I suggest you take a look at AWWA C-950 to observe the
different:
a) Types
b) Grades
c) Liners
of RTRP. In addition, epoxy resin is superior. I recently witnessed mechanical testing conducted on GRE pipes as per
ASTM D-638, 1599 & 2412. I accepted old MTC for ASTM D-2925; since elastic modulus can readily be interpolated and is based on the resin characteristics.
I would strongly recommend AWWA C-950 to the basis of design and inspection.
Cheers