Chemistry at work
MarMac Foam Grout Diapers provide a functional barrier between the harsh and sometimes corrosive environment for the steel pipe joint. Under most conditions, portland cement is alkaline (pH of about 12.5). Due to the presence of calcium hydroxide, a passivating iron-oxide film forms on the steel joint resulting in almost complete corrosion inhibition. Foam Grout Diapers protect against leaching, which leads to reduction of pH in the cement grout surrounding the joint steel. They also resist the intrusion of salts, chlorides, acids, and sulfates that can affect the inhibitive properties of the grout. Foam Grout Diapers also isolate the protective grout from aggressive soils that correlates with high corrosive electrical current.
Features & Benefits
- Protects against leaching, which leads to reduction of pH in the joint grout cement.
- Defends against intrusion of salts, chlorides, acids and sulfates that can affect the inhibitive properties of the joint grout cement.
- Guards the protective joint grout cement from aggressive soils that can cause high corrosive electrical current.
All outside field joints shall be sealed by the polyethylene foamed lined grouting band method. The fabric shall be spun-bonded polypropylene with a minimum of three ounces per square yard weight. The fabric shall be of sufficient strength and stability to retain the fresh portland cement grout without leakage. The fabric shall be hemmed on each edge with steel strap or wire contained within each hem. The steel strappings or wire and their seals shall be of sufficent tension to hold the weight of the grout without failure.
The foam liner material shall be Ethafoam® 221 PGB manufactured by Dow Chemical Co or an approved equivalent. The foam shall be a multicellular, closed-cell polyethylene plastic foam with a density of 1.8-2.2 lbs/cubic foot. The cell size shall be 3.0-3.7 mm.
The cells of the foam liner shall be open and hollow on the surface facing inward towards the pipe. The smooth polyethylene skin surface shall be attached to the fabric of the grout band. The foam liner and fabric shall be *wide and having a length **sufficient to cover the circumference of the pipe and overlap after closure.
The joint shall consist of two parts sand to one part portland cement, mixed with sufficient clean water to maintain a freely pouring consistency.
Note: take care to not over-hydrate. The grout consistency should be that of a very thick cream.
|Density||1.9 – 2.2 lbs/ft2|
|Minimum Weight||3 oz/yd2|
|Material||Heat-treated or hot-rolled steel|
|Standard||Class 1, Type I|
|Coating||Waxed or painted/waxed|
MarMacʼs Foam Grout Diaper is applied around the pipe with the skived, open, hollow cells of the foam facing the pipe, evenly bridging the joint. The tab ends of the foam-lined Grout Diaper extend beyond the strap exit hems. The tabs are folded back and tension is applied to the straps around the pipe. The seals are then crimped.
With the tabs folded back, the pouring gate is exposed at the top of the pipe. Portland cement is then poured into one side of the joint recess until the grout flows under the bottom of the pipe. The grout is then poured from the opposite side until the entire recess is full. A stiffer grout mix may be used at the top if necessary.
When full, the tab is folded across the pouring gate. The tab is then lapped and pressed tight into the fresh grout. A sufficient amount of grout can be placed on top of the tabs to cement closure and seal while backfilling.
- The width of the Foam Grout Diaper will be governed by the width of the joint space and the type of pipe being used. The width should be sufficient to bridge the joint space and be secured to the pipe walls on each side of the joint without failure due to slippage.
- The length of the Foam Grout Diaper will be governed by the circumference, with extended tab lengths to accomplish overlapping of the ends once the joint has been filled with grout.
Pipe Sizes: 12-144″
Cement-Coated Steel Pressure Pipe