Media

Repair System Extraordinary

Construction World – January 2008

The Municipal Corporation of Delhi choose Integral Crystalline Waterproofing to completely block leakage of water at its sewerage pumping station on a riverbank. ICW provides long-term protection, says Leo Connell.

Cracks are bound to occur in a concrete structure howsoever careful one is with the construction and the maintenance. They can lead to leaks that damage the interiors, corrode steel reinforcements, and shorten the building’s life. But as a crack-repair job in Delhi attests, leaking water can be stopped in its tracks by integral crystalline waterproofing (ICW).

The Municipal Corporation of Delhi has its sewage pumping station next to a tributary of the Yamuna in Jasola. Since the building is on the bank of the river and the base of the pumping station is at an astounding 9 m below grade, it encountered a high water table.

The high hydrostatic pressure led to leakage through the joints and cracks of the thick concrete walls and
raft slabs in the plant room. The water gushed in – nearly two metre in height – endangering expensive equipment. To dewater the room, the Delhi Development Authority had to keep two powerful pumps working constantly. Though an effective short-term solution, this was too costly and unreliable in the long-term.

Choosing the right method
Several options were considered for the repair, which was a challenge as the positive (water) side of the structure was virtually inaccessible. The project team finally chose a cementitious, reactive application known as “Integral Crystalline Waterproofing”. Its merits are many, including ease of use; an ICW application requires no special equipment or skilled labour, preventing application error and saving time and money. ICW can also be applied in damp and wet conditions, a key factor in the Delhi case.

Even more important, the best ICW systems improve with time. Long-term reliability was a major consideration as the pumping station sat above usable space. A key advantage of the system is the ability to seal the concrete around the repair area, beyond the crack itself. Moreover ICW can reactivate itself to seal fresh cracks in weeks, months, or even years after the application. It is also immune to UV rays, resistant to hydrostatic pressure and will not break down over time.

How ICW Works
When ICW is applied to existing concrete, crystalline chemicals are absorbed into it by capillary action and diffusion. Once inside, they begin growing crystals and filling the spaces between concrete particles. As long as moisture remains present, the crystals continue to grow, reaching lengths of many inches over time. Once the concrete has cured, the crystalline chemicals remain dormant until another dose of water enters (through a new crack, or rising water table) and causes the chemical reaction to begin again.

The ability to reactivate in the presence of water gives crystalline-treated concrete the ability to “self seal”. When cracks form due to curing shrinkage, settling, seismic activity, etc, water entering through them causes new crystals to grow, blocking and filling the cracks. The power to self-seal cracks is a unique crystalline-technology feature, and one of the most useful, helping to cut dramatically long-term maintenance and repair costs.

The Delhi repair job
The following steps were taken to repair the pumping station. The treatment was carried out from the inside (negative side) of the plant room.

1. 
2. The surface was sandblasted clean to remove particles or contaminants that might inhibit the integral crystalline waterproofing technology, and to open the concrete surface to allow for deeper penetration of crystalline chemicals.
3. A 2.54-cm (1 inch) chase was chiselled, cleaned and pre-wet along the length of the major cracks and leaking joints along the wall and raft slabs.
4. The chase was packed with cementitious, highly concentrated crystalline dry packs. Within two minutes the leakage had stopped.
5. The cracks and joints were then treated with highly concentrated dry packs followed by a waterproofing grout.
6. The entire surface area was brush-applied with two treatments of cementitious, crystalline slurry coating.

The leakage to the pump room slowed down immediately after the repair process, and stopped altogether within days. As a result, the Delhi Development Authority was able to stop the dewatering process. Today, the Sewage Pumping Station remains dry.

“Kryton carried out an effective repair process by plugging the leakage of the pump house at a depth of 9 m below grade,” said the Office of the Executive Engineers for the Delhi Development Authority. “The application was very effective.”

Not all ICW is the same
Besides repairs for extensive cracking, ICW can be brush-applied to virtually any surface to fortify and waterproofing concrete. It is ideal for treating concrete basements, foundations, walls, tunnels, bridges, dams, water containment and wastewater treatment facilities, and, of course, pools.

Benefits of ICW crack repair system
Along with its excellent crack repair properties, integral crystalline waterproofing technology offers a number of key benefits for repairing existing concrete. These includes:

• Permanent solution – becomes a part of the concrete matrix so it will not crack, peel, tear or wear-away. Even against high hydrostatic pressure. Unlike injection methods, which are best on the day they are applied, crystalline applications become more effective with time.
• Protect reinforcing steel – adds to the longevity of concrete structures by preventing the penetration of waterborne contaminants and chloride-laden liquids that cause the corrosion of reinforcing steel.
• Save weeks on construction schedules – can be applied to green concrete, or even added to the ready-mix truck. There is no need to wait for membrane application and back-filling can begin right away.
• Integral crystalline waterproofing can be applied to the negative side of a structure. Repairs can be completed from the inside without digging up the perimeter, destroying landscaping and incurring extra cost, or from the outside without having to drain containment tanks.
• The best systems provide additional self-sealing properties that will stop leaking through microcracks for the life of the concrete.

ICW can also be used as an admixture in new concrete construction. By eliminating the need for external waterproofing membranes, it saves construction time and costs and allows for larger building footprints and blind wall construction. ICW admixtures help strengthen concrete and minimise future cracking, and they last the lifetime of the structure. Some ICW manufacturers, such as in the case of the Aura Tower, produce a joint design system, which can be used in conjunction with the admixture to seal new joints and ensure a truly watertight, completely tanked structure.

A number of companies, including Kryton International, offer integral crystalline waterproofing systems, featuring products for new and existing concrete structures and joints. When selecting an ICW system, it is important not to confuse true crystalline products with those that are simply concrete densifiers or pore blockers. By wary also of products that claim to grow crystals but really only crystallise as they dry – these products will not permeate the concrete, nor will they reactivate in the presence of water to fill cracks. Ask whether the product you are considering contains sillicates, stearates, or talc – these offer temporary waterproofing at best. And be sure your manufacturer offers a long-term warranty on all crystalline products.