Media

Concrete International – May 2007

Even before its completion, concrete cracks threatened the successful opening of the Aura Tower, a new luxury high-rise in Zapopan, Mexico. With the grand opening fast approaching, workers found that the facility’s swimming pool had numerous shrinkage cracks (Fig. 1) that were allowing water to leak into the structure below. The developer needed a fast, long-term solution that would allow the pool to be ready for residents on opening day and beyond.

Background
The Aura Tower’s swimming pool was built above a parking garage and a power utility room, so the pool
structure incorporated PVC waterstops at cold joints and an asphalt membrane lining. When the contractor ran a flood test, however, water flowed into the garage and utility room. Inspection revealed that the membrane had failed, and water was penetrating through the concrete at shrinkage cracks, cold joints, pipe and drain connections, and light fixtures. Further, it was found there were over 4500 ft (1370 m) of cracks (many up to 1/8 in. [3 mm] wide) and joints requiring repair.

Selecting the Right Crack Repair
After considering a number of repair options, including various urethane and epoxy injection methods, the project team chose to apply a cementitious, reactive material known as integral crystalline waterproofing (ICW). The team preferred this system because ICW would require no special equipment or skilled labor to install, could be applied in wet conditions, and would continue to improve with time. The ICW system would therefore not only save time and money, it would have long-term effectiveness
and reliability.

Fig. 2: The integral crystalline waterproofing is absorbed into the concrete where the crystals grow to block the passage of water

How ICW Systems Work
When applied to existing structures and exposed to water, the chemicals in an ICW are absorbed into the
concrete by capillary action and diffusion. Once inside the concrete, the chemicals begin growing crystals that fill capillaries and voids in the concrete matrix (Fig. 2). This continues as long as moisture remains present. If the concrete dries, the chemicals sit dormant until another dose of water (perhaps through a new crack or a rising water table) causes the chemical reaction to begin again.

The ability to reactivate in the presence of water gives crystalline-treated concrete the ability to selfseal.
When cracks form due to curing shrinkage, settling, or even seismic activity, entering water causes
new crystals to form and grow, blocking and filling the cracks. This ongoing activity can dramatically
reduce long-term maintenance and repair costs for a concrete structure.

Crack Repair at the Aura Tower
The following steps were taken to repair the extensive concrete cracks in the swimming pool:

• Fig. 3: After chiseling out a groove along each crack or joint, the crack repair material containing a high concentration of crystalline waterproofing chemicals was mixed to a putty-like consistency and pressed into the grooves. Two coats of an ICW slurry were then applied

   The surface was sandblasted to remove the asphalt membrane and open the concrete surface to allow deeper penetration of the chemicals;

• Joints and cracks wider than 0.02 in. (0.5 mm) were prepared by chiseling out a chase along the
  length of the crack. The chases were then cleaned and prewetted;
• A cementitious crack repair material containing a high concentration of crystalline waterproofing chemicals was mixed with water to a putty-like consistency and packed into the prepared cracks and joints (Fig. 3) as well as at the perimeters of pipe, drainage, and light connections;
• Two treatments with a cementitious, crystalline slurry were brush-applied over the entire interior surface of the pool; and
• The pool was flood tested before a decorative coating was applied.
• Nine members of the application team worked around the clock for 3 weeks during the rainy season (the surface was always wet) to complete the repair. Two days after completion, the pool was flood tested and all leakage was stopped. The hotel opened on schedule with fully operating
  recreational facilities—including the swimming pool (Fig. 4).

Not just for Crack Repair
ICWs can be used not only to repair concrete cracks, they can be brush-applied to virtually any concrete
surface to waterproof and thereby help to protect against contamination and corrosion. ICWs are ideal for treating below-ground concrete structures, bridges, dams, water containment and wastewater treatment facilities, and, of course, pools. ICWs can also be used as admixtures in new concrete construction to provide waterproofing that lasts the lifetime of the structure.

By eliminating the need for external waterproofing membranes, ICW applications allow blind wall construction, thereby saving construction time and cost.

Choose A Durable System

Fig. 4: Two days after completion of the crack repair, the pool was successfully flood tested. After applying a decorative coating, the building and pool were opened on schedule

ICW systems are applicable for both new and existing concrete structures. Although initially somewhat
skeptical, the project team for the Aura Tower is now a strong proponent of integral crystalline waterproofing.
Based on their successful experience of sealing over 4500 ft (1370 m) of cracks, they have since specified
ICWs for several new below-grade projects in Mexico. When selecting an ICW system, look for true crystalline products that will permeate the concrete and reactivate in the presence of water to fill cracks. Also, be sure the manufacturer offers a long-term warranty on all crystalline products.