p. j. d. anjaneyulu m. k. m. v. rathnam dr. u. ranga raju

P.J.D.Anjaneyulu* et al.(IJITR) INTERNATIONAL JOURNAL OF INNOVATIVE TECHNOLOGY AND RESEARCH

Volume No.2, Issue No.6, October – November 2014, 1627 – 1631.

2320 –5547 @ 2013 http://www.ijitr.com All rights Reserved. Page | 1627

P. J. D. ANJANEYULUPursuing M. Tech. in Structural Engineering

Department of Civil Engineering,D. N. R. College of Engineering & Technology

Bhimavaram, West Godavari Dist,Andhra Pradesh, India.

M. K. M. V. RATHNAMAsst. Professor, M.Tech.



Dr. U. RANGA RAJUProfessor, M.Tech., Ph. D.



Abstract- Durability of concrete structures has been a topic of research for a long time. Manymodifications and various attempts are being made by Engineers and scientists have been proposed inconvectional concrete in order to improve its overall performance, including strength and durability. Anattempt has been made to study the comparison between M50 grade SCC and CVC with steel fibersdosage of 30 Kg/m³, 60 Kg/m³, and 90 Kg/m³ with aspect ratio of 35 and subjected to durability andmechanical strengths. In this experimental work, the scc concrete was designed using different availablemethods. From those, by trial and error, quantities for mix were obtained with satisfied properties ofSCC. Trials have been made based on NAN SU method and finally arrived at the quantities, whichsatisfied the properties of SCC i.e., slump flow test, L-Box test, U-Box test and V-Funnel test. To this mix,steel fibers of different aspect ratios and varied quantities of 30, 60 and 75kg/m3 were added.Thefollowing parameters were studied under the durability aspect viz., weight loss, strength and consumptionof solutions. The durability studies were carried out by conducting the tests viz., Water Absorption,Marine Water Attack, Magnesium Sulphate Attack, Sodium Sulphate Attack and Hydrochloric Acid.

Keywords: conventional concrete, self-compacting concrete, steel fiber, mix design.

I. INTRODUCTION

Concrete technology has made a tremendous stridein the past decade. Concrete is now no longer amaterial consisting of cement, aggregates, waterand admixtures but it is an engineered materialwith several new constituents performingsatisfactorily under different exposure conditions.Concrete today can be tailor made for specificapplications and it contains different materials likemicro silica, colloidal silica and many otherbinders, filler and pozzolanic materials. Thedevelopment of specifying a concrete according toits performance requirements rather than theconstituents and ingredients has openedinnumerable opportunities for producers and usersto design concrete to suit to their specificrequirements. The type of concrete that is designedto a specific application is known as highperformance concrete. ACI defines highperformance concrete [HPC] as “Concrete thatmeets special performance and uniformityrequirements that cannot always be obtained byusing conventional ingredients, normal mixingprocedure and typical curing practices.” HPC

should have at least one outstanding property viz.compressive strength, high workability enhanceresistance to chemical or mechanical stresses,lower permeability, high durability etc..

1.1 Conventional concrete (CVC)

For a long time, Concrete was considered to bevery durable material requiring a little or nomaintenance. The assumption is largely true,except when it is subjected to highly aggressiveenvironment. We build concrete structures inhighly polluted urban and industrial areas,aggressive marine environment, and harmful sub-soil water in coastal area and many other hostileconditions where other materials of constructionare found to be non-durable. Since the use ofconcrete in recent years, have spread to highlyharsh and hostile conditions, the early impressionthat concrete is very durable material is beingthreatened, particularly on account of prematurefailures of number of structures in the recent past.

In the past, only strength of the concrete wasconsidered in the concrete mix design procedureassuming strength of concrete is an all pervading




factor for all other desirable properties of concreteincluding durability. For the first time, the piousoption was proved wrong in late 1930’s when theyfound that series of failures of concrete pavementshave taken place due to frost attack. Although thecompressive strength is a measure of durability to agreat extent it is not entirely true that the strongconcrete is always a durable concrete. In additionto strength of concrete another factor,environmental condition or what we generally callexposure condition has become an importantconsideration of durability.

In the recent revision of IS: 456-2000, one of themajor points discussed, deliberated and revised isthe durability aspects for concrete.

One of the main reasons for deterioration ofconcrete in the past is that too much emphasis isplaced on concrete compressive strength. Thedegree of hardness of the environmental conditionto which concrete is exposed over its entire life isequally important. Therefore strength anddurability have to be considered explicitly at thedesign stage. Generally, construction industryneeds faster development of strength in concrete sothat the projects can be completed in time or beforetime. This demand is catered by high early strengthcement, use of very low Water-Cement ratiothrough the use of increased cement content andreduced water content. The above steps result inhigher thermal shrinkage, drying shrinkage,modulus of elasticity and lower creep coefficients.With higher quality of cement content concreteexhibits greater cracking tendencies because ofincreased thermal and drying shrinkage. As thecreep coefficient is low in such concrete, there willnot be much scope for relaxation of stresses.Therefore, high early strength concretes are moreprone to cracking than moderate or low strengthconcrete. The structural cracks in high strengthconcrete can be controlled by the use of sufficientsteel reinforcements. But this practice does not helpconcrete durability, as provision of more steelreinforcement will only results in conversion ofbigger cracks into smaller cracks.

1.2 Self-Compacting Concrete (SCC)

Self-Compacting concrete is specific part of highperformance concrete which distinguishes itselfwith self-consolidation properties with high flowability. HPC finds very useful application in theprecast industry because of its requirements forhigh early strength flow ability. The introduction ofplasticizers, super plasticizers and pozzolanicmaterials had a tremendous influence on theconcrete technology and its benefits subsequentlyfiltered down to precast industry. Manytechnological developments have providedincremental advances in the design and placement

of concrete in structures. In this, the most importantdevelopment is self-compacting concrete [SCC].Hence, SCC will be the future of concretetechnology. The principle of self-compactingconcrete is not new. Specific applications such asunder-water concreting always require freshconcrete, which could be placed without the needfor compaction, since vibration is simplyimpossible. Early self-compacting concretes reliedon very high contents of cement paste the mixesrequire specialized and well-controlled placingmethods in order to avoid segregation. The highcontents of cement paste made them prone toshrinkage and high heat of generation. The overallcosts were varied and its applications remainedmore. This led to the development of admixtures,which served the purpose of producing SCC aseasy one. The admixtures consist of high rangeWater Reducing Agents (WRA) and ViscosityModifying Agents (VMA).

II. MATERIALS USED

1. Cement:

OrdinaryPortland cement of 53 grade conformingto Bureau of Indian Standards was used in thepresent investigation. The cement was tested forvarious properties as per IS 12269-1987.

2. Silica fume:

The high level of fineness and practically sphericalshape of silica fume results in good cohesion andimproved resistance to segregation. However, silicafume is also very effective in reducing oreliminating bleed and this can give rise to problemsof rapid surface crusting. This can result in coldjoints or surface defects if there are any breaks inconcrete delivery and also to difficulty in finishingthe top surface. The silica fume used in the presentwork was obtained from M/S. Fosroc chemicals,Navy-Mumbai.

3. Fly ash:

Fly ash used in the test was obtained from ThermalPower Station at Vijayawada.

4. High Range Water Reducing Admixture (HRWA)/Super plasticizers:

As the Water-Cement ratio is very less, to achievethe required workability, a high range waterreducer, Conplast SP430 A2 was used in mixproportioning. The Conplast SP430 A2 issulphonated Naphthalene Polymer obtained fromFORSOC CHEMICALS was used. Dosage ofchemical was 0.80% and 1.1% for CVC and SCCrespectively.

5. Water:

Potable water from local resources was used formixing and curing of concrete cubes.




6. Fine aggregate:

The river sand, passing through 4.75 mm sieve andretained on 600 μm sieve, conforming to Zone II asper IS 383-1970 was used as fine aggregate in thepresent study. It is clean, inert and free fromorganic matter, silt and clay.

7. Coarse aggregate:

Broken hard Granite was used as coarse aggregate.The combination of 12.5 mm and 10 mm sizecoarse aggregates were used for all mixes.

8. Steel:

The steel reinforcement was tested in the laboratoryfor its strength and ductility. High yield strengthdeformed bars (HYSD) are used.

9. Steel Fibres:

The Steel Fibres used for the present experimentalwork were:

Length of the fibre - 35 mmDiameter of the Fibre - 0.9 mmAspect Ratio - 38

Volume Fractions- 30 Kg/m3, 60 Kg/m3& 90Kg/m3 to volume of the concrete was used for thepresent study.

10. Marine Water :

The marine Water is obtained from natural seawater near Visakhapatnam. The marine waterconsists 34.8% salinity at the time of testing.

11. Magnesium Sulphate (MgSO4) :

The magnesium Sulphate is obtained from locallyand is manufactured in Molychem, Mumbai withminimum assay of 99.8%.

12. Sodium Sulphate (Na2SO4) :

The sodium Sulphate was procured locally and ismanufactured in Universal laboratories Pvt. Ltd.,Mumbai with minimum assay of 99.0%.

III. TESTS OF SCC

The concrete composition is now determined andthe super plasticizer dosage is finally selected onthe basis of concrete tests are as following:

Filling Ability:-

1. Slump Flow Test

2. V-Funnel Test

3. T50 slump flow

Passing Ability:-

4. L-Box test

5. U-Box test

Segregation Resistance:-

1. V-Funnel T5min

The following is a brief summary of the mostcommon tests currently used for the presentassessment of fresh SCC:

3.1 Slump Flow Test:

The basic equipment used is the same for theconventional concrete slump test i.e., slump cone,Tampering Rod and a smooth surface table. But thetest method differs from the conventional one, theconcrete sample placed into the mould is notrodded and when the slump cone has been removedand the sample has collapsed. The diameter of thespread sample is then measured horizontally on thetop of the surface of the concrete but not verticallyas in the conventional slump test. Also measuringthe diameter of the spread, the time that it takes forthe collapsed sample to spread diameter of 500 mmis measured in T50 seconds. This method gives theFILLING ABILTY of the fresh SCC.

Fig 1: Slump Cone Apparatus

3.2 V-Funnel Test:

Though the test is designed to measure flow ability,the result is affected by concrete properties otherthan flow. The inverted cone shape will cause anyliability of the concrete to block to be reflected inthe result – if, for example there is too much coarseaggregate. High flow time can also be associatedwith low deformability due to a high pasteviscosity, and with high inter-particle friction.

While the apparatus is simple, the effect of theangle of the funnel and the wall effect on the flowof concrete is not clear.

Fig 2: V-Funnel Apparatus




3.3 L-Box Test:

This method uses a test apparatus consisting of avertical section and a horizontal section, which theconcrete is allowed to flow on the release of a trapdoor from the vertical section passing throughreinforcing bars placed at the intersection of thetwo areas of the apparatus. The time is also takenfor the passing of concrete for 200 mm from thegate which is made by the steel rods kept at adistance of 35 mm centre to centre is T20 seconds.

Then measure the heights on each side i.e., H1 &H2. This test gives the PASSING ABILITY of thefresh SCC as well as FILLING ABILITY.

Fig 3: L-Box Apparatus

3.4 U-Box Test:

This is the method of conducting to observe theFILLING ABILITY as well as PASSINGABILITY of the fresh SCC. This apparatus is madein the shape of U with steel rods of spacing 35 mmcentre to centre. So, allow the concrete to pass fromvertical wing through this gate to other wing formeasure the height of each wing of the U-Box.

Fig 4: U-Box Apparatus

IV. MIX DESIGN

The Japanese concept for design of SCC is basedon a method proposed by Okamura and Ozawa7.The authors have proposed a simple mix-proportioning system assuming general supplyfrom ready-mixed concrete plants. The coarse andfine aggregate contents are fixed so that self-compactability can be achieved easily by adjustingthe water to powder volume ratio andsuperplasticizer dosage only. The mixed design asproposed is: • Coarse aggregate content is fixed at50% of the solid volume; • Fine aggregate contentis fixed at 40% of the mortar volume; • Water-

powder ratio in volume is assumed as 0.9 to 1.0depending on the properties of the powder; and •Superplasticizer dosage and the final water-powderratio are determined so as to ensure the self-compactability. The value of water to powdervolume ratio (Vw/Vp) is optimized by mortar flowtest and Mortar Funnel Test. Takada8 consideredthe slump flow value of 650±30 mm and the V-funnel time of 11±2 s as adequate value for theworkable SCC. Further to increase the viscosityand thereby reduce the deformity an organicstabilizer ‘welan gum’9 was used. In organicstabilizer, there is a polymer formation of 3-dimensional framework which increases theviscosity and water adsorption.

V. CONCLUSION

1. The modified NAN SU method providesrequired mix proportion, for concrete gradesup to M50 while satisfying the flowcharacteristics of SCC.

2. The required strength and durability of theconcrete mixes were obtained by somemodifications made in the available NAN SUmethod.

3. Addition of steel fibres improved the durabilityaspects of Self compacting concrete up to0.75% volume fraction.

4. The loss in weight and compressive strengthsof SCC and CVC were negligible undermarine and sulphate attacks due to lesspercentage reduction of loss.

5. SFRSCC resist the acid and marine attackswithin tolerable limits and the optimum dosageof fibres for better performance was found tobe at 0.5 percent.

6. NAN SU method provides less quantity ofcement in normal grades of concrete that is notsufficient to bind all the ingredients in the mix.

7. Ultimate load carrying capacity of FCVC andSFRSCC beams are same for the fibre dosageof 0.75% volume fraction.

8. The SCC is not economical due to increasingthe powder content with rarely availablepowders, but it is most suitable forconstructions without any damages and is donewith sufficient less skilled labor.VI. SCOPE FOR FUTHER STUDIES

1. Optimization of powder content and superplasticizer to achieve economy in construction.

2. Studies may be conducted with increasingcement content for the Nan-Su method toachieve strength and durability characteristics.

3. Further studies are made on specimens atdifferent ages under different environmentalconditions.




VII. REFERENCES

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[7] ACI materials Journal (ACI Mater J) ISSN0889-325X-John Strieder Woods, H. 1968.“Durability of Concrete Construction”, ACI,Monograph No. 4, Detriot, MI.

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[26] Asha and Sundarajan “Evaluation of Seismicresistance of exterior beam-column jointswith detailing as per IS: 13920-1993” IndianConcrete Journal, FEB 2006, Vol. 80.

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[29] Bartos, J. M., “Measurement of KeyProperties of Fresh Self-CompactingConcrete –Time Development of theMaterial Properties and the Bond Behavior”,LACER No.5, PP. 115-123 (2000).

[30] Ouchi, M., Macoto, “DevelopmentApplications and Investigations of SCC”,International Workshop, Kochi, Japan(2000).

[31] Ouchi, M., M. Hibino and H. Okamura,“Effect of super plasticizers on SelfCompacting of Fresh Concrete”, TRR 1574,PP. 37-40 (1996)

p. j. d. anjaneyulu m. k. m. v. rathnam dr. u. ranga raju

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