Compaction of Wearing Course 1

[BigH]

Can anyone out there tell their own jurisdiction's or project's specificaitons on the required level of % of 100% Marshall density is used for primary compaction of 40mm bituminous concrete wearing course?? 19mm nominal aggregate. Thanks.

 

[Ron]

A typical range is ultimately from about 93 percent to 96 percent of the lab density. Some of that depends on the size of the lot tested. If you are testing for large placement (roadway), the a typical procedure is to use a "control strip" where the density of the control strip has to be 96 to 98 percent of the laboratory density and then the roadway must be 95 to 98 percent of the control strip. The control strip is done to "calibrate" the rolling procedure.

If small lot (parking lot), I would go with 96-98 percent of the laboratory density.

 

[BigH]

Thanks Ron. No, this is a major 4 lane National Highway. The specs call for 98% Marshall Density. Indians think the bigger the number the better. That is why they use 95% modified Proctor for all embankments even though the damn foundation soils will settle 500mm!!

Best to you and thanks.

 

[Ron]

BigH...if you have to justify your lower compaction, you can point out that "overcompacting" the surface course can lead to "bleeding", which reduces skid resistance and causes premature failure. It's ok to let the traffic do some of your compaction for you over the years, as long as it isn't too much that would lead to rutting.