Cement water proofers

A cement water proofer is a material added to cement mortar or concrete to make it impervious (water-tight) by reducing the water absorption and permeability of the hardened mass.

Types and action

1. Pore fillers (pore-blocking): very fine inert materials such as fly ash, talc, bentonite, hydrated lime, chalk or silica fume. They fill the voids between particles, so water cannot enter.
2. Water repellents (hydrophobic): soaps, stearates, fatty acids, oils and wax emulsions. They line the pores and make them repel water.
3. Crystalline waterproofers: react with water and free lime to grow crystals that block the pores.
4. Integral liquid waterproofers: ready-made liquid compounds mixed into the mixing water.

Uses

• Basements, water tanks, swimming pools, retaining walls.
• Roof slabs, terraces, bathrooms and toilets.
• Plaster for damp walls; damp-proof courses.

Points

• The dosage is usually 2-3% by weight of cement, as recommended by the manufacturer.
• Good compaction, a low water-cement ratio and proper curing are also needed; the water proofer alone is not enough.