BS EN 13877-1 sets the framework for concrete pavement design in the UK, but applying it in Portsmouth demands more than a desk study. The city sits on a mix of London Clay, Wittering Formation sands and reclaimed ground around the naval dockyard and Port Solent, where groundwater often sits less than a metre below finished level. In our experience, the biggest variable is not the concrete mix, it is the subgrade reaction modulus. Assuming a default k-value from a textbook when you are working over estuarine silts on the north side of Portsea Island will put the slab at risk of curling and joint faulting within three years. We combine in-situ permeability testing with dynamic plate load tests to derive a k-value that actually represents the formation beneath the capping layer, not a generic assumption from a borehole log fifty metres away.
A rigid pavement is a structural element, not a wearing course. Joint design and subgrade support dictate its lifespan more than concrete strength ever will.
Process overview
Local context
On the western side of Portsea Island, near Tipner, we have seen groundwater rise through open joints and liquefy the fines in a Type 1 sub-base within a single tidal cycle. The slab ends up bridging over a void, and the first 11.5-tonne axle load that hits the joint pops the corner. Portsmouth's tidal range of nearly 5 metres means the groundwater regime is anything but static: it pulses with the tide, and if the pavement drains are not designed to daylight at low water, the sub-base becomes a reservoir. We detail edge drains with perforated pipes wrapped in geotextile and connect them to outfalls that are checked for barnacle and silt blockage every six months. Overlooking this turns a 30-year design life into a maintenance liability inside five years, particularly on dockyard haul roads where downtime costs more than the concrete itself.
Reference standards
BS EN 13877-1:2023 – Concrete pavements – Part 1: Materials, BS EN 13877-2:2023 – Concrete pavements – Part 2: Functional requirements, DMRB CD 239 – Rigid pavements (UK Highways, formerly HD 26/06), BS 1377-9:1990 – In-situ plate load tests, BS 8500-1:2023 – Concrete – Complementary British Standard to BS EN 206
Additional services
Joint layout and structural design
We produce full jointing plans — contraction, expansion and construction joints — with dowel schedules and tie bar specifications. The design accounts for shrinkage restraint, thermal warping and the fatigue induced by container stackers, reach stackers and ro-ro traffic at the ferry terminal.
Subgrade and sub-base specification
Our team carries out plate load tests and in-situ CBR assessments on the formation to define the sub-base thickness and material type. Where London Clay is within 300 mm of formation, we specify a capping layer with a minimum soaked CBR of 5% and a separation geotextile to prevent upward migration of fines.
Typical parameters
Quick answers
How much does rigid pavement design cost for a typical Portsmouth industrial yard?
For a yard of 500–2,000 m², the design package — including subgrade assessment, joint layout, thickness calculation and drainage detailing — typically falls within the range of £1,340 to £5,410 depending on the access constraints, traffic loading data and whether dynamic plate load testing is required on site.
Why is rigid pavement preferred over flexible pavement at Portsmouth port?
The main reason is resistance to point loads and fuel spillage. Reach stackers and container handlers impose high static loads on small contact patches, and flexible asphalt tends to rut and deform. Diesel and hydraulic oil soften bitumen over time, whereas a well-cured C40 concrete slab is chemically resistant. The higher initial cost is offset by lower maintenance and fewer operational closures.
How do you handle the risk of reflective cracking from the sub-base joints?
We avoid inducing a plane of weakness by specifying an unbound sub-base with a separation geotextile, or a cement-bound sub-base with saw-cut joints offset from the slab joints by at least 300 mm. The offset prevents crack propagation vertically through the slab, which we verify through a Westergaard-based stress check at the joint location.
What joint spacing do you recommend for a bus depot near Hilsea?
For an unreinforced slab in Hilsea, where the ground is predominantly gravelly sand over London Clay, we typically specify contraction joints at 4.5 m spacing in both directions with dowel bars at 300 mm centres. This controls cracking from thermal contraction and keeps joint openings small enough for effective aggregate interlock under bus traffic.