DISCUSSION

The California Bearing Ratio (CBR) test is a simple strength test that compares

the bearing capacity of a material with that of a well-graded crushed stone ( thus, a high

quality crushed stone material should have a CBR @ 100% ). It is primarily intended for,

but not limited to, evaluating the strength of cohesive materials having maximum particle

sizes less than 19mm ( 0.75 in. ) ( AASHTO, 2000 ). It was developed by the California

Division of Highways around 1930 and was subsequently adopted by numerous states,

counties, U.S federal agencies and internationally. As a result, most agency and

commercial geotechnical laboratories in the U.S are equipped to perform CBR tests. The

basic CBR test involves applying load to a small penetration piston at a rate of 1.3mm

( 0.05’’) per minute and recording the load penetrations ranging from 0.64mm ( 0.025 in.)

up to 7.62 mm ( 0.300 in.) . Figure is a sketch of a typical CBR sample .

Along these experiments, we have two of problems such as the area of

experiments and the distant between the experiment and geotechnical lab for do a

penetration test. It’s because there have some blocking by the vehicles. The effect is we

took a time to do the next procedures. While the first problem be the issues for our group

because we can’t move clearly around the CBR tool. It’s because the CBR area very

nears the drain and can be dangerous for us.

So, to solve the above problem we suggest a few of solution. First, prepare the

suitable mean the experiment area is big and far from the hazard like the drain. Second is

all the CBR tool must place in the highway lab but not at geotactic laboratory. By this

way, the students can’t save the time and the data is more accurate when the student can’t

focus 100%.

CONCLUSION

California Bearing Ratio (CBR) is a test widely used to evaluate soil and soil

aggregate support values for structural pavement design. The objective is achieved. The

Califirnia Bearing Ratio ( CBR) value of the given crushed aggregate is 31% when the

dry density is 242.9 Kg/m³. Then from the graph we know that the optimum moisture

content is 8.09% and the maximum dry density is 255.65 kg/m for the given crushed

aggregate have the CBR value 31% and the value is less than 50%. So, that is has poor

rating and it is not suitable use for base of road construction.

REFERENCES

Highway Engineering ( BFC 3042), University Tun Hussein Onn Malaysia.

Ahmad Kamal Ariffin Bin Abd Rahim, Monograf Kejuruteraan Jalan Raya Dan

Lalu Lintas, UTHM.

http://home.iitk.ac.in/~madhav/expt14.html

http://en.wikipedia.org/wiki/California_bearing_ratio

http://eprints.utm.my/4064/