Hasan Rizvi, CICO Technologies Limited, New Delhi.

Waterproofing is considered to be an important part in modern construction. The word Waterproofing’ may be a misnomer as it is virtually impossible to provide absolute exclusion of water or moisture from a masonry/concrete structure. The process is basically an attempt to exclude maximum amount of water or moisture from a structure.

Waterproofing is essentially required where there is hydrostatic head of water to be resisted or where unusually dry conditions must be maintained. On the other hand damp proofing maybe defined as the treatment to retard the passage of water with application of suitable treatment methodology coating or integral waterproofing compounds.

The basic causes of defects in buildings are due to usage of excess water (high w/c/ ratio), by excess water we mean that, adding more water than required for hydration. This leads to formation of capillaries, pores, gel pores through which water can penetrate into the structure thus endangering the durability of the structure.

Concrete possesses a pores and capillaries and in this respect, it is fundamentally different from metal. The capillary and pore structure allows water under pressure to pass slowly through the material. Concrete subject to chemically polluted environment also gets deteriorated and damaged. It is here where polymer technology can be advantageously utilized to provide protection against the attack by water under pressure, acid and alkalis and chemically polluted environment.

Usually water intrusion in concrete structures is through the following areas:
  • Basement
  • Bathroom/ Kitchen sunken portion
  • Roof
There are various systems tried and tested by CICO Technologies Limited over a span of 75 years for various sectors of the building. These tested systems are described here.

Basement (System of waterproofing treatment to the underground/ basement structures.)

Raft Portion

  • The sub-base concrete (lean concrete) should be rendered smooth with ‘Cement: Sand’ mortar in the ratio of 1:3 by weight of cement while sub-base concrete is still green.
  • Then apply two coats of Tapecrete P-151, acrylic polymer modified cementitious slurry coating in a ratio of 1:2 i.e. 1 kg Tapecrete P-151 mixed in 2 Kg cement. This slurry should be applied by brush.
  • Over the Tapecrete P-151 topping one should provide a protective plaster of 12 mm thickness. This is done to protect the Tapecrete applied surface against probable mechanical damage due to dragging of reinforcement while placing it.
  • Cast the RCC slab admixed with a superplasticizer like CICO Plast SUPER.
  • This should be followed by injection grouting by placing 12 mm NBMS threaded nozzles of 75 mm length placed in a grid pattern. The spacing should not exceed 1.5 m c/c in the slab.
  • Then inject the cement slurry admixed with CICO non-shrink polymeric waterproof grouting compound through the nozzles.
  • Finally the nozzles should be sealed by CICO quick setting compound.

Retaining Wall

  • Cast the RCC walls admixed with a superplasticizer.
  • Place and fix 12 mm NBMS threaded nozzles of 75 mm length by drilling in a grid pattern (from inside) with maximum spacing of 1.5 m c/c.
  • Then inject grout with cement slurry admixed with CICO non-shrink polymeric waterproofing grouting compound
  • This should be followed by application of two coats of Tapecrete P-151 acrylic modified cementitious slurry coating over the properly rendered external face of the retaining wall.
  • Provide 12 mm thick cement plaster on the external face of the retaining wall.

Roof (System of roof waterproofing treatment.)

  • The roof should be cleaned of all loose mortar, laitance and existing treatment so as to expose the mother R.C.C. roof surface.
  • Then cut grooves at a height of 200 mm from roof slab all along the parapet walls if there is no spring of the parapet wall.
  • Moisten the surface with water. Then apply one coat of Tapecrete P-151 acrylic modified cementitious slurry coating (this slurry coating consists of 1 kg Tapecrete P-151 mixed with 2 Kg cement.)
  • Place the fiberglass cloth over the slurry coat and follow by Tapecrete P-151 brush topping. The brush topping slurry consists of Tapecrete P-151 mixed with cement and silica quartz (1:2:2) by weight.
  • A protective screeding should be provided over this treatment.
Refer Figure 2 for details.

Bathroom/Kitchen (System of waterproofing treatment for Toilet / Kitchen sunken areas.)

  • Clean the RCC sunken slab and vertical portion of all dirt and loose material etc. with a wire brush.
  • Make corner fillets with polymer mortar of 25 X 25 mm size at all joints. Seal all pipe joint with polymer mortar. Then apply Tapecrete P-151 slurry coat on these pipe joints followed by wrapping it with fiberglass cloth again apply a second coat of Tapecrete slurry.
  • Moisten the RCC sunken slab and apply one coat of Tapecrete P –151 slurry coating.
  • Lay fiberglass cloth over the slurry coated surface.
  • Apply a second coat of Tapecrete P-151 slurry over the fiberglass laid surface.
  • Apply one coat of brush topping over the second coat of acrylic polymer modified cementitious slurry coating.
  • Provide a protective plaster over the treated surface as a protective layer, Figure 3.
The above systems of waterproofing has worked perfectly well in thousands of buildings and even various government agencies are considering to change their specification of conventional box type system for basements to chemical injection and acrylic polymer modified cementitious coating system.

NBMCW April 2006