Ride-on laser guided screed and rebars

[shamrock12]

Just recently had 4” concrete approach slab poured in front of my shop. The concrete contractor used a ride-on laser guided screed which I have never seen before and thought it was interesting and cool; however, I wondered what happen to the chaired rebars when they drive over them? Rebars are 1/2” spaced 2 feet on center supported by 1” chairs. Base was built out of 4” layer of crushed concrete compacted prior to the pour. Machine is 1150 pounds plus 250 pounds operator which would come out to approximately 350 pound per wheel. Do rebars get deformed? What happen if the machine drives over a chair already embedded in concrete?

This is the machine they used:

S-485 Laser Screed Leveling Machine, Power Screed | Somero

With incredible pulling power and OASIS control system, the Somero S-485 laser screed is the world's top ride-on screed leveling machine. Contact us now to order!

www.somero.com

 

[PopcornSutton]

First, once the concrete is down and under the rebar (glad they used chairs) the weight of work won't bother them, within reason.

The laser guidance on the machine would only be good for a flat level slab. Your approach would have a slop and I doubt it was used.

 

[jack stand]

I'd bet that almost half of the machines weight is the screed that during use is no longer suspended by the machine.
Laser guided slope control has been around forever and you probably have a very nice shop approach!
Now a picture would be great.

 

[ConCretin]

Properly supported steel reinforcing will bounce back after the machine passes over it. Any minor deformations aren't generally an issue.

 

[mike93lx]

The laser guidance on the machine would only be good for a flat level slab. Your approach would have a slop and I doubt it was used.

Lasers can definitely do slopes. They don't have to be set level

 

[PopcornSutton]

Lasers can definitely do slopes. They don't have to be set level

I know, but do you think someone would program it for a short driveway approach?

Heavy equipment can be outfitted with GPS and an operator can move/fill as needed per the contours.

 

[mike93lx]

I know, but do you think someone would program it for a short driveway approach?

Heavy equipment can be outfitted with GPS and an operator can move/fill as needed per the contours.

If they thought it justified bringing out the equipment, I would assume they used it as designed

 

[PopcornSutton]

If they thought it justified bringing out the equipment, I would assume they used it as designed

I suppose you're right.

 

[ConCretin]

The OP never said it was a short driveway approach. I suspect that if the contractor went to the trouble of hauling his laser screed out, it was a sizable placement. Hand screeding sloped concrete isn't the easiest thing in the world when the screed doesn't reach the formwork. It was probably easier to punch in a few grades than it was to set physical reference points or calculate elevations for wet screeding. Plus he was able to do it with less labor and produce a higher quality product.

Kudos to him for investing in this kind of equipment.

 

[shamrock12]

The new slab actually is an extension to the existing 14’ wide approach that was 24’ deep and is now 73’ deep. So they did 686 square footage extension. I thought they were going to use handheld power screed so I was surprised when they rolled out this laser guided machine. I believe they only shot a few points and then it was all set. I did notice the screed dip about a quarter inch lower along the centerline (longitudinal) in a slight V-pattern (barely noticeable) which I am not sure why it happened but they did run into trouble with the laser about halfway into the pour. Turned out the laser was bouncing off my shop window glass confusing the machine so we placed a piece of cardboard between the laser and the shop (laser was setup on the existing slab) so not sure if it had anything to do that.

It did produce a beautiful straight line grade at 2% from the existing slab to the end of approach; however, with a minor issue on one corner of approach end. Apparently some concrete got built up a bit too high against the formwork in the corner causing a shallow puddle to form when it rains. I took my 6 foot level and found approximately half an inch of difference in elevation. Most likely a quarter inch too high in the far corner and a quarter inch too low next to it toward the centerline which is where the shallow puddle developed. It concerns me a bit that spalling might occur in the future after some freezing thaw cycles. Obviously grinding the high spot would help fix some but then doing so would ruin the beautiful broomed finish. I could see this happening on a level slab pour but would have never expected that on a sloped pad with 2% grade so I was surprised to see that. What are your thoughts? Should I leave it alone and accept it as is? See photos below. They were taken after it has dried off some.

 

[BigGarage]

What are your thoughts? Should I leave it alone and accept it as is?

Yes, don't worry about it.

Dennis

 

[PopcornSutton]

Nice looking slab, joints nice and straight. Real shame about the end.