CBR: An Effective Measuring Tool

Posted by PCTE on July 3rd, 2015

The CBR (California bearing ratio) test is a type of penetration test used to evaluate the mechanical strength of base courses and road subgrades. It was developed before the Second World War by the California State Highway Department, thus the system's name. It was originally developed to measure soil's load bearing capacity and determining its suitability for road-building. Today, CBR is also used for measuring load bearing capacities of soils under paved airstrips and unimproved air strips.

Harder surfaces receive a higher CBR rating. Tilled farmlands, for instance, usually receive a CBR rating of 3, while moist clay or turf is rated at 4.75. Moist sand may offer a CBR of 10. The standard material used for this particular test is crushed California milestone. It has a CBR value of 100.

CBR test is used in the field as part of site investigation. It is performed as an arbitrary strength test, considered to replicate wheel loads and stress soils. It determines the thickness of materials required for the road construction.

The CBR test is done by measuring the amount of pressure it takes to penetrate a soil sample using a plunger of a standard area. The resulting pressure is then divided by the pressure required to achieve equal penetration on the standard crushed rock material. High quality sub bases usually have CBR values between 80 and 100%, maximum.

This soil test is more suitable for testing soils with maximum particle size of up to 20 mm. for material with particles greater than this, plate bearing tests are more appropriate. This technique involves driving a cylindrical plunger at a uniform rate into the tested ground with the help of a four wheel drive vehicle, which serves as the reaction load that provides the force. Newer, more portable devices can now be used to perform plate load bearing tests without the need for large vehicles that limit the capacity of the testing method to wide, open surfaces.

Both CBR testing and plate load bearing testing are carried out at surface level to ensure accurate results. They are normally performed between 500 and 1000 mm, in 20 to 30 m intervals along the proposed centerline of the construction site. Three tests are usually enough to gauge the load-bearing capacity of a particular surface. Typically (assuming that surfaces have been prepared in advance), a single operator can carry out as many as 8 o 10 CBR tests within a day, giving him the capability to churn out results instantly on site.

About the Company:

PCTE supplies a range of equipment from around the world to offer you a one stop shop with all of the latest equipment. Concrete Non Destructive Testing (NDT) comprises testing a property of concrete, largely without damaging the concrete to assess some parameter that either directly or indirectly provides a required characteristic of the concrete or its embedment. For more details, you can contact us at the website.


PCTE

About the Author

PCTE
Joined: November 21st, 2013
Articles Posted: 36

CryptoSlots: $1,000,000 Jackpot & Provably Fair Games
Provably Fair games, exciting wins, huge bonuses. ★CryptoSlots★ is your crypto casino of choice. Sign up in seconds to start winning!
MXC | Bitcoin Trading Platform-Bitcoin_Litecoin Real-time Price Quotes | MXC Exchange
MXC Exchange is the world's leading digital asset platform. It provides real-time price quotations in multiple currencies such as BTC, LTC and ETH, and supports hundreds of digital assets trading and investment information. MXC Exchange is best choice
Bitcoin Exchange | Cryptocurrency Exchange | Binance
Binance cryptocurrency exchange - We operate the worlds biggest bitcoin exchange and altcoin crypto exchange in the world by volume
BitStarz Online Casino
BitStarz is an award-winning bitcoin casino offering more than 2,200 casino games including slot machines, blackjack, poker, roulette, baccarat, bingo and more!
HOTBIT Crypto Exchange
Hotbit is one of the professional digital asset exchange platforms that provide trading services among major digital currencies like Bitcoin, Litecoin and Ethereum for users from all over the world.
Dualmine - Multiply your Bitcoin, Ethereum, Litecoin and Dogecoin
Start cloud mining and increase your crypto capital now! Unique product offering the mining of the most profitable cryptocurrencies in the cloud - BTC and ETH. You can mining one of them or both at the same time. Your hardware is already running and waiti