Flexible Pavement Subgrade Question
Flexible Pavement Subgrade Question
(OP)
We have high clay soils in this area of Central Texas and this is a high volume of traffic street (arterial). The contract was awarded with the contractor having Option A- 2.5" HMAC over 8" crushed limestone compacted base course over 6" lime stabilized subgrade or Option B 2.5" HMAC over 12" crushed limestone compacted base course over MC 30 prime coat or an emulsion applied to raw subgrade.
The contractor is going with Option B. We are having doubts about Option B.
Has anybody had experience with the Option B pavement section? For this area, lime stabilized subgrade is the standard, so for me, I am out of my comfort zone with Option B.
Thanks
The contractor is going with Option B. We are having doubts about Option B.
Has anybody had experience with the Option B pavement section? For this area, lime stabilized subgrade is the standard, so for me, I am out of my comfort zone with Option B.
Thanks





RE: Flexible Pavement Subgrade Question
Depending upon your position one may sometimes elect to walk away of some work where good practices are not being followed, but if not the convenient thing a written statement with copy receipt may do something to salvage future liabilities if the other parties are not wanting to follow some sound warning.
RE: Flexible Pavement Subgrade Question
Did you ask TX LTAP? (http://tee
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928
RE: Flexible Pavement Subgrade Question
ACtrafficengr- Your answer is more in line with what I am looking for. You have confirmed my feelings that a prime coat is not enough to stop the migration.
RE: Flexible Pavement Subgrade Question
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928
RE: Flexible Pavement Subgrade Question
RE: Flexible Pavement Subgrade Question
As AC noted, fines migration won't be stopped by the emulsion...it is a feeble attempt at a water resistive barrier, that doesn't really need to be there...the filter fabric would be more effective.
I agree with BigH...go with what is known to work. Changing things in areas of known difficult can be a very expensive experiment.
RE: Flexible Pavement Subgrade Question
Contractually, if the contractor has been given an option, you can issue a Change Order for a different spec... Contractually, it's your only recourse.
Dik
RE: Flexible Pavement Subgrade Question
Who is your client (or are you the client)?
Is there an actual issue with the pavement section, or is it that YOU are just uncomfortable with it?
Is that section used on other projects that you have not been involved with?
Have you reviewed the actual design, that I would assume has been engineered by a consultant (or 2) to meet the standards of the governing agency?
Has the agency who is getting the road reviewed and accepted the design options?
While there are some valid concerns, there are also some assumptions that the design does not meet the standard of practice in the area just because it is not widely used. Is this true, or is it that it doesn't meet YOUR standard of practice?
By the way, what are the subgrade soils? Plenty of advice being given without the basic site information. We too have expansive clays, but they do not cover 100 % of the area. On our expansive clays, we prefer full depth asphalt; however, lime/cement treatment may also used, as well as aggregate base (without a tack coat, fabric or subgrade treatment).