District 2 LCCA Projects

Project Number	Route	Letting Date	Posted Date	Comments End	Document Links	Comments
0410-53	US 71	2/26/2027	10/23/2024	11/14/2024	0410-53 Documents	0410-53 Comments

District 2 Comments

SP 0410-53, US 71, Letting date 2/26/2027

Comment from Dan Labo, Concrete Paving Association of Minnesota, djlabo@cpamn.com, 10/25/2024

*The 20-year concrete design and 35-year concrete design are identical. Please explain the rationale why identical concrete pavement structures have different maintenance activity cycles over the life-cycle. It appears that this LCCA functionally only includes 2 designs.
*A true 20-year concrete design would most likely be an undoweled pavement. Why are undoweled concrete pavements not being considered? Please include the districts rationale for excluding this option. Many Minnesota counties successfully use undoweled pavements for similar roads.
*Running an undoweled concrete design through pavementdesigner.org (which is approved for use on State Aid projects) using the key design details provided in the documents provided, over FDR, results in an undoweled pavement of 4.25" (rounded up to nearest 1/4").
*Running an undoweled concrete design through pavementdesigner.org (which is approved for use on State Aid projects) using the key design details provided in the documents provided, over milled HMA (unbonded, though in reality this would be placed directly on the milled surface), results in an undoweled pavement of 4.5” (rounded up to nearest ¼”).
*Alt design: if a 7" pavement doweled concrete pavement is desired, the district could pave over FDR (much like the bituminous design) or could mill 5" and place a 7" doweled whitetopping design (to match final elevation of bit. design). Were these options considered? Please explain if not considered. Please provide the rationale for exclusion if they were considered. My calculations show 7" over a 5" mill, would have this design be about 120% of bituminous, with the expected design life well over 100 years. Does the district think a roughly 25% first cost increase is worth the 5x+ design life increase? Please explain your rationale as part of this response.
*Alt design: 6" doweled pavement, you could use 3/4" dowel bars as other states have used (i.e. Iowa). A 4" mill, 6" doweled pavement would have this design be about 110% of bituminous, with the expected design life being well over 100 years. Here, you could have dowels and a substantially increased design life, and the LCCA would be within ALT-bid thresholds (despite being a substantially longer life pavement and getting nearly no credit for it).
*Alt design: 6" undoweled pavement: a 4" bill, 6" undowelded pavement this would be the low LCCA, with bituminous being about 101%. The 6" concrete design would again have over a 100-year design life and with a lower LCCA than other options. Why has the district not considered this option? It stands to greatly benefit the public as it's substantially more cost effective. A roughly $300k initial cost increase would result in 5x the design life, which greatly increases ROI.
*Alt design: 5" undoweled pavement: a 3" mill , 5" undoweled pavement this would be the low LCCA, with bituminous being about 115%. The 5" concrete design would again have over a 100-year design life and with a lower LCCA than other options, beyond alt-bid thresholds even. Why has the district not considered this option? It stands to greatly benefit the public as it's substantially more cost effective.
*Alt design: 5” undoweld pavement over FDR (identical to bituminous design except for mainline pavement). The LCCA shows this option to be essentially identical to the 5” bituminous design but achieves a 5x design life increase, greatly increasing ROI.
The FHWA and others have highlighted the fact that LCCA is particularly useful when iterations are performed in order to attempt to find more cost-effective solutions. Several alternative designs have been provided which validate the value of iterations as noted by the FHWA; as several superior options have been found, likely resulting in a new lowest LCCA option. The initial LCCA showed bituminous being substantially superior to concrete over the LCCA (at 159.4%), and it can easily be shown that concrete is lower-cost over the LCCA (by up to 115%); which represents a dramatic swing. Thank you for providing an opportunity to comment, and we look forward to seeing a revised LCCA and draft pavement change being posted soon in accordance with MN Statute 178.145 Sub. 2b.

Pavement Design Engineer responses 12/2/2024

"The 20-year concrete design and 35-year concrete design are identical..."

Response: The roadway is not conducive to a 5” Whitetopping due to extensive stripping on a Full Depth HMA pavement. The minimum 20 year PCC design is a 7” doweled pavement which happens to be a 35 year PCC design.

"A true 20-year concrete design would most likely be an undoweled pavement..."

Response: This roadway has extensive HMA stripping so a Whitetopping design is not an appropriate rehab for this pavement.

"Running an undoweled concrete design through pavementdesigner.org (which is approved for use on State Aid projects) using the key design details provided in the documents provided, over FDR, results in an undoweled pavement of 4.25" (rounded up to nearest 1/4")."

Response: Pavementdesigner.org is not approved for MnDOT projects, just State Aid projects. The last time I did a PCC pavement on top a FDR, CPAM said next time just do a mill and fill with PCC pavement.

"Running an undoweled concrete design through pavementdesigner.org (which is approved for use on State Aid projects) using the key design details provided in the documents provided, over milled HMA (unbonded, though in reality this would be placed directly on the milled surface), results in an undoweled pavement of 4.5” (rounded up to nearest ¼”)."

Response: Pavementdesigner.org is not approved for MnDOT projects, just State Aid projects. A 4.5” HMA mill and 4.5” PCC fill will have 4” of 2002 HMA remaining on top of 7.5” of 1977 stripped HMA. The roadway distress is coming from the layer of stripped HMA on top of soft existing soils. An FDR design would remix & recompact the stripped HMA layer with a layer of geogrid would improve the strength and stiffness of the new subbase.

"Alt design: if a 7" pavement doweled concrete pavement is desired, the district could pave over FDR (much like the bituminous design) or could mill 5" and place a 7" doweled whitetopping design (to match final elevation of bit. design)..."

Response: These options were considered but the price of PCC pavement is higher than the neighboring districts, making it less competitive to HMA pavement. A 5x in design life on paper does not correspond to the service life that being achieved in the field, do have actual performance data to prove this concept? The PCC pavement design is design to reduce mid panel cracking and faulting, once dowels are introduced, the faulting becomes negligible. All pavement models do not account for environmental effects (weather, salt usage, etc…) which affect the PCC pavement more than traffic.

"Alt design: 6" doweled pavement, you could use 3/4" dowel bars as other states have used (i.e. Iowa)..."

Response: CPAM did not want me to use 1” dowels for 6” PCC pavement due to constructability, why is ¾” dowel more constructable than a 1” dowel? The roadway distress is coming from the layer of stripped HMA on top of soft existing soils and a mill & PCC fill will not address this problem.

"Alt design: 6" undoweled pavement: a 4" bill, 6" undowelded pavement this would be the low LCCA, with bituminous being about 101%..."

Response: The roadway distress is coming from the layer of stripped HMA on top of soft existing soils and a mill & PCC fill will not address this problem. A 5x in design life on paper does not correspond to the service life that being achieved in the field, do have actual performance data to prove this concept?

"Alt design: 5" undoweled pavement: a 3" mill , 5" undoweled pavement this would be the low LCCA, with bituminous being about 115%..."

Response: The roadway distress is coming from the layer of stripped HMA on top of soft existing soils and a mill & PCC fill will not address this problem. MnDOT experience with 5” whitetoppings shows it will never come close to a 100 year service life.

"Alt design: 5” undoweld pavement over FDR (identical to bituminous design except for mainline pavement)..."

Response: The last time I did a PCC pavement on top an FDR, CPAM said next time just do a mill and fill with PCC pavement. A 5x in design life on paper does not correspond to the service life that being achieved in the field, do have actual performance data to prove this concept?