Part-1 Restoration and rehabilitation, repairs of the structures

Restoration procedure
NDT and restoration related

1. Repair, Restoration and Retrofitting of structures Part-1 Dr. Kumar Srinivasan B.E(Civil), M.Tech (structures), Ph.D. MISTE, MICI, MCSI

2. Contents 1.Basic terminology and definitions 2. Causes of Distress 3.Observation of Defects/Distress 4.Address and Assessment of the Problem 5.Types of Distress 6.Classification of Repair Material 7.Distress and Remedial Measures 8.Materials for cracks and cracks repair technic 9.Restoration case studies 10.Questionires

3. 1.Basic terminologies and definitions

4. REPAIR, RESTORATION AND RETROFITTING Repair : To bring back the position of the structure either whole or part to its previous condition so that it gives performance same as previous. (Most of the time it is not related to strength aspect) Some examples of repair……. Checking the wiring of building Replastering of any wall if required Repairing of damaged flooring Repair of door and window Checking or repairing of pipe line connections, gas line connections and plumbing serveries. Relaying of damaged roof tiles etc

5. REPAIR, RESTORATION , REHABILITATION AND RETROFITTING Re storation : The process of re-establishing the previous condition of the building by the materials and methods (Regain the forms and functionality of a structure) Some of the examples of Re storation … .. T o treat the building without affecting the functionality and material form Re m oval o f da m aged portion o f m a s on r y and reconstr u cting it using same type units with rich mortar mix. Treatment for water seepage and structural damage without changing the originality Restoration of heritage or monumental building structures Renovation : Process of substantial repair or alteration that extends a building’s useful life without changing the purpose (Repairing or replacing the components like door window tiles etc )

6. REPAIR, RESTORATION AND RETROFITTING Rehabilitation : Rehabilitation of a building means altering or upgrading a building or a structure to present need by means of modification or alteration. Some of the examples of Rehabilitation… .. To modify the structure for more usage/utility ( Eg. Increase capacity of the party hall) To modifying the building for appearance aspect etc

7. REPAIR, RESTORATION AND RETROFITTING Retrofitting : The process of strengthening of structure along with the structural system, In compliance with all relevant codal provisions during its service period. or It is the modification of existing structures to make them more resistant to load /seismic activity, ground motion, or soil failure due to earthquakes. Ea r thquake c r ea t e s gre a t devast a ti o n /damage i n ter m s of l i fe, m oney and failures of structures. Earthquake Mitigation is an important field of study from long time . Seis m ic Re t rof i tting i s a c o ll e ction m iti g ation tech n iques for Earthquake Engineering. It is o f u t m ost i m portance f or h i storic m onu m ents, are a s prone to severe earthquakes and tall or expensive structures The retrofit techniques are also applicable for other natural hazards such as tropical cyclones, tornadoes, and severe winds from thunderstorms.

8. REPAIR, RESTORATION AND RETROFITTING When is Seismic Retrofitting Needed ? The two circumstances are:- Ea r thquake da m aged bu i ld i n g s, and Ea r thquak e - vulnera b le buildings(with no exposure to severe earthquakes) Some examples of retrofitting ……… (Refer IS13920,1893) Increasing the lateral strength in one or both directions, by reinforcement or by increasing wall areas or the numbers of walls and columns Giving unity to the structure by providing a proper connection between resisting elements. Eliminating features that are sources of weakness, asymmetrical plan distribution of resisting members, abrupt changes of stiffness from one floor to the other. Avoiding the possibility of brittle modes of failure by proper reinforcement and connection of resisting members. (IS13935)

9. 2. Causes of Distress

10. What is distress??? Distress can be symptoms indicating the defects present in the structure

11. Causes of distress 1.Accidental loading 2.Chemical Reaction a. Acid attack b. Alkali silica Reaction c. Sulphate attack 3.Construction Error 4.Corrosion of Embedded metal 5. Design errors a. Improper design b. Poor design detail 6.Erosion (a. abrasion b. Cavitation)

12. 7. Freezing and Thawing 8. Settlement and Movements 9.Shrinkage a. Plastic shrinkage b. Drying shrinkage 10.Temperature Changes a. Internally generated b. Externally Generated c . Fire 11.Weathering

13. “Observe and Guess/Find the cause of Distress” 3. Observations of Defects or Distress

14. Acid Attack Alkali aggregate Reaction Sulphate attack Physical Observations and Identification of causes some of the distress

15. Formwork movement Corrosion of embedded bar Improper Cover Physical Observations and Identification of causes some of the distress

16. Physical Observations and Identification of causes some of the distress Defective Design Weather action(F&T) Erosion

17. 4. Address and Assessment of the Problems How to Address ???

18. Problems to be Addressed Aging of structures-Expected life and performance Deterioration of concrete-causes and effects Durability considerations Distress diagnostics and performance monitoring-Non-Destructive test methods. Damage assessment and evaluation models Structural condition assessment Analysis and Design of repairs-suitable repair techniques Materials for protection, repair and rehabilitation Repair Techniques Strengthening techniques Seismic retrofitting

19. 5. Types of Distress

20. Types of Distress 1. Blow holes 2. Disintegration 3.Cold Joints 4.Honeycombing 5.Crazing 6.Cracking 7.Spalling 8.Deflection 9.Corrosion 10.Settlement Cracks

21. 6.Classification of Repair material

22. 6.Classification of Repair material 1. Patch repair material a. Cement mortar b. Polymer modified or polymer mortar 2 Injection Grout a. Cement grout b. polymer grout 3. Bonding Agents a. Polymer emulsion b. Polymer resin type

23. 6.Classification of Repair material 4 . Resurfacing material a. Protective coating/membranes b. overlay chemicals 5. Other repair material a. Corrosion inhibitor b. Catholic protection etc

24. 7.Distress and Remedial measures

25. Types of Distress 1.Blow holes Blow holes are individual, generally rounded, cavities on vertical surfaces of concrete, generally less than 10 mm across. They are caused by air in the concrete being trapped against the form face, sometimes due to insufficient The occurrence of blow holes can be minimised by the use of a suitable release agent on the surface of the formwork and the use of adequate vibration. In addition the concrete should have adequate workability. Blow holes will not affect performance of the concrete structure.

26. F ill these with rich cement mortar – but in some cases because of the importance of the structure and its future durability it should be sealed and finished with Polymer mortar using Polymer Latex of a reputed manufacturer ( Nitobond SBR,Butonal )in prescribed dosage. Repair Technique

27. 2 .Disintegration – It is the defects either by scaling or Dusting Scaling – Concrete scaling is the local flaking or peeling off of the near-surface due to environmental factors like freezing and thawing. Other factors that may contribute to the initiation of concrete scaling are the use of low-strength concrete, deicing salts, and a high water-cement ratio in a concrete mixture.

28. Repairing Concrete Scaling Remove loose concrete  and clean the surface having any dirt and debris. Dampen the cleaned concrete area and apply a thin layer of cement paste before concrete placement for resurfacing. Place proper concrete  type to resurface the damaged area.  Latex-modified concrete  (polymer-modified cement concrete) is a good option. Apply pressure on the concrete while the finishing operation is being performed.

29. Dusting -White powdery formation on the surface of hardened concrete that receives excessive traffic. Formation of loose powder resulting from bleeding(lighter particle raised to top) disintegration of surface of hardened concrete is called dusting or chalking. Sandblast or high-pressure washer to be used remove the weak surface layer. To minimize or eliminate dusting, apply a commercially available chemical floor hardener, such as sodium silicate (water glass) or metallic zinc or magnesium fluorosilicate (MgSiF 6) , in compliance with manufacturer’s directions on thoroughly dried concrete. If dusting persists, use a coating, such as latex formulations, epoxy sealers, or cement paint. Repair technique Dusting

30. 3. Cold joints - A cold joint happens when fresh concrete is poured on top of existing concrete. It looks like a huge crack and some people mistaken them with structural cracks. The truth is that cold joints rarely create structural integrity issues. Concrete Cold joint is defined as the plane of weakness in concrete due to an interruption or delay in the concreting operations.

31. Repair Technique The use of bonding agents(   MasterBrace 1414 , Nitobond ) to enhance adhesion between old and new concrete. The use of mechanical connectors , such as  dowel bars , to increase structural continuity.  The use of epoxy injection/Crack sealant  

32. 4. Honey Combing - It refers to voids caused by the mortar/binder not filling the spaces between the coarse aggregate particles. The honeycombs are caused by improper workability of concrete, using stiff concrete which is hard to place. Additional water cement ratio than the allowable limit on-site for better workability. The excess amount of water cement ratio will result in separation of aggregates from the mortar. Excess Vibration cause separation of aggregate

33. Remove all the loose aggregate and concrete from the affected honeycombed area. Do this gently with the help of a wire brush. Next, clean the concrete surface of dirt and fine particles with a brush. Wash the surface with water and allow it to dry for about 2 to 3 hours. Install a formwork if required or apply a high-strength grout. Prepare a grout mixture with water and binder (GP-2 or  MP Birla Cement Ultimate Build right, Sika grout 214 etc ). Fill the affected honeycombed area with the grout mixture and Allow it to dry for about 24 hours. Repair Technique

34. 5.Crazing - It is the network of fine random cracks that are formed due to the shrinkage of the layer relative to the base concrete. It does not pose any structural or Serviceability problem. Excessive Use of Cement  – To give a smooth finish on the concrete finish, labours try to sprinkle cement on the surface. Later the cement will dry and make way to crazing. Excessive Vibration  – Excessive vibration on the concrete makes the aggregate to settle down and let the cement slurry to the top which develop the crazing Use of High Workability Concrete  – Using high  workability concrete  for easy placement often contains excess water which makes the cement to settle at top.

35. Prepare a V-shaped groove along the crack using hand tools or a pneumatic tool Clean the groove using either air or water-blasting Allow the surface of the groove to dry Apply poly urethane sealant generously to the groove and allow it to cure.

36. 6.Cracking- Cracking is the line of separation in the plane of failure. Type of structure and nature of cracking is the major concern. Cracks in the concrete does not always mean that the structure is unusable. A. Structural Cracks - Structural cracks are those that may occur due to deficient designs , overloading , abnormal vibrations , use of inferior quality materials ,foundation placed on uncompacted /loose soils , adoption of improper construction practices, poor workmanship, etc. B . Non -Structural Cracks - These cracks occur due to the internally induced stresses in building material or due to the temperature induced movement of the materials. These cracks appearance of the structure may give a feeling of instability . (Crack treatment Discussed separately)

37. 7 . Spalling of Concrete Spalling is a term used to describe areas of concrete which have cracked and delaminated from the substrate. There are a number of reasons why spalling occurs including freeze thaw cycling, the expansive effects of Alkali Silica Reaction or exposure to fire. However, the most common cause of spalling is the corrosion of embedded steel reinforcement bars or steel sections. Corroding steel can expand up to 10-16 times its original volume, exerting stress on the surrounding concrete.

38. 9.Erosion - It could be due to abrasion by water carried derbies. E rosion Causes smooth , well-worn abraded surface of concrete, while in cavitation- erosion concrete appears to be very rough and pitted .

39. 8 .Deflection -It is the bending or sagging of the reinforced concrete structural elements like beams, slabs, columns, etc., which can be due to overloading, corrosion, or by creep in concrete.

40. Deflection treatment

41. 9.Corrosion - Rusting of steel in concrete, this results in cracking or spalling . A protective oxide film is present on the surface of the steel reinforcement due to the concrete alkalinity. This layer is called passivity. The process of carbonation will affect this protective passivity layer. This layer can also be affected by the presence of chlorides in water or in oxygen. The reinforcement corrosion process   Electrical current flows between the cathode and anode, and the reaction results in an increase in metal volume as the Fe (Iron) is oxidized into Fe(OH)2 and Fe(OH)3 and precipitates as Fe(OH)2 (rust color). Water and oxygen must be present for the reaction to take place .

42. Effects of corrosion  Cracking & Spalling : In compressive members, cracking and spalling of concrete reduces the effective cross section of the concrete, thereby reducing the ultimate compressive load capacity.  Reduction of structural capacity : The research conducted on flexural beams found that in steel with more than 1.5 percent corrosion, the ultimate load capacity began to fall, and at 4.5 percent corrosion, the ultimate load was reduced by 12 percent, probably as a result of reduced bar diameter. Chloride Attack

43. Corrosion protective techniques 1. Protective coating (Corrosion inhibitor) 2.Sacrifical anode method 3.Chloride removal method etc.

44. Corrosion inhibitors

45. 10.Settlement Cracks One of the most common causes of building cracks is a settlement. This occurs when the soil beneath the foundation compresses or shifts, causing the foundation to sink or settle. This can cause cracks in the walls, ceilings, and building floors. Refer Case study

46. 8 . Materials for Cracks and Cracks Repair Technics The various materials used for repairs of cracks are: Cement Slurry Cement Mortar Epoxy resin Polymer Modified Cementitious Products P polyurethane/Polysulphide

47. CRACK REPAIR TECHN ICS Epoxy-injection Grouting Routing and Sealing Stitching Prestressing steel Providing additional Reinforcement Drilling and plugging

48. 1.Epoxy-injection Grouting

49. Treatment for crack in RC members. (RC Slab and Retaining wall) Existing concrete surface to be cleaned thoroughly to remove dust particles by air & water jet. ‘U’ Grove shall be made along the crack and cleaned with air and water jet. 12 mm dia 50mm deep holes shall be drilled at 250mm c/c spacing as indicated in sketch to fix grouting nozzles. 10 mm dia PVC/TEFLON nozzles/packers shall be fixed into the drilled holes using anchor grout as per specification. Cleaned ‘U’ grooves along cracks shall be sealed with epoxy putty/mortar. Pressure grouting with low viscosity epoxy/monomer shall be carried out until refusal is reached under a pressure not less than 3- 4kg/cm 2 .

50. 2.Routing and Sealant

51. 2.Routing and Sealant

52. 3. STITCHING Stitching may be used when tensile strength must be re-established across major cracks. Stitching involves drilling holes on both sides of the crack grouting in U-shaped metal units with short legs called staples or stitching dogs

53. Prestressing steel Post-tensioning is often the desirable solution when a major portion of a member must be strengthened or when the cracks that have formed must be closed. This technique uses pre stressing strands or bars to apply a compressive force. Adequate anchorage must be provided for the prestressing steel and care is needed so that the problem will not merely migrate to another part of the structure.

54. Additional Reinforcement for Crack Repair Conventional reinforcement Cracked reinforced concrete bridge girders have been successfully repaired by inserting reinforcing bars and bonding them in place with epoxy. This technique consists of sealing the crack, drilling holes that intersect the crack plane at approximately 90 deg ,filling the hole and crack with injected epoxy and placing a reinforcing bar into the drilled hole.

55. 9 .Restorations Case study

56. Case studies 1: Settlement of floors INDUSTRIAL STRUCTURES

57. Sign of differential Settlement .

58. Sign of differential Settlement.

59. Sign of differential Settlement.

60. View of Existing flooring removal to expose the soil beneath the grade slab

61. Soil excavation done up to 1.5m level

62. Soil excavation in progress till 2.5m level

63. Subgrade preparation in progress after completing the excavation of soil

64. Drilling of holes using auguring machine for installing bamboo piles

65. Placing of bamboo inside the hole

66. Filling of m-sand inside the bamboo

67. Compaction of soil using static roller and vibrator plate compactor

68. Backfilling of soil in layers of 300mm thickness

69. Wet mix laying

70. Compaction of wet mix using static roller and vibrator plate compactor

71. Provision of polythene sheets to prevent damage of concrete by ingress of water which contains chloride and sulphate salts

72. Steel fabrication work

73. Providing and applying bonding agent for the bonding between old and new concrete

74. Casting of m20 grade concrete

75. Concrete Slump test Cube Casting

76. Curing of concrete in progress for proper strength development and durability of concrete

77. Groove cutting done to provide control joints in concrete and to avoid cracking of concrete and long- term damage

78. Laying of Granite FLOORING

79. View of floor after completion of strengthening works

80. 2.CASE STUDY ON RESTORATION OF RESIDENTIAL BUILDING AFFECTED BY UNEQUAL SETTLEMENT DUE TO FULLY FILLED SOIL

81. Cracks near openings

82. Cracks in External walls

83. Cracks in External walls

84. Cracks in Flooring

85. Cracks in internal walls

86. Soil testing

87. RESTORATION CASE STUDY-3

88. 2.1Treatment to avoid seepage in the basement Hydrostatic pressure isn’t in your basement but around it. This pressure forms when groundwater builds up in the soil around your foundation and has nowhere to go, causing it to force itself against your basement walls and floor slab This pressure pushes the water into the basement through cracks and joints, with water most commonly being pushed through the floor-wall joint.

89. View of cracked and uplifted floor in the location. 2.2Treatment for cracked and uplifted floor.

90. View of Leakage/dampness/damp patches/peeling of paint in RC members 2.3 Treatment for Leakage/dampness/damp patches/peeling of paint in RC members.

91. Treatment for Leakage/dampness/damp patches/peeling of paint in RC members. Existing concrete surface to be cleaned thoroughly to remove dust particles by air & water jet. 12 mm dia 75mm deep holes shall be drilled at 1000mm c/c spacing as in the damped areas to fix grouting nozzles. 10 mm dia PVC/TEFLON nozzles/packers shall be fixed into the drilled holes using anchor grout as per specification. Pressure grouting with low viscosity, elastic, solvent free, polyurethane resin grouting shall be carried out until refusal is reached under a pressure not less than 3- 4kg/cm 2 . The grouting shall be carried out from bottom to top and alternate holes shall be grouted at a time. Projected nozzles shall be cut in flush with the adjacent concrete surface.

92. 2.4 View of separation cracks between masonry walls and RC members

93. Treatment for separation cracks between masonry walls and RC members. Plaster in this region about 20mm on either side of the crack to be removed and loose particles shall be cleaned using wire brush. ‘U’ groove of 12 mm wide 6 mm deep shall be made all along the crack at the interface of masonry wall and RC member junction and cleaned. The Groove shall be filled with flexible sealant like Tacksel / Polysulphate sealant / silicon sealant or any other equivalent.

94. View of cracks in Masonry walls. 2.5 Treatment for Cracks in Masonry walls .

95. Treatment for cracks in Masonry walls. Existing plaster along the crack shall be removed on either side of the crack for a width of about 300 mm (on either side of the wall) and cleaned. Mortar joints along the crack shall be deep raked and filled with cement mortar. Weld mesh of size 50 x 50 x 3 mm shall be fabricated and fixed across the crack using ‘U’ nails. Re-plastering the region with CM 1:4 as per standard practice.

96. 2.6 Treatment for Dampness/deteriorated plaster in masonry walls . View of dampness/deteriorated plaster in masonry walls

97. 2.7 Provision of Saucer drain along the length of retaining wall

98. 2.8 Treatment for expansion joint in the (fresh and hardened concrete) flooring.

99. Retrofitting PART-2 This part will be discussed in next session

100. Now this Forum is Open for Discussion

101. [email protected]