What is a CBR Test?
A CBR (California Bearing Ratio) Test is used to determine the strength of soil, subgrades, and other unbound materials beneath highways, pavements, and working platforms. The results are expressed as a percentage, with higher values indicating a stronger, more stable formation.
CBR testing is commonly required for:
- Highway and road design approvals
- Pavement and car park construction
- Subgrade and sub-base material verification.
- Site formation validation for new developments.
Why Do I Need a CBR Test?
A CBR test provides assurance that the ground or placed materials meet the required strength criteria for the intended loading.
Typical reasons include:
- Meeting local authority or highway agency specifications
- Verifying that imported fill or capping material is suitable for use
- Confirming that the site’s formation is fit for construction
- Reducing the risk of future settlement or failure of pavements/roads.
Common Applications
- Road, highway, and car park construction.
- Industrial yards and hardstanding areas.
- Embankment and fill validation.
- Piling mats and working platforms.
How is a CBR Test Carried Out?
CBR tests can be performed in-situ (on site) or in a laboratory setting, depending on project requirements.
In-situ CBR testing typically involves:
- A plunger being pressed into the soil at a controlled rate.
- Recording the resistance to penetration at specific depths.
- Converting the results into a CBR percentage value.
Laboratory CBR testing involves taking samples from site and testing them under controlled conditions.
Why Choose SEP Technical?
- Testing carried out in accordance with BS 1377-4:1990
- Experienced engineers delivering accurate, reliable results
- Fast turnaround with clear reporting
- Nationwide coverage and flexible scheduling
Frequently Asked Questions
- Do I need CBR testing or Plate Bearing testing?
CBR testing is typically required for roads and pavements, while Plate Bearing testing is often used for crane bases, piling mats, or heavily loaded areas. SEP Technical can advise on the best option for your project.
- How long does the test take?
In-situ testing can often be completed in a single day, with results available shortly after. Laboratory testing may take longer depending on sample curing and preparation.
- How much does a CBR test cost?
Pricing depends on location, access, and whether the test is carried out on site or in a laboratory.
- What CBR value do I need?
Requirements vary depending on project type and specification. For highways and pavements, local authority standards will usually dictate the minimum CBR percentage.
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