Unconfined Compressive Strength(UCS) for stabilised subbase materials

[defg]

I'm carrying out cement stabilization on different gavel materials for use as stabilised subbase C1 by using different percentage of cement.The percentages used are 2.5%,3% and 3.5% of cement.The moulded specimens were cured for seven days in a water tight plastic bags and immensed in a water bath of a constant temperature of 25centigrades.The samples were then soaked in water fopr four hours prior to crushing.The very interesting phenomena here it that the test results show that the 2.5%of cement gave better strength than 3%cement. We have tried to repeat the tests precisely,but we have got the same results.According to my experience I could hope that the higher the cement the higher the strength to be achieved!What is the reasons for this!

 

[Ron]

With such low cement contents, cement distribution within the sample is a problem. Sometimes the distribution is good and you get good strength...sometimes it's not so good (inadequate mixing) and the strength suffers.

 

[civilperson]

One case: The optimum of strength per dollar of mixed cement/soil was around 5-6% by dry weight for well graded granular soil with less than 6% passing #200 sieve. (75% portland & 25% flyash in Rita Ranch of Tucson, AZ).