Building crack,types,causes & its repairing

This presentation is all about cracks occur in building.It includes all types of cracks,its major causes and repairing techniques and finally a conclusion from which viewers can fully understand
about building cracks.

1. BUILDING CRACKS PRESENTED BY :- GAUTAM SWALA

2. Contents:- Introduction Principal causes of cracks Repairing of cracks Conclusion

3. INTRODUCTION A crack is a complete or incomplete separation of concrete, brick walls into two or more parts produced by breaking or fracturing.

4. Classification of Cracks Structural Cracks Non- Structural Cracks 1. Structural Cracks : Structural cracks are due to poor construction sites ,overloading and poor soil bearing. Generally wider than 3 mm. These cracks should be addressed immediately. (A) Nature -wise:

5. 2. Non-Structural Cracks : These are caused by changes in the moisture content and thermal movement. It can also be caused by following conditions : Creep Vegetation/Trees Generally, less than 3 mm

6. Thin Crack : Less than 1 mm in width Medium Crack : 1 to 2mm in width Wide Crack : More than 2 mm in width Crazing : Occurrence of closely spaced fine cracks at the surface of material is called crazing. (B) Width-wise :

7. (C) Shape-wise : 1.Straight 2.Toothed 3.Horizontal ,vertical & Diagonal crack

8. 4.Stepped 5.Random

9. Permissible Crack Width (As per ACI) EXPOSURE CONDITIONS MAXIMUM ALLOWABLE CRACK WIDTH IN MM DRY AIR 0.41 HUMIDITY, MOIST AIR 0.30 WETTING AND DRYING 0.15 WATER RETAINING STRUCTURE 0.10

10. Principal Causes of Cracks 1. Foundation Movement & Settlement of Soil 2. Faulty workmanship & poor construction practice 3. Elastic Deformation 4. Growth of Vegetation 5. Poor structural design & specifications 6. Temperature effect

11. 1. Foundation Movement & Settlement of Soil Shear Cracks in buildings occurs when there is large differential settlement of foundations due to one of the following causes : Unequal bearing pressure under different parts of structure. Bearing pressure being in excess of bearing strength of soil.

12. (c) Low factor of safety in a design of foundations. (d) Local variation in nature of supporting soil.

13. Preventive Measures : - Under reamed pile foundation . SBC is not exceeded. Soil should be well compacted.

14. 2. Faulty workmanship & poor construction practice Causes : Premature removal of forms. Cold joints. Segregation. Selection of poor quality cheap materials

15. Preventive Measures : Water Cement Ratio Proper Curing Support for forms Design recommendations

16. 3. Elastic Deformation Structural components of a building under elastic deformation due to dead and superimposed live loads in accordance with hook’s law. The amount of deformation depend upon elastic modulus, magnitude of loading and dimension of component.

17. 4. Growth of vegetation Firstly, crack occurs on exterior walls due to above causes. Then, soil and some small seed is collected through wind inside cracks which comes in contact with moisture & finally led to the growth of vegetation. If these plants are not removed well in time , they cause severe cracking of walls.

18. 5.Poor structural design & specifications Firstly, It’s important to do soil investigations to determine type of foundation It is critical for the structural designer and architect to know whether the agency proposed to carry out construction has the requisite skills and experience to execute their design.

19. 6. Temperature Effect : Volume Changes. Volume relation to temperature is expressed by coefficient of thermal expansion. Volume change induced stress.

20. Preventive Measures : Adequate insulating or terracing treatment. Painting exterior walls with some sun reflective finish Introducing of expansion and contraction joints at appropriate locations.

21. Repairing of Cracks Epoxy injection Routing and Sealing the crack Stitching Grouting Overlay of cracks

22. 1.Epoxy injection Cracks as narrow as 0.05mm can be bonded by this method Firstly, clean the surface with the wire brush Then , Establish entry and venting ports at close intervals along the cracks Remaining exposed surface of cracks are sealed by epoxy paste Now, inject epoxy under pressure Finally, hammer the ports & finish the surface to grinder.

23. 2.Routing and Sealing the crack This method involves enlarging the cracks along its expose face & filling & sealing it with a suitable joint sealant. This procedure is most applicable to approximately flat surfaces such as floors & pavements.

24. 3. Stitching Firstly, drill holes on both sides, cleaning the holes. Then, anchoring the U-shaped metal units in the holes with either a non-shrink grout or an epoxy resin.

25. 4. Grouting This method is effective in stopping water leaks but it will not structurally bond cracked sections. Firstly, clean the concrete along the crack & then fill it with portland cement grout. Water cement ratio should be kept low to maximize the strength & minimize shrinkage.

26. 5. Overlay of cracks Slabs containing fine dormant cracks can be repaired by applying an overlay, such as polymer modified portland cement mortar, or by silica fume concrete.

27. Conclusion: It is impossible to guarantee against cracking yet attempts can be made to minimize development of cracks Not all types of cracks require same level of attention. The causes of crack can be controlled if proper consideration is given to construction material & technique to used. In case of existing cracks, after detail study & analysis of crack parameters, most appropriate method of correction should be adopted for effective & efficient repair of crack.

28. THANK YOU