Soil stabilization with cement or lime
Soil stabilization with cement or lime
(OP)
Can anyone tell me how the soil stabilization process works. Is it required for the ground to be graded first before applying the cement? Is the cement spread on the soil and mixed in place with the soil or does it require the soil to be excavated and mixed in the equipment before placing it back on the ground? If it is in-situ mixing, is water applied at the same time the cement is spread on the ground? Is there a delay time before compaction can begin?
Also does anybody if this is an expensive process?
How does it compares cost wise to excavating and backfilling with gravel?
Thanks!
Also does anybody if this is an expensive process?
How does it compares cost wise to excavating and backfilling with gravel?
Thanks!





RE: Soil stabilization with cement or lime
BoMag makes a mixer that contractors can use. It looks like a big rotor tiller. For this method you'd distribute a desired layer of lime or cement and then set the equipment to mix the lime or cement into the desired layer thickness.
What you have to do is a bench test on the material. So, step one is to collect a sample and then make a few batches in the laboratory to see how a given percentage of lime/cement affects the moisture-density relations. Once you optimise the percentage, you can then figure out what it will take in the field.
Yes it's expensive. Then again, so is the wholesale removal and replacement of otherwise workable soil. Somewhere in this there is an engineering economic that must be considered.
Good luck. I'm sure others have different and valuable experience.
f-d
¡papá gordo ain’t no madre flaca!
RE: Soil stabilization with cement or lime
Once you experience it even crudely, even where no lab work is done ahead of time, it is almost like magic the way things improve.
I will say one thing about cement stablization that soured me a little. A roadway subgrade stabilized with about 5 percent in a clay sure looked nice when built, but frost action later destroyed much of the strength.
RE: Soil stabilization with cement or lime
RE: Soil stabilization with cement or lime
Going back to the selection of the appropriate bindrs, if there are sulfates present in the ground, these can and will combine with water, calcium, allumina or silica and form expansive products. There are a number of accepted methods for dealing with this, however if you get it wrong, it really is a big problem. Some binders such as PFA and GGBS can help restrict the formation of expansive by-products, but with higher sulfate contents this can still occur. Total sulfates of < 0.2% should be OK subject to appropriate testing, sulfates between 0.2 and 1.0% MAY be ok but it needs extensive testing and sulfates over 1% are not reccomended for treatment with lime and cement.
RE: Soil stabilization with cement or lime
Not too sure about adding water. More frequently, you are using the lime or cement to react against the water in the soil. To add water would defeat this purpose.
This is a very important warning!! Quite often marine clays (i.e., sensitive clays that really need stabilization) have disseminated (sp) grains of pyrite. Pyrite will readilyy oxidize and liberate sulfuric acid. Chemical reactions with liberated sulfides and lime or gypsum - expecially in a basic environment can lead to the formation of ettringite. The formation of ettringite can damage overlying structures.
f-d
¡papá gordo ain’t no madre flaca!
RE: Soil stabilization with cement or lime
RE: Soil stabilization with cement or lime
RE: Soil stabilization with cement or lime
RE: Soil stabilization with cement or lime
What is more popular, mixing with rotovator or using pugmill continuous mixing plant?"
It depends on the project and the type of plant available.
The first question is how thick is your pavement construction?
Other posters may correct me, but I believe the rotovator type insitu mixer will work to a maximum of a 150-200mm thick layer. So if you can grade off to finished sub-base level and then add cement (or lime) to the existing soil, compact and finish. Then go for the rotovator without question.
Next option you need 300mm thickness stabilised material. Then you have to remove the first layer. The lower layer can be treated by rotovator and the second layer either placed and again stabilised by spreading cement and rotovating, or it could be passed through a pugmill first for the cement to be added.
Another option is that the existing soils are not used at all. You remove say 300mm of existing soil. You find a nearby borrow pit where there is gravel which in it's natural state would not be suitable as a subbase material, but with the addition of cement is satisfactory. In this case again you either place the material in layers and spread cement followed by rotovator or you process through a pugmill.
If soils are to be removed and reused, or brought to site, I like pugmills for CSM as they are quick and accurate. If there is no need to remove the existing soil rotovators are the way.