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Concrete Paving Hairline Crack Repair
1) Defects on concrete paving can be due to the use of excessive water, poor cement, poor construction practices, improper mixture proportioning, dirty or low quality aggregate and inadequate curing.
2) A deficiency must be differentiated from the actual cause and it is imperative that causes and not symptoms are dealt with wherever possible or practical. For example, cracking is a symptom of distress that may have a variety of causes.
3) Hollow spaces and cavities left in concrete mass on surface or inside the concrete mass where concrete could not reach. These look like honey bees nest, honeycombs which are on sides are visible to naked eyes and can be detected easily as soon shuttering is removed.
4) Due to non-reaching of concrete to all places in which cavities and hollow to hollow pockets are created. Main reasons are improper vibration during concrete, less cover to
reinforcement bars and use of very stiff concrete (this can be avoided by controlling water as per slump test).
5) Selection of the correct repair technique for cracking depends on knowing whether the
cracking is due to repeated thermal cycling, accidental overloading, drying shrinkage,
inadequate design or construction, or some other cause. Only after the cause or causes are known can rational decisions be made concerning the selection of a proper repair system.
Preparation & Repair Methods
a. As per manufactures recommendation approved repair materials shall be applied by skilled mason assuring that this material pushed to fill all surface voids.
b. All identified surfaces to be repaired shall be chipped out with V-grove shape carefully and clean the surface surroundings to expose dense and sound concrete and ensure no feathered edges at the area perimeter of the chipped surface any exposed steel
reinforcement shall be thoroughly cleaned and treated as required according to the manufacturer recommendations as per the selected material to be used for the repair.
c. Chipping with a V-Grove cut to the depth of the developed cracks to enlarge and
clean the area by blowing out with oil free compressed air washes the chipped and allows drying.
d. Brushes apply of suitable repair material on the exposed steel reinforcement rods and chipped surface. Mix components of the approved repair materials shall be applied according to the manufacturers’ instructions.
