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California Bearing Ratio
(CBR) Testing
A Specialist Service by Perry Testing Ltd
Perry Testing Ltd offers comprehensive CBR testing services to ensure your
construction projects are built on strong foundations. Our expert technicians
provide reliable soil strength assessments for roads, highways, and other
infrastructure projects across the UK.

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History and Purpose of CBR Testing
Originally developed by the California State Highway
Department in the 1930s, CBR testing has become a
fundamental soil strength assessment method adopted
worldwide.
Perry Testing Ltd has integrated this essential test into our
comprehensive suite of geotechnical services, helping clients
ensure their pavements can support anticipated axle loads.
Adopted as standard in ASTM, AASHTO, BS1377
specifications
Provides empirical measure of soil bearing capacity
Enables optimised pavement thickness and material
selection

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CBR Test Methodology at Perry Testing
Preparation
Our technicians prepare the test site and equipment,
ensuring compliance with BS1377 standards.
Penetration
A cylindrical plunger penetrates soil at precisely 1.25 mm/min
rate using calibrated equipment.
Measurement
Load readings are recorded at 2.5 mm and 5.0 mm
penetration depths for accurate assessment.
Calculation
CBR value = (load on soil / load on standard crushed rock) ×
100%
Higher CBR indicates stronger, more stable soil conditions.

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In-Situ CBR Testing Expertise
Perry Testing's Field Approach
Our specialists conduct on-site assessments to evaluate natural
soil conditions in their undisturbed state.
Accounts for actual site moisture conditions and
compaction
Uses precision hydraulic equipment for consistent load
application
Digital recording systems for continuous data collection
Immediate preliminary results available on-site
Perry Testing Ltd brings over 25 years of experience to every in-
situ CBR test we perform.

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Equipment and Apparatus
Penetration Plunger
Standard 50 mm diameter plunger with
precision-machined face for consistent
results
Load Application System
Calibrated hydraulic jacks and digital load
cells for accurate force measurement
Measurement Systems
Digital dial gauges accurate to 0.01mm for
precise penetration measurement
Perry Testing Ltd maintains UKAS-calibrated equipment to ensure consistent, reliable results across all projects.

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Interpreting CBR Test Results
1
CBR Value Classification
Perry Testing provides detailed classification of results:
Very poor: CBR < 2%
Poor: CBR 2-5%
Medium: CBR 5-10%
Good: CBR 10-20%
Excellent: CBR > 20%
2
Engineering Implications
Our experts help clients understand what results mean for
their projects:
Low CBR (<5%) may require soil stabilisation or
replacement
Medium values guide pavement layer thickness
requirements
High CBR (>10%) indicates strong, load-bearing soils
suitable for direct construction
Perry Testing Ltd delivers comprehensive reports with actionable recommendations based on CBR results.

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Applications of Perry Testing's CBR Services
Transportation
Infrastructure
Highways and motorways
Local road networks
Airport runways and taxiways
Railway subgrades
Commercial Development
Industrial estates
Car parks and loading areas
Retail development foundations
Logistics centre hardstandings
Quality Assurance
Construction phase verification
Material selection validation
Compliance with design
specifications
Post-construction assessment

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tel:01923 551 889


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Perry Testing Ltd: Your CBR Testing Partner
Why Choose Perry Testing?
UKAS accredited laboratory facilities
Experienced technicians with geotechnical expertise
Rapid turnaround times for time-sensitive projects
Comprehensive reporting with clear recommendations
Complementary testing services available
Contact us today to discuss how our CBR testing services can
support your next construction project.
Email: info@perry-ltd.com | Phone: 01923 551 889
Perry Testing Ltd
Your trusted partner for construction materials testing