Shore Pac^® Definition & Formulations

Shore Pac is not a hazardous waste, nor does it pose any threat to waters when disposed of according to manufacturer’s guidelines.

Shore Pac is approved for use by The Federal Highway Administration, (FHWA) and is used in State Departments of Transportation throughout the nation. The method for disposing the drilling slurry Shore Pac on Drilled Shaft Projects has been listed within this website.

Shore Pac is a dry granular synthetic anionic polyacrylamide. Shore Pac is manufactured from co-polymerization of acrylimide and acrylic acid or its inorganic salts. The molecular weight (in the region of several million Daltons) and negative charge density varies (by variation of the ratio of acrylimide and acrylic acid monomer units).

In general the “polymer” used in Shore Pac is designated as non hazardous and is water soluble or water dispersible. The term polymer simply means – many parts, or is an organic chemical having a molecular weight above 200, with greater than eight repeating units. Polymers very greatly in function and basic properties, such as stability, charge, and molecular weight. In general, polymers can be classified as natural, modified-natural, or synthetic. The term “monomer” simply means – a large molecule made up of simple repeating units. A polymer is a compound that consists of a chain of repeating base units, called monomers. Shore Pac is a synthetic polymer.

Shore Pac is a very high molecular weight synthetic polymer with negative charges on the backbone. Its high molecular weight gives viscosity to water at low concentrations.

When Shore Pac is dissolved in aqueous solution, the very long polymer chains dissolve and orient randomly in the fluid in coils. In fresh water, the repulsion of the negative charges on the backbone of the polymer chains causes the coils to expand and to occupy a large volume in the fluid. When the fluid is sheared, the expanded polymer chains are located in different fluid layers in the shear field. The uncoiling of these expanded polymer chains dissipates mechanical energy and results in viscosity.

The high molecular weight polymer chains are so long that different parts of individual polymer chains bridge different solid particles. It is this adsorption on surfaces and bridging of solid surfaces that makes this polymer effective in keeping solids consolidated while drilling a foundation. In addition, the adsorbed layer of hydrophilic polymer on rock surfaces slows down the diffusion of water into the rock.