L.J.M. Houben

1. Birth and Growth of Transversal Heaves in Asphalt Pavements with Hydraulic Blast Furnace Slags Road Base L.J.M. Houben Road and Railway Engineering

2. Research in 2007 on 9.3 km long section of motorway A32 and on hydraulic blast furnace slags road base material taken from the road Research carried out in commission of and in cooperation with: ▪ Regional Service Noord-Nederland ▪ Centre for Transport and Navigation of Dutch Ministry for Transport, Public Works and Water Management

3. Asphalt Pavement Structure A32 190 mm asphalt concrete 200 mm hydraulic blast furnace slags sand sub-base (thickness variable) natural clay subgrade Constructed in 1986-1988 Investigated blast furnace slags road base material 20 years old

4. Hydraulic Blast Furnace Slags Aim in the eighties: ▪ high base stiffness, so ▪ thinner asphalt layers

5. Hydraulic Blast Furnace Slags Very hydraulic blast furnace slags!

6. Motorway A32 in 2007 Transversal heaves

7. Motorway A32 in 2007 Inventory of transversal heaves on basis of ARAN measurements

8. Motorway A32 in 2007 Results from ARAN measurements: ▪ height of heaves: 3 to 27 mm ▪ length of heaves: 1 to 6 m ▪ average distance between heaves: 40 to 100 m ▪ at some locations: clusters of heaves at distance of 5 to 20 m In 2005 most serious heaves were milled off

9. FWD measurements and corings 2 short sections selected from ARAN measurements:

10. L eft traffic lane (o pen to taffic ) R ight traffic lane x * 0,9 m Location of coring FWD measurements and corings Done around 5 heaves and in between heaves FWD measurement

11. FWD measurements and corings Done May 23, 2007 Asphalt temperature 21°C - 27°C

12. FWD deflection curves 1st section

13. Modulus of blast furnace slags road base 1st section Centre of heaves: 30 – 50 MPa Some other locations: 100 – 300 MPa Rest: 500 – 4200 MPa

14. Cores nr. 9 nr. 24

15. Laboratory tests on bound blast furnace slags Through sawing 12 specimens (diameter 150 mm, height between 37 and 167 mm) Low specimens: ▪ dynamic modulus of elasticity ▪ indirect tensile strength High specimens: ▪ coefficient of linear thermal expansion ▪ compressive strength

16. Dynamic modulus of elasticity 6 specimens Room temperature 5 loading frequencies (0.5, 1, 2, 5, 10 Hz) 2 perpendicular directions

17. Dynamic modulus of elasticity Independent of loading frequency 800 – 12500 MPa Up to factor 1.4 for 2 directions

18. Coefficient of linear thermal expansion 4 specimens Temperature increase from 5°C to room temperature

19. Coefficient of linear thermal expansion

20. Coefficient of linear thermal expansion -6 On average coefficient of linear thermal expansion = 8.10 /°C

21. Compressive strength 4 (low) specimens (correction) Room temperature Force controlled test; loading rate 2 kN/s (related to tests on concrete)

22. Compressive strength On average compressive strength = 2.7 MPa

23. Compressive strength Because of horizontal cracks in specimens: ▪ somewhat too low compressive strength ▪ very large vertical displacements: ▫ non-realistic modulus of elasticity (very low) ▫ non-realistic Poisson’s ratio

24. Mechanical model for birth and growth of transversal heaves Similarity with (horizontal) buckling of long welded rails at very high temperatures Compressive stresses in bound blast furnace slags due to obstructed chemical expansion and thermal effects If compressive stress exceeds compressive strength: ▪ crushed zones: birth of first series of heaves ▪ stress relaxation in remaining bound material

25. Mechanical model for birth and growth of transversal heaves Further chemical expansion and thermal effects of bound blast furnace slags: ▪ growth (height) of first series of heaves ▪ birth of second series of heaves Etcetera At (very) long term: complete destruction (crushing) of whole blast furnace slags road base

26. Mechanical model – temperature of base Temperature of base: T1 = 15 + ΔT1.sin(30.t1) (°C) where: ΔT1 = temperature amplitude (°C) of base, taken as ΔT1 = 10°C t1 = time of construction of base (in months after May 1), with 0 ≤ t1≤ 11

27. Mechanical model – mechanical properties of base after 20 years

28. Mechanical model – time dependent mechanical properties of base Total obstructed deformation

29. Mechanical model – time dependent mechanical properties of base Modulus of elasticity

30. Mechanical model – time dependent mechanical properties of base Compressive and tensile strength

31. Mechanical model – time dependent mechanical properties of base Mechanical model calibrated for A32 for following conditions: ▪ measured average mechanical properties of bound blast furnace slags road base material ▪ measured average pattern of heaves (height, length, distance) after 20 years ▪ time of construction: May 1 (15°C)

32. Calibrated mechanical model Maximum compressive stress vs. strength (average properties, construction May 1)

33. Calibrated mechanical model Distance between transversal heaves (average properties, construction May 1)

34. Calibrated mechanical model Height of all (2) series of transversal heaves (average properties, construction May 1)

35. Results from mechanical model After calibration calculations for 12 combinations of: ▪ level of mechanical properties (low, average, high), data given earlier ▪ time of construction, i.e.: ▫ February 1 (5°C) ▫ May 1 (15°C) ▫ August 1 (25°C) ▫ November 1 (15°C)

36. Results from mechanical model Distance between transversal heaves

37. Results from mechanical model Height of first (dominant) series of transversal heaves

38. Conclusions The higher the mechanical properties and the lower the temperature during construction, the more serious the problem of transversal heaves: ▪ heaves earlier in time ▪ higher heaves ▪ more heaves

39. Conclusions The more hydraulic the blast furnace slags: ▪ the greater the short term profit (stiffness) ▪ the larger the long term problem (heaves, bearing capacity) Compromise on basis of ageing tests

40. Thank you

41. FWD deflection curves 2nd section

42. Modulus of blast furnace slags road base 2nd section Centre of heaves: 30 – 50 MPa Rest: 50 – 200 MPa Dramatically low!

43. Grading of blast furnace slags 1st section Binding in all cores

44. Grading of blast furnace slags 2nd section Binding in all cores

45. Indirect tensile strength 7 specimens Room temperature Force controlled test; loading rate 0.2 kN/s (related to tests on concrete)

46. Indirect tensile strength On average indirect tensile strength = 0.52 MPa

47. Mechanical model – temperature of base Temperature of base: T1 = 15 + ΔT1.sin(30.t1) (°C) where: ΔT1 = temperature amplitude (°C) of base, taken as ΔT1 = 10°C t1 = time of construction of base (in months after May 1), with 0 ≤ t1≤ 11 Temperature T2 of base at any time t: Construction at February 1: T2 = 15 + ΔT1.sin(30.t-90) (°C) Construction at May 1: T2 = 15 + ΔT1.sin(30.t) (°C) Construction at August 1: T2 = 15 + ΔT1.sin(30.t+90) (°C) Construction at November 1: T2 = 15 + ΔT1.sin(30.t+180) (°C) where: t = time (in months after time of construction), so the age of the base Difference ΔT2 between temperature at time t and temperature at construction: ΔT2 = T2 – T1 (°C)

48. Time-dependent mechanical behaviour of hydraulic blast furnace slags Tensile strength s.[1-√(240/t)] σt = e . σt20y (MPa) where: σt = tensile strength (MPa) s = parameter; s = 0.25 (Eurocode 2, 2005) t = age of the base (months) σt20y = tensile strength after 20 years

49. Time-dependent mechanical behaviour of hydraulic blast furnace slags Compressive strength s.[1-√(240/t)] σc = e . σc20y (MPa) where: σc = compressive strength (MPa) s = parameter; s = 0.25 (Eurocode 2, 2005) t = age of the base (months) σc20y = compressive strength after 20 years

50. Time-dependent mechanical behaviour of hydraulic blast furnace slags Modulus of elasticity γ E = β.σc . E20y (MPa) where: E = modulus of elasticity (MPa) γ = parameter; γ = 0.3 (Eurocode 2, 2005) E20y = modulus of elasticity after 20 years β = parameter; value follows from boundary condi- tion after t = 240 months (20 years): β.σc20y = 1