What are “mortar mechanism” and “stone contact mechanism” in bituminous materials?

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“Stone contact mechanism” applies to well graded aggregates coated with bitumen (e.g. dense bitumen macadam) where the traffic loads on bituminous roads are resisted by stone-to-stone contact and by interlocking and frictional forces between the aggregates. It is essential to adopt aggregates with a high crushing strength. The bitumen coatings on the surface of aggregates merely serve to cement the aggregates together.

“Mortar mechanism” involves the distribution of loads within the mortar for gap-graded aggregates (e.g. hot rolled asphalt). The mortar has to possess high stiffness to prevent excessive deformation under severe
traffic loads. It is common practice to introduce some filler to stiffen the bitumen.


This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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