A common mistake we see in Kilkenny is rushing into pavement construction with an assumed CBR value, only to find the limestone till or alluvial clay beneath the road doesn’t hold up after a wet winter. The soaked CBR can drop by half compared to what you’d expect from a dry summer sample. That miscalculation leads to overbuilt sections wasting aggregate or, worse, underdesigned pavements that rut within two seasons. Getting a proper laboratory CBR test on a remoulded specimen – compacted at the right moisture and density for the job – avoids that gamble entirely. Because Kilkenny’s pavement layers sit on everything from well-graded gravels near the Nore to soft silts on the outskirts, we run the test to TII specifications and deliver the design CBR you can actually rely on. And if the formation is marginal, we’ll often suggest pairing the CBR data with a plate load test to verify in-situ stiffness before you commit to the section depth.
A soaked CBR value taken from a properly compacted sample tells you more about your pavement’s lifespan than a dozen dry density tests.
Local geotechnical context
In Kilkenny, we’ve noticed that imported fill from local quarries can be more variable than the quarry certificates suggest – a few loads of silty fines mixed into the clean limestone can slash the CBR from 30% down to 5%. That’s the sort of thing you don’t catch with a visual inspection alone. If you skip the laboratory CBR test at this stage, you’re essentially designing your pavement blind. A low CBR subgrade forces you to thicken the capping and base layers significantly, which eats into your budget fast. Testing early means you can either treat the weak material with a binder, replace it under controlled conditions, or adjust the pavement design to match the actual numbers, keeping the project cost predictable. The test also provides the documentation needed to satisfy TII and local authority approvals without pushback during construction.
Frequently asked questions
What does a laboratory CBR test cost in Kilkenny?
A standard laboratory CBR test on a remoulded sample, including the 96-hour soaked condition, typically runs between €130 and €190 per specimen depending on whether you need the Proctor compaction curve run alongside it and if swell measurement is included. We quote per sample, not per value, so you get both the 2.5 mm and 5.0 mm penetration results in the same test.
How long does it take to get a CBR test result?
For a soaked CBR test, you’re looking at about 5 working days from when we receive the sample. The 96-hour soaking period is fixed by the standard, and after that we need a day for the penetration test and reporting. Unsoaked CBR results can be turned around within 24 hours if it’s urgent.
How much soil do you need for a CBR test?
We need about 25 kg of disturbed, representative soil per CBR specimen. If you want us to run the Proctor compaction test alongside it to establish the optimum moisture content and maximum dry density, add another 20 kg. The material should be bagged and sealed on site to preserve the natural moisture, and we’ll sieve it in the lab before compaction.
What’s the difference between a laboratory CBR and a field CBR?
The laboratory CBR test is done on a remoulded sample compacted under controlled conditions in a mould, which gives you the design value for pavement thickness. A field CBR test, often done with a dynamic cone penetrometer, gives an in-situ reading of the ground as-is. The lab test is preferred for design because it accounts for worst-case moisture after soaking, while field tests are better for construction quality control.
Does the CBR test work for all soil types in Kilkenny?
The laboratory CBR test works well for most soils, but there are limits. For granular materials with particles larger than 20 mm, we replace the oversized fraction with material passing the 20 mm sieve, which can sometimes overestimate the CBR. For very soft silts and peats found in some low-lying areas around Kilkenny, the CBR value can be so low that a plate load test or a vane shear test gives more useful design parameters for ground improvement decisions.
