roughen concrete surface of garage ramps for traction

[ajk1]

The contractror has put a smooth trowel finish on a new parking structure ramp, nothwithstanding our spec requirement for a non-slip swirl trowel finish. How can we rectify so cars have proper traction, without doing it in a way that will be a maintenance issue? Is there equipment that can modify the concrete surface to increase traction, and if so, what is the equipment called? I was thinking of something that would cut shallow closely spaced grooves, transverse to the direction of car travel, into the concrete surface.

 

[BAretired]

Let the contractor propose something. It's his error.

BA

 

[BUGGAR]

What is a non slip swirl trowel finish? Any finish with a trowel will be smooth. Isn't a swirl trowel finish just a steel trowel finish applied by a rotary finisher? How did you specify non slip.

It's common to grove transverse, closely spaced grooves in highways so the equipment exists.

 

[Canuck67]

Grooves in a herringbone pattern are common. I have been called in to deal with issues on steeper ramps that had trowel or thin waterproofing membrane finishes.

As BA suggests, let the contractor propose a solution. Scarification of the top surface may work, but will slightly reduce the concrete cover to the reinforcement. The end result of scarification is a series of closely spaced grooves, but it likely won't look all that great. A heavy shotblasting might also work, but I would want to test that first.

 

[TLHS]

Out of curiousity, is there a reason you wouldn't have just broom finished it originally? It's a less labour intensive finish.

 

[ajk1]

Standard finish on parking garages where there is no waterproofing traffic topping required by CSA S413 (i.e for slab-on-grade and for the cast-in-place topping on top of precast double tee slabs) is a non-slip swirl trowel finish. Perhaps I am not using the precisely right terminology. Perhaps the correct terminology is "manual swirl trowel finish". Yes a broom finish can also be done, but that is not what I generally see in parking garages. I will check the correct terminology with a concrete finisher, but my main question is how to correct the slab which has already been cast.

Yes, as per standard practice when the contractor makes a mistake, we have asked the contractor how he proposes to correct it, but he says that he is not sure.

If scarification produces a series of parallel closely spaced grooves, then thatwould do it. But I did not realaize that was what scarification did. If you are sure that it does, then that is what we should ask the contractor to do. Are you sure that "scarification" produces a neat clean regular appearance of parallel shallow (2 mm?) grooves?

 

[TehMightyEngineer]

What about acid etching the concrete surface in a series of stripes? Probably quite labor intensive but should make a rough surface with minimal concrete removed.

Maine EIT, Civil/Structural.

 

[cvg]

non slip swirl trowel is not a standard finish for ramps, only for exterior flat slabs, this should have been rough broom or scored, for example:

Texturing
shall be performed by applying a longitudinal burlap drag fol lowed by longitudinal texturing using steel tines.

Tine texturing shall be performed so that the grooves produced will be uniform in spacing, depth, and width.

Texture grooves shall be 1/8 ± 1/32 inch in width and 5/32 ± 2/32 inch in depth. The center-to-center spacing of the grooves shall be 3/4 ± 1/8 inch. If necessary, hardened concrete shall be textured by any method that will produce the required grooves.

 

[TLHS]

Scarifying would probably work if it's really shallow. Depending on the equipment you might get little grooves or it might just take the smoothness out. You can also look up concrete grooving. It's more of a cutting process. It's apparently a common thing for barns. They come and either cut a series of lines or a grid pattern into the concrete. Do a google search for concrete grooving and maybe throw barns in if the result isn't very good.

 

[ajk1]

cvg- thanks for the very specific information. This is what I was looking for. since the rampo slab was not burlap dragged, is the tine texturing ok without the burlao drag?

For my inforamtion, can you clarify the following for me:

a) On an above-grade precast parking garage with say 60 foot wide by say 150 foot long ramps, which double as parking floors and are usually at <5% slope, the cast-in-place topping has what I would describe as a swirl pattern to the finish, with the peaks of the swirls slightly above the troughs. Is that not what you would call a swirl trowel finish? Is that made with a broom (I would not have thought so)?

b) The finish that I see on most municipal sidewalks is a broom finish. This is a pattern of straight lines transverse to the direction of the sidewalk. Is that the type of finish that you say should be used on the ramps? Which type of ramp do you mean that the broom finish should be used on - parking floor rampos (slope <5%) or non-parking floor ramps (generally 10% or more slope)?


TLHS- ok, thanks.

 

[Canuck67]

ajk1,

See attached photo of a scarified surface. I have worked with it in the past and it does create uniform grooves of small depth, however, scarification machines vary and you would want to verify with a test sample or similar.

The uniformity of the grooves is up to the care and control of the operator. If they are not careful, the grooves will be wavy.

 

[ajk1]

Canuck67 - That is really very good. Yes a picture is worth a thousand words. Thank you very much.

 

[cvg]

swirl is done using a steel trowel, not a broom. it doesn't really make a good non slip surface for cars, only slightly rough

rough broom
turf drag
burlap drag
tining
all provide significantly more friction for sloped surfaces and vehicles with wet tires. Anything more than 5% I would say needs a good non-slip surface.

search google for a lot of references for this, for instance here's a couple

http://roadwaystandards.dot.wi.gov/standards/cmm/cm-04-18.pdf

http://www.wsdot.wa.gov/research/reports/fullreports/637.2.pdf

 

[TLHS]

Also, you should note that uniform grooves are going to be noisier than the finish you originally specified. So keep that in mind if it's a concern.

 

[ajk1]

I am not concerned about pavement noise -- this is not a highway with vehicles travelling at 100 km/h. It is a parking garage. My questions and comments are all to parking garages, not to highways. I can see that a swirl trowel finish is inappropriate for a highways, as the crests of the swirls would likely wear down quickly under truck traffic and high speeds.

The swirl trowel finishes that I have specified and seen on many garages are fairly rough in my opinion. So I wonder if we are talking about the same thing. Maybe there are picture illustrations somewhere of the what the various finishes look like. Anyway, I lived for 20 years in an apartment complex that had a fairly steep entrance ramp that had interlocking pavers and a snow melting system below. The surface of the interlocking pavers had a smooth finish, certainly smoother than a swirl trowel finish. I never slid down or had any problem. I think there are quite a few such installations. So I am wondering why a swirl trowel finish is deemed to be no good on a ramp. Perhaps it would eventually wear down. But so would a broom finish.

For the tined finish, can the depths of the grooves be regulated? Want to keep them as shallow as possible to avoid any possible damage to the snow melting system.

Should the grooves run transverse or parallel to the length of the ramp? I would think they should parallel to avoid collecting water in the grooves. Do you agree?

Thanks.

 

[Ron]

ajk1....abrasive blasting will provide a roughened surface. For flatwork use Blastrac...a small machine with a variety of grit blast capability.

 

[bridgebuster]

I had a similar situation recently, except the contractor was trying to bond a concrete overlay to a smooth concrete surface.

http://www.eng-tips.com/viewthread.cfm?qid=366315

The sawcut grooving that Canuck67's photo should work. We typically do that on bridge decks in NY for skid resistance.

 

[ACtrafficengr]

My first thought was the thin high-friction polymer overlays that FHWA is pushing for crash reduction, but if the concrete is that smooth, I'd worry about adhesion.

 

[ajk1]

Ron - I had thought of shotblast, but it seems to me that does not leave as rough a finish as a manual swirl trowel finish (like is used on the cast-in-place topping in precast garages), unless it is aggressively shotblast and then it leaves a surface that does not look good. What do you think? I think we are going to go with the tined groove repair (as per Canuck67's comment and photo), with the grooves running parallel to the direction of traffic (same as on highways).

 

[Airsmybag]

Wheel type scarifiers can have the cutters set up to make grooves of any desires spacing. I would use cutters with carbide buttons. Operator skill is important. A chalk line on the concrete and a "front site" on the machine are a good idea to maintain parallel passes. Grooves on a highway are parallel to tafic to reduce road noise and to allow tires to displace water to prevent hydroplaning. Grooves on a parking ramp should be perpendicular to the traffic dirction to provide traction.

Shot blasting will roughen concrete by removing the cement and sand between the pieces of larger aggregate. A coarse seel shot (390) should be used. A good operator can do it with minimal patterning. The size and hardness of the aggregate will effect the possible profile produced. a scarifier is not descriminate.. it will cut aggregate and cement matrix.

Be careful that the rebar is not too close to the surface. That can open another bucket of worms if rebar is exposed.

airsmybag