Performance specifications for cementitious grouts used in post-tensioned concrete systems - PowerPoint Presentation

1. Performance specifications for cementitious grouts used in post-tensioned concrete systemsManu K. MOHAN, M. S. Student Radhakrishna G. PILLAI, Associate Professor Manu SANTHANAM, ProfessorRavindra GETTU, ProfessorIndian Institute of Technology MadrasChennai, INDIASeptember 19-22, 2018ICI-IWC 2018NIMHANS convention center, Bangalore, IndiaMinistry of Human Resource Development andMinistry of Housing and Urban AffairsGovernment of India

2. Grouted, post-tensioned (PT) systems are commonly used in large concrete structuresSource : https://www.google.co.in and FDOT report (2003)High-rise buildingsNuclear vaultsLong-span segmental bridgesSilosStrands are embedded in plastic ducts and the interstitial spaces are supposed to be filled with grout

3. Premature corrosion has been observed in many YOUNG bridgesMandovi, 12Ynys-y-Gwas, 33Malle, 13Bickton Meadows, 15Niles Channel, 16Mid Bay,15447 bridges in UKBan during 1992 – 1996(Woodward, 1988)

4. Premature corrosion has been observed in many YOUNG bridgesVarina-Enon, VirginiaAt 17 yearsFDOT 2003Anchorage zone in a PT girder

5. Premature corrosion has been observed in many YOUNG bridgesSunshine Skyway, FloridaAt 8 yearsFDOT 2001Anchorage zone in PT column

6. Why such premature corrosion?Voids in ducts  exposed strandsAnchorage zone in a PT girderAnchorage zone in PT columnA metro rail bridge

7. Why such premature corrosion?Chloride ingress  Corrosion of strandsChlorides

8. Why such premature corrosion?Carbonation of ‘top’ grout  Localized corrosionCO2

9. Are the new grouts good enough?- Formation of soft grout should be avoidedInadequate specs.  Voids  Premature corrosion

10. Methods to assess the fluidity and its retention of PT groutsFlow cone testSpread test Flow cone (EN445:2007)Grout spread(EN445:2007)CylinderSmooth plate

11. Methods to assess the bleed resistance of PT groutsStandard bleed (SB) testWick-induced bleed (WB) testPressure-induced bleed (PB) testInclined tube bleed (IT) testStandard bleed (SB) testPressure-induced Bleed (PB) testInclined-tube testWick-induced bleed (WB) testPCG = Plain cement groutSBG = Site batched groutPPG = Pre-packed grout (commercial)TF = Tendon Fill

12. Fluidity (Efflux time, T0) of commercial groutsTFPCG = Plain cement groutSBG = Site batched groutPPG = Pre-packed grout (commercial)TF = Tendon FillGood quality PT grouts may get disqualified by the current efflux time test and viceversa !We have to use other tests to qualify/disqualify PT groutsKamalakannan et al 2018

13. Recommended specifications for fluidity and its retentionFlow cones with smaller orifice diametersThixotropic grouts with very low w/cPropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)RecommendedEfflux time, T0 (s)T0 ≤ 25 (EN 445 Flow cone) T0 ≤ 25 5 ≤ T0 ≤ 30(ASTM C939 Marsh cone) T0 ≤ 25 (EN 445 Flow cone) Efflux time 30 min.after mixing, T30 (s)1.2 T0 ≥ T30 ≥ 0.8 T0and T30 ≤ 25Not mentioned Not mentioned 1.2 T0 ≥ T30 ≥ 0.8 T0and T30 ≤ 25Efflux time 180 min.after mixing, T180 (s)Not mentionedNot mentionedNot mentioned1.4 T0 ≥ T180 ≥ 0.6 T0and T180 ≤ 252 mm orifice

14. Mixture proportion of the grouts studiedMaterialQuantity (kg/m3)PPG1PPG2PPG3PPG4PPG5PPG6PPG7PPG8PPG9OPC1473112010881119951951951951951Fly ash-1(Class F)03205120317317317317317Fly ash-2 (Class F)000480317317317317317Silica fume1641600000000Water458432432432428428428428428HRWR1.801.441.441.431.431.531.431.431.43Viscosity modifier000.800.790.5000.800.630.63Nano clay000001.58000SRA0000000031.7water/binder0.280.270.270.270.270.270.270.270.27

15. Fluidity and its retentionPPGs 1, 2, and 3 met the requirementsGrouts with low efflux time need not have required fluidity retention (e.g., PPG6)GroutT0T30T180PPG 1121319PPG 2141524PPG 3181925PPG 4293037PPG 5242627PPG 61518281.2 T0 ≥ T30 ≥ 0.8 T0 and T30 ≤ 251.4 T0 ≥ T180 ≥ 0.6 T0 and T180 ≤ 25×××Acceptance criteriaPPG = Pre-packaged grout

16. Recommended specifications for fluidity (Spread, S)Rarely used, though a simple testPropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)RecommendedGrout spread, S0 (mm)S0 ≥ 140S0 ≤ 25 5 ≤ S0 ≤ 30(ASTM C939 Marsh cone) S0 ≤ 25 (EN 445 Flow cone) Grout spread 30 min.after mixing, S30 (mm)1.2 S0 ≥ S30 ≥ 0.8 S0 and S30 ≥ 140Not mentioned Not mentioned 1.2 S0 ≥ S30 ≥ 0.8 S0and S30 ≤ 25Grout spread 180 min.after mixing, S180 (mm)Not mentionedNot mentionedNot mentioned1.4 S0 ≥ S180 ≥ 0.6 S0 and S180 ≥ 120

17. GroutS0S30S180PBG 1167161141PBG 2158153136PBG 3151146122PBG 411711486PBG 512812190PBG 6160151130Fluidity and its retention (Spread, S)PPGs 1, 2, 3, and 6 met the requirements××1.2 S0 ≥ S30 ≥ 0.8 S0 and S30 ≥ 1401.6 S0 ≥ S180 ≥ 0.6 S0 and S180 ≥ 120Acceptance criteria

18. Recommended specifications for bleed resistancePropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)RecommendedBleed (%)  Standard Not mentioned Not mentioned ≤ 0.1≤ 0.1 Wick-induced≤ 0.3≤ 0.3≤ 0.3≤ 0.0Wick-induced bleed testStandard bleed testStandard bleed and wick-induced bleed tests must be done

19. Recommended specifications for bleed resistancePropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)RecommendedBleed (%)  Pressure-induced (at 350 kPa)Not mentioned Not mentioned ≤ 0.1≤ 0.1 Inclined tube test≤ 0.3≤ 0.3≤ 0.3≤ 0.3

20. Bleed resistance of existing PPGs and other indigenous groutsPT grouts used in today’s construction industry do not meet the recommended specificationsUpper limit = 0.3 %(EN 447:2007)Kamalakannan et al. 2018, Ashok 2015, Ramya, 2015

21. Bleed resistance of the groutsPPG3 and PPG5 has very low bleed and can be used for PT columns××

22. Recommended specifications for dimensional stabilityCompressive strength is not a screening testGood dimensional stabilityTotal and autogenous shrinkagePropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)RecommendedCompressive strength (MPa) 7-day≥ 27≥ 27≥ 21≥ 2128-day≥ 30Not mentioned≥ 35≥ 35Hardened volume change (%)ExpansionNot mentionedNot mentioned≤ 0.1 at 24 hours ≤ 0.2 after 28 days≤ 0.1 at 24 hours ≤ 0.2 after 28 daysShrinkageNot mentionedNot mentionedNot mentioned≤ 0.2 after 28 daysASTM C1090 test for measuring expansionASTM C157 specimens for measuring the shrinkage

23. Cube compressive strength and shrinkage for the groutsPPG4 has highest compressive strength; PPG6 has lowestShrinkage strains were reduced with the use of SRATotal shrinkageAutogenous shrinkage

24. Visual observations on grout cylinders/tendons can also be used as performance testsFrothy material floats or forms at the top surface of groutAshok Gorantla 2016, http://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/13028/Segregation in the lab specimensSegregation in the field tendons

25. Modified performance specifications for PT groutsParameterAcceptance criteriaTest methodStandardFresh state (very crucial)Efflux time, T0 (s)T0 ≤ 25Flow Cone test as per EN 445:2007EN 447:2007Efflux time 30 minutesafter mixing, T30 (s)1.2 T0 ≥ T30 ≥ 0.8 T0and T30 ≤ 25Efflux time 180 minutesafter mixing, T180 (s)1.4 T0 ≥ T180 ≥ 0.6 T0and T180 ≤ 28Gout spread, S0 (mm)≥ 140Grout spread test as per EN 445:2007Grout spread 30 minutesafter mixing, S30 (mm)1.2 S0 ≥ S30 ≥ 0.8 S0 and S30 ≥ 140Grout spread 180 minutesafter mixing, S180 (mm)1.4 S0 ≥ S180 ≥ 0.6 S0 and S180 ≥ 120Bleed (%) Standard, wick bleed and inclined tube test as per EN 445:2007Pressure-induced bleed test as per ASTM C1741EN 447:2007 and PTI M55.1-12Standard-Wick-induced≤ 0.3Pressure-induced (at 350 kPa)≤ 0.1Inclined tube≤ 0.3Setting time (hrs.) Setting time test as per ASTM C953EN 447:2007 and PTI M55.1-12Initial≥ 3Final≤ 24

26. Modified performance specifications for PT groutsParameterAcceptance criteriaTest methodStandardDesiredCompressive strength (N/mm2) ASTM C942 with the moulds complying to ASTM C 109EN 447:2007 and PTI M55.1-123 day≤ 107 day≤ 2728 day≤ 30Very CrucialHardened volume change (%)ASTM C1090 for expansion and ASTM C157 or ASTM C1698 for shrinkagePTI M55.1-12Expansion≤ 0.1 at 24 hours &≤ 0.2 after 28 daysShrinkage≤ 0.2 after 28 daysCrucialDeleterious ions (% of binder)Ion Chromatography or Chemical analysisEN 447:2007 and PTI M55.1-12Chloride (Cl2-)≤ 0.08Sulphates (SO42-)≤ 4.00Sulphides (S2-)≤ 0.01A set of stringent specifications must be used to achieve good quality PT grout

27. Avoid the filling of duct with water before groutingChances are very less that the grout will entirely displace the waterStrands may get corroded and left as it isThere may be significant delays between the placing of strands in the duct and the prestressingAshok Gorantla 2016Signs of strand corrosion in a duct that was filled with waterwater filled duct prior to groutingVentwater flowwater flowIncreasing gradientInlet

28. Grout must be pumped from the lowest points to get complete filling of the ductVentDead end anchorageDuctStressing anchorageInletVentsInletVentMin.1 mGrout flowGrout flowGrout flowGrout flowIncreasing gradient

29. Grout flowing out of the other end does not mean that the tendon is filled with groutA simplified schematic of typical tendon profile (Not to scale)

30. Void formation can be avoided by keeping anchors “face-down” and appropriate vents

31. Cementitious cover/cap can attract humidity and moisture and cause corrosion near the endshttp://www.fhwa.dot.gov/bridge/pt/pt.pdfPT systems with ends covered with cementitious materials~ 13 years!Crack-resistant bituminous coating is better than cementitious coatingSevere corrosion at the anchorages

32. ConclusionsEfflux time alone should not be used to disqualify a thixotropic groutBleed resistance is very important to avoid void formation inside the ducts Retention of flow/bleed resistance are important to checkA set of stringent performance specifications can significantly improve the quality of the PT grouting and life of PT bridges. PT grouts developed in this study meets all the critical specifications and the grouts have a good balance between the fluidity and the bleed resistance.The grouting practices are also very importantFuture work Specifications with smaller orifices and their correlation with bleed

33. Tendons are the backbone of pre- and post-tensioned concrete structuresWe must do whatever we can to prevent corrosion of these expensive and important systems – an extra care at the beginning in achieving this is really worth in the long term.Thank Youpillai@iitm.ac.in

34. Thank You(pillai@iitm.ac.in)Visit our stall

35. Thank you

36. Performance specifications for flowable cementitious grouts for post-tensioned concrete systemsManu K. Mohan, M. S. Student Radhakrishna G. Pillai, Associate Professor Manu Santhanam, ProfessorRavindra Gettu, ProfessorIndian Institute of Technology MadrasChennai, INDIASeptember 21, 2018Innovative world of Concrete (ICI-IWC 2018)NIHAMS convention center, Bangalore, India

37. Specifications for PT grouts from various standards were reviewedPropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)MORTH (2005)IRS (1997)IS 1343 (2012)FreshEfflux time, T0 (s)T0 ≤ 25 (EN 445 Flow cone) T0 ≤ 25 5 ≤ T0 ≤ 30(ASTM C939 Marsh cone) ---Efflux time 30 minutesafter mixing, T30 (s)1.2 T0 ≥ T30 ≥ 0.8 T0and T30 ≤ 25- - - - - Grout spread, S0 (mm)S0 ≥ 140-----Grout spread 30 minutesafter mixing, S30 (mm)1.2 S0 ≥ S30 ≥ 0.8 S0 and S30 ≥ 140 - - - - -Bleed (%) Standard --≤ 0.0---Wick-induced≤ 0.3≤ 0.3≤ 0.0≤ 0.3--Pressure-induced (at 350 kPa)--≤ 0.0---Inclined tube test≤ 0.3≤ 0.3≤ 0.3---Setting time (hours) Initial (Ti)Ti ≥ 3Ti > 33 ≤ Ti ≤ 123 ≤ Ti ≤ 12--Final (Tf)Tf ≤ 24Tf < 24-Tf ≤ 24--

38. Specifications for PT grouts from various standards were reviewedPropertyEN 447 (2007) & ISO 14824 (2012)fib Bulletin No. 20 (2002)PTI M55 (2003)MORTH (2005)IRS (1997)IS 1343 (2012)HardenedCompressive strength (MPa) 7-day≥ 27≥ 27≥ 21≥ 28≥ 17-28-day≥ 30-≥ 35≥ 30-≥ 27Dimensional stabilityHardened volume changeExpansion--≤ 0.1 at 24 hours ≤ 0.2 after 28 days---Shrinkage------DurabilityDeleterious materials (%)      Chloride (Cl-) ≤ 0.10≤ 4.10≤ 0.08≤ 0.1-≤ 0.1Sulphate (SO32-)≤ 4.50≤ 4.50-≤ 4--Sulphide (S2-)≤ 0.01≤ 0.01-≤ 0.01--Most of the existing specifications are inadequate/not complete for developing a good quality PT grout

39. Limitations of the of the PT grout specifications - FluidityFluidity is measured using flow cones of different orifice diametersFlow cones of small orifices should be usedNot suitable for thixotropic grouts with very low w/c ratioGrout spread gives a good indication of the fluidity and must be usedNon-uniform pre-shear changes the fluidity Retention of fluidity is measured for 30 minutes onlyGrouting operations can last for couple of hours after mixingFluidity retention should be checked up to 3 hours

40. Reasons for tendon corrosion and corrosion propagation are..Chloride induced corrosionChloride ions reach strands because of the incomplete fillings, voids, exposed strandsCarbonation induced corrosionDue to bad quality end caps and presence of voidsReduces the pH of the grout pore solutionPropagation due to the galvanic couplingCorroded region couples with passive regionUnwanted voids (formed due to bleed water) are the root cause for moisture/chloride ingress leading to strand corrosion in PT structures

41. Effects of SCMs, superplasticizers and VMAs on the flow properties of grouts – a summaryGrout compositionResearch findingsReference20 - 30 % fly ashSNF based SP Plastic viscosity, yield stress, and bleed reducesKhayat et al. 2008,Krishnamoorthy et al. 2002 5 - 20 % Silica fumeSNF based SP &Cellulose based VMAFluidity decreases drasticallyBleed can be reducedHope et al. 1988Khayat et al. 1999Sonebi et al. 201020 – 50 % GGBS &SMF based SPFluidity increasesBleed can be reducedBras et al. 20136 – 20 % MetakaolinPCE based SP & Polysaccharide VMA Increased flow time, compressive strength and yield stress. Bleed reducesSonebi et al. 2013

42. Test methods and the effect of temperature and humidity – a reviewGrout compositionResearch findingsReferenceOPC with special admixtureAdmixture to control bleedDevised test methodsWick-induced bleed testPressure induced bleed testSchupack 1971,19745 - 20 % Silica fume, GGBS andSNF superplasticizerSimple field test to assess the flow and washout lossKhayat, 199810 – 20 % silica fumeSNF superplasticizerGrout fluidity increase with increase in temperature and humidityDiedrichs, 1989

43. Effect of inert fillers – a reviewGrout compositionResearch findingsReferencePortland cement & PCE based superplasticizer Indirect relationship of yield stress and bleed resistance, effect of chemical admixtures on the rheological parametersRoussel, 2009Nugyen, 2011Portland cement, Limestone filler upto 45%, PCE based SPFormation of soft groutHamilton et al. 2014Soft grout layer at the topPre-packaged, highly flowable and bleed resistant grouts are not available in India and many parts of the world

44. The following materials were identified for designing the groutsBindersOPC 53 GradeClass F Fly ash – 621 m2/kgClass F Fly ash – 536 m2/kgSilica fumeChemical additivesPCE-based superplasticizerCellulose-based VMANanoclay1

45. Physical properties of the bindersPropertyOPCFly ash-1Fly ash-2Silica fumeWater demand for normal consistency of cement paste (%)30---Initial setting time (minutes)175---Final setting time (hours)275---Specific surface area (m2/kg)31062853615000Specific gravity3.152.32.42.2Mean diameter (µm)154.53.50.41

46. Chemical composition of the bindersChemical compositionQuantity (% by mass)CementFly ash 1Fly ash 2Silica fumeSiO220.8859.3260.5696.8Al2O35.5429.9532.67 -Fe2O34.714.324.44 -CaO61.701.281.410.4MgO1.060.610.23 -(Na2O)e0.200.160.12 -LOI2.27---Determined using XRF

47. Physical properties of admixturesPropertySuperplasticizerViscosity modifying agentNanoclayCommercial NameMelflux 2651 FTylose MHActi-gel 208FormPowderPowderPowderColourYellowWhiteYellowOdourOdourlessOdourlessOdourlessDensity (kg/m3)45013001400pH 6.5 - 8.56 - 86-7Drying lossMaximum 2%Maximum 1%Maximum 1%

48. Approximate binder compositions were obtained using particle packing approach (EMMA)(OPC + FA1) mixParticle packing methodOptimum gradation volume ratiosModified Andreasson model (q = 0.23)

49. The particle packing of the designs from EMMA were confirmed using Puntke test20 cm3 of powderWater is added gradually until the surface becomes glossy due to the layer of excess waterPacking density VW = Vol. of water in cm3VP = Vol. of powder (20 cm3)Puntke test

50. Puntke test results for the (OPC + FA1) mixOPC (Vol %)% Volume proportionsPacking density50:500.60055:450.61458:420.61860:400.61165:350.60870:300.604(OPC + FA1) mix

51. w/b, SP dosage, and VMA dosage were determined Normal consistency test (Vicat apparatus) - w/bWick-induced bleed test - VMA dosageFlow cone test – SP dosage VMA (%) SP (%)00.020.030.040.05058627881970.0737516571820.0825375762710.0920284859640.1018233141480.1110121722250.121012162123 VMA (%) SP (%)00.020.030.040.0501.9 ml00000.072.0 ml00000.082.1 ml00000.092.2 ml00000.102.5 ml00000.113.8 ml00000.124.9 ml1 ml0.5 ml00Effect of superplasticizer and VMA on bleedEffect of Superplastizer and VMA on flow time

52. SP dosage, and VMA dosage were determined- graphical representationEffect of superplasticizer and VMA on bleedEffect of Superplastizer and VMA on flow time

53. Mixing procedure and sequence adoptedDry blending of cement and mineral admixture in Hobart mixerAdd water to high shear mixerAdd the pre-blended grout material to the mixing water at 300 rpmIncrease speed to 1500 rpm and continue mixingSequenceDuration(s)1201560300Control panel3 HP motorMixing bowlKamalakannan et al. 2018; Bras et al. 2010

54. Yield per bag and material cost were calculated GroutPPG1PPG2PPG3PPG4PPG5PPG6TFYield per 25 kg bag (l)15.2815.4815.8415.6016.1115.7415.84No. of 25 kg bags for 1m3 grout63636463646364Material cost per 25 kg bag (INR)193208200237225217200Material cost for 1m3 of grout (INR)12631134371270614457141751372012706