'Stone Matrix Asphalt' (SMA) differs from conventional dense bituminous macadam (DBM) in that SMA:
Choose the correct answer
Has no aggregate (only bitumen and filler)
Gap-graded stone-on-stone skeleton with mastic (filler + fibre + bitumen) — very rut-resistant and durable
Uses cement instead of bitumen
Only used for footpaths
Correct Answer
B. Gap-graded stone-on-stone skeleton with mastic (filler + fibre + bitumen) — very rut-resistant and durable
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SMA: gap-graded mix with stone-on-stone skeleton (coarse aggregate interlocking), held together by bitumen mastic (cellulose fibre + filler + bitumen). High stone content (70–75%): rutting resistant. High bitumen content (6–7%): durable, crack resistant. Fibre prevents bitumen drainage. Used on high-traffic expressways. Costlier than DBM but 30–50% longer life.
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