GSB
crushed stone
Granular Sub-Base (GSB) — the foundation layer of any flexible or rigid road pavement, conforming to MoRT&H Clause 401. Supplied in any of the six standard gradings (I through VI) to suit project drawings.
About GSB
Six grading options per MoRT&H Table 400-1, with Grading IV and V being the most commonly specified for state and national highway work. CBR specification is ≥30% at four-day soaked condition for sub-base use. Liquid limit ≤25%, plasticity index ≤6%.
Where GSB fits — and where it doesn't
Specifying the right aggregate size and grade saves cement, simplifies placement, and avoids rework. Below is a quick guide based on IS / MoRT&H norms and what we see ordered from our Chimakurthy crusher across Prakasam district.
Use GSB for
- Road sub-base for highways, MDR, PR roads
- Sub-base for cement concrete pavements (rigid pavement)
- Industrial flooring sub-base
- Container yard and parking pavement sub-base
- Rail track ballast sub-base (where MoRT&H spec is referenced)
- Township internal road sub-base
Don't use GSB for
- Direct wearing course (use WMM or bitumen)
- Concrete coarse aggregate (use 20 mm crushed stone)
Common questions about GSB
Which GSB grading do I need for a state highway?
Can GSB be used as backfill?
GSB supplied across Ongole and Prakasam district
GSB is loaded ex-works at our Chimakurthy crusher for projects across Ongole and the wider Prakasam district. The distance shown against each town is the pickup distance from the crusher gate — tap any town for project-specific notes and round-trip times.