ay Sulphuric acid is also one of the main acidifying agents of acid rain Muchhigher concentrations can occur in industrial environments !nother source of severe sulphuricacid attac-, "hich is very common "orld"ide, is that "hich generates by bacteria in concretese"age systems The anaerobic bacteria generates hydrogen sulphide gas "hich can dissolve in"ater condensed on the "alls of the concrete conduits, pipes, and manholes above the se"ageline level "here aerobic bacteria can produce sulphuric acid .ndustrial "aters contain enoughsulphate ions to potentially damage the 0ortland cement concrete by forming deleterious solubleal-ali sulphatesThe main obective of the present investigation is to study the durability characteristics of

bacterial concrete and to develop the mathematical model for the durability characteristics The

11 Associate Professor of Civil Engineering, GRIET,Hyderbad-50000, India,

ve!"ada#g!ail$co!% Professor of Civil Engineering, &'T(HCEH, Hyderabad-5000)5, India,

rao*vs*!ed+ri#g!ail$co! PG t+dent of Civil Engineering, &'T(HCEH, Hyderabad-5000)5, India, s+s.!a$seesa#g!ail$co!

mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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durability properties investigated in this study are acid attac-, permeability, "ater absorptioncapacity, porosity and sorpitivity

BACTERIAL CONCRETE

#acterial concrete is produced by incorporating spores of bacteria of a special -ind #acillusSubtilis $%3 of 1&' bacterial cells ( ml in the concrete matri) at the stage of preparation of theconcrete by mi)ing the spore suspension in concrete mi)ing "ater The homogeneouslydistributed bacterial spores in hardened concrete matri) gets activated and germinate to becomemetabolically active vegetative cells that are able to convert the organic nutrient compounds intoinsoluble inorganic calcium carbonate based minerals "hich "ill fill up the pores present in theconcrete

EXPERIMENTAL INVESTIGATIONS

a) Studi! "# A$id atta$% &!i!ta#$

The obective of the present investigations is to study the effect of aggressive chemicalenvironment on compressive strength loss and "eight loss of bacterial and controlled concretee)posed to different concentrations of 3 and ' 42S56T!t 't("d""*+7 %oncrete cubes of si8e 1&&mm ) 1&&mm ) 1&&mm, of ordinary grade M2&,standard grade M6& and high strength grade M9& bacterial and controlled concretes are castand cured for 29 days They are immersed in different concentration of 42S56 The percentage"eight loss, percentage compressive strength loss is evaluated at 29, :& and 12& days of e)posure #acterial and controlled concrete cube specimens of different grades are immersed inacid solutions

,) Studi! "# Wat& -&'a,iit+

/ater absorption, sorptivity and "ater permeability measurement are some methods to determinethe "ater penetrability of concrete ! tria)ial cell permeability apparatus method used for determining "ater permeability of concrete utili8es Darcy;s


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specially designed cells and a constant air pressure of 1' -g(cm2 is maintained by using air compressor throughout the e)periment for a given interval of time The standard test pressurehead to be applied to the "ater should be 1& -g(cm2 The Auantity of percolated "ater collected ismeasured at periodic intervals .n the beginning, the rate of "ater inta-e is larger than the rate of outflo" !s the steady state of flo" is approached, the t"o rates tend to become eAual and the

outflo" reaches ma)imum and stabili8es /ith further passage of time both inflo" and outflo"generally register a gradual drop 0ermeability test shall be continued for about 1&& hours after the steady state of flo" has been reached and the outflo" shall be considered as average of allthe outflo"s measured during the period of 1&& hours Then the coefficient of permeability -, inm(sec based on Darcy;s la" for a falling "ater head, "hich is applicable at steady state flo"conditions, can be computed on 29 days aged specimens, using the follo"ing formula

BC

! T 14 (


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The aim of this study is to determine the total "ater absorption capacity and measure the volumeof voids present in controlled and bacteria incorporated concretes of ordinary M2&, standardM6& and high strength M9& grades as per !STM %:62+13 The total Auantity of "ater absorbed is related to the total open porosity, "hile the -inetics of the process depends principally on the distribution of the pore si8es This test also measures the capillary rise of

"ater, the most common form of liAuid "ater migration into concrete "hich is inversely proportional to the diameter of the pores The smaller the diameter of the pores, the greater "ill be the capillary absorption !bsorption is the capacity of a sample to hold "ater "hile capillaryis the rate at "hich the "ater fills the sampleT!t 't("d""*+7 %oncrete cube samples of si8e 1&& ) 1&& ) 1&& mm are casted and cured for 29 days for testing Dry the samples in the oven for 26 hours at :&H% and record their "eightsRepeat the drying process until the mass of the each sample is constant, that is, until thedifference bet"een 2 successive measurements, at an interval of 26 hours, is no more than &1of the mass of the sample 5nce the samples have been completely dried and the constant mass isrecorded mo, place them in a container or bea-er, on a base of glass rods and slo"ly cover "ithde+ioni8ed "ater until they are totally immersed "ith about 2 cm of "ater above them !t

programmed intervals of time, ta-e each sample out of the container, blot it Auic-ly "ith a dampcloth to remove surface "ater, and then record the mass of the "et samples mi and the time of measurement on the data sheet Re+immerse the samples in "ater and continue measuring untilthe difference in "eight bet"een 2 successive measurements at 26+hour intervals is less than 1of the amount of "ater absorbed !t this point, ta-e the samples out of the "ater and dry themagain in an oven at :&H% until they have reached constant mass as above Record this valuemd on the data sheet !t each interval, the Auantity of "ater absorbed "ith respect to the massof the dry sample is e)pressed as7

Mi 1&& ) mi + mo(mo 2/here mi "eight -g of the "et sample at time ti* mo "eight -g of the dry sampleRecord these values on a data sheet and on a graph as a function of time The length of theintervals during the first 26 hours depends on the absorption characteristics of the materials%oncrete samples should be "eighed a fe" minutes after immersion, and then at increasingintervals 1' min, 3& min, 1 hour, etc for the first 3 hours !ll samples should then be "eighed9 hours after the beginning of the test and then at 26+ hour intervals until the Auantity of "ater absorbed in t"o successive measurements is not more than 1 of the total massGor measuring the "ater absorption capacity and volume of permeable voids, a balance, "ater bath, and container suitable for immersing the specimen are needed for performing the test !fter the 1&&)1&&)1&& mm cube samples "ere cured for 29 days, three samples "ere put into an ovenat :&H % for 26 hours The dried samples "ere ta-en from the oven and allo"ed to cool for about3& minutes The samples "ere then "eighed Ma using a balance "ith an accuracy "ithin &&1grams The samples "ere submerged in the "ater tan- for 26 hours !fter 26 hours, the samples"ere removed from the "ater tan- and their surface "as dried "ith a paper to"el to obtain asaturated surface dry SSD condition The "eight M b of the SSD samples "as measured .nthe ne)t step, the samples "ere put into a "ater bath "ith boiling "ater for ' hours Then thesamples "ere removed from the boiling "ater and left to cool for 12 hours Then "eights of thesamples "ere measured Mc 5n the same day, the apparent "eight of each sample Md "asmeasured by immersing the samples in the "ater using a hanging balance Ising the measured"eights Ma to Md and the eAuations from the !STM %:62 standard test, the follo"ing parameters are obtained


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/ater !bsorption %apacity /!% JM b+Ma( MaK ) 1&& 3 Volume of permeable voids V0V Jg2 + g1( g2K ) 1&& 6

"here7 Ma mass of oven+dried sample in air, -g* M b mass of surface+dry sample in air after immersion, -g * Mc mass of surface+dry sample in air after immersion and boiling, -g and Md apparent mass of sample suspended in "ater, -g

g1 dry bul- density -g(m3

* g2 apparent density -g(m3

* L density of "ater 1&&& -g(m3

Ginally total porosity F0; or percentage of interconnected pore space "as calculated using theformula given belo"

Total porosity Vv(V /sat+ /dry ( L/ V '/here, Vv volume of voids in cc /sat+ /dry in grams*

V total volume of specimen in cc 1&& ) 1&& )1&& mm3 /here L/ the unit mass of "ater 1 g(cc

/dry and /sat denote the "eight of the dried and fully saturated samples, respectively0orosity of concrete is usually determined by dividing the volume of voids of the sample by its bul- volume #ul- volume of each sample is determined using the measured lengths anddiameters of the samples Volume of voids for each sample is determined by subtracting its grain

volume the volume of the solid portion of concrete e)cluding the volume of pores from its bul- volume Total porosity therefore considers both permeable and impermeable voids "hereasapparent porosity considers only impermeable voids

d) Studi! "# S"&-ti5it+

The obective of this study is to determine the sorpitivity of controlled and bacteria incorporatedconcretes of ordinary M2&, standard M6& and high strength M9& grades as per !STM%1'9' Sorptivity measures the rate of penetration of "ater into the pores in concrete bycapillary suction .t is also a measure of the capillary forces e)erted by the pore structure causingfluids to be dra"n in to the body of the material .t provides a relative measure that combines pore si8e diameter and number of pores present The depth of "ater absorbed into concreteincreases linearly "ith respect to the sAuare root of "etting time .n terminology, the sorptivity isthe change in volume of "ater absorbed per unit area against the sAuare root of time /ater absorption and sorptivity can suggest useful data regarding the pore structure of the concreteT!t 't("d""*+: Determining the sorptivity of a sample in the lab is a simple, lo" technologytechniAue, all that is reAuired, is a scale, a stop"atch and a shallo" tub of "ater The samples1&& ) '& mm si8e cylindrical specimens are preconditioned to a certain moisture condition,either by drying the sample for E days in a '&H% oven The sides of the concrete sample aresealed, typically "ith electrician;s tape or by sealant "hile the suction face and the face oppositeit "ere left unsealed %ylindrical concrete specimens "ere placed on a filtered support spongeso that the "ater level "as 1&1 mm above the inflo" face The sample is immersed to a depthof '+1& mm in the "ater then the initial mass of the sample and time of start are recorded The procedure of recording mass of the sample "as repeated, consecutively, at various times such as1' min, 3& min, 1 hr, 2 hr, 6 hr, : hr, 26 hr, 69 hr and E2 hr The gain in mass per unit area over the density of "ater . is plotted versus the sAuare root of the elapsed time Nt The slope of theline of best fit of these points ignoring the origin is reported as the sorptivity coefficient -The rate of "ater absorption or sorptivity -, is the slope of .+ Nt graph m ( min1(2 or -g( m2 ( NminGor one dimensional flo", it can be stated that 4all, 1?9?7

. - ) Nt :


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/here - is sorptivity coefficient and . /(! ) d/ the amount of "ater absorbed in -g! !rea of the c(s of the specimen that is in contact "ith "ater m 2d density of the medium in "hich the specimen "as dipped 1&&& -g(m 3 in case medium is"ater

#ecause of small initial surface tension and buoyancy effects, the relationship bet"eencumulative "ater absorption -g(m2 and sAuare root of e)posure time t &' sho"s deviationfrom linearity during first fe" minutes Thus, for the calculation of sorptivity coefficient, onlythe section of the curves for e)posure period from 1' min to E2 hrs, "here the curves "ereconsistently linear, "as used for the calculation of sorptivity

TEST RESULTS AND DISCUSSION

The tables 1 and 2 sho"s the compressive strength, "eights, percentage loss of compressivestrengths and percentage "eight loss of bacterial and controlled concrete specimens e)posed to3 and ' concentrations of 42S56

Table 17 %ompressive strengths and /eights of various grades of controlled and bacterialconcrete specimens e)posed to different concentrations of 42S56

=rade of %oncrete

Type of specimen

!cidO)posure

%ompressiveStrengthM0a

/eights -g

Days of .mmersion Days of .mmersion

29 :& 12& 29 :& 12&

M2&

%ontrolled3 42S56 299: 2E?? 26?1 266 239 233

' 42S56 2911 2E&2 261' 23? 233 23&

#acterial 3 42S56 32&? 31'? 2?62 269 26: 26&

' 42S56 312: 3&?? 299? 26' 263 23'

M6&

%ontrolled3 42S56 6?11 69'9 66&' 2'1 269 261

' 42S56 6966 6E9: 62'9 269 26' 23'

#acterial3 42S56 :&69 :&11 '9?2 2'3 2'& 266

' 42S56 :&&? '?99 'E&? 2'2 269 239

M9&

%ontrolled3 42S56 ?2?& ?21: ?&&2 2'3 2'1 263

' 42S56 ?2:: ?1?' 9?19 2'2 26? 261

#acterial3 42S56 11E9? 11:?' 116'' 2'1 26? 266

' 42S56 11:'9 11'&1 113&9 2'& 26E 261


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Table 27 loss of %ompressive strength and loss of /eights of various grades of controlled

and bacterial concrete specimens e)posed to different concentrations of 42S56

=rade of %oncrete

Type of specimen

!cidO)posure


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attac- and sulphate attac- The percentage loss of compressive strength and "eight in 42S56solution is higher

6 Grom the durability studies carried out on controlled and bacteria incorporated concretes of M2&,M6& and M9& grades revealed that the percentage loss of compressive strengths and percentageloss of "eights are very less in all grades of bacteria incorporated concretes "hen e)posed up to

12& days to 3 and ' concentrations of 42S56 acid "hich confirms that the bacteriaincorporated concrete resistance to acid attac- deterioration is better than conventional concretedue to the formation of highly impermeable calcite in the pores of the concrete "hich acts as amicrobial sealant

' So it can be inferred that #acteria incorporated concrete is more durable and less attac-ed thancontrolled concrete at all the ages and can perform better in severe aggressive environments dueto its high impermeability and al-alinity of concrete mass

The tables 3 and 6 presents the coefficients of permeability values determined as per .S 3&9' andD.> 1&69 for all grades of controlled and bacteria incorporated concrete specimens of age 29days

Table 37 %oefficients of 0ermeability for controlled and bacteria incorporated concrete specimensof age 29 days

=rade of %oncrete

Type of specimen 0ressure head4 m

Buantity of "ater collected

ml

%oefficient of permeability) 1&+? m(sec

Reduction

M 2&%ontrolled 1&& ?922 231 +

#acteria treated 1&& 11'E &2E 99

M 6&%ontrolled 1&& E9&& 196 +

#acteria treated 1&& 1&3? &2' 9:

M 9&%ontrolled 1&& 29'& &:E +

#acteria treated 1&& ??1 &23 ::

Table 67 Depth of 0enetration for controlled and bacteria treated concrete specimens of age 29days

=rade of %oncrete

Type of specimenDepth of /ater 0enetration

mm

ReAuirement as per M5RT@4 6th Revision

%lause 1E1:'

M 2& %ontrolled 232'mm Ma)imum permissible limit

#acteria treated '

M 6&%ontrolled 1E

#acteria treated 6

M 9&%ontrolled '

#acteria treated 1


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0 1 2 3 40

0.5

1

1.5

2

2.5

f(x) = - 0.02x + 0.29

R² = 1

f(x) = - 0.82x + 3.25

R² = 0.94

Control Concrete Linear (Control Concrete)

Bacterial Concrete Linear (Bacterial Concrete)

Coefcient o permeability

x 10-9 m/sec

Gig 17 Sho"s the variation of coefficients of permeability in bacterial concrete and controlledconcrete for various grades

0 1 2 3 40

5

10

15

20

25

f(x) = - 2x + .33

R² = 0.92

f(x) = - 9x + 33

R² = 0.9!



Depth o Water Penetration(mm)

Gig 27 Sho"s the variation of Depth of "ater penetration in bacterial concrete and controlledconcrete for various grades


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Grom the presented test results, it "as observed that significantly lo"er "ater permeability isobserved in bacteria induced specimens than controlled specimens under 1&&m "ater headReduction in "ater permeability of specimens treated "ith bacteria is nearly 99, 9: and ::in M2&, M6& and M9& grade concretes respectively, of age 29days .t sho"s that all grades of bacteria incorporated concretes are less permeable than the controlled concretes the reason

attributed is that the bacteria incorporated concretes has improved pore structure due to precipitation of calcite crystals subseAuently reduction in the porosity of the concrete "hichsubstantially reduces the permeability of the concrete There "ere no signs of physical "ater transmission through high strength grade M9& of bacteria induced concrete specimens under 1&& meters "ater head for first E2 hrs because the "ater permeability in these concretes "as verylo" !t the end of the test, the Auantity of "ater collected is relatively very less So it isunderstood that "ater permeability test as per .S 3&9' is not given correct results for highstrength grades M9& To determine "ater permeability of high strength grades, "ater penetration depth in measured at the end of 26 hrs, as per D.> 1&69, by splitting the concretecylinder samples The main idea of this test as per D.> 1&69 is that "ater penetrates the concretespecimens under a set pressure for a set period of time So depths of penetration are measured to

evaluate the "ater impermeability of all grades of controlled and bacteria incorporated concretesThe depth of "ater penetration measured in bacteria induced specimens "hen tested in D.> 1&69"ater permeability tests corresponds to the Pvery lo" permeabilityQ Depth of penetration isreduced in bacteria built+in specimens by nearly E: in all the grades of concrete .n the case of #acteria incorporated concrete, bloc-ing of the pores due to calcite mineral precipitates reducesthe "ater permeability so the depth of penetration is very lo" "hen compared "ith "ater penetration depths in controlled concrete The figure 3 depicts the amount of "ater absorption"ith time Table ' give the "ater absorption capacity /!% and volume of permeable voids of all grades of controlled and bacteria incorporated concrete specimens

0

1

2

3

4

5

!

"20 Controlle# "40 Controlle# "80 Controlle#

"20 Bacterial "40 Bacterial "80 Bacterial

ti$e ($in)

%$o&nt of 'ater aore# (" * )


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0 1 2 3 40

0.02

0.04

0.0!

0.08

0.1

0.12

0.14

0.1!

f(x) = - 0.01x + 0.05

R² = 1

f(x) = - 0.0!x + 0.19

R² = 0.98



Porosity

Gig '7 Sho"s the variation of 0orosity in bacterial concrete and controlled concrete for variousgrades

%oncrete specimens incorporated "ith bacteria sho"ed significantly less "ater absorptioncapacity compared to controlled specimens This decrease in "ater absorption capacity of allgrades of bacteria incorporated concretes is attributed to the reduction of pores in the concrete/ater !bsorption %apacity /!% of bacteria incorporated concrete specimens is reduced bynearly '& to E' for lo" to high grade concretes as compared "ith /!% of controlled concrete

specimens due to pore plugging "ith bacteria produced calcite minerals thereby modifying the pore structure of the cement sand matri) The absorption characteristics indirectly represent thevolume of pores and their connectivity 0orosity of concrete specimens is reduced by nearly 36 +E3 "ith induction of bacteria into concrete for high to lo" grades The possible reason for thisis calcite mineral precipitation in the pores reduced the average pore radius of concrete Thismeans that the time ta-en for the "ater to rise by capillary action in bacteria incorporatedconcrete is longer and thus proved that these bacteria induced concretes are less porouscompared to the control concrete The rate of "ater absorbed into concrete through the poresgives important information about the microstructure and permeability characteristics of concrete Volume of permeable voids present in bacteria incorporated concrete is less by '&+:' than in controlled specimens


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Table :7 Sorptivity %oefficients of controlled and bacteria incorporated concrete specimens of different grades

=rade of the %oncreteSorptivity %oefficient - ) 1&+3

m(min&' 0ercentage reduction

%ontrolled %oncreteM2& &126 +M6& &&?2 +M9& &&'' +

#acteria incorporatedconcrete

M2& &&?1 2::M6& &&E1 229M9& &&'1 ?3

0 1 2 3 4

0

0.02

0.04

0.0!

0.08

0.1

0.12

0.14

f(x) = - 0.02x + 0.11

R² = 1

f(x) = - 0.03x + 0.1!R² = 1



!orpti"ity Coefcient (#) x 10-$

m/min0%&

Gig :7 Sho"s the variation of Sorptivity in bacterial concrete and controlled concrete for variousgrades

Grom table : it is apparent that sorptivity decreases systematically for bacteria treated concretespecimens for all grades The sorptivity coefficients of bacteria incorporated concrete specimens

are lo" for all grades "hen compared "ith corresponding grades of controlled concretespecimens because the pores in the bul- paste or in the interfaces bet"een aggregate and cement paste is filled by the mineral precipitation hence, the capillary pores are reduced The capillaryabsorption coefficient - is greatly influenced by the addition of microorganisms to the concreteThe reduction in capillary due to induction of bacteria into concrete specimens is bet"een ? to 2E for high to lo" grades The "ater absorption, capillary and porosity characteristics indirectlyreflect the durability performance of the bacteria incorporated concrete


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MATHEMATICAL MODELLING

! mathematical model is a description of a system using mathematical concepts and language !Simple linear Regression model is adopted to measure the durability characteristics of bacterial

concrete based on the grade of the concrete The follo"ing Simple linear regressionmathematical models are proposed to predict the durability characteristics of bacterial concretefor various grades of the concrete7

Table E7 Mathematical models for various durability characteristics of #acterial concrete and%ontrol concretes

Du&a,iit+ C(a&a$t&i!ti$ C"#t&" C"#$&t Ba$t&ia C"#$&t

Sorptivity %oefficient - ) 1&+3

m(min&'y +&&36') &1'?3

R &??93y +&&2) &111

R 1

0orosityy +&&'') &1?

R &?E'9

y +&&1) &&'

R 1/ater !bsorption %apacity /!%

y +2&') E61R &?'6

y +12&') 39:33R &?:'6

%oefficient of permeability) 1&+? m(sec

y +&92) 326:ER &?62E

y +&&2) &2?R 1

Depth of /ater 0enetration mmy +?) 33R &?:63

y +?) 33R &?:63

The variations bet"een the predicted and e)perimental results is very less validating the above proposed models for predicting durability characteristics for various grades of bacterial concrete

C"#$u!i"#!#ased on the investigations carried out, the follo"ing conclusions can be dra"n71. The bacteria induction into concrete enhances the resistance to acid attac- deterioration

due to formation of bacteria precipitated impermeable calcite crystals "hich "ill plug the pores present in the concrete

2 The investigations sho"s that bacteria incorporated concretes "ere less permeable thanthe control concretes the reason is that the bacteria incorporated concrete has improved pore structure due to precipitation of calcite crystals subseAuently reduction in the porosity of the concrete "hich substantially reduces the permeability of the concrete

3 .t can concluded that all grades of bacteria incorporated concretes have less "ater absorption capacity compared to corresponding grades of controlled concrete specimens

due to pore plugging "ith bacteria produced calcite minerals This reduction of porosityin bacteria incorporated concretes indicates the presence of less volume of permeablevoids /ater !bsorption %apacity /!% of bacteria incorporated concrete specimens isreduced as compared in controlled concrete specimens inferring the reduced e)tent of volume of pores and their connectivity in bacteria induced concrete

6 Volume of permeable pores V0V of bacteria incorporated concrete specimens arereduced since calcite mineral precipitation in the pores reduced the average pore radius of concrete by inducing pore discontinuity in the hydrated cement paste This means that the


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time ta-en for the "ater to rise by capillary action in bacteria incorporated concrete arelonger and thus proved that these concrete are less porous compared to the conventionalconcrete

' The mathematical model predicted accurate results "hen compared "ith e)perimentalresults

REFERENCES

1 De Muync-, /, Debrou"er, D, De #elie, >, Verstraete, /, 2&&9, P#acterial carbonate precipitation improves the durability of cementitious materialsQ, %em %oncr Res 39 E, pp1&&'1&16

2 4en- M $on-ers, !ran Thissen, =erard Muy8er, 5gu8han %opuroglu, Ori- Schlangen, 2&1&,P!pplication of bacteria as self+healing agent for the development of sustainable concreteQ,Ocological Ongineering Volume 3:2&1&, pp23&+23'

3 >avneet %hahal, Rafat SiddiAue, 2&13, P0ermeation properties of concrete made "ith fly ashand silica fume7 .nfluence of ureolytic bacteriaQ, %onstruction and #uilding Materials, Volume

6? 2&13, pp 1:11E66 >emati, M, Voordou", =, 2&&3, PModification of porous media permeability, using calciumcarbonate produced en8ymatically in situQ On8yme Microb Technol 33 ', pp:3':62

' Rama-rishnan V, 2&&E, P0erformance characteristics of bacterial concrete+a smart biomaterialQ,0roceedings of the Girst .nternational %onference on Recent !dvances in %oncrete Technology,/ashington, D%, 2&&E, pp:EE9

: Varenyam !chal, !bhieet Mu-eree, M Sudha-ara Reddy, 2&13, P#iogenic treatment improvesthe durability and remediates the crac-s of concrete structuresQ, %onstruction and #uildingMaterials 2&13, Volume 69, pp1'

E Varenyam !chal, Uiangliang 0an, >ilufer 58yurt, 2&1&, P.mproved strength and durability of fly ash+amended concrete by microbial calcite precipitationQ, Ocological Ongineering 2&1&,Volume 3E, pp''6+''?

9 /i-tor V and $on-ers 4 M, 2&11, PDevelopment of bacteria+based systems to increase concretestructures durabilityQ, .nternational /or-shop on Structural

icise 2015 full paper -papr id 151

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