Stabilised Proctor testing

[defg]

I'm carrying out stabilization on subbase materials by usung 3% of cement.I have made a modified Proctor by using same percentage of cement.The values of the Maximum dry density(MDD) obtained were found lower compared to the modified Proctor without cement.According to my experience I could expect the one with cement to be more than the one without cement.Ihave repeated the testing several times but the results remain same.The procedure used was as follows:6kg of subbase materials were weighed less 3% of 6kg(to take the place of cement)=5820grams of subbase materials and then 3% of cement(180grames)were added to the subbase material making a total of 6kg as before and the Proctor testing was conducted as mormal.Iam I wright or I should add the 3%percent cement directly to the 6kg of subbase materials without reduction?Please assist!

 

[VAD]

I see nothing particularly wrong with the results obtained.The addition of cement increases the fines content and possible water for optimum moisture. Depending on the fines in the subbase material there may be too much on the addition of the cement as well that would detract from a higher compaction. This needs to be examined. The addition of cement is to produce a stronger material when the cement hydrates. This would certainly be more advantageous than the increased density of the non cement materia. How much variation is there in the densities?

It seems that you are looking only at desity to provide resistance to deformation rather than the effect of the cement in producing a modified material. On the other hand the low cement content may not be seen as providing sufficient strength but acting as a filler to improve density, which then translates into better strength and deformation characteristics. I have added cement as afiller to sand asphalt bituminous mix and have tested them both after 24 hours and after 7 days and have noted that the Marshall stability increased considerably.

Cement content is normally expressed as percent by weight of dry soil.

For your material I would add a percent or two more and derive the benefit of a stronger material. However cracking is another issue.

Hope this discussion helps some what

 

[GeoPaveTraffic]

defg,

In my experience the addition of lime or cement to soil always results in a decrease in density. The best way to determine if the soil/lime/cement mixture is being propertly mixed and compacted is to watch the operation from begining to end. Once the material has been mixed and compacted, let it set for a few hours to over night, then test it with a footing probe or pocket penetrometer. If the proceedure has been completed correctly, then the soil will be very hard, PP=4.5+ tsf and footing probe indent of less than 1 inch.

If someone else just must see a density test, i.e. the owner or building inspector, run the test and approve the compaction based on "...density, strength, and observations..."