Case 2

Remedial (see also Remedial)

If the area affected is not too large, blisters should be burst to remove all the water. Remove the paint layer, dry it, seal up with sealer and then repaint [1,2].

When isolated blistering has occurred, sand down the paint film, clean and repaint. In the case of severe blistering, clean and allow surfaces to dry and then paint.

The standard codes of painting practice should be followed. The primers, undercoats and finishing coats should be correctly selected and properly applied allowing adequate drying time between each coat [5,6].

There is no point repainting without first finding out the source of the moisture. The cause of the water seepage or condensation must first be determined and removed.

The following are some recommended practices:

Failure of waterproofing

Prior to the repair to the waterproofing, the defective layer of paint has to be scraped off. The plaster around the area of water seepage will be hacked to expose cracks or other concrete defects.

If basement is waterproofed with a tanking system or admixture, Polyurethene grout injection is one of the most cost effective repair method. It will seal up the holes and cracks in the concrete as well as seal up the passage of water from the soil.

Polyurethane (PU) Grouting is specially designed for providing water control in static joints or cracks in concrete structures. The grout material, when mixed with a certain amount of accelerator, will react with water or moisture and expand to form a tough, closed-cell rubber that is essentially unaffected by corrosive environment.

Polyurethanes are products of the petrochemical industry. They are very durable when exposed to external conditions and retain their gloss well. They can be obtained as elastomers, solid and rigid materials or flexible coatings. Major cracks or localized porous concrete can be repaired by this method.

In the application, PU reacts upon with the water in the slab and expands its volume and thus fills the cracks or pores in the slab. Therefore, it acts as a sealer over the cracks. The repairing process can be completed within half a day. Accelerator agents can be used to speed up the setting time of the grout.

Advantages of typical Polyurethane systems:

• Negative side application possible
• Deep penetration into very small cracks
• Foam increases in volume to fill cavities and voids
• Adjustable gel times
• Excellent bond to wet surfaces
• Underwater injection approved
• Good elastic strength, tolerant of movement
• Inert after curing, constant volume, no shrinkage
• Tolerates unavoidable debris
• Approved for contact with potable water
• Easy to handle
• Tolerant to mixing variations and field conditions
• Materials within the system are compatible
• Does not create new cracks

Limitation of Polyurethane systems:

• Polyurethane will be cured to become a rubber- like substance. Hence, it will not provide strength for structural cracks.

Use of water plug to seal the water passage from the weak points

First chisel a V-shape groove at the column and floor joint. Next, pack the Hydraulic plug into the groove. It will expand when it comes into contact with water and hence, seal off the leakage.

Breathable Paint

Choose a mould-proof and/or breathable paint if moisture wall cannot be avoided.

The video below describes the concept of a breathable paint:

How to Deal with Blistering & Peeling by ROXSiL Breathable Paint – Courtesy of Roxsil

How to Deal with Efflorescence by ROXSiL Breathable Paint – Courtesy of Roxsil