Bonding Agents: The Good, the Bad, and What Works. Bond with Your Concrete

Transcription

1 Bonding Agents: The Good, the Bad, and What Works Bond with Your Concrete Jose DonJuan Graduate Research Assistant Kyle A. Riding, Ph.D., P.E. Associate Professor Department of Civil Engineering Kansas State University

2 Objectives Explain concrete partial depth repair procedure Discuss common failure mechanisms of concrete partial depth repairs Discuss concrete bonding agent best practices

3 Background Concrete patching most common repair technique Commonly used to repair localized problems: Shallow joint spalling Scaling Joint rot Typical for transverse & longitudinal joints Figure from ACPA

4 Repair Failure Examples 4

5 Repair Selection Damage Size Partial Depth Repair NO Spall > 6 long and 1.5 wide? NO May be able to wait on repair YES Spall depth < 1/3 of depth NO YES Dowels still function? NO Consider Full Depth Repair or Other Repair Strategy YES Spalling Caused by: D cracking Dowel Bar misalignment Spalled cracks ASR YES 5

6 Construction Steps (ACPA) Locate repair boundaries Remove deteriorated concrete Clean repair area Prepare joint Apply bonding agent Mix and place repair material Figure from FHWA 6

7 Layout Sawcut 3 4 from detected damage Patch Damaged Area Sawcut 3 4 from detected damage Repair Size Minimum length 12 in Minimum width 4 in Go beyond problem by 3 4 in Combine close patches (<2 ft) Repair entire joint if more than 2 patches

8 Remove Deteriorated Concrete Concrete Removed by chipping hammer or carbide mill, lighter (15 lb) chipping hammers are preferred Figure from ACPA Spall Sawcut 2, d/3 Joint 8

9 Figure from ACPA

10 Cleaning Need to remove loose material sandblasting or high pressure water works well Clean area with compressed air (90 psi recommended) Make sure compressed air is free of oil and moisture Check dust by wiping with dark cloth Figure from ACPA Figure from FHWA

11 Compressible material can be placed before concrete placement Styrofoam Asphalt impregnated fiberboard Fiberboard Can be sawcut after placement Sawcut joints can be sealed Joints

12 Figure from ACPA

13 Bonding Agent Application Bonding agents have been used to enhance bond with the existing concrete Common bonding agents: Sand cement grouts Epoxy bonding agents Latex modified grouts Acrylic modified grouts Placed on bottom and sides 1/16 to 1/8 thick by scrubbing, brooming, or with a stiff brush Figure from FHWA

14 Placement & Finishing Mix in portable mixer Slightly overfill repair Consolidate using an immersion vibrator Should screed and finish with trowel (from center of repair outwards) Can check with straight edge Cure with plastic or curing compound Figure from ACPA 14

15 Seal Joints 15

16 Repair Material Selection Repair durability dependent on: Material property compatibility: ie. Similar thermal properties, low drying shrinkage, similar modulus to concrete Bond quality Proper Jointing Durable materials: air content, durable aggregates Curing Commonly fail because: Wrong repair method used to address cause Poor/ incompatible repair material Installation problems/ not removing all bad concrete 16

17 Loading in Repairs: Bond Stress As the concrete shrinks, it puts stresses on the bond layer 17

18 Bond Quality Repairs often fail because of poor bond Variables tested in other studies Various surface roughness Increasing repair concrete compressive strength Concrete additives Using steel anchoring Introducing thermal cycles Surface moisture conditions Recent partial depth repairs in Kansas cited contractors waiting too long between bonding agent application and repair concrete placement

19 Bonding Agents KDOT requires use of a bonding agent using 3 parts water, 1 part portland cement Other states such as CA just specify that grout should be thick & creamy Evaluation of time from bonding agent application on effects of bond strength

20 Bonding Agents Evaluated 3 grouts with different water to cement ratios 1 epoxy bonding agent 2 latex bonding agents 3 rapid repair materials 1 control w/o bonding agent surface dry 1 control w/o bonding agent SSD

21 Potential Bond Test Methods Slant Shear Test Direct Uniaxial Tension (Pulloff) Direct Shear (Guillotine) New New New Old Old Old 21

22 Phase I Laboratory testing Phase II Testing Methods Illinois Standard Method of Test for Shear Strength of Bonded Polymer Concrete Field testing Pull off tensile tests on field slabs Figure from ACI 548.5R, 1998

23 Illinois Standard Method of Test for Shear Strength of Bonded Polymer Concrete Adapted the IDOT standard Illinois Standard Method of Test for Shear Strength of Bonded Polymer Concrete Based on the Brookhaven Shear Test Compares shear bond of steel blank substrates and concrete substrates Tests bond after freeze thaw cycles We tested shear bond with and without freeze thaw cycles

24 Guillotine Testing Substrate Concrete Samples 4 x 4 inch Concrete Cylinders 602 lb/yd 3 of Type I Portland Cement Concrete 235 lb/yd 3 of Water 1552 lb/yd 3 of MCM KP Fine Aggregate 1552 lb/yd 3 of Crushed Course Aggregate 6% + 1% Air Content.39 w/c ratios

25 Substrate Samples Substrate Samples

26 Guillotine Testing Repair Mortar Type III Portland Cement Grout 0.4 W/C Ratio 2.75 Sand to Cement Ratio Local fine aggregate used

27 Guillotine Tests Bonding Agents Portland cement paste at 3, 0.5, and 0.33 w/cm Epoxy Two part epoxy Meets Requirements of ASTM C minute setting time PVA Bonding Agent Reemulsifiable polyvinyle acetate Apply by diluting solution with 1:1 ratio of water then brushing over surface 1 2 hour working time Acrylic Bonding Agent non reemulsifiable latex bonding agent Apply over a SSD surface with a brush

28 Guillotine Tests Rapid concrete repair materials tested for comparison Magnesium Phosphate Pavemend Calcium Sulfate Aluminate

29 Guillotine Tests Surface Preparation Sand Blasted with # glass beads Surface prior to bonding agent application

30 Guillotine Tests 30 concrete samples were made using type I cement. 15 steel pucks samples were used per test

31 Phase 1 Bonding agents were applied in a room kept at 73 F and 50% humidity The bonding agents and rapid repair materials that required chemical mixing were mixed in a well ventilated room at 73 F with 60 % humidity Bonding agent was allowed 0, 2, 5, 15 and 30 minutes of drying time before 1.25 layer of repair mortar was applied and tampered

32 Setting Time Effects 3 1 Portland Cement Grout

33 Setting Time Effects 0.5 w/c Portland Cement Grout

34 Setting Time Effects 0.3 w/c Portland Cement Grout 0 30

35 Composite Samples Guillotine Tests 24 hours of curing with closed lid in 73 Room Composite Sample

36 Guillotine Tests After 3 days of curing time 3 concrete samples for each bonding agent drying time were put through 5 Thermal cycles. Samples were placed in an oven with a constant temperature of 120 F + 2 F for a period of 22 hours Moved to a temperature of 73 F + 2 F for two hours for thermal stabilization Placed in a freezer with a constant temperature of 0 F + 2 F for 22 hours Moved to a temperature of 73 F + 2 F for two hours for thermal stabilization

37 Guillotine Tests Samples were loaded to failure using a guillotine shear test Load rate of.22 in/min was applied with maximum load recorded

38 Results Control and Rapair Repair Materials Shear Stress (psi) Control CTRL SSD Mag. Phosphate Pavemend CSA cement 0 5 F T cycles No thermal cycling steel control 38

39 Results: 3 1 w/c grout Shear Stress (psi) Steel Pucks Thermal Cycles Non Thermal Cycles Setting time (min)

40 Results: 0.5 w/c grout Shear Stress (psi) Non Thermal Cycles Thermal Cycles Setting Time (min) Note: Steel puck samples would not bond to repair mortar

41 Results: 0.3 w/c grout Thermal Cycles 700 Non Thermal Cycles Setting Time Note: Steel puck samples would not bond to repair mortar Shear Stress (psi)

42 Results: Epoxy Bonding Agent Shear Stress (psi) Steel Pucks Thermal Cycles Non Thermal Cycles Setting Time (min)

43 Results: PVA Bonding Agent Shear Stress (psi) Steel Pucks Thermal Cycles Non Thermal Cycles Setting Time (min)

44 Results: Acrylic Bonding Agent 1000 Shear Stress (psi) Steel Pucks Setting Time (min)

45 Results: Steel Control Shear Stress (psi) w/cm Epoxy PVA Acrylic Setting Time (min)

46 Results: 5 Freeze Thaw Cycles Shear Stress (psi) Setting Time (min) 3 1 w/cm.5 w/cm.3 w/cm Epoxy PVA Acrylic

47 Results: No Thermal Cycling Shear Stress (psi) Setting Time (min) 3 1 w/cm.5 w/cm.3 w/cm Epoxy PVA Acrylic

48 Polymer Modified Concrete Polymer envelopes cement hydration products with film Latex modified Concrete OPC Pictures courtesy of David Fowler 2/8/2014 CE 816 Concrete Pavement & Bridge Repair 48

49 Field: Where the Rubber Meets the Road 2/8/2014 CE 816 Concrete Pavement & Bridge Repair 49

50 Phase 2 Field Tests Slabs Constructed Build three repair strips in slabs Filled 2 strips with bonding agents and repair concrete 1 strip had only repair materials placed with control concrete Aluminum disk epoxied to surface to attach to pull off tester 2 diameter core drilling Repair Concrete Old Concrete

51 Phase 2 Site Preparation Ground Leveled Forms set up and Leveled

52 Concrete placed Phase 2

53 Vibration Phase 2

54 Screed Phase 2

55 Float Phase 2

56 Phase 2 2 nd Field Slab Voids cast into concrete

57 Phase 2 Surface Preparation Edges saw cut outside of cast void Bottom roughened to concrete surface profile of 5 6

58 Phase 2 2 Field Slabs 8 X 24 X 10 6 X 24 X 10 3 strips 8 X 2 X 24 Repair material placed 0,5,15,45 minutes after bonding agent placed

59 Epoxy Setting Time

60 Acrylic Setting Time

61 PVA Setting Time

62 Curing 62

63 Pull Off tests Followed ASTM C 1583

64 Data Failure Modes 1 Substrate 2 Bond Interface 3 Repair Material 4 Epoxy Interface PVA Epoxy Acrylic W/C grout 1 1 Grout 3 1 Grout

65 Data Compress Strengths 7 Day Compressive Strength (psi) Slab 1 Slab 2 MGP CSA PM RC1 RC

66 Data Day Tensile Strength Pull off Strength (psi) MGP PM CSA Control Dry Control SSD 0 1

67 Results: 7 Day Tensile Stress (psi) "3 1 Grout" "1 1 Grout" "0.5 Grout" "Epoxy Agent" "PVA Agent" "Acrylic Agent" Setting Time (mins)

68 Conclusions Epoxy and PVA bonding agents provide the best shear strength Rapid repair materials showed little difference in shear strength with and without temperature cycling Pavement & magnesium phosphate cements showed excellent bond to steel Epoxy and PVA bonding agents not very sensitive to time from application, as long as it has not set up Too low of a w/c or too high of a w/c makes the bonding agent strength decrease with drying in shear or direct tension test Repair material should be placed within 15 minutes for cement grouts If a portland cement grout will be used, 1:1 is recommnded 68

69 Acknowledgements Mid America Transportation Center for funding this project Ryan Benteman KSU Research Technologist 69

70 References A.S.C.E. (2013) Reportcard for America's Infrastructure. Infrastructure Report Card. Al Ostaz, A. I. (2010). Deterioration of Bond Integrity between Repair Material and Concrete due to Thermal and Mechanical Incompatabilities. Journal of Materials in Civil Engineering 22(2), Courard, L. P. (2013). Near to Surface Properties affecting Bonding Strength in Concrete Repair.. Cement & Concrete Compositions. Julio, E. B. (2004). Concrete to Concrete Bond Strength Influence of the Roughness of the Substrate Surface. Construction and Building Materials, 18, Julio, E. B. (2006). Influence of Added Concrete Compressive Strength on t he Adheasion to an Existing Concrete Substrate. Building and Environment, 41, Langlois, M. P. (1994). Durability of Pavement Repairs: A Field Experiment. Concrete International 16(8), Li, G. (2003). A New Way to Increase the Long Term Bond Strength of New to Old Concrete by the use of Fly Ash. Cement and Concrete Research, Parker, J. F., Ramey, G., Moore, R., & & Jordan, J. J. (1985). A Field Evaluation of Factors Affecting Concrete Pavement Surface Preparation. Transportation Research Record, Parker, J. R. (1985). A Study of Bond Strenth of Portland Cement Concrete Patching Materials. Transportation Research Record, 1041, Rosenburg, A. (2010, may 8). Using Fly Ash in Concrete. Retrieved 12 18, 2013, from Precast: fly ash in concrete/ Santos, D., M.D, S. P., & Dias da Costa, D. (2012). Effect of Surface Preparation and Bonding Agent on the Concrete to Concrete Interface Strength. Construction and Building Materials, 37, Winkelman, T. (2002). Bonded Concrete Overlay Performance in Illinios. Springfield, Illinios: Illinios Department of Transportation.