Page 103 - Construction Waterproofing Handbook

2.66 CHAPTER TWO
Panel clay systems require the most extensive surface penetration of clay systems.
Honeycomb and voids should be filled with clay gels before panel application. Special
prepackaged clay is provided for application to changes in plane, and gel material is used
at protrusions for detailing.
Several grades of panels are available for specific project installation needs. These
include special panels for brine groundwater conditions (Fig. 2.86), and reinforced pan-
els for horizontal applications where steel reinforcement work is placed over panels.
Panels are lapped onto all sides of adjacent panels using premarked panels that show nec-
essary laps.

Bentonite sheets
2
Bentonite sheet systems are manufactured by applying bentonite clay at 1 lb/ft to a layer
of chlorinated polyethylene. They are packaged in rolls 4 ft wide. The addition of poly-
ethylene adds temporary waterproofing protection during clay hydration. This polyethyl-
ene also protects clay material from prematurely hydrating if rain occurs before backfilling
and adds chemical-resistant properties to these systems.
Some manufacturers have developed sheet systems for use in above-grade split or
sandwich slab construction. However, constant wetting and drying of this system can alter
the clay’s natural properties, and waterproofing then depends entirely upon the polyeth-
ylene sheet.

Bentonite and rubber sheet membranes
Bentonite and rubber sheet membrane systems add clay to a layer of polyethylene, but also
compound the bentonite in a butyl rubber com position. Materials are packaged in rolls
3 ft wide that are self-adhering using a release paper backing. They are similar to rubber-
ized asphalt membranes in application and performance characteristics.
These combination sheet systems are used for horizontal applications, typically split-
slab construction in parking or plaza deck construction. As with rubberized asphalt sys-
tems, accessories must be used around protrusions, terminations, and changes in plane.
The polyethylene, butyl rubber, and bentonite each act in combination with the others, pro-
viding substantial waterproofing properties.
Unlike other clay systems, concrete substrates must be dry and cured before application.
Care must be taken in design and construction to allow for adequate space for clay swelling.

Bentonite mats
2
Bentonite mat systems apply clays at 1 lb/ft to a textile fabric similar to a carpet backing.
This combination creates a carpet of bentonite material. The coarseness of the fabric
allows immediate hydration of clay after backfilling, versus a delayed reaction with card-
board panels.
The textile material is not self-adhering, and adhesives or nailing to vertical substrates
is necessary. Protection with a polyethylene sheet after installation is used to prevent pre-
mature hydration. This system is particularly effective in horizontal applications where the
large rolls eliminate unnecessary seams. This lowers installation costs as well as prevents
errors in seaming operations.
Properties of typical clay systems are summarized in Table 2.8.