Our field crew rolls into Mackay with a pneumatic roller, a water truck, and a portable Proctor compaction kit mounted on a flatbed. For every road subgrade we treat, we first run a Modified Proctor compaction test in situ to establish the maximum dry density and optimum moisture content for the material. That data feeds directly into the lime or cement dosage calculation. The mixing rig then works the stabilizer into the top 300 mm of the pavement formation at a controlled speed of 4 km/h, ensuring uniform blending across the full width of the haul road or local street. We calibrate every batch against the target compaction curve before the roller makes its first pass.
A plasticity index jump from 12 to 22 within 200 mm of formation level can turn a routine stabilization job into a full rework.
Methodology and scope
A common mistake contractors make in Mackay is assuming the sandy loam that looks uniform on the surface retains the same plasticity index at depth. We have seen cases where the PI jumps from 12 to 22 within 200 mm of the design formation level, turning a routine stabilization job into a rework. To avoid that, we always run a full set of Atterberg limits and a granulometry curve on samples from every 50 m of the alignment before mixing begins. When the fines content exceeds 35 %, we switch from cement to a lime-based treatment to handle the clay reactivity properly. The key parameters we track are:
Plasticity Index target reduction: minimum 50 % of original value
Unconfined compressive strength after 7 days: ≥ 1.5 MPa
Maximum dry density variation: ± 2 % of Proctor optimum
Once these targets are met, we proceed with the CBR test on the stabilized layer to validate the design modulus for the pavement structure.
Technical reference image — Mackay
Local considerations
In Mackay we often see that the high water table during the wet season — the water level can sit at 1.2 m below surface after a 200 mm rainfall event — saturates the active zone of the pavement formation. If the stabilizer is mixed into a wet subgrade without first drying it back to optimum moisture, the cement hydration reaction is compromised and the layer never gains design strength. We bring a portable thermal dryer to lower the moisture content by up to 4 percentage points before mixing. That extra step costs a few hours but prevents the catastrophic cracking and pumping that we have seen on several local access roads where the stabilizer was applied on a wet subgrade.
We collect disturbed and undisturbed samples along the road alignment every 50 m, run Atterberg limits, granulometry, and Modified Proctor tests, then formulate the stabilizer blend (cement, lime, or fly ash) to meet the specified UCS and CBR targets.
02
Field Mixing & Compaction Control
Using a self-propelled stabilizer with an integrated water metering system, we treat the subgrade to the required depth, followed by density testing using the sand cone method and nuclear gauge readings at 20 m intervals to verify compaction compliance.
03
Curing & Performance Verification
After compaction we apply a bituminous curing membrane to prevent moisture loss, then extract core samples at 7 and 28 days for UCS testing. We also run soaked CBR tests on remolded specimens to confirm the design modulus for the pavement design.
Applicable standards
AS 1726 – Geotechnical Site Investigations, Austroads Guide to Pavement Technology Part 4D – Stabilised Materials, AS 1289.5.1.1 – Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort
Frequently asked questions
What is the typical cost range for road soil stabilization in Mackay?
The typical cost range for soil stabilization for roads in Mackay is between AU$1,350 and AU$4,360 per project, depending on the treatment depth, stabilizer type, and total area. Final pricing is confirmed after the mix design phase.
What is the difference between cement and lime stabilization for Mackay soils?
Cement stabilization works best on granular soils with a plasticity index below 15, while lime is preferred for clay-rich soils with PI above 20. In Mackay, where the subgrade often contains reactive clays from the alluvial deposits, lime is commonly used to reduce swell potential and improve workability.
Do you provide a NATA-accredited laboratory report for the stabilized material?
Yes, all our compaction, UCS, and CBR tests are performed in a NATA-accredited laboratory (ISO 17025) with full traceability. The report includes the mix design, density records, and strength results, and is signed off by the responsible engineer.
Can soil stabilization be done during the wet season in Mackay?
It can be done, but requires careful moisture management. We use portable thermal dryers to lower the moisture content of the subgrade before mixing when the water table is high. The work is typically scheduled after at least 48 hours of dry weather to avoid working on saturated ground.
