Benchmark your project

Over the years, Simtec have found that around 95% of compliance levels are not being met on projects, mainly due to low-quality or incorrect materials being used. The remaining 5% were simply a result of not adhering to best practices. The Simtec OCB datasheets can help mitigate those risks.

Every contract Simtec undertakes is measured against the Simtec Optimum Compliance Benchmark TM data consisting of best practice criteria designed to help achieve consistently high compliance approval and avoid the cost of delay or remedial work.

The integrity, rigour, and safeguarding Simtec have provided over the last 12 years has established Simtec as a trusted testing partner to firms across the UK’s construction sector.

Documenting the best in practices and procedures to produce the conditions for an optimum compliance outcome, Simtec go beyond the minimum compliance requirements for all clients.

Example OCB Datasheet

Unbound Layer Testing CBR (Determination of the equivalent California Bearing Ratio using the plate bearing test)

Validation of results

By using a UKAS accredited testing organisation results will be accepted by all UK Government agencies, including Highways England and local authorities.

Referencing standard(s)

BS1377: Part 9: 1990 Clause 4.1 Design Manual for Pavement Foundations CD 225 IAN73/06 Rev 1:2009 (Withdrawn)

Establishing testing layers

In most cases (depending on the layer thickness) formation and capping requires a 450mm diameter plate and a Sub-base requires a 300mm diameter plate.

Adhere to specified min CBR % for the relevant Local Highways Authority or Highways England.

Preparation & compaction

Formation & Sub-Formation: Proof roll the Subgrade before test. Capping Layer materials require compaction to the requirements of Table 6/1 – Series 600 of the SHW.

Type 1 Sub-Base: Ensure appropriate thickness and adequate compaction. Avoid segregation of stone materials and ensure smooth level test surface.


Kentledge provision should be in excess of 6 tonnes and have an accessible flat area to seat the jack. A Back Hoe digger or a 360 excavator is ideal.

Length of time

Kentledge is required for the duration of the test. Testing at each location typically lasts 30 mins. Individual test duration will vary according to the ground conditions.

Weather conditions

Weather does not adversely affect the testing regime. However, rain over a prolonged period will distort the CBR value of both the formation and sub-base layers. Avoid testing when the surface is frozen or affected by frost and snow or is saturated.

OCB Disclaimer

Simtec Materials Testing Ltd will in no event be liable for any loss or damage, including without limitation, indirect or consequential loss or damage, or any loss or damage whatsoever arising out of, or in connection with, the use of this website or our OCB (Optimum Compliance Benchmark) guides. Any reliance you place on such information, tips, help, and advice is, therefore, strictly at your own risk.