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WhatAreEnzymes

According to the U.S. Department of Transportation Several Thousand Enzymes are currently known and put to many uses. Common uses are found in cosmetics, hair shampoos, detergents and industrial cleaning agents. Soil enzymes occur naturally, produced by soil bacteria to catalyze reactions with nitrogen, carbon dioxide and other soil nutrients.

These enzymes can be manufactured by fermentation processes. They are non-toxic and environmentally harmless. An enzyme is by definition an organic catalyst which rapidly carries a chemical reaction to completion without becoming a part of the end product, the reaction being one that would normally take place at a much slower rate. To better understand what is happening in the case of the compaction enzyme, we can look at compaction of clays and silts in nature: the formation of shale.

Similar processes take place when a compaction enzyme is added to the mixture in soil and aggregate compaction, but at a greatly increased reaction rate. Processes that normally take millions of years are rushed through in a matter of hours and days.

In a reaction such as one taking place between clays and organic materials to “waterproof” the clay, large quantities of organic material are required. Stimulating the growth of soil bacteria can provide a source from a large soil fraction for crushed aggregates with some clay, a biotechnique is used where a bacteria culture is introduced to the system to generate the organics from the carbon dioxide in the air.

The enzyme combines with the large organic molecules to form a reactant intermediary, which exchanges with the clay lattice, breaking down the clay structure and causing the cover-up effect which prevents any further absorption of water or the resultant swelling with loss of density. The enzyme is regenerated by the reaction and goes on to perform again. Because the ions are very large, little osmotic migration takes place, and intimate mixing is required. This is generally aided by the destructive effect of the organic ions on the clay lattice. Compaction of the aggregate mass near optimum moisture by construction equipment produces the desired high densities characteristics of shales. High densities are essential to the process, particularly with lower clay contents. The resultant surface has many of the characteristics of a solid, durable shale, yet produced in a fraction of the time required by nature.

Reference: U.S. Department of Transportation Federal Highway Administration
FHWA-FLP-92-011 Final Report July 1992

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