Some sites need concrete. The consultant's specification calls for it, the client wants a hard surface that can be swept clean, or the road runs past a building where a concrete look is part of the design. GridMats S4 is our answer for those sites: a concrete road whose finish is the hexagon pattern of the grid.
This article explains how S4 is built, bay by bay, and when we would point you to another system instead.
What S4 is
The OC-HD 40 grid is set on a bedding of M30 or M40 PQC while the bedding is green, and its cells are filled flush with the same concrete. The concrete stops at the top of the cells, so the hexagon cell tops are the finish: no overlay, no grinding and no groove cutting.
The bedding is the same grade as the fill. We never use a lean mix, DLC or PCC under the grid, and we never put the grid under a slab.
How it is built, in outline
This is a broad outline. The step-by-step S4 SOP, with its hold-point checklists, comes with a paid order, and we train your contractor's team on it.
- The ground and the separation layer. The subgrade is compacted to CBR 8 or more, and a non-woven geotextile separation layer goes over it. At Godrej, Vikhroli, Mumbai, the road bed was prepared first, then the separation layer and the edge restraints went in.
- The base and the bedding. GSB and/or WMM to the design, well compacted, then a bedding of M30 or M40 PQC, its thickness set by the design.
- The grid. OC-HD 40 goes on the bedding while it is green and is anchored with U-nails to our SOP; at Aditya Birla, National Park Guindy, Chennai, you can see the nails in the grid before the concrete.
- Bays and joints. The cell walls act as the joints within a bay. Expansion joints go only at bay edges and against structures; at Guindy, a foam filler board marks each bay edge.
- The fill and the finish. The cells are filled flush with the same PQC, with no layer above the grid, and the surface is power-floated to bring out the honeycomb. The mix design is approved before the first pour, the slump is checked on every truck and the finish height is checked at the cell tops.
- Curing. The road is cured for 7 days before traffic. Cubes are taken at 7 and 28 days on every pour.
Much of this work is done at night where the road cannot close by day: the concrete at Godrej and at Guindy was placed and finished at night.
When it opens
- Traffic after 7 days of curing.
- Full traffic at 14 days.
- Full load at 28 days.
Because the road is built bay by bay, the bays already cured can carry traffic while the next ones are poured.
Who builds it
S4 is built by your contractor's execution team, trained by GridMats with our S4 SOP, which comes with a paid order. For orders of 2,000 m² or more, our trainer comes on site for up to 3 days, once you confirm in writing that the site is ready and your team is available, and demonstrates about 100 m² to the project agreement and the SOP. Smaller orders are trained online. Defect liability is 1 year (DLP), our standard practice.
Carbon, with its basis
A life-cycle assessment by Smarter Dharma puts S4 at 23.8 kg CO2e per m², against 92.1 kg CO2e per m² for a conventional concrete road. The grid itself is 100% recycled polypropylene.
In service
We have built S4 on 17 sites since 2019. Among them:
- Aditya Birla, National Park Guindy, Chennai: honeycomb-finish roads and walkways, poured at night between kerbs.
- Godrej, Vikhroli, Mumbai (2026): a campus road, filled bay by bay and finished at night.
- Nest Ira, Devanahalli (2023): township roads through a wooded plot.
- PGP Glass, Gujarat: an apron at the loading bays, with trucks on it.
- GMR Hyderabad Airport: a service corridor, built between flights.
- Prestige Tranquility, Bengaluru (2021): concrete placed in the grid over a broken asphalt road.
When to choose something else
- Lowest cost is the priority. S1 cement-treated gravel or S2 stone chip usually costs less, including under daily heavy trucks.
- The rain should go into the ground. S4 is a sealed surface. S2 and S3 are permeable: the rain is managed below the surface, with edge and outfall drains only where the levels need them.
- Full load before 28 days. S2 opens the same day; S1 takes light traffic at 3 days and trucks at 7, once the 7-day cubes reach 2 MPa.
Your road will differ
S4 is priced per site, from its own design: the base, the concrete grade and local rates all change the figure. Ask for your free estimate: our engineers follow with the design, the bill of quantities and the cost comparison against your conventional section.