Injection Systems for Concrete Structures. Causes, Remedies and Repairs

Transcription

1 Injection Systems for Concrete Structures Causes, Remedies and Repairs

2 Overview - General introduction - Reason for cracks - Different types of cracks - Crack characteristics - Crack investigation and repair work - On site investigation - Injection step by step - Construction related cracks - Curtain and Grid Injection - Choice of the right injection material - Standards 2

3 Cracks in concrete structures Cracks are an element of any reinforced concrete structure. Cracks are not a failure of the concrete. They are part of the function of the reinforcement. 3

4 Crack Characteristics Crack Formation A Separation crack caused by tension Schnitt A-A affects the entire cross-section N N A Bending crack caused by bending moment affects half of the cross-section M B M Schnitt B-B B C Shear cracks Schnitt C-C slanting toward axis of a member Q M C 4

5 Cracks in concrete structures Types of cracks Surface cracks Negative effect for durability Separating cracks Negative effect for watertightness Negative effect for durability Negative effect for strength

6 Cracks in concrete structures Limits of the crack width depending on the construction Inside structures, dry Outside structures, wet Structures in contact with de-icing salt Structures in contact with sea-water Water tank structures 0,40 mm 0,30 mm 0,18 mm 0,15 mm 0,10 mm Source: ACI 224R-90 (American Concrete Institute) 6

7 Cracks in concrete structures Width of a crack The width of a crack is a basic element for the correct choice of an injection material. Fine cracks normally require a injection material with a low viscosity. Injection materials with a higher viscosity can be helpful in case of wide cracks. 7

8 Cracks in concrete structures Minimum width of a crack according to German regulation Injection Injektion Impregnation Tränkung EP-I 0,10 mm EP-T 0,20 mm PUR-I 0,20 mm 0,30 mm Waterproofin schliesse g n dehnfähig Ductile ZL-I 0,80 mm ZL-T 0,80 mm ZS-I 0,25 mm ZS-T 0,40 mm 8

9 Cracks in concrete structures Movement of a crack In case of crack movement a flexible injection material like a polyurethane resin is necessary. Attention!!! All flexible materials have only a very limited extensibility. The crack must be injected at its maximum width to limit the expansion of the material. 9

10 Cracks in concrete structures Criteria for crack repair work Width of a crack Movements of a crack Stage of moisture of a crack 10

11 Cracks in concrete structures Reasons of crack repair work Durability of the construction Closing a crack to avoid the ingress of damaging substances (e.g. corrosion due to chlorides) Watertightness of the construction Closing a crack to refit the sealing function of the concrete structure. Strengthening of the construction Force transmitting injections to rebuild the strength of a structure (e.g. after a unique overload)

12 Cracks in concrete structures Stages of moisture in cracks Dry cracks Wet cracks Cracks with flowing water without pressure Cracks with flowing water under pressure 12

13 Cracks Investigation on site State of dampness Crack width Crack width changes (short- or long-term?) Crack structure (how deep?) General state of Crack (dust, oil or any other bond-breaking substances?) 13

14 Cracks Investigation on site State of dampness The State of dampness is important for the selection of the Injection System Dry cracks Is water penetration possible? Is the impact of water on crack area detectable Are the crack edges visibly dry Assessment of crack edges via dry cores? 14

15 Cracks Investigation on site Damp cracks Colour shade change of crack area, but no water discharge Signs of recent water discharge Are crack edges visibly damp or matt damp? Assessment on dry cores 15

16 Cracks Investigation on site Water bearing cracks without pressure Is water detectable in crack area? Are water leaks in fine drops from the crack more or less? 16

17 Cracks Investigation on site Water-bearing Cracks under pressure A continuous water stream from crack 17

18 Injection of cracks and voids 18

19 What is the objective? Closing To inhibit or hinder the entry of corrosion-promoting substances in structural components Waterproofing the Crack To eliminate crack-related leaks in building components Structural-strengthening of Crack To join both crack edges to restore tensile and compressive strength Flexible repairs Join both crack edges and gain limited flexibility 19

20 Crack Repair by Injection Method Definition Procedure for filling cracks and cavities under pressure with drillhole (mechanical) or surface packers using the appropriate injection method and material. Injection with drill-hole (mechanical) packers is used: when drilling is possible for low and high pressure injection Injection with surface packers Is used: when no drilling is possible when there is no water (structural crack repair) For low pressure injection (<20bar) 20

21 Crack Repair by Impregnation Method Used to fill cracks without pressure in areas near the surface Is used On horizontal surfaces ONLY when no pressure is required For fine cracks when there is no water Filling ratio Venting 21

22 Application Technique Crack Injection with Mechanical Packers Crack Injection with Surface Packers Impregnation 22

23 direction of injection Cracks in concrete structures Application of a drill-hole packer View C-C

24 Cracks in concrete structures direction of injection Application of a surface packer patching Nail has to be removed after hardening of the adhesive View A-A t: depth of injection by a packer r: distance between the packers Source: ZTV-Ing., German regulation

25 Crack Injection with Mechanical Packers Drill packer holes at a 45 angle to the concrete Ø of drill hole = Ø of packer + 2mm Drill hole depth: ~d ~45 d: building component thickness d/2: Spacing - from packer to packer - from packer to crack 25

26 Cracks in concrete structures Application of a drill-hole packer 26

27 Cracks in concrete structures Application of a drill-hole packer only in case of very thin constructions 27

28 Start the Injection process Install the mechanical packers Tighten the mechanical Packers 28

29 Fix the non-return valve on the first (lowest) packer Start Injection process at the first packer 29

30 When the injection material flows out of the second packer, fix nonreturn valve on it as quick as possible Repeat this procedure from packer to packer If necessary, a secondary injection is carried out Stop injection at the first packer and continue at the second 30

31 Cracks in concrete structures 31 Impression from the construction side

32 Cracks in concrete structures 32 Impression from the construction side

33 Cracks in concrete structures Impression from the construction side 33

34 Cracks in concrete structures 34 Impression from the construction side

35 Cracks in concrete structures 35 Impression from the construction side

36 Cracks in concrete structures 36 Impression from the construction side Direction of the injection in walls: From the bottom to the top

37 Cracks in concrete structures 37 Impression from the construction side

38 Cracks in concrete structures 38 Impression from the construction side

39 Basic rule for choosing the injection pressure for crack injection Pmax. = (concrete strength x 10)/3 Example: Concrete Class C25/30 (EN 206-1) = 30 N/mm 2 (for cubes) Pmax. = (30 x 10)/3 = 100 bar 39

40 Crack Injection with Surface Packers Prepare the substrate by blast cleaning or mechanically by grinding etc. Then clean by brush and vacuum 40

41 Place a steel nail through the surface packer into the crack to prevent the injection canal from being blocked by the patching material Install the surface packer with the patching material d: building component thickness Type SP 41

42 Patch the surface of the crack ensuring that the packer and the crack on the surface are fully covered by the patching material 42

43 As soon as the patching has cured (~24h), remove the nail and fix the nonreturn valve on the first packer and start the injection process When the injection material flows out of the second packer, fix nonreturn valve on it as quick as possible Stop injection at the first packer and continue at the second Repeat this procedure from packer to packer If necessary, a secondary injection is carried out 43

44 Calculation Aid for Patching Material e.g.: PU Injection: Elastic patching material Rate of consumption for patching: Approx. 0.5 kg per running meter Layer thickness = 3 mm Width = 100 mm 44

45 Impregnation Methods Paint the crack with a paint brush open the crack and fill in the injection material Filling ratio Venting 45

46 Cracks in concrete structures Quality of the crack repair work Impregnation Injection 5 mm or 15 x crack width 80 % 46

47 Cracks related to Construction Leaking construction joints - Waterproofing is missing - Waterproofing with poor performance - Incorrect application (fixing, welding ) - Insufficient concrete compaction 47

48 Leaking joints Reasons of leaking joints 48

49 Leaking joints Impressions from the construction side 49

50 Leaking joints Construction joints repair work Injection Packer Construction Joint 50

51 Leaking pipe penetrations 51

52 Leaking waterproofing details Pipe penetration repair work Difficult repair work because of the potential damage of the pipe by drilling the holes. Patching Penetration 52

53 Surface sealing of leaking Concrete Structures 53

54 Where do we find these leaking building components? underground car parks basement buildings underground constructions, tanks, reservoirs, pools 54

55 Objective of Surface Sealing To eliminate leaks in underground building components Creating a new sealed surface (curtain) in foundation pits in direct contact with the building structure or within the structure Repair existing waterproofing system 55

56 Surface sealing of leaking concrete structures by means of injection are used if traditional ways of laying bare and renewing the watertighness(no possibility to reach the leaking structure from outside) installing new joints installing shotcrete shells injecting cracks and cavities ARE NO LONGER POSSIBLE! the costs of conventional sealing is unreasonably high 56

57 Application Technique Curtain Injection with Polyacrylate Gels 57

58 Curtain Injection The packers are placed in a grid with a distance between cm. The right distance shall be checked by a test injection. You need detailed information of the soil to choose the right material, the right packer distance and the right way of application. Curtain injection 58

59 Grid Injection The packers are placed in a grid with a distance between cm. The right distance shall be checked by a test injection. The depth of the holes is 2/3 of the construction. The construction must be injectable. Injektionsschleier Grid injection Bohrkanäle im Raster 59

60 Grid injection Impressions from the construction side 60

61 Start the Injection process Drill holes horizontally through the leaking building component Ø of drill hole = Ø of packer + 2mm The distance between the packers are 30 50cm apart 61

62 Install mechanical packers Tighten the mechanical Packers 62

63 Fix button head (non-return) fittings on the first packer at the lowest row of drill holes Start Injection process at the first packer 63

64 When the injection material flows out of the second packer, fix non-return valve on it as quick as possible Stop injection at the first packer and continue at the second Repeat this procedure from packer to packer If necessary, a secondary injection is carried out 64

65 Important Notes for the Application of Injection Systems: Make sure that there are no drainage pipe or services in or behind the surface Start injection with low pressure Always work by injecting from the bottom to the top During Injection, wear safety glasses, gloves and helmet Provide sufficient air exchange Never stand directly behind the packer 65

66 Properties Injection Materials AC AC AC H 2 O H 2 O H 2 O AC AC AC AC H 2 O H 2 O H 2 O AC AC AC AC AC 66

67 Properties of Polyurethane Injection Materials High flexibility, even below 0 C Foam formation with water contact (if there is no defoamer) Good adherence to dry and wet surfaces Different properties: PU Foams (reactivity, expansion rate, elasticity, end product ) Different properties: Resins: Viscosity, hydrophilic/hydrophobic, elasticity 67

68 Properties of Epoxy Injection Materials High mechanical properties (compressive, tensile strength ) Good adherence to dry and damp surfaces High chemical resistance Different properties of different formulations (viscosity, elasticity, tensile strength, end product ) 68

69 Properties of Cement Microfine Binders Good mechanical properties (esp. compressive strength) Good adherence to dry and wet surfaces Good flow properties Different properties of different cements and admixtures (fluidity, setting point, thixotropy) 69

70 Properties of Polyacrylate Gels Low viscosity No inherent strength (soft, elastic) Adjustable reaction time (30sec 5min) Environmental safety Polyacrylate Gels should always be used in direct contact with damp or water saturated conditions Polyacrylate Gels are corrosive (be careful with steel reinforcement!) 70

71 Main Injection Material Parameters Viscosity Expansion Reaction Time Potlife Flexibility Adhesion/Bond Durability Permanent Sealing Resistance Environmental Hazard/Toxicity 71

72 Selection of Injection Packers Injection Packers are filler necks used as connection pieces Between the injection pump and the structure. There are two different groups of packers: Mechanical packer Surface packer Nipple or Cone head Flat head 72

73 Selection of Injection Packers 73

74 Standards: EN 1504 Part 5: Crack-filling materials Harmonizes product norms Specification of mandatory requirements General Rules: Responsible for CE-Marking The Producer by declaration of conformity to the regulations and CE marking; attests that the characteristics of the product conform to harmonised norms, for the specified construction EN 1504 Part 5 regulates neither the use of the material at the construction site nor the quality control of the work performed 74

75 Standards: EN 1504 Part 5: Crack-filling materials Products within the EN : Polyurethane Resins Epoxy Resins Microfine Cement No PUR-Foams and Acrylates 75

76 Certificates, Standards and Test Reports Drinking Water Certificates Other Test Reports 76

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