CONCRETE PAVEMENT ELEVATION TOO LOW

[bobbert]

I am new to your forum. I appreciate it.

I have a 6" thick, 12' Width, 1500' length section of concrete pavement that needs to be raised approximately 15" and widened to 24' in width. In the Houston Texas area the soils demand lime stabilization.

One solution is to remove and dispose of the existing pavement, place fill, and construct the new pavement section. This is a costly solution due to the removal and disposal of the existing concrete.

I am considering placing 6" depth by 12' width of crushed concrete adjacent to the 12' section which is too low. Then placing 8-10 inches of stabilized material on top of the 24' section (12' of concrete & 12' crushed concrete). Afterwards placing the 24' section of concrete pavement at the proper elevation.

Does anyone have any other suggestions?

I will use your suggestions and contact local contractors for cost estimates.

Your help is appreciated.

Thanks

 

[dicksewerrat]

Do an in-place destruction of the existing pavement. This will turn it into a modified crushed base. Add more base amterial to the proper depth on the virgin soils. then place your new concrete pavement. You may want to put a 'geogrid' fabric over the entire base before the pavement goes down to control reflective cracking.

 

[bobbert]

Great Idea, Thanks.

I will consider your method and obtain proposals for such in finding a solution. The geogrid fabric is a welcomed idea.

Thanks

 

[DRC1]

Is it possible to excavate the new 12 ft wide section to the bottom of the existing concrete, stabilize the base and fill to approx. 11" over the existing concrete. the crushed concrete shuold make a good base. For the amount you have to do, it would be worth a test area.

 

[BurntOnDirt]

Will the width be extended equal on each side of existing conc.?

 

[bobbert]

Dear BurntOnDirt:

The additional 12' pavement section is adjacent to and on one side of the existing 12' pavement section. Pardon the delay in responding to your help question. I returned today from the Grand Canyon, what an amazing Earth moving event.

Your question is interesting, what are you thinking?

Thanks,

 

[Focht3]

If the site is in Houston, then lime treatment may or may not be needed. Particularly when you are raising site grade 15 inches (38 cm.) Where is the site? Bellaire? Katy? The Woodlands? You can generally expect to encounter highly plastic soils for sites south of Buffalo Bayou -

I have a different suggestion: why not leave the driveway in place and put the new structure over it? I think that's what [blue]DRC1[/blue] was alluding to. You might have one lane that didn't perform as well, but that shouldn't be much of an issue with roughly 18 inches of crushed rock fill beneath the new pavement. And you shouldn't be looking at much in the way of truck traffic.



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[KRSServices]

I would lean more towards the leaving the existing structure in place and adding to it, with one caveat, concerning the widening, will this involve the use of excavation and the use of borrow materials?

If so, my concern would be to ensure the widened lanes have suffiecient bearing so as to prevent a shearing due to the unequal base and subgrade materials. The base on the widened portion should be designed conservatively so that this shearing action will be minimized.

KRS Services

http://www.krs-services.com

 

[bobbert]

Dear KRSServices & Focht3:

The site is well south of Buffalo Bayou, located in Brazoria County, Texas. The site is not a driveway, it is approximately 1500' in length, with 6" concrete paving. Most certainly, lime stabilization treatment will be required to some degree. Final geotechnical reccommendations will determine the amount and procedures for stabilization.

Focht3, I do not believe that that DRC1 was "alluding" to concerns about a driveway.

KRSServices, you share the same concern that I have. Shearing of the pavement due to an unequal base of subgrade materials.

Thanks for your help, it is very appreciated.

 

[KRSServices]

Bobbert,

Have you considered stabilization of the gravels with a resin product? I use a tall oil product (from the southeastern USA) to stabilize oilfield leases, padsites, gravel roads and base gravels up here in Alberta with success. I'm happy with the results so far. Just a thought.

However, go with whatever the geotechnical report recommends.

KRS Services

http://www.krs-services.com

 

[Focht3]

Sorry for the use of the word "driveway" - meant to say "pavement". The intent of my comments stand.

Brazoria County. An interesting area - have cousins that live in Pearland, spent a lot of time in Surfside/Freeport area while in high school (S.P. Waltrip [HISD].) Friends in Alvin, Lake Jackson, West Columbia. And I worked on the embankments for Columbia Lakes resort when Tenneco still owned it; and a few underpasses along 288. (My first encounter with a 14 ft long wild [nesting female] alligator in 4 ft tall grass happened at Columbia Lakes...) Highly plastic clays, shallow groundwater, low lying terrain - with lots of rain. And shallow (red) non plastic water bearing silts, particularly near Vogel Creek. You want to avoid open excavations in this area whenever possible -

Asphalt doesn't last too long in this area when the base is placed directly on subgrade - lime treated or not. A compacted thickness of 8 inches (20 cm) of lime treated subgrade (LTS) will crack over time, allowing subgrade pumping. And water will have easy access to the subgrade via the base material. Recycled concrete won't fare too well in this environment if the material typically lacks the fines found in Class 2 base. As a minimum, I'd put a layer of geotextile between the LTS and recycled concrete. But a 4 inch layer of lean concrete (no rebar) would be a better option. This will make the new section behave closer to the existing section, and add strength to boot -

What else have you considered?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[KRSServices]

Bobbert,

If the conditions described by Focht3 are accurate, I've built miles of roads on muskeg and worse conditions than you have described. First off, do you have access to some 2" minus pit run and some 1" road crush? I have used several versions of the following structure for a number of years. The subject road section is only 450 m. Last year I constructed about 1.5 miles this structure on a 14 m wide urban road (47'). The structure was actually about 30", but the silts were relatively firm. In a particularly ugly fluvial fan (wet/saturated silts and clays, high groundwater, constant de-watering), we had a design based on the 4' structure.

For a heavy loading, the structure is going to need to "float" or bridge as it were. Excavate 3' to 4', or as necessary to ensure a 3' to 4' constructed structure, including asphalt. The excavation will need to occur with a wide pad and have to proceed gingerly to minimize disturbance from station 0+000 to 1+500. Place a heavy geocloth on the bottom and up the side of the sub-ex. Begin placing the pitrun very carefully from 1+500 to 0+000. Since the silts are saturated and wet, the first lift will probably be 8" or so. Static roll, and if it begins to shift, get off of it and let it settle down. Reinforce with some geogrid, placed by hand. Begin placing another lift of pitrun followed by the 1" crush. Next place 3/4" road crush as your base and at least 4" of ACP.

The pitrun placed on the geogrid should be able to withstand some vibratory compaction. If the conditions are very wet or quite soft, the pit run should be substituted with 1.5 " crush.

The structure, which should be reviewed by a geotech maor familiar with your setting, could be:

- 6" ACP
- 10" 3/4 Crush
- 8" 1" Crush
- 12" Pit Run or 1.5" Crush
- Geogrid
- 18" pit run
- Heavy fabric

Total structure: about 42" (including ACP)

This would be tied into both sides of the existing structure. I would also investigate the use of the crush to raise the grade without disturbing the existing structure. Depending on the costs, it may be cheaper to recycle the concrete and construct the new grade as a uniform structure. Since freezing will not be an issue, this should be a good statring point if you are still looking for ideas.

PS, your site personnel had better know what they are doing because particularly in the early stages of backfill, too much disturbance will be disasterous and costly.

Gene

KRS Services

http://www.krs-services.com

 

[DRC1]

Focht 3 was right, I was suggesting leaving the existing pavement intact and in place. The filter fabric to exclude fines is an excellent suggestion. The base is going to be rather thick on the new section so it would seem it would be okay. However I am not from Texas (although I have visited several times and enjoyed it thoroughly), so some of the guys from Texas in the forum can probly give you better detailed suggestions. Good Luck!

 

[bobbert]

Thanks to all for the information and help.

I will provide basic plan and profile drawings for the proposed top of curb elevations for the pavement and drainage improvements.

In addition, provide several methods for the removal/reuse of the concrete in the form of details included in the plans. Bid documents will contain options and specifications for the contractors for the various procedures.

Anyone have other suggestions?

Thanks,

 

[SirAl]

An interesting thread. As per usual, some good suggestions brought forward.

If the information is not available on file, I would undertake a coring and drilling program to verify existing roadbed soil conditions. In general, I prefer the crack & seat approach of breaking the concrete prior to construction. I am not a big fan of 'sandwich' construction in most situations as this could trap free water between the new and old pavements. Never the less, if subgrade conditions are poor, you could open a 'Pandora's Box' by disturbing a structure that is currently bridging a mess.

 

[KRSServices]

Bobbert,

You may want to consider inserting a few Provisional Items in your contract with reference to additional excavation or "specialized aggregates or materials" in case some really nasty conditions are discovered. This will help to mitigate the costs from spiralling. SirAl had a very good idea with reference to coring the existing area to get a snapshot of existing conditions.

KRS Services

http://www.krs-services.com