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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.

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  1. 1. Dr. K.V.Krishna Reddy / International Journal of Engineering Research and Applications(IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1161-11651161 | P a g eA Comparative Study on Methods of Curing Concrete –Influenceof HumidityDr. K.V.Krishna Reddy1Professor & Principal, Chilkur Balaji Institute of Technology, Hyderabad-75, AP, IndiaABSTRACTEfficient uninterrupted curing is thekey to quality concrete. Proper curing ofconcrete is crucial to obtain design strength andmaximum durability. The curing perioddepends on the required properties of concrete,the purpose for which it is to be used, and thesurrounding atmosphere namely temperatureand relative humidity. Curing is designedprimarily to keep the concrete moist, bypreventing the loss of moisture from theconcrete during the period in which it is gainingstrength. Curing may be applied in a number ofways and the most appropriate means of curingmay be dictated by the site or the constructionmethod. The present paper is directed toevaluate effectiveness of different curingmethods and study the influence of climate onthe strength properties of concrete.Key Words: Curing of concrete Hydration ofcement Relative humidityI. INTRODUCTIONConcrete is the key material used in various typesof construction. The quality of concrete is definedby its strength and durability. The compressivestrength of concrete is one of the most importantand useful properties that quantify the quality ofconcrete. For concrete, to gain the requiredstrength, hydration of cement in the mix must becomplete. Proper hydration of cement ensures goodquality concrete with sufficient strength. For properhydration to occur, fresh concrete must be placed ina favourable environment. An attempt is made inthis work to highlight the affect of different curingmethods and that of climate on the quality of theConcrete.II. RESEARCH METHODOLOGY1.1 Concrete MixDesign of concrete mix is a crucial stage in thepreparation of fresh concrete which involvesselecting suitable ingredients and determining theirrelative amounts with an objective of producing aconcrete of the required strength, durability andworkability as economically as possible. Theproperties of different ingredients required forpreparation of concrete viz. cement, fine aggregate(sand), coarse aggregate (crushed stone), water andsuper plasticizer (as necessary) are presented videTables 1 to 3.Ordinary Portland cement of 53 grade satisfyingthe requirements of IS: 12269-1987 with 28-dayscompressive strength of 58.5 Mpa is used. Thephysical properties are given in the Table 1.Natural River sand confirming to Zone II (Mediumsand) of IS: 383-1970 with fineness modulus of2.81 is used as fine aggregate and Crushed angulargranite metal with 12mm downgraded size from alocal source with a fineness modulus of 7.24 wasprocured to be used as coarse aggregate. The sieveanalysis of fine and coarse aggregates are as intables 2 and 3 respectively.SP430 supplied by M/sFosroc Chemicals Limited is considered for superplasticizerMix design was done aiming at M60 gradeconcrete as per ACI regulations. After a number oftrails the final mix proportion is determined to be1:1.35:2.19:0.29:0.8. The quantity of raw materialsper cubic meter of concrete is as depicted in Table4Table1 Physical properties of OPC 53 grade cementProperties Test Results IS : 12269-1987Standard Consistency 32%Initial Setting Time 42 min 30 minFinal Setting Time 360 min 600 minSpecific Gravity 3.15Fineness (residue on 90µ IS Sieve) 2.6% 10%Compressive Strength3 day7 day28 day27.0 MPa41.2 MPa58.5 MPa20 MPa30 MPa50 MPa
  2. 2. Dr. K.V.Krishna Reddy / International Journal of Engineering Research and Applications(IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1161-11651162 | P a g eTable2 Sieve Analysis of Fine AggregateSieveSizeWt. retained(gm) (gm)% Wt.RetainedCumulative %Wt. RetainedCumulative % Wt.Passing4.75 13.5 1.35 1.35 98.652.36 42 4.2 5.55 94.451.18 243 24.3 29.85 70.15600 µ 334 33.4 63.25 36.75300 µ 234 23.4 86.65 13.35150 µ 80.5 8.05 94.7 5.3<150 µ 53 5.3 100 --Table 3 Sieve Analysis of Fine AggregateSieveSizeWt. Retained(kg)% WT.RetainedCumulative %Wt. RetainedCumulative % Wt.Passing80 0 0 0 040 0 0 0 020 0.7 35 35 6510 1.15 57.5 92.5 7.54.75 0.13 6.5 99 12.36 0.009 0.45 99.45 0.551.18 0 0 99.45 --600 µ 0 0 99.45 --300 µ 0 0 99.45 --150 µ 0 0 99.45 --Table 4 Quantities of raw materials per one cubic meter concreteMix Cement (kg) Fine Aggregate(Kg)Coarse Aggregate(kg)Water(kg)Super plasticizerM60 504.21 683.24 1108.13 141.61 4.66811.2 Curing methodsDifferent curing methods namely ponding, jute bagcuring, single layered membrane curing, doublelayered membrane curing and air curing areconsidered to study the affect of different methodsof curing and climate on the quality of concrete.The curing compounds used for membrane curingare C1-ia white pigmented liquid paraffin basedcuring compound confirming ASTM C 309 Type2Class A. C2 - a wax based paraffin emulsionconfirming ASTM C 309 Type2 Class B. C3 – awhite pigmented wax based compound confirmingASTM C 309-74. Concrete samples were testedafter curing of 3 days, 7 days and 28 days. Curingcompound was sprayed immediately after removalfrom moulds and in case of the double coat thesecond coat was applied after 5 minutes ofapplication of first coat. Jute bag curing was doneby spraying water once in the morning at 10 amand in the evening at 4.00pmIII. 3 DATA ANALYSISConcrete was prepared in a pan mixer and cubemoulds were filled using a vibrating table. Thecuring was done by all the methods cited inresearch methodology. Fig. 1 depicts the curingtechniques used. The Compressive strength wasdetermined on the compression testing machine atthe end of 3 days, 7 days and 28 days of curing.The entire casting and testing procedure for the jutebag curing and air curing was done twice, once inDecember and then in February. Day to dayMetrological data was collected for the entiremonth of December and February. Table 5 showsaverage values of the data collected. Thecompressive strength of the 15cmX15cmX15cmconcrete cubes are presented vide Tables 6Table 5 Meteorological data for the months of December and FebruaryMonth Max. Temp.(0C)Min. Temp.(0C)Rel. Humidity (%)0530 hrsRel. Humidity(%) 1730 hrsDecember 26.53 14.29 73 38.68February 34.8 18.9 56 32
  3. 3. Dr. K.V.Krishna Reddy / International Journal of Engineering Research and Applications(IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1161-11651163 | P a g eFigure 1 Ponding, Jute bag curing, Membrane Curing and Air Curing of Concrete CubesTable 6 Compressive strength of concrete for different types of curingSno. Type of curing Compressive strength (MPa) at the end of3 days 7 days 28 days1 Ponding 33.59 44.13 66.132Membrane curing with C1Single coat29.05 38.39 58.213Membrane curing with C1Double coat31.6 41.04 614Membrane curing with C2Single coat30.1 38.49 56.95Membrane curing with C2Double coat30.84 39.86 59.866Membrane curing with C3Single coat25.94 33.03 50.67Membrane curing with C3Double coat29.05 38.39 58.218 Jute Bag curing-December 30 43.92 61.239 Jute Bag curing- February 27.2 36.49 51.5810 Air Curing-December 33.3 40.56 49.8911 Air Curing-February 23.85 32.6 38IV. RESULTSThe test results are plotted as shown in Figure 2-4. Rate analysis is done to check the cost effectiveness of thedifferent types of curing methods based on the rates in the market. It is found that curing compounds are costeffective.0.00 10.00 20.00 30.00AGE IN DAYS20.0030.0040.0050.0060.0070.00COMPRESSIVESTRENGTH(MPa)12341 PONDING2 C1 DOUBLE COAT3 C2 DOUBLE COAT4 C3 DOUBLE COATFig.2 Compressive Strength of concrete for Ponding and Double coat membrane
  4. 4. Dr. K.V.Krishna Reddy / International Journal of Engineering Research and Applications(IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1161-11651164 | P a g e0.00 10.00 20.00 30.00AGE IN DAYS20.0030.0040.0050.0060.0070.00COMPRESSIVESTRENGTH(MPa)21341 PONDING2 C1 SINGLE COAT3 C2 SINGLE COAT4 C3 SINGLE COATFig.3 Compressive Strength of concrete for Ponding and single coat membrane0.00 10.00 20.00 30.00AGE IN DAYS20.0030.0040.0050.0060.0070.00COMPRESSIVESTRENGTH(MPa)123451 PONDING2 JUTEBAG DECEMBER3 JUTEBAG FEBRUARY4 AIR DECEMBER5 AIR FEBRUARYFig.4 Compressive Strength of concrete for Ponding, Jute bag and Air curingV. ACKNOWLEDGEMENTAt the outset the author would thank the Head,CED, Vasavi college of Engineering for hisvaluable guidance and Project batch students fortheir effort during experimentation.VI. CONCLUSION1. Use of curing compounds resulted in strengthup to 85 to 90 % of ponding.2. White based curing compounds were foundeffective than membrane based Curingcompounds.3. A double layer application of a high efficiencyindex curing compounds such as C1 and C2 didnot significantly improve the concreteproperties when compared with thecorresponding single layer application.However a double layer application of a lowefficiency index curing compound C3 clearlyimproved the concrete properties whencompared with the corresponding single layerapplication. The results indicated that, if a highefficiency index curing compound is uniformlyapplied with a sufficient amount, no doublelayer application is necessary.4. Air curing during December with relativehumidity (73%) and temperature (26.530C)showed that 28 days compressive strength wasin comparison with jute bag curing as the cubes
  5. 5. Dr. K.V.Krishna Reddy / International Journal of Engineering Research and Applications(IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1161-11651165 | P a g ecould have absorbed the moisture which helpedin gaining strength.5. Air Curing during February with relativehumidity (56%) and temperature (34.80C)resulted in a compressive strength of 38Mpawhich is 76.16% of the strength achievedthrough air curing in December showingrelative humidity as prime factor in determiningthe quality of concrete.6. Compound curing is found to be cost effectivecompared to conventional jute bag curing sinceponding is not suitable in-situ for allcomponents of the structure.REFERENCES1. Kosmatka, S.H.; Panarese, W.C. (1988).Design and Control of Concrete Mixtures.Skokie, IL, USA: Portland CementAssociation. pp. 17, 42, 70, 184.2. Zain M.F.M (2007) Ef f ect of dif f erentCuring Methods on the Properties ofMicro Silica Concrete. Australian Journalof Basic and Applied Science, 1 (2): 87 –95, 20073. ACI Committee 308 - Standard Practicefor Curing Concrete ACI 308-92.American4. Concrete Institute, Detroit, Mich., 1992,2000.5. ACI 211.1 – 91 Standard practice forselecting proportions for normal, heavyweight and6. mass concrete7. IS 12269: 1987 – Specifications for 53Grade of Ordinary Portland cement8. IS 383: 1970 – Specifications for coarseand fine aggregates from natural sourcesfor9. Concrete10. IS 2386: 1963 – Methods of test foraggregates for concrete11. IS 1199: 1959 – Methods of sampling andanalysis of concrete12. IS 516: 1959 – Method of test for strengthof concrete13. IS 4031: 1988 – Methods of physical testsfor hydraulic cement14. Properties of Concrete, A.M. Neville,Fourth Edition, Pearson Education.