Cracks in Concrete

2-Classifications 2-Classifications 3-Concrete removal, preparation 4-References Cracks in Concrete 1-lntroduction

1-lntroduction the concrete cracks are caused due to many reasons as repeated thermal cycle, accidental overloading, drying shrinkage, inadequate design or construction, or some other causes. This seminar is to provide guidance on classification of concrete cracks and discusses removal of the existing concrete,preparation of concrete surface to receive repair materials and methods for repairing the reinforcement bars.

2-Classifications 2-1 SHRINKAGE CRACKS. 2-2 CRACKS DUE TO CARBONATION OF CONCRETE. 2-3 CRACKS IN REINFORCED SLABS. 2-4 CRACKS IN BEAMS. 2-5 CRACKS IN COLOUMNS. 2-6 CRACKS IN REINFORCED WALL. 2-7 CRACKS DUE TO STRUCTURAL PROBLEMS.

2-Classifications 2-1 SHRINKAGE CRACKS. Common crack is shown widely in walls and slabs so must put joint every 12 m, And for cover of reinforcement bars when it is more than 4 cm or less than 1 cm so must put mesh of wires and improve the mix.

2-Classifications 2-2 CRACKS DUE TO CARBONATION OF CONCRETE. Especially in coastal area the carbonation of concrete allows humidity to reach to the bars then corrosion will occur. So must make cover of bars more than 4 cm and paint the concrete and improve the mix.

2-Classifications 2-3 CRACKS IN BEAMS thermal Cracks : As vertical cracks through total height of beam and same thickness and in L/5 of beam near support ; Bending Cracks : These cracks exist in maximum moment zones at middle of span and at support

2-Classifications 2-3 CRACKS IN BEAMS shear Cracks : Cracks at 45 with horizontal axis (diagonal tension ) Reason : shear reinforcement is less than required Torsion Cracks : Continuous Cracks at 45 with horizontal axis (diagonal tension )

2-Classifications 2-4 CRACKS IN COLOUMNS Bending Cracks : These cracks exist in maximum moment zones Cracks due to stirrups : Vertical Cracks Reason : lateral tension Cracks due to settlement : Horizontal Cracks Reason : tension force because Horizontal or vertical movement Of foundation.

2-Classifications 2-5 CRACKS IN REINFORCED SLABS. Reason : the reinforcement bars is less than required.

2-Classifications 2-6 CRACKS IN REINFORCED WALL Bending Cracks : These cracks exist in maximum moment zones when wall does as beam shear Cracks : Cracks at 45 with horizontal axis (diagonal tension ) Cracks due to weight : Horizontal Cracks

2-Classifications 2-7 CRACKS due to structural problems.

3-Concrete removal, preparation 3.1-Surface preparation Methods of surface preparation-Typical methods a) Chemical cleaning. In most cases chemical cleaning methods of surface preparation are not appropriate for use with the Concrete repair materials. However, with certain coatings under certain conditions, it may be possible to use detergents, phosphate, and various proprietary concrete cleaners. it is important that all traces of the cleaning agent be removed after the contaminating material is removed. b) Acid etching. Acid etching of concrete surfaces has long been used to remove laitance and normal amounts of dirt. The acid will remove enough cement paste to provide a roughened surface which will improve the bond of replacement materials. c) Mechanical preparation. This technique consists of mechanically removing thin layers of surface concrete using such equipment as impacting tools (breakers. scabblers), grinders, and scarifier. Depending on the equipment used, a variety of surfaces may be obtained. d) Abrasive preparation. This technique consists of removing thin layers of surface concrete using abrasive equipment such as sandblasters, shotblasters, or high pressure water blasters.

3-Concrete removal, preparation 3.1-surface preparation 3.2-Reinforcement repair Removal of concrete surrounding steel removal of the deteriorated concrete surrounding the reinforcement Quantity to remove. All weak, damaged and easily removable concrete should be chipped away Inspection of reinforcing steel steel is capable of performing as intended by the designer Cleaning of reinforcement steel.

4-References 1-CONCRETE REPAIR MANUAL VOLUME1 ….ACI,ICRI,BRE,CS USA 2-DETERIORATION AND REPAIR OF REINFORCED CONCRETE IN THE ARABIAN GULF VOLUME Bahrain 3-CRACKS IN REINFORCED CONCRETE STRUCTURES 1997 EYGPT 4-REASONS OF BUILDINGS COLLAPSE 1999 EYGPT 5-STRUCTURAL EVALUATION 1998 SYRIA 6-REHABILITATION OF BUILDING 2000 SYRIA