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Waterproofing of Water Tanks

PREFACE

 

When it comes to the waterproofing of water tanks, constant hydrostatic pressure combined with rigid and porous structure of concrete pose serious challenges for an effective and lasting job.

 

All water containing and water retaining structures should meet the strictest specifications from the conception to the design and finally the materialization of the project.

THE CONCRETE

 

Cracks number and width is controlled from sufficient and properly placed steel reinforcement.

 

Aim for a water/cement ratio W/C:0,45. Try PCE superplasticizers.

 

Concrete synthesis, placement as well as curing practices should conform to the local regulations of concrete technology for water resisting concrete.

WATER RESISTING ADMIXTURES

 

The first successful movement is to use a PCE superplasticizer. This should reduce size, number and continuity of pores.

Pore blockers as silica fume  can be used or hydrophobic materials to line the concrete pores and thus reduce capillary absorption by altering the intermolecular forces in the system concrete – air – water.

LEVELING MORTAR

 

Depending on the smoothness of concrete substrate a leveling mortar layer should be used.

 

Usually these leveling mortars are quite thin (less than 6mm thick). To reinforce them and increase their adhesion  an SBR LATEX is usually used.

 

A common formula :

Portland cement: 1 part

 

Moist, sharp sand: 3 parts

 

SBR Latex: 0,2-0,25 parts

 

Clean water: as required to achieve desirable consistency.

CONSTRUCTION JOINTS

 

All not movable joints e.g. new to aged concrete, floor to wall joints, casting interruption joints should be preventively sealed with bentonite waterstops. The same is valid for all through-wall penetrations.

WATERPROOFING OPTIONS

All cementitious materials used in water tanks should better be certified for contact with potable water.

(1) Rigid, one-component cementitious waterproofing products.

 

These products are suitable only for below ground concrete water tanks. We are strongly in favor of crystalline cementitious waterproofing.Crystalline products actually offer a double defense line against water ingress. The first line is the waterproof layer on the surface and the second is the in depth pore blocking.

 

Crystalline products  work with the crystallization process. Proprietary active salts of the product penetrate deeply in concrete mass using substrate humidity as a carrier. That’s why the substrate should be fully saturated with water.

 

When the active salts meet free lime, complex chemical reactions take place and new salts are produced to totally block the pores!

This is a real structural modification of the concrete! No comparison could be made with conventional one-component cementitious products!!

(2) Flexible, two-component cementitious waterproofing products.

For above ground water tanks, mixed type water tanks or water towers the choice is one-way. Flexible cementitious waterproofing. These products have impressive crack bridging capabilities further enhanced by suitable reinforcements.

Chris Strogilis

http://maconwaterproofing.blogspot.com

About the Author

Civil engineer with postgraduate studies in MBA and Marketing