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Study of causes, prevention, remedies and repairs of cracks

BY CIVILTHINGS.COM

Objectives

• Introduction�Types of cracks & couses�Prevention of cracks�Procedure for repairing of cracks
• Conclusion

Introduction

• Cracks in the building is a universal problem faced throughout the world. Building components components could be caused by externally applied forces such as dead, live, wind, seismic loads or foundation settlement or could it be induced by internally due to temperature variations, chemical actions.

Types of Cracks

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• Flexure Cracks �Torsionan Cracks
• Tension cracks
• Horizontal Cracks
• Diagonal Cracks
• Vertical Cracks

Flexural cracks

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�Flexure implies twisting, cracks in strengthened concrete beams subjected to for the most part�Begins in strain zone i.e. delicate of the beam. The width of flexural cracks in beams for here�and now stacking may prompt be limited and long haul stacking; the crack might be expanded or uniform over the par

Flexure Cracks

Torsionanl Cracks

• The beams are subjected to torsion alongside shear power and twisting moment. Shear power and twisting moment happens at loads acting ordinary to the plane of bowing. Loads from the bowing plane causes torsional moment

Torsionanl Cracks

Tension Cracks

• Tension cracks are formed in beams subjected to shrinkage and temperature changes. �Usually these cracks tend to propagate over the full depth of cross section of the beam.

Tension Cracks

Horizontal Cracks

• Horizontal cracks are to be appeared in reinforced concrete column at the beam- column junction due to shear force,This type of crack is often due to unbalanced soil and hydrostatic water pressuring pressing against your foundation wall. You may notice the foundation bowing inwards and water leaking into your basement. Both block and poured foundations can develop horizontal

Horizontal Cracks

Diagonal Cracks

• Diagonal cracks in cross walls of a multi-story load bearing structure:�These cracks are due to differential strain in the internal and external load bearing walls to which the cross walls are bonded. When walls are unevenly�loaded with wide variation in stress in different parts, excessive shear stress is developed which causes cracking in the walls.

Diagonal Cracks

Vertical Cracks

• Vertical cracks in the top most storey at the corner�These cracks are caused due to shrinkage of RCC roof slab on initial drying�as well as due to thermal contraction, exerting an inward pull on the walls in both directions.

Vertical Cracks

Prevention

1. TO PREVENT CRACKS DUE TO MOVEMENT DUE TO CHEMICAL REACTION.�TO PREVENT CRACKS DUE TO CRACKING DUE TO VEGETATION�SURFACE FILING METHOD.�CEMENTITIOUS GROUTING METHOD

• To prevent Cracks due to Movement due to Chemical Reaction�For structural concrete in foundation, if sulphate content in soil exceeds 0.2 per cent or in groundwater exceed 300 ppm, use very dense concrete and either increase richness of mix to 1:1.5:3 or use sulphate resisting Portland cement/super-sulphated cement or adopt a combination of the two methods depending upon the sulphate content of the soil.

• To Prevent Cracks Due to Cracking Due to Vegetation�Do not let trees grow too close to buildings, compound-walls, garden walls, etc, taking extra care if soil under the foundation happens to be shrinkable soil/ clay. If any saplings of trees start growing in fissures of walls, etc. remove them at the earliest opportunity.

• Surface Filling Method:�For cracks of width of micro-cracks less than 0.2mm, it is the most simple technique used and to apply brush polymer or to apply elastomeric sealant on the surface in order to prevent moisture content, carbon dioxide and other harmful materials. But the main drawback is that it belongs to repair only shallow surfaces and not deep cracks and cracks not suitable to water pressure.

• Cementitious Grouting Method:�It is used for repair of wide cracks. It is a mixture of cementitious material and water that is proportioned to produce a proper consistency. Cement-based grouts are available in a wide range of consistencies; therefore, the methods of application are different for different material.

Procedure of repairing cracks

• Crack Repair Methods�This several methodologies have been shown to be feasible for repairing of existing cracked and following the evaluation of the concrete crack structures, a suitable repair procedure can be selected.

• CHEMICAL GROUTING�Chemical mortars are made up of solutions of two or more chemicals (such as urethanes, sodium silicates and acrylic homides) which together form a gel, a solid precipitate or a foam, unlike cement mortars, which consist of suspensions of solid particles in a liquid

Conclusion

Proper construction methods should be used during construction to prevent formation of crack.�However if there are any cracks, visual inspection should be done first. Cause of the cracks should be done with first before repairing.�Evaluation of cracks can be done by different technique like crack compactor and ultrasonic testing.

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