research paper estimation of marine salts behavior around the bridge structures€¦ · ·...

151

Int. J. Struct. & Civil Engg. Res. 2014 Senthil Kumar C and Naveenraj V, 2014

ESTIMATION OF MARINE SALTS BEHAVIORAROUND THE BRIDGE STRUCTURES

The development of chloride penetration models is essential for the assessment of the servicelife of concrete structures exposed to marine environment. Simple models are derived fromFick’s 2nd law of diffusion are at present the best way to predict chloride penetration in practicalsituations. However these models need to be calibrated with experimental results. This paperpresents an experimental study where the parameters used in the penetration model wherecalibrated to allow the prediction of long term chloride content in concrete. The results showedthat the concrete cover and concrete quality requirements stated in the present codes need tobe increased so that an acceptable service life can be achieved.

Keywords: M30, Strength, Corrosion

1 M.E. Student, Department of Civil Engineering,, Nandha Engineering College, Erode, Tamil Nadu, India.2 Assistant Professor, Department of Civil Engineering,, Nandha Engineering College, Erode, Tamil Nadu, India.

INTRODUCTIONService life prediction is becoming one of themajor tasks in the design of concretestructures. The durability design must be basedon consistent models that can describe thedeterioration models more accurately.

In marine environment, the service life ofreinforced concrete structures depends mainlyon deterioration due to reinforcementcorrosion. Two stages can be considered inthis mechanism; the initiation periodcorresponding to the critical chloridepenetration up to the level of reinforcement andthe propagation period related to thereinforcement corrosion and its detrimentaleffects on the structure.

ISSN 2319 – 6009 www.ijscer.comVol. 3, No. 4, November 2014

© 2014 IJSCER. All Rights Reserved

Int. J. Struct. & Civil Engg. Res. 2014

Research Paper

The high corrosion rates generally observedin marine environment and the difficulty inmodeling this mechanism and its effect on thestructures led to the usual consideration ofservice life as the initiation period.

AIM AND SCOPE OFINVESTIGATIONAIM• In world as consists of more than 70% cover

by oceans, river, etc., with salty content.

• Bridge is only way to travel, exchange agoods by land.

• Bridge structure is structural element whichare constructed by means of concrete

Senthil Kumar C1* and Naveenraj V2

*Corresponding Author: Senthil Kumar C, [email protected]

152


ingredients in salty water which can easilycorrosion in bridge column.

• Which result is reducing strength due tocorrosion of reinforcement in column.

• To prevent and overcome the damage byincreasing the concrete cover and concretequality requirements and prevent thecorrosion of the reinforcement.

• Additionally it can be used for fixedformwork in column.

• The strength, durability, and compressivestrength of column structure element arestudied and performed in this project.

MATERIALSMaterial investigation is done to test thevarious materials that are used in makingconcrete cubes. According to these test resultsobtained we designed the mix ratios for thematerials and prepared the concrete cubes,beams and cylinders. The information aregiven below,

CementOPC of 43 grades in one lot was procured andstored in air tight container. The cement usedwas fresh, i.e., used within three months ofmanufacture. It should satisfy the requirementof IS 12262. The properties of cement aredetermined as per IS 4031:1968 and resultsare tabulated.

Fine AggregateA fine aggregate obtained from the river isused for experimental purpose. The lessamount of clay and silt (<3% by weight). Thehire from silt, clay, salt and organic materialand it was clean and dry. It is of size retainedin 1.19 micron sieve.

BULKING OF FINEAGGREGATE• Table the representative of sample of sand,

from the available lot at sight.

• Fill the graduated jar with sand up to certainweight compacting.

• Level the sand surface by gentle motion andnote down this height.

• Now pour the water into the graduated jarcontaining sand till the sample issubmerged.

• Cover the jar with the disk and give somemotion.

• The tamping rod should be moved throughout into sample in the jar, so as to ensure toremoved of entrapped air completely.

Constituents Natural Sand (%) Test Method

SiO2 80.78 IS: 4032-1968

Al2O3 10.52

Fe2O3 1.75

CaO 3.21

MgO 0.77

Na2O 1.37

K2O 1.23

TiO2 Nil

Loss of ignition 0.37

Table 1: Chemical Composition ofManufactured Sand and Natural Sand

S. No. Properties Values

1. Size Passing through4.75 mm sieve

2. Fineness modulus 2.54

3. Specific gravity 2.78

4. Water absorption 1.0%

Table 2: Properties of Natural Sand

153


COARSE AGGREGATEThe coarse aggregate is strongest and porouscomponent of concrete. Presence of coarseaggregate reduces the drying shrinkage andother dimensional changes occurring on accountof movement of moisture. The coarse aggregateused passes in 19 mm and retained in 11.4 mmsieve. It is well graded (should of different particlesize and maximum dry packing density andminimum voids) and cubical in shape.

WaterOrdinary drinking water available in theconstruction laboratory was used for casting allspecimens of this investigation. Water helps indispersing the cement even, so that every particleof the aggregate is coated with it and broughtinto ultimate contact with the ingredients.

It reacts chemically with cement and bringsabout setting and hardening of cement. Itlubricates the mix and compact property.Potable water, free from impurities such as oil,alkalis, acids, salts, sugar and organicmaterials were used. The quality of water wasfound to satisfy the requirement if IS: 456-2000.

MIX DESIGNGeneralMix design can be defined as the process ofselecting suitable ingredients of concrete anddetermining their relative proportions with the

1. 600 550 9.09

2. 650 590 10.17

3. 700 650 7.14

Percentage of Bulking 8.8

Table 3: Bulking of Fine Aggregate

S. No.Initial

Height ofSand

Height of SandAfter Adding

Water

BulkingFactor

object of producing concrete of certainminimum strength and durability aseconomically as possible. The main objectiveis to stipulate the minimum strength anddurability. It also reveals the relation betweenaggregate and paste. The other conditionsbeing equal, for workable mixes the strengthof concrete varies as an inverse function of thewater/cement ratio. Since the quantity of waterdepend upon the amount of paste, it isimportant that as little paste as possible shouldbe used and hence the importance of grading.

1:1:2.18

Casting and CuringThe mould specification, preparation of mouldthe method of casting and curing arediscussed in following.

Casting Mould PreparationThe PVC mould dia 180 mm, 600 mm heightwas placed in position on an even surface. Allthe interior faces and sides were coated withmud oil to prevent the sticking of concrete tothe mould.

MixingThe concrete using grade M30 (1:1:2.18) withwater cement ratio 0.37 were used. Concreteis mixed in roller type of mixing machine.

Figure 1: Concrete Mixing

154


PlacingConcrete is properly placed beneath and alongthe sides of the mould with help of trowel.

CompactionHand compaction was done for all the cubesused in the test. The damping mild steel rodshaving point ends were used to poke theconcrete and it is placed in vibrating table tomake compaction complete.

Test of Specimen and ResultAnalysisTesting of concrete plays an important role incontrolling and confirming the quality of cementconcrete. Conventional column are tested forits strength characteristics.

Testing of SpecimenCompression TestThe cubes of size 150 x 150 x 150 mm areplaced in the machine such that load is appliedon the opposite side of the cubes as casted.Align carefully and load is applied, till thespecimen breaks. The formula used forcalculation.

Figure 2: Casting of Column

CuringThe specimen is striped after 24 hours. Thetest cubes were cured for duration of 28 daysin a curing tank. With chloride content.

Figure 3: Curing of Column

Figure 4: Compression Test

155


Compressive Strength = Total Failure Load/Area of the Cube

Split Tensile TestThe test is carried out by placing cylinderspecimen of dimension 150 mm diameter and300 mm length, horizontally between theloading surface of compression testingmachine and the load is applied until failure ofthe cylinder along the vertical diameter. Thefailure load of the specimen is noted.

The failure load of tensile strength of cylinderis calculated by using the formula

Tensile strength = 2P/3.14 DL6.2.2

where,

P – Failure of the specimen

D – Diameter of the specimen

L – Length of the specimen

points loading adopted on an effective spanof 400 mm while testing the prism. The load isapplied until the failure of the prism. By usingthe failure load of prism.

Flexural strength = Pl/bd2

P – Failure load of the prism

l – Length of the prism

b – Breadth of the prism

d – Depth of the prism

Figure 5: Split Tensile Test

Flexural TestThe test is carried out to find the flexural strengthof the prism of dimension 100 x 100 x 500 mm.The prism is then placed in the machine insuch manner that the load is applied to theuppermost surface as cast in the mould. Two

Figure 6: Flexural Test

S. No.Speciman Compressive Strength N/mm2

Cube 7 days 28 days

1. 1 16.89 29.01

2 17.10 29.15

Cylinder Split Tensile N/mm2

2. 1 0.95 2.35

2 0.98 2.40

Prism Flexural Test N/mm2

3. 1 4.09 6.40

2 4.01 6.17

Table 4: Test Results

Test SetupColumn has been tested in loading frame withproper procedure. The axial load is applied

156


gradually and the strain readings were takenat regular intervals of loading. The loading iscontinued up to the ultimate load level and thefailure pattern has been studied.

Apparatus

RC column,

Loading frame,

Load Po = ccAg + (SCCC)ASC

Figure 7: Testing of Column

Initial Crack 184 KN

Maximum Load 211 KN

No of Cycle(s) 355

Table 5: Column Resullt

CONCLUSION• The non use of concrete proves to be more

effective penetration in concrete column.

• May increase of concrete cover in columnto achieve good axial compressive strength,penetration control and corrosion.

• Compressive strength is decreased due tocuring in salty solution.

• Total ultimate load carrying capacity of thespecimen is devastatingly low. Since the

load carried is about 240 kN whereas theordinary is about only 109 kN.

SUGGESTION FOR FUTUREWORK• Use various sizes of cover for column with

different Mix of column specimen withvarious loading.

• Investigation of production of various sizesof Cover for column with different curing 28days, 54 days, and 84 days.

• Experimental Investigation of waterpermeability test after testing of column.

REFERENCES1. Costa A and Appleton J (1999), “Chloride

Penetration into Concrete in MarineEnvironment-Part I: Main ParametersAffecting the Penetration”, Materials andStructures, Vol. 218, pp. 252-259.

2. Costa A and Appleton J (1999), “ChloridePenetration into Concrete in MarineEnvironment-Part II: Prediction of LongTerm Chloride Penetration”, Materials andStructures, Vol. 32, June, pp. 354-359.

3. ENV 206 (1990), “Concrete, Performance,Production, Placing and ComplianceCriteria”.

4. IS: 456-2000 “Code of Practice for Plaina of Indian Standards”, New Delhi.

5. Mangat P S and Gurusamy K (1987),“Chloride Diffusion in Steel FibreReinforced Concrete”, Cem. Concr. Rcs.,Vol. 17, No. 3, pp. 385-396.

6. Mangat P S and Molloy B T (1992),“Factors Influencing Chloride-InducedCorrosion of Reinforcement in Concrete”,Materials and Structures , Vol. 25,pp. 404-411.

research paper estimation of marine salts behavior around the bridge structures€¦ · ·...

Documents