We roll out with a concrete mixer and slipform paver to handle rigid pavement design on Bunbury's sandy and lateritic soils. The rig spreads, vibrates, and trowels the slab in a single pass — a process that demands precise subgrade preparation. Before we pour, we run plate load tests and CBR assessments to confirm the subgrade modulus. This sequence cuts delays and avoids costly overdesign. For projects with heavy traffic, we also check the subrasante vial stiffness to finalize the slab thickness. It's a methodical workflow that has delivered results from the Bunbury port precinct to residential estates in Glen Iris.
A rigid pavement in Bunbury must resist both heavy freight loads and the corrosive effect of coastal moisture. We design for a 30-year service life with minimal maintenance.
Methodology and scope
Local considerations
Bunbury sits on the Swan Coastal Plain, a region with high groundwater levels and a history of localised flooding during winter rains. If rigid pavement design ignores drainage, water trapped under the slab causes pumping, joint faulting, and premature cracking. We've seen slabs fail within five years on industrial sites where no subgrade drainage was installed. To prevent that, we include a 150 mm drainage layer of crushed rock and a geotextile separator. The risk is real: Bunbury's annual rainfall averages around 750 mm, and a poorly drained pavement can lose half its design life.
Applicable standards
AS 1726 – Geotechnical Site Investigations, AS 4678 – Earth Retaining Structures, AS/NZS 1170 – Structural Design Actions, Austroads Guide to Pavement Technology Part 2
Associated technical services
Industrial Pavement Design
For container yards, truck terminals, and heavy equipment storage areas, we design jointed reinforced concrete pavements that handle 10-tonne axle loads. The design includes dowelled contraction joints and a saw-cut pattern that controls cracking. We follow Austroads Part 2 and AS 1726 for subgrade characterisation.
Municipal Road Pavement Design
For local roads and collector streets in Bunbury, we produce plain concrete pavement designs with tie bars at longitudinal joints. The mix uses 32 MPa concrete with a target flexural strength of 4.5 MPa. We also specify a 100 mm lean concrete subbase to spread the load evenly across the subgrade.
Typical parameters
Frequently asked questions
What is the typical cost for rigid pavement design in Bunbury?
The cost for a full design package — including site investigation, traffic analysis, slab thickness calculation, and joint layout — ranges from AU$3,100 to AU$8,590 depending on the project area and complexity. A small residential street is at the lower end; a port or industrial yard is at the higher end.
How does Bunbury's coastal setting affect the concrete mix design?
Coastal moisture carries chlorides that can corrode steel reinforcement. We specify a minimum cement content of 380 kg/m3, a water-cement ratio below 0.45, and 50 mm cover over reinforcement. The mix also includes a corrosion-inhibiting admixture to extend the service life.
What subgrade tests are required before designing a rigid pavement?
We run a minimum of three CBR tests at the natural subgrade level, along with a plate load test to measure the modulus of subgrade reaction (k-value). If the soil is sandy, we also conduct a sieve analysis to check for fines content that could affect drainage.
Can rigid pavement be placed on reactive clay soils common in Bunbury?
Yes, but it requires a treatment layer. We recommend a 200 mm lime-stabilised subbase on clays with a plasticity index above 20. The stabilisation reduces shrink-swell movement and provides a uniform support for the concrete slab. Without it, differential movement can cause slab cracking within two years.