California-Bearing-Ratio-CBR-Testing 
                     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.
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
CBR Test Methodology at Perry Testing
Penetration
Preparation
A cylindrical plunger penetrates soil at precisely 1.25 
Our technicians prepare the test site and equipment, mm/min rate using calibrated equipment.
ensuring compliance with BS1377 standards.
Calculation
Measurement
CBR value = (load on soil / load on standard crushed 
Load readings are recorded at 2.5 mm and 5.0 mm rock) × 100%
penetration depths for accurate assessment.
Higher CBR indicates stronger, more stable soil conditions.
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.
Equipment and Apparatus
Penetration Plunger Load Application System Measurement Systems
Standard 50 mm diameter plunger Calibrated hydraulic jacks and digital Digital dial gauges accurate to 
with precision-machined face for load cells for accurate force 0.01mm for precise penetration 
consistent results measurement measurement
Perry Testing Ltd maintains UKAS-calibrated equipment to ensure consistent, reliable results across all projects.
Interpreting CBR Test Results
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CBR Value Classification Engineering Implications
Perry Testing provides detailed classification of results: Our experts help clients understand what results 
mean for their projects:
• Very poor: CBR < 2%
• Poor: CBR 2-5% • Low CBR ( 20%
• 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.
Applications of Perry Testing's CBR Services
Transportation Infrastructure Commercial Development Quality Assurance
• Highways and motorways • Industrial estates • Construction phase verification
• Local road networks • Car parks and loading areas • Material selection validation
• Airport runways and taxiways • Retail development foundations • Compliance with design 
• Railway subgrades • Logistics centre hardstandings specifications
• Post-construction assessment
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: [email protected] | Phone: 01923 551 889
Perry Testing LtdYour trusted partner for 
construction materials testing