Explain how green strength and permeability are affected by: a)Grain shape of the sand, b)Grain size of the sand ,c)Grain size distribution

1)      The grain size and distribution influences many sand properties like permeability, flowability, refractoriness, surface fitness and strength etc.

2)      Fine grained sands gives surface fineness but possesses low permeability.

3)      Coarse and uniformly graded sand imparts high permeability, high flowbility and maximum refractoriness.

4)      For the same clay content in clay bonded sand, green strength is higher in case of fine sands as compared to coarse sands.

5)      Grain shape:

a)      Rounded grains: high permeability, low strength

b)      Sub-angular grains : better strength, lower permeability

c)      Angular grains: higher strength, low permeability