Spalling Concrete

[Haqyusof]

hi im from Malaysia and im new in this group. Hope you guys can help me.
My issue is spalling concrete occurred on the ceiling slab (600mm x 600mm x 60mm in depth). the reinforcement bar is not corroded and no sign of water ingression. Above the defective concrete is ramp area and open air . the concrete cover is 50mm+
What is the cause of the spalling concrete.?

 

[jayrod12]

Is it possible someone tried installing a shallow drop-in type expansion anchor? I've seen something similar happen however there was 100% evidence of something heavy attempting to be hung from the concrete with only 40mm of embedment. It popped off a similar sized chunk of concrete.

 

[BridgeSmith]

The broken concrete above the bottom mat of reinforcing indicates to me that likely something very heavy with a small area of contact was dropped on the floor above; perhaps something like a large safe or vending machine dropped on its corner.

Where is the spall relative to the floor above? Would you be able to mark it on the photo?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Haqyusof]

This is a concrete spalling location.
can it be the vibration of a heavy vehicle? From the information I got, there was a food truck event being held around the road, and the ramp was the exit and entry point for the food truck. The weight of the food truck is estimated at 3 tons

 

[Ingenuity]

Was the spalling a recent occurrence, or present for some time?

May be a failed rod anchor embedment, similar to that jayro12 stated. The adjacent hangers have spring dampers indicating that they support/hang mechanical equipment, so I assume this area is a mechanical equipment room.

Maybe the anchor temporarily supported a chain block (hoist) and someone lifted too heavy equipment and resulted in failed anchor and spalled concrete.

 

[hokie66]

Jayrod12's theory sounds likely to me. A short expansion anchor installed wholly within the cover concrete would have limited tensile capacity.

 

[Haqyusof]

The hanger had been installed long before. This damage occurred in the HEX room and the damage has just occurred. This building has been around for 10 years. Is caused by a vibration of a heavy vehicle on the ramp.?
what is the best caused should i tell them?

 

[Haqyusof]

From the information I got, no one is drilling or installing the expansion anchor on the ceiling slab surface.

 

[phamENG]

Are those pavers or stamped concrete on the ramp surface? Is there any sign of damage to the surface that would indicate an impact as BridgeSmith suggested?

Have you been able to look closely at the point of failure? What is the condition of the concrete in the vicinity of the spall? Is it solid, or is it flaky/powdery? How about the bars? We can see there's no corrosion, but what about other damage? Any appearance of tensile elongation? It's a long shot, but unless you can prove otherwise I wouldn't rule out an overload situation right there. Though, given the proximity to the beam it may be a compression failure rather than tension - you'd have to look at the design more holistically than we can with the limited information.

 

[kieran1]

Is poor concrete compaction a possibility? trapped air void in small area leading to spalling over time when loaded from above?

Kieran

 

[JAE]

Is this a case where this slab is bending in a two-way action, with both x and y tension stresses - combined with some significant horizontal shear stress near the bottom at the rebar interface?

Are there other areas near "corners" of slabs where smaller cracking or spalling is starting as well?

 

[hokie66]

Would be interesting to hear from Ron, but I wonder if it could be alkali-aggregate reaction. A petrographic study would determine if the blowout is caused by the concrete material itself.

 

[bridgebuster]

@Hagyusof - a few questions: How old is the slab? Did you sound the bottom to determine the extent of the spall/hollow? How much bottom cover? What's the gradation of the aggregate?

I've see plenty of under bridge deck spalls. it's usually caused by rebar corrosion but I don't see any rust. Sometimes you can get a small air pocket or water pocket and that can cause a blowout. I noticed a fracture above the main blowout.

 

[hokie66]

bridge,
The OP said the structure is about 10 years old, and the bottom cover is "50mm+".

 

[r13]

Moisture and high humidity can cause the problem, if there is crack and internal weakness. I didn't see any coarse aggregate, is there sand pocket somewhere?

 

[Tomfh]

Some sort of punching failure due to extreme point load? Is there any damage on the top surface?

I’d be removing all the underside spalling and looking really closely top and bottom to get a clearer picture.

 

[Tomfh]

A short expansion anchor installed wholly within the cover concrete would have limited tensile capacity.

But why would that cause a 600x600 blowout?

 

[hokie66]

Tomfh,
Yes, it think I agree. Hadn't focused on the size of the spall.

More and more, I am leaning toward defective concrete. As retired13 pointed out, there doesn't seem to be much coarse aggregate, and I wonder about an alkali-aggregate reaction.

 

[Haqyusof]

i didn't see another crack from below. mean is not AAr reactions. but i get the photo of crack on the above ramp. but the crack is about 4ft away from the spalling concrete.

 

[r13]

If you suspect the problem was from the drive way, you can use "pull chain" method to detect presents of defectsive concrete by hearing the sound. I don't know the better way to handle from below but to remove the remaining loose concrete and hammering around.