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Pavement design using roller-compacted concrete
7

Pavement design using roller-compacted concrete

Pavement design using roller-compacted concrete

(OP)
O.K. for starters, I know nothing about RCC (roller-compacted concrete).  What I know is they use it for gravity dams, it has about a zero slump, and it's compacted using a roller (duh).  I'm assuming that it's batched on site, as a concrete delivery truck needs some slump to mix and chute from the back side of the truck. Then again. . .

Here's a few of my questions:  If you design an 8-in thick industrial pavement using 4-in slump, 4,000 psi, 6 percent air content concrete, how would you design an alternate for RCC?  How do you get air content into the RCC?  

Of what possible benefit would you get from a program such as this:

http://www.cement.org/bookstore/profile.asp?id=2309

Thanks in advance for any/all assistance.  We have a client that wants us to specify RCC for his developemnt and we are talking about a 1,100 cy pavement job.  I think the scale of the job sounds too small for this design change.  Then again. . .

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

RCC has no specified air content and is not delivered in transit mixers or generally using a chute. the book by the PCA is likely a very good resource, although I have not used it because I have been more involved with the dams. I have gotten good advice by talking with PCA engineers.  

RCC can be batched on-site or done at a central plant and delivered to the site. It is generally handled as you would handle borrow material on an earthwork project and not unlike the process for soil cement. Dump trucks for delivery, graders and dozers to spread it, smooth vibratory rollers to compact. Place in 12-inch lifts and compact to the final thickness. No finishing, just 7 day cure like any other concrete.

My question is how will you get a smooth riding surface? RCC and soil cement are usually done for the base course with a riding course placed on top.

RE: Pavement design using roller-compacted concrete

fattdad...I have designed several RCC pavements for industrial applications.  We were not necessarily concerned with "ride quality" as in a surface tolerance comparable to conventional PCC; however, we did require at least a surface flatness as the industrial applications must have a relatively flat surface on which to work or dangerous conditions can result.

RCC is usually batched at the site or you might be able to convince a ready mix supplier to batch it at a nearby plant; however, with essentially no slump and no latent water, you can't have a long travel distance.

Otherwise, I agree with cvg's comments.

RE: Pavement design using roller-compacted concrete

Find a local RCC installation and show it to the client as a typical example and then explain the differences between that and what you may suggest. This should help to satisfy some of his early opinions and show that you are looking into his suggestions.

Dick

RE: Pavement design using roller-compacted concrete

Depending on the moisture content you may be able to deliver by truck mixers and discharge by chute. Another option would be to use a continuous mixer (pugmill) on site.

I also don't know anything about RCC but expect with the use of a grader you would get similar tolerances to CSM which is roadbase tolerance rather than concrete slab.

I think its the wrong spec for the job and PQ Concrete would be a better option.  

RE: Pavement design using roller-compacted concrete

(OP)
to put this matter into context:  My client is a manufacturer of Portland cement and knows full-well what RCC looks like.  They have likely seen it on other projects.  This is a case where I may be less informed than my client.

I had never thought of finding a local batch plant and having the zero-slump RCC delivered in a dump truck. Believe it or not, that may actually work as I have a supplier close by the job.

cvg mentioned 12-in thick lifts.  I like the sound of that, but it seems thick for an industrial pavement.  Is 8 in an option for placing RCC (i.e., is 12 typical minimum)?

How do you manage air content?  Is it a moot point owing to the fact that even with compaction, you'll end up with an air content that'll ultimatly work for freeze-thaw conditions?

Thank you all so much for your help!

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

12 inch loose lifts, compact down to about 8". For most of my projects which are dams, levees etc. the finished thickness is much greater than 8" and the RCC would be similar to mass concrete, however there is no reason you can't place just one lift, compact it to 8" finished thickness and be done. If 8" is your final thickness, I would avoid trying to place it in more than 1 lift as the lift interface could become a cold joint if work does not progress quick enough. Durability tests can be run to determine the resistance to freeze thaw and erosion. The mix design should also include tests to determine the necessary cement content vs compressive strength. I would advise doing these tests before bidding the contract.

Regarding timing for transporting and placing the mixture, these are specs from my most recent project:

A.    The CONTRACTOR shall minimize the total elapsed time between the addition of water to the mixture and the completion of compaction.  Time limits for handling, transportation, and compaction of the RCC shall be as follows:
a.    Maximum transportation time from mixing to the start of spreading shall be 30 minutes.
b.    Compaction shall start within 15 minutes of spreading.
c.    Maximum elapsed time between introduction of water to the mix to final compaction shall be 60 minutes.
 

RE: Pavement design using roller-compacted concrete

fatdad -

This is an opportunity to work with/for your client so he can use the project as a demonstration project and you can document the use and application for a non-mass installation. If the client is one of the large international cement producers that have more knowledge and technical support than an ordinary concrete engineer.

The specs you posted require nothing more than a stop-watch to insure quality, which is minimal.

Do not worry about air content since that is in realm of cast concrete and not zero-slump concrete. The vibration and compaction will change the air content of the placed concrete plus there is no guarantee that the air is too much more than the normal 1.5% generally in any concrete.

When you are dealing with zero-slump or very low slump concrete, the shape of the aggregate (rounded, spherical, etc., has is a very big factor in the performance. It is not that much different than the soil proctor tests commonly run using the locally available aggregates. It is good to have a supplier that is experienced with RCC concrete, but that could be controlled by your client, since concrete suppliers have their prime cement suppliers and cement producers also have their prime customers/producers. The best of both worlds would be a concrete supplier that is vertically integrated to the cement/aggregate supplier from a standpoint of technical assistance and future projects.

Dick

RE: Pavement design using roller-compacted concrete

(OP)
Just to add some further insight.  I learned today that my client wants RCC at their site to showcase an alternate and an effective use of this alternate in pavement construction.  What better way to showcase a portland-cement bawed product in a non-typical setting then your own facility!

One item of note:  We are somewhat concerned about how to handle contraction joints in RCC installation.  Recognizing that all concrete cracks (and that RCC is concrete), and recognizing that the service load will be fully-loaded highway trucks that are moving portland cement cracks that loose aggregate interlock may lead to premature failure.  In a slump concrete, we can use dowel baskets at the control joints as a backstop to aggregate interlock.  In RCC I guess this is not an option.  That said, I'm suspecting that RCC is less susceptable to slab curl and the like.

I really appreciate everybody's comments.  My client has good relations with the Portland Cement Association and is working with their engineers to look at RCC design for the anticipated loading and site-specific CBR values.  I'll give you all an update.

Have a great weekend!

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

fattdad, I would be in the same boat as you with RCC used in an industrial pavement application.  Please keep us advised as to how this goes.  But without knowing much, I would think that the RCC would be thicker than the normal concrete pavement.  I normally start with 8" for industrial pavements, so 12" finished depth for a RCC pavement without all the jointing issues sounds attractive to me.

RE: Pavement design using roller-compacted concrete

Interesting thread. Based on fattdad's info about his client I withdraw my comment that PQ Concrete would be more suitable than RCC.

Having had a think about this and compared to the use of CSM (cement stabilised material) I would investigate using a paver (i.e the type used with bitumenous road surfacing). I think a good level control could be achieved and the augers tend to lay the material evenly prior to compaction. The semi-dry (or dry??) concrete could then be supplied by a pugmill at site, into trucks and then reversed up to the paver.  

RE: Pavement design using roller-compacted concrete

fattdad

If the cement producer is really controlling things, they may have their mind on a certain type of application and want it done correctly, since it is critical for them to do it right.

Although concrete pavers use less cement they have been used successfully in international projects with heavy loads on marginal soils (heavy duty straddle loaders in ocean ports handling multiple containers or for airport taxiways). This could also be an attractive alternate, depending on the clients engineering/promotional interest.

If not, just rely on the technical support offered by the client and learn something with a different application. - you know this is not a project that the budget is not as important as the performance and educational/promotional value.

Dick

RE: Pavement design using roller-compacted concrete

fattad,

Any chance when the project goes to construction you could give us a heads up?  I believe you and I are in the same vicinity, and if the project is nearby I would like to see the RCC placement process if possible.

Dan

RE: Pavement design using roller-compacted concrete

For your work what is the difference between RCC and cement stabilized aggregate base?  Not much - you can batch it in a batch plant or in a pug mill - moisture content needs to be controlled and you might need to be 1% or so above optimum for effects on drying.  In our work in China - the cement treated aggregate base was placed using an asphalt paver in 12 inch lifts and compacted.  Got good results on tolerances in placement - likely much better than using a grader or bulldozer.  (Note, in Laos, we also placed the untreated base course with an asphalt paver).

RE: Pavement design using roller-compacted concrete

For a parking lot, I'd use an concrete paving machine. then roll for compaction. The surface will be better than just dump out and push around with a grader.

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Pavement design using roller-compacted concrete

Interesting article published by PCA today:

Diamond Ground RCC Replaces Failed Asphalt on US Highway 78

U.S. Highway 78 in Aiken, S.C., had deteriorated to the point where a thin resurface treatment was not a viable option. Looking for a solution to replace the failed asphalt roadway, the South Carolina Department of Transportation (SCDOT) explored multiple options, primarily focusing on minimizing traffic disruption, long-term durability, and cost of construction. The repair method chosen consisted of milling out the distressed asphalt and replacing it with 10 inches of roller-compacted concrete (RCC). To provide the desired ride quality for high speed traffic SCDOT chose to diamond grind the RCC surface rather than cover it with a thin asphalt or conventional concrete surface.

When it was successfully completed in August 2009, the diamond ground RCC pavement paved the way to add high-speed roads to the list of RCC pavement applications. For typical roads with speed limits of 45 mph or higher, a smooth road has an International Roughness Index (IRI) of 85 inches per mile or less. Approximately one week after placement, a milling machine was used to remove higher surface spots of RCC. This was followed by diamond grinding to provide the final smooth surface. After grinding, the pavement IRI was determined to be within the range of 50 to 60 inches per mile.

This project marks the first successful completion of diamond grinding RCC pavement for a major road in United States.

 

RE: Pavement design using roller-compacted concrete

(OP)
CVG,

Thanks!  I'll forward this to my colleagues and client.  This project is moving forward and I'll followup when I have anything.

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

Air content is referring to entrained air within the concrete paste itself. You will never have 0% air in any concrete aas long as it has a paste (consisting of mortar)
Even though you are rolling the concrete and getting full compaction, you will still have air entrapped withing the paste.  Don't think of it in terms of "air voids." Now I am no Dam Engineer by far, but I know concrete very well.  It's probablly safer to batch a mix with minimum entrapped air.  All entrapped air content is really good for is workability.  I personally hate entrained air in any mix.  However, you can't get rid of it even if you exclude air admixtures out of the mix design. It naturally is incorporated by the mixing action.  PCA makes an excellent book on this.  It's really an essential book if you are into concrete structures PERIOD. Every engineer needs to read it. Good Luck!

RE: Pavement design using roller-compacted concrete

(OP)
o.k., but we use air entrainment to control freeze thaw damages - not just for workability.

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

...and freeze thawing.

Thnx

RE: Pavement design using roller-compacted concrete

unless you are using conventional slump concrete - which you aren't, you will not have a significant amount of entrained air. You will have some entrapped air and you might assume 1.5 percent, but that is not the same thing as entrained air. RCC mixes are not designed for air entrainment.

RE: Pavement design using roller-compacted concrete

(OP)
So, how do you make RCC durable for freeze-thaw conditions?  I'd think the face of an RCC dam would undergo such cycles and the consequence would be unfavorable.  Are there admixtures for RCC that provide entrained air?

Be nice to me, as I'm really not that familiar with RCC, but do understand nobody wants a road that busts all up after the first really cold winter - ha.

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

I know here in Florida, almost every concrete plant batches concrete with liquid admixtures. Typically a bread and butter mix has 5 to 6 ounces per cubic yard. Rule of thumb is 1 ounce/yd^3 gives you 1% air....8 ounces/yd^3 gives you 8% air. Its not exact, but a rule of thumb in the business.

There are a few manufacture's who produce good quality liquid admixtures....

Darex is a brand I'm more familiar with.
Masterbuilders INC.
Boral INC.

Anyways, yes air admixtures are quite common!
 

RE: Pavement design using roller-compacted concrete

(OP)
Oh my (we seem to be going around in circles).  Yes, air admixtures are quite common in ready-mixed concrete.  I want to know how is RCC prepared to protect it from freeze thaw. Then again, maybe it's not prepared that way.  I don't know. Do you know whether RCC uses admistures to provide entrained air? Then again, in Florida maybe it's not to common. . .

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

Sorry fatt dad, I'm a concrete guy not a dam man.

Digger

RE: Pavement design using roller-compacted concrete

(OP)
Yeah, this is not a dam project.  You can read the entire thread above and get the overall idea of what I'm working on if you want to. . .

f-d

¡papá gordo ain't no madre flaca!

RE: Pavement design using roller-compacted concrete

I have been involved on a number of RCC pavements, primarily for industrial plants in the northeastern BC /northwestern Alberta Area. The mixing process that I am most familiar with, the aggregates are fed continuously from a surge bin (or a series of bins) via conveyor to a continuous pug mill.  Cement is applied continuous from a vane onto the aggregate stream prior to entering the pug mill.  Mixing water is applied to aggregate and cement in the pug mill. The end product is a zero slump material, truck hauled to the paving location.  I am not aware of any air entrainment ever having been added to the mixing water on the projects that I've been involved with.  I'm not sure on how air could be tested accurately in the final mixed product, short of coring and running a linear traverse on the hardened concrete.  With that stated, I am not aware of any serious durability issues with the RCC that we have tested in our frigid neck of the woods.   

RE: Pavement design using roller-compacted concrete

No knowledge on RCC, just guessing.
Would that the type of aggregates, percentage of fines, level of compaction have something to do with its duribility?

RE: Pavement design using roller-compacted concrete

Sounds like a fairly simple operatiion.

RE: Pavement design using roller-compacted concrete

diggerman:

You shall be able to answer my question in general sense. Appreciate your comments.

RE: Pavement design using roller-compacted concrete

The RCC can be paver placed as BigH mentioned.  The placed RCC is compacted like Asphaltic Concrete using pneumatic (rubber tire) rollers and steel vibratory rollers.  We test it in the field for density and moisture, referenced to a modified proctor.  We also form cylinder specimens in steel moulds for compressive strength and beam specimens for flexural strength. As for durability, we may assess the aggregates for L.A. Abrasion. Desired gradation characteristics would correspond with a good crushed granular base course product, perhaps cleaner on the bottom end.

RE: Pavement design using roller-compacted concrete

SirAl - sounds exacting like the CTAB (cement treated aggregate base) that we used in China - and it was placed with paver.  

RE: Pavement design using roller-compacted concrete

A few seem good abstracts/papers on "durability of RCC dam/pavements. The PDF seems in line with the first. The second is quite general.



1. China Experience (DAM - Freeze & Thorw Resistance Study):
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2G-4FSCV75-5&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1160014096&;_rerunOrigin=google&_acct=C000050221&_version=1&;_urlVersion=0&_userid=10&md5=b0e46c27cfd6fa18243aa03d5c641e4b

2. PCA Article (RCC Pavements):
http://www.cement.org/pavements/pv_rcc.asp

3. Abstract from University of Wisconsin Milwaukee (PDF)
 

RE: Pavement design using roller-compacted concrete

BigH - Agreed, the mix, delivery, and placing of RCC are very much the same as CSBC, more powder though.  Other than that, not a whole lot different.  CSBC was used here for years as the base structure (or component thereof) for road pavements.  The main draw back has been seasonal movements in our road beds from frost penetration.  The CSBC readily cracks under flexture, the cracks of which reflect through an ACP pavement, increasing maintenance costs, decreasing rideability, etc.   As such, there has been a move away from CSBC in recent years.
 

RE: Pavement design using roller-compacted concrete

CSBC has a much lower compressive strength than RCC without the forming or shrinkage issues. RCC is generally designed with strengths similar to conventional formed concrete and higher. You will get the same or better performance than conventional PCCP.

RE: Pavement design using roller-compacted concrete

cvg - not necessarily true.  The RCC on two dams of which I am aware had 365 day compressive strength requirements of between 12 and 14 MPa (1700 to 2000 psi) - total cementitious (cement and fly ash) of 130 kg/m3 (220 lb/ye3).  The real consideration is the weight (mass) and achieved compaction level.

RE: Pavement design using roller-compacted concrete

that may be true but seems low. I'm sure performance is fine for mass concrete dam. must have been poor quality aggregate or very little cement or both. we can get over 2,000 psi in 7 days around here using river bottom sand and gravel with no processing (except to remove the 2 inch and larger rocks) and only 6 percent cement (including fly ash). last project I worked on had two mixes with the higher strength mix being 5,000 psi at 28 days.

RE: Pavement design using roller-compacted concrete

The dams I noted are judged low-paste RCC (different from high-paste) with 60:40 cement-fly ash ratio.  What was the maximum size of your agg?

RE: Pavement design using roller-compacted concrete

material was screened for 2 inch maximum size

RE: Pavement design using roller-compacted concrete

Thought that is what appears to be happening in RCC in the States.  Some are using 40mm minus.  The ones I am talking about use up to 63 mm with 10% larger than 40 mm.

RE: Pavement design using roller-compacted concrete

posted on ENR yesterday -

Newly rebuilt Missouri dam uses roller-compacted concrete

A rebuild of Missouri's Taum Sauk Upper Reservoir dam -- following a disastrous over-topping in 2005 that sent a 20-foot wave down the mountain on which it is built -- is almost finished, and the newly reinforced earth-and-rockfill dike should be ready by April 1. The new dam uses roller-compacted concrete that was made by pulverizing rocks from the old dam. Engineering News-Record (1/27)

http://enr.ecnext.com/coms2/article_inwd100127TaumSaukUppe-1

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