Fundamental mechanical properties of asphalts and laboratory tests

Fundamental mechanical properties of asphalts and laboratory tests 

Fundamental mechanical properties of materials constitute the necessary data for designing any structure. Elasticity modulus, compressive strength, tensile strength and shear strength can be designated as fundamental mechanical properties. Their resistance to fatigue and permanent deformation can be characterised as mechanical performance. 

Something similar also applies to the analytical design approach of flexible pavements. The main difference with other structures composed of reinforced concrete, or steel, lies in the fact that asphalts (bituminous mixtures) do not behave as elastic material but as viscoelastic material owing to the presence of bitumen. The rest of the structural materials of pavements, such as compacted aggregates, stabilised aggregates or soil with binders other than bitumen, as well as untreated soil, may be characterised as materials with elastic behaviour. 

The fundamental property of asphalts related to stress and strain is called stiffness modulus, which is distinguished into dynamic and static stiffness modulus. 

The mechanical behaviour of asphalts is determined by resistance to tensile forces, known as resistance to fatigue cracking, and resistance to compressive forces, known as resistance to permanent deformation. The first is expressed by the relationship between tensile strain and number of loadings, known as the fatigue equation. The second is expressed by the relationship between compressive strain and number of loadings, known as the creep equation. 

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