Unbound Materials

Unbound granular materials, consisting of crushed products, natural gravels, soil aggregate mixtures, by products and modified materials. Their strength is obtained primarily through particle interlock.

Properties

The properties required of an unbound granular material that are likely to affect the performance of a pavement are shear resistance, modulus, shrink/swell potential, durability and permeability and its compactability from construction viewpoint.

Properties analogous with unbound materials may be considered as four basic groups:

  1. Coarse fractions—retained on a AS 4.75 sieve, possessing properties that have the ability to resist the effects of crushing and water under load, retention of a cubicle and angular shape and resistance to breakdown in service and the provision of an abrasive surface.
  1. Fine fractions—passing an AS 4.75 sieve, possessing properties that have a marked effect on the stability of the material. The plastic properties providing the measure of the cohesive quality, also the amount of volumetric expansion that can result from the wetting and drying of the material, they also control the degree of interlocking and packing of the particles.
  1. Particle size distribution—which affects both the density and stability of a material as well as its workability.
  1. Strength and ability to resist deformation—characteristics of the material to withstand the loads imposed upon the pavement.

A paper on INGREDIENTS OF AN UNBOUND GRANULAR PAVEMENT FOR A SUCCESSFUL SPRAYED SEA Granular construction