The concept of blending materials to achieve uniform grading has formed the corner stone of road building for centuries.  In recent decades empirical tests have been developed to ensure the materials selected offer a practical balance between strength and cohesiveness.  The objective of every road builder is to compact the materials to maximum density to achieve a tight water resistant matrix that will remain intact and hold its load bearing capacity in the varying climatic conditions.  The quantity and quality of the binding material is critical as over - reactive fines are sensitive to moisture and temperature variation and this has a considerable negative impact on the engineering performance.  Consequently, the supplies of good gravels have decreased while the supplies of overburden and high clay gravels are plentiful.  The avoidance of these reactive materials is well founded as the chemistry of clays and their platelets formations are complex.

Clays occur in deposits of greatly varying nature.  No two deposits have exactly the same clay and frequently different samples of clay from the same deposit differ.  It is therefore worthwhile to give brief consideration to the origin and mineralogy of clay.  This information has been included to give the reader an appreciation of clay chemistry.  The understanding of this is not critical to being able to use Endurazyme in a road building application.

Geology

Primary igneous rocks that gave clays on weathering were the granites, gneisses, feldspars, pegmatite's, etc.  The weathering of these primary rocks was achieved by the combination of the mechanical action of water, wind, glaciers and earth movements working together with the chemical action of water and carbon dioxide all of which was assisted by variations in temperature over time.

Mineralogy

The basic rocks from which clays are formed are complex aluminosilicates.  During the weathering these become hydrolysed, the alkali and alkaline earth ions form soluble salts and are leached out.  The remainder consists of hydrated aluminosilicates of varying composition and structure, and free silica.  It is the orientation of this predominantly silica structure that gives clay its unique plastic property.  Silicates form platelets of varying sizes.  It has been observed that these platelets in any one aggregate are of quite different size and shape and that they are not stacked with any apparent regularity in the vertical direction.  This suggests that aggregate of high clay contents are not stable structures.  Not only do they differ markedly for soil in different classifications, but the properties in any given soil may vary to an almost equal degree with changes in conditions such as degree of saturation, water content and density.  Possibly less well known is the fact that the engineering characteristics of soils are also dependent upon certain fundamental properties of clay particles and clay water systems to the extent that they may be varied, the behaviour of soil in engineering applications may be affected.  There are two practical consequences to the situation described above.  One is the prospect that the engineering behaviour of soils can be predicted with more confidence and greater accuracy when the significant variables are identified.  The other is that it is becoming possible and economically feasible to improve the engineering characteristics of soils under certain conditions by modifying not only the density and consistency as has already been done but also certain fundamental properties.  The fundamental properties of clay particles are mineral, composition and the type of exchangeable ion that the clay contains.