Which compactive effort to use for stabilised layer?

[defg]

Dear Sir,
I'm carrying out a stabilised layer of subbase materials(C1),the general specification states that it should be compacted at 95%,other books state that it is 97% and the revised one corresponding to the project staes that compaction shall be 98%.Please which compaction between the three is proper and correct without affecting the streght of the stabilised layer?Also what is the expected compaction of stabilised subbase materials compacted with a light hammer 2.5kg/62blows/5layer,Intermediate compaction 4.5kg/30blows/5layers and Heavy compaction 4.5kg/62blows/5layers.And which copmaction is appropriate for stabilised subbase layer C1?
Please assist.

 

[GeoPaveTraffic]

The proper degree of compaction for any layer is dependent on many factors, such as purpose of layer, type of soil, and standard local practice. We don't have any of this information.

My first suggestion is to talk to the project geotechnical engineer. If there is no project geotechnical engineer, you should consider hiring one. Lacking that, the project specifications require 98% of some standard compaction value; that is what you should use.

 

[BigH]

Since this is in the environmental section rather than the earthworks or other geotechnical ones, the level of compaction (and the variation from OMC) would be that which would correspond to the density required to meet permeability requirements. You would normally compact clayey soils on the wet side of optimum for permeability purposes. You probably should develop a set of curves showing %compaction at a specific water content (either standard or modified depending on your bias) vs coefficient of permeability - immediately and on saturation.

 

[iandig]

As a follow up to the previous posts which I concur with entirely, the degree of compaction you require will be dependant upon the required end-performance. In order to confirm the required degree of compaction, you need to know how strong/stiff/impermeable the material needs to be. I would suggest that when you undertake the compaction tests, you also measure the 'end-performance' property you are designing against i.e. Shear Strength/CBR/Stiffness Modulus/UCS/permeability etc... Then by plotting the relationships between density and moisture, density and 'required end-performance' you can identify the acceptability envelope for the material. Don't forget to determine the particle density for each mix as this will help in plotting the data. Also make a decision as to when the moisture content will be determined. Because you are adding hydraulic binders to the soil, some of the water in soil will be bound up with the binder, which will continue for several days changing the moisture content even when the soil is not drying in an oven. I would suggest that all moistures are measured after 24 hours of drying at 105-110ºC, and not as some test standards require 'to constant mass'.
I hope this helps.