Wich important tests are required on crushed stone base course?
Wich important tests are required on crushed stone base course?
(OP)
I'm currently supervising a road designed to a bitumen standard-surfacedressing.The pavement layers composes of stabilised subbase,crushed stone base(CRR)and surfacing.Now I'm at base course stage and in principle Ihave already analysing the most important tests required for the assessment of the rock to be used as stone base.The tests already conducted are grading analysis,P.I,ACV,LAAV,SSS(5cycles)and TFV dry/TFVsoaked.Is pertographic analysis important in this case?and what else important tests to be conducted?





RE: Wich important tests are required on crushed stone base course?
RE: Wich important tests are required on crushed stone base course?
Triaxial Compression for Base Materials
Not sure what the ASTM no. on this would be.
RE: Wich important tests are required on crushed stone base course?
Generally, we require stability testing (CBR or similar), in-place density checked against AASHTO T180 (modified Proctor) with a requirement for 98 to 100 percent compaction. If it is a graded aggregate base (which I assume this to be) we would require a gradation to check against specifications (usually state Departments of Transportation provide requirements for gradation on such materials).
As cvg noted petrography would not be indicated unless you suspect a reactivity or other problem with the parent rock material.
Even though the graded aggregate base is not directly exposed to traffic abrasion, you might consider abrasion testing on the aggregate as it is a good indicator of overall durability of the aggregate (absent reactivity).
I assume from your posting you are either from the UK, Australia or S. Africa. I'm not sure what your acronyms refer to, so you might give us a bit more information on those.
RE: Wich important tests are required on crushed stone base course?
RE: Wich important tests are required on crushed stone base course?
min. comp. strength, psi Gr1 Gr2
lateral pressure 0 psi 45 35
lateral pressure 15 psi 175 175
Included in the Test Method is the use of a triaxial chamber, membrane, confining pressure, capillary wetting, axial load measuring device, etc.
THE TRIAXIAL-COMPRESSION TEST IS USED TO DETERMINE THE FUNDAMENTAL STRENGTH CHARACTERISTICS OF MATERIALS USED IN THE CONSTRUCTION OF FLEXIBLE PAVEMENTS.
This requirement along with P.I., L.L., gradation, wet ball, and a minimum 98% compaction has yielded some very good base courses over the years.
RE: Wich important tests are required on crushed stone base course?
rEGARDS
RE: Wich important tests are required on crushed stone base course?
The minimum unconfined compressive strength for the stabilised subbase is 1MPa.Trial compression for the crushed stone base(CRR/CRS)is not specified in the specification.
RE: Wich important tests are required on crushed stone base course?
You're close to a resilient modulus approach, but the analytical techniques generally do not use your results directly.
Since your triaxial criteria are closely intertwined with other strength criteria (higher compressive strength generally yields higher stability), I suspect you are getting good results by default, as your specifications are likely tight and require good field control.
Stability can be directly related to a compaction curve as in the CBR. The same is not necessarily true of compressive strength.
Most construction materials testing laboratories do not necessarily have the capability to perform triaxial testing. Further, the cost and time required for the process is more expensive than stability and density testing.
Thanks for a different perspective, though.
RE: Wich important tests are required on crushed stone base course?
RE: Wich important tests are required on crushed stone base course?
The axial loading combined with the criteria mentioned above (mainly P. I., gradation and wetball) restrict the material significantly. This provides a high quality base that is easy to work, and the finish (if done correctly) is slick and smooth. This material (when processed correctly) sets up like concrete.
I am familiar with the CBR test method, but only with regard to soils. Also have had some experience with Mr, but only in Research Project form.
RE: Wich important tests are required on crushed stone base course?
RE: Wich important tests are required on crushed stone base course?
BigH
Obviously, here in the states, agencies spec. matl.s based on availability and locally available resources. I beleive this to be responsible for some of the rather punitive requirements in place. Just because a material is readily available does not necessarily mean it is of minimum quality, as you well know.
Of course, I prefer rigid pavements to flexible: 13" to 15" CRCP is my favorite cherry on top.
My general geographic work area(s) would be the southwest and southeast.
RE: Wich important tests are required on crushed stone base course?
In this case, LBR = Limerock Bearing Ratio, which is equivalent to about 80% CBR.
For DOT work, the minimum carbonate content is 60 to 70 percent- this allows the base layer to 'set.'
RE: Wich important tests are required on crushed stone base course?
RE: Wich important tests are required on crushed stone base course?
You lucky so and so. S. Florida...now that that sounds like a winner.
I like the limestone.....have had considerable experience with it. If set-up correctly, it is tough to beat.
RE: Wich important tests are required on crushed stone base course?
I would recommend 1-1/2 inches of Type S3....no S1 except on moderate to heavily traveled roadways, and NEVER for a parking lot.
RE: Wich important tests are required on crushed stone base course?
We usually spec 1.5 inches bituminous for low volume road sections such as parking lots. The quality of the ubiquitous sand and limerock material lets you get away with that, but poor drainage can still kill the road.
RE: Wich important tests are required on crushed stone base course?
Are you with one of the "megafirms" or local firm?
RE: Wich important tests are required on crushed stone base course?
RE: Wich important tests are required on crushed stone base course?
Hope your work is holding up. Looks like some things are starting to unfold again.
RE: Wich important tests are required on crushed stone base course?