The enzymes are adsorbed by the clay lattice, and then released upon exchange with metals cations. They have an important effect on the clay lattice, initially causing them to expand and then to tighten. The enzymes can be absorbed also by colloids enabling them to be transported through the soil electrolyte media. The enzymes also help the soil bacteria to release hydrogen ions, resulting in pH gradients at the surfaces of the clay particles, which assist in breaking up the structure of the clay [1].

An enzyme is by definition an organic catalyst that speeds up a chemical reaction, that otherwise would happen at a slower rate, without becoming a part of the end product. The enzyme combines with the large organic molecules to form a reactant intermediary, which exchange ions with the clay structure, breaking down the lattice and causing the cover-up effect, which prevents further absorption of water and the loss of density. The enzyme is regenerated by the reaction and goes to react again. Because the ions are large little osmotic migration takes place and a good mixing process is required [1].

Compaction of aggregates near the optimum moisture content by construction equipment produces the desired high densities characteristic of shale. The resulting surface has the properties of durable “shale” produced in a fraction of the time (millions of years) required by nature. The idea of using enzyme stabilization for roads was developed from enzyme products used for treatment of soil to improve horticultural applications. A modification to the process produced a material, which was suitable for stabilization of poor ground for road traffic. When is added to a soil, the enzymes increase the wetting and bonding capacity of the soil particles. The enzyme allows soil materials to become more easily wet and more densely compacted. Also, it improves the chemical bonding that helps to fuse the soil particles together, creating a more permanent structure that is more resistant to weathering, wear and water penetration.

University of Minnesota Department of Civil Engineering, 2005