Chemistry at work
MarMac Grout Bands are chemistry at work by providing a functional barrier between the harsh and sometimes corrosive environment for the pipe joint steel. 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 joint steel resulting in almost complete corrosion inhibition. Grout Bands protect against leaching that leads to ruction of pH in the cement grout surrounding the joint steel. They resist intrusion of salts, chlorides, acids and sulfates that can affect the inhibitive properties of the grout. Grout Bands also isolated the protective grout from aggressive soils that correlates with high corrosive electrical current.
- Protects against leaching that leads to reduction of pH in the cement grout surrounding the joint steel.
- Resists intrusion of salts, chlorides, acids and sulfates that can affect the inhibitive properties of the grout.
- Isolates the protective grout from aggressive soils that correlates with 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 Down 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.
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Also ask about MacWrap for Manholes, RCP and Box Culverts.
* The width of the foam grout band will be governed by the width of the joint space and the type of pipe that is 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 band will be governed by the circumference, with extended tab lengths, to accomplish overlapping the ends after the joint is filled with grout.