Specification-led GSB supply for road, highway and infrastructure projects across North and South Goa, matched against the applicable project grading, MoRTH Clause 401 and project specification.
Its grading and physical requirements are selected according to the applicable project specification, with MoRTH Clause 401 providing the principal reference framework for road and bridge works in India.
GSB is a specified blend of natural sand, crushed gravel, crushed stone, crushed slag, or a combination, proportioned to meet a defined sieve/grading curve — not a single aggregate size and not an uncontrolled crushing by-product. MoRTH's own specification states the material "shall be blended at source/crusher to achieve the specified gradation and shall be jointly checked at the site for conformance."
GSB is not the road surface. It sits below the base course, contributing to load distribution, subgrade protection and — for the gradings used as a sub-base-cum-drainage layer — moisture management within the pavement structure.
GSB distributes traffic load down to the subgrade, protects the subgrade from moisture ingress, and — for Gradings V and VI specifically — serves a sub-base-cum-drainage function, managing water movement within the pavement structure.
Pavement performance is never the result of one layer alone. It depends on subgrade condition, GSB grading and compaction, the base course above it, the surface layer, drainage design and construction workmanship, together — not any single material in isolation.
GSB is not the surface layer, not WMM, and not subgrade — it is the sub-base, positioned between the two.
GSB grading is governed by MoRTH Specifications for Road and Bridge Works, Fifth Revision, Clause 401 (Section 400), together with applicable subsequent amendments/circulars and the project-specific contract specification. Always verify the current applicable specification for your project — engineering standards are periodically revised.
| Grading | Particle-size context | Preferred placement | Fines note | Drainage relevance |
|---|---|---|---|---|
| Grading I | Close/coarse-graded, up to 75mm | General sub-base | ≤5% passing 0.075mm (general reference) | — |
| Grading II | Alternative envelope | General sub-base | Project-specific | — |
| Grading III | Finer envelope | Preferably lower sub-base | Project-specific | — |
| Grading IV | Finer envelope | Preferably lower sub-base | Project-specific | — |
| Grading V | Coarser, open-graded tendency | Sub-base-cum-drainage layer | Project-specific | Yes — primary drainage role |
| Grading VI | Coarser, open-graded tendency | Sub-base-cum-drainage layer | Project-specific | Yes — primary drainage role |
No grading is universally "better" — each serves the structural or drainage role the contract assigns it. Grading selection depends on contract specification, pavement design, layer function and drainage requirement, not the product name alone.
California Bearing Ratio (CBR) measures the resistance of a compacted material to penetration under a standardised test, relative to a reference crushed-stone standard. In practical terms, it helps engineers evaluate whether a material provides the support a pavement layer requires.
Where applicable under the governing specification, GSB acceptance may include a minimum soaked CBR requirement — commonly a 4-day soaked CBR of 30% is cited for Grading I sub-base material as a general reference. This is the standard's general requirement, not a claim about OM Group's tested material for a specific consignment. Confirm the project-specific requirement and current material test data before approval.
Fines passing the 0.075mm sieve are restricted under the applicable grading — commonly 5% for Grading I as a general reference — and the material must be reasonably free of organic and deleterious matter. Excessive plastic fines (clay/silt behaviour) increase moisture sensitivity and can compromise compaction and, in Grading V/VI applications, drainage performance.
Controlled fines are not the same thing as "bad material," and the presence of some fines is not automatically a specification failure — a well-graded material needs a proportion of finer particles to achieve density. The distinction that matters is between fines controlled to a grading envelope and uncontrolled fines in an unclassified material, which is why crusher dust cannot be assumed equivalent to GSB (see comparisons below).
No "zero fines" or "100% clean" claim is made on this page — that isn't what the specification requires, and it isn't what any real graded material achieves.
MDD (Maximum Dry Density) is the highest dry density a material can achieve under a standard laboratory compaction test. OMC (Optimum Moisture Content) is the moisture content at which that maximum density is achieved. Laboratory compaction establishes the reference density/moisture relationship that field compaction is then measured against — the two are distinct measurements and are never conflated on this page.
Where specified by the governing project specification, field density is commonly targeted at a minimum of 98% of laboratory MDD, achieved at moisture near OMC. Moisture control matters because compaction achieved too dry or too wet of OMC falls short of the density the design assumes, regardless of how well-graded the material is.
Where sub-base is laid in more than one layer, each layer is commonly specified at a minimum 150mm compacted thickness — a general reference requirement, confirmed against the project specification.
| Parameter | What it measures | Why it matters | Typically assessed via |
|---|---|---|---|
| Sieve analysis / grading | Particle-size distribution against the target envelope | Confirms the material meets the specified grading curve | IS sieve analysis methods |
| CBR | Load-bearing capacity under standardised penetration | Confirms structural support for the pavement design | Soaked CBR test |
| Fines content | Percentage passing 0.075mm | Controls moisture sensitivity and compaction behaviour | Wet sieve analysis |
| Plasticity | Behaviour of the fine fraction | Excess plasticity increases moisture sensitivity | Atterberg limits (where specified) |
| Moisture content | Water content relative to OMC | Affects achievable field density | Standard moisture-content methods |
| Density / compaction | Field density relative to laboratory MDD | Confirms the layer meets the compaction target | Field density testing against lab MDD/OMC |
| Aggregate Impact Value | Resistance to sudden impact, where applicable | Indicates aggregate toughness | IS 2386 (Part 4) / IS 5640 |
| Water absorption | Aggregate porosity, where applicable | High absorption can trigger a Wet Aggregate Impact Value requirement | IS 2386 (Part 3) |
| Sand equivalent | Clay/fine content of the minus-4.75mm fraction, where applicable | Screens for excessive clay-like fines | IS 2720 (Part 37) |
Engineers and QA/QC teams typically specify and check these parameters as acceptance criteria; contractors typically confirm them before dispatch or placement. Not every parameter is tested for every shipment. Documentation and test data available depend on the source, material, project specification and buyer requirement.
GSB and WMM are not interchangeable materials. GSB forms the sub-base layer, while Wet Mix Macadam (WMM) is generally used as a base-course material above the sub-base. WMM is mixed with water at a plant to a tighter grading than GSB and compacted as the structural base course.
Neither is universally "stronger" — they occupy different, specified positions in the pavement, governed by different MoRTH clauses (GSB: Clause 401; WMM: Clause 406).
Water Bound Macadam (WBM) is a traditional construction method using a different grading and a binding/screening process, rather than a pre-blended graded material laid in one operation. WBM remains a recognised construction method under applicable specifications — it is not "obsolete," and its use depends on the project's specification rather than GSB being an automatic replacement.
20mm and 40mm aggregate are single-size fractions — one particle size, not a graded blend. GSB is a specified blend of multiple sizes meeting a sieve/grading curve, per Clause 401's blending requirement. Ordering 40mm aggregate and using it as GSB does not meet Clause 401's grading requirement — it cannot replace GSB without first being blended to the specified curve.
Crusher dust and quarry dust are fine crushing by-products, not classified to any grading. Unclassified crusher dust is not a substitute for specification-compliant GSB unless it is processed and graded to meet the applicable project specification. Using uncontrolled dust in a sub-base risks excessive fines, poor compaction, and drainage shortfall in Grading V/VI applications specifically.
Subgrade is the prepared soil foundation beneath GSB — a different material entirely, tested and specified under separate geotechnical criteria, not an aggregate product. They are sequential layers in the pavement structure, not alternatives to each other.
Sub-base layer for highway and state-road pavement construction, subject to project specification and pavement design.
Sub-base construction across rural and urban road projects, matched to the applicable grading.
Sub-base supply for industrial access roads and logistics-park development.
Commercial and residential site-development roads and approach roads, subject to project specification.
Broader infrastructure and approach-road works requiring a specified sub-base layer.
Sub-base material for widening and rehabilitation work, where applicable to the project's pavement design.
Every application above is subject to project specification and pavement design — this page is a technical reference, not a design substitute.
OM Group supplies Granular Sub-Base across North and South Goa, matched against the applicable project grading and specification. OM Group coordinates sourcing, confirms the grading against your project's requirement, and manages delivery scheduling as part of a single procurement relationship that can also cover aggregates, sand and Ready Mix Concrete.
No turnaround time is promised without confirmation against the specific project and quantity.
Buyer protection, stated plainly: ordering GSB by appearance rather than grading, confusing GSB with single-size aggregate, overlooking the plasticity/fines requirement, assuming one grading suits every layer without checking the contract, and not confirming quantity basis (m³ vs tonne) before ordering are the most common mistakes worth avoiding.
Before ordering, confirm:
Send these details to OM Group for a project-specific quotation.
| Product | Granular Sub-Base (GSB) |
| Applicable standard (reference) | MoRTH Clause 401, Section 400, Fifth Revision, plus applicable amendments |
| Grading | Confirmed against project specification (Grading I–VI) |
| Fines (passing 0.075mm) | Per applicable grading — general reference only |
| CBR | Per applicable grading — general reference only |
| Compaction target | Where specified, commonly 98% MDD — general reference only |
| Applicable test methods (general reference) | IS 2386 series, IS 2720 (Part 37), IS 5640 |
| Documentation | Available on request, depending on source, material and project requirement |
| Availability and lead time | Confirmed against project requirement |
GSB price depends on required grading, quantity, source, delivery location and transport distance, project documentation/testing requirements, current availability and market conditions. No fixed or "starting from" figure is published without a genuine current rate — OM Group quotes against the specific requirement.
Definition
GSB (Granular Sub-Base) is a graded granular material placed and compacted over prepared subgrade to form the sub-base layer of a road pavement, per MoRTH Clause 401.
Granular sub-base is the same material as GSB — a specified blend of graded granular material forming the sub-base layer beneath a road's base course and surface.
GSB material is natural sand, crushed gravel, crushed stone, crushed slag, or a combination, blended to meet a specified MoRTH grading envelope rather than supplied as a single particle size.
GSB stands for Granular Sub-Base, the sub-base layer of a road pavement structure.
No. "Road metal" is a colloquial term sometimes used loosely for various aggregate materials. GSB is specifically a graded blend meeting MoRTH Clause 401, not any crushed stone used on a road.
Technical
MoRTH Clause 401, in Section 400 of the Specifications for Road and Bridge Works, is the principal Indian reference governing Granular Sub-Base material, grading and construction requirements.
MoRTH Table 400-1 sets out Gradings I through VI. Gradings III and IV are preferably used in the lower sub-base; Gradings V and VI serve as a sub-base-cum-drainage layer. Grading I and II are used for general sub-base construction, per the project's contract specification.
GSB CBR (California Bearing Ratio) measures the load-bearing capacity of the compacted sub-base material relative to a reference crushed-stone standard, used to evaluate whether it provides the support the pavement design requires.
Where applicable under the governing specification, a minimum 4-day soaked CBR of 30% is commonly cited for Grading I as a general reference requirement. The project-specific requirement and current material test data should always be confirmed before approval.
Sieve analysis is the test that determines a material's particle-size distribution, used to confirm GSB meets its specified grading envelope.
GSB compaction is the process of densifying the placed material to a target field density, commonly a minimum 98% of laboratory Maximum Dry Density where specified by the governing project specification.
MDD (Maximum Dry Density) is the highest dry density a material can achieve under a standard laboratory compaction test, used as the reference for field compaction targets.
OMC (Optimum Moisture Content) is the moisture content at which a material achieves its Maximum Dry Density under laboratory compaction.
Fines content is restricted because excessive plastic fines increase moisture sensitivity and can compromise compaction and, in drainage-role gradings, water movement through the layer.
Where water absorption exceeds 2% (per IS 2386 Part 3), the material is additionally required to pass a Wet Aggregate Impact Value test (IS 5640) under the governing specification.
Comparison
GSB is the sub-base layer; WMM (Wet Mix Macadam) is the base course above it, mixed with water at a plant to a tighter grading. The two are governed by different MoRTH clauses and are not interchangeable.
No. WBM (Water Bound Macadam) is a different, traditional construction method with its own grading and binding/screening process, distinct from a pre-blended graded GSB material.
Not as supplied. 40mm aggregate is a single particle size, while GSB is a blend of multiple sizes meeting a grading curve. It cannot be called or used as GSB without first being blended to the specified grading.
No. Crusher dust is an uncontrolled fine crushing by-product, not classified to any grading, and is not a substitute for specification-compliant GSB unless processed and graded to meet the applicable project specification.
Subgrade is the prepared soil foundation beneath GSB — a different material entirely, tested under separate geotechnical criteria. They are sequential pavement layers, not substitutes for each other.
Gradings V and VI are used as a sub-base-cum-drainage layer under MoRTH Clause 401, serving a primary drainage role within the pavement structure.
Application
GSB is used as the sub-base layer in highways, state and rural roads, urban roads, industrial roads, logistics parks and site-development projects, subject to project specification and pavement design.
Yes, GSB is a standard sub-base material for highway pavement construction, with the specific grading determined by the project's pavement design.
Yes, GSB is commonly used for access roads and site-development work on commercial and residential projects, subject to the project's specification.
Yes, GSB is used as the sub-base for industrial roads and logistics-park development, matched to the applicable grading and project specification.
Yes. Grading selection, layer thickness and compaction requirements are all determined by the project's pavement design and contract specification, not assumed from the product name alone.
Procurement
Share your project location, required grading, quantity, specification and delivery schedule through the Request a Quote form, or contact OM Group directly by phone or WhatsApp.
The grading required is set by your project's contract specification and pavement design, not by this page — confirm the specified grading (I–VI) with your engineer before ordering.
Grading/sieve analysis, CBR, relevant physical test results, source information and delivery documentation are the common requests — availability depends on the source, material and project requirement.
GSB price depends on grading, quantity, source, delivery distance, documentation/testing requirements and current market conditions — OM Group quotes against the specific requirement.
There is no fixed published rate — price depends on grading, quantity and delivery location. Share your requirement with OM Group for current pricing.
Quantity is calculated from your project's sub-base area, thickness and design — share your BOQ or drawings and OM Group can work from that.
Yes. GSB can be quoted and coordinated alongside aggregates, sand and Ready Mix Concrete on a single procurement relationship.
Local
OM Group supplies Granular Sub-Base across North and South Goa. Request a quote on this page or contact OM Group directly.
OM Group supplies GSB across Goa, coordinating sourcing and specification confirmation as part of its road and infrastructure materials range.
Yes, GSB is supplied across North Goa.
Yes, GSB is supplied across South Goa.
OM Group supplies GSB across Goa, sourced and confirmed against the applicable grading and project specification. Sourcing and specification confirmation are coordinated as part of OM Group's supply relationship.
Share your required grading, quantity, project location and specification. OM Group will confirm the appropriate supply requirement and commercial details.