Thread: Efflorescence and thin cracks on concrete porch/deck

This is an open, raised concrete "deck" with poured concrete over corrugated steel with steel framing. There are very thin cracks with efflorescence in the concrete at the end of the deck on the surface. Wondering if efflor is from water getting into the cracks or water possibly traveling under the concrete and on top of steel and migrating upward. Any ideas as to what is happening and how significant this is?

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To answer part of your questions:
Concrete is porous.
Concrete wicks, absorbs water.
Water defies gravity.

Questions: 1: Where is the corrugated steel in relationship to grade?
2: You mention the concrete deck is open. Does this mean open to the elements?

I see no efflorescence issues per-say.
Cracks can be from shrinkage, expansion, poor curing, removing the frame prematurely, poor concrete batch, PSI strength, , etc...
The cracking at the ends leads me to believe batch, cement hydration curing.

Any images from further back?

Originally Posted by ROBERT YOUNG

To answer part of your questions:
Concrete is porous.
Concrete wicks, absorbs water.
Water defies gravity.

Questions: 1: Where is the corrugated steel in relationship to grade?
2: You mention the concrete deck is open. Does this mean open to the elements?

I see no efflorescence issues per-say.
Cracks can be from shrinkage, expansion, poor curing, removing the frame prematurely, poor concrete batch, PSI strength, , etc...
The cracking at the ends leads me to believe batch, cement hydration curing.

Any images from further back?

Hey Robert,

Its more of a raised patio and its about 8 feet off the ground. Yes, open to elements with no cover. Here are a few more photos.

My concern is that water may be entering the area between the concrete and corrugated metal and migrating to the far (downward most) end of the patio, then finding a way upward due to possible lack of drainiage plane. Or, water may just simply be entering at the surface.

I would say that water is getting under that concrete and wicking up though the stamped concrete. Either way that patio is not long for this world.

There are (2) guarantees with concrete. One, it will get hard, & two, it will crack.
So whether water is absorbed or wicked is your conundrum?
It is dried cured/curing concrete being supported by corrugated steel.
Within the concrete should be steel bar, re-bar.

I see no issues with the concrete.
Call in the specialist...to have then take a kick at it.
Its aging and cracking and so am I.

How do the supports and corrugated pan look?

Originally Posted by Scott Patterson

I would say that water is getting under that concrete and wicking up though the stamped concrete.

Morning Scot.
Hope you are in good health and spirits today.

While some may agree, others like myself may not.
One thing we can agree on, water is allowing minerals to rise to the surface and remain after the evaporation has completed.

IMO, nothing more than "Plastic-shrinkage cracks."
Do not let perception influence your hypothesis.


These plastic-shrinkage cracks are most common in slabs. Relatively short and have occurred before final finishing on days when wind, a low humidity, and a high temperature occur.

Here is a great articular on Concrete by the CFA or Concrete Foundations Association. No need for scholarly articles in this instance but there are many is required…

Best regards.

The additional photos give a clearer picture. Look up plastic shrinkage cracking. I think the cracking is an installation issue and the efflorescence is the result of the cracking.

Shrinkage Cracking on Stamped Concrete - The Concrete Network
Stampable Overlay Efflorescence - The Concrete Network

Thanks, guys. Yes, I had recommended a specialist but I may not hear what that person says, so I wanted to try and get more info for next time I see this. Yes, this structure (and other similar ones this house has) would be very expensive to construct.

Originally Posted by Randall Clark

This is an open, raised concrete "deck" with poured concrete over corrugated steel with steel framing. There are very thin cracks with efflorescence in the concrete at the end of the deck on the surface. Wondering if efflor is from water getting into the cracks or water possibly traveling under the concrete and on top of steel and migrating upward. Any ideas as to what is happening and how significant this is?

Randel, upon further reflection, this type of stamped concrete covering would be sealed and likely yearly or by-yearly.
That is an elaborate raised deck. I removed much of my prior post seeing I would likely estimate a higher cost for that raised concrete deck and everything attached. must have been a nice home to inspect.

If you can, ask the homeowner for the results of the concrete surface tests, if any were performed.

I suspect what appears to be efflorescence at a glance, is nothing more than surface tension mars from using the wrong concrete weather coating.
Hypothesis, the clearcoat molecular bond breaks as it is stretched leaving a haze you can not see through.
There might be efflorescence under the coating but over time it would leave a convex impression.A bump.

Question, Randal, did you use you finger to feel the surface at the suspect efflorescence?
Did you use a awl or knife to scrape a small area, about 1/4 inch off the surface?

In this situation, I suspect efflorescence would be hard crystalline mineral.
The deck is flat, horizontal and facing the atmosphere. Not vertical. Also susceptible to foot traffic that would effect a powdery residue.


Just my 2 cents.
.

I have constructed a dozen steel pan concrete decks and swear by the process
The steel pan is supported by decay resistant i.e.pressure treated framing built with a border and center girder if needed No joists The steel pan has 1/4 inch rebar and good to go
Very careful to keep wet as the concrete cures extreme heat actually very hot to the touch is created because of the steel pan I recommend constant soaking for 24hrs

- - - Updated - - -

I have constructed a dozen steel pan concrete decks and swear by the process
The steel pan is supported by decay resistant i.e.pressure treated framing built with a border and center girder if needed No joists The steel pan has 1/4 inch rebar and good to go
Very careful to keep wet as the concrete cures extreme heat actually very hot to the touch is created because of the steel pan I recommend constant soaking for 24hrs

- - - Updated - - -

I have constructed a dozen steel pan concrete decks and swear by the process
The steel pan is supported by decay resistant i.e.pressure treated framing built with a border and center girder if needed No joists The steel pan has 1/4 inch rebar and good to go
Very careful to keep wet as the concrete cures extreme heat actually very hot to the touch is created because of the steel pan I recommend constant soaking for 24hrs

- - - Updated - - -

I have constructed a dozen steel pan concrete decks and swear by the process
The steel pan is supported by decay resistant i.e.pressure treated framing built with a border and center girder if needed No joists The steel pan has 1/4 inch rebar and good to go
Very careful to keep wet as the concrete cures extreme heat actually very hot to the touch is created because of the steel pan I recommend constant soaking for 24hrs

- - - Updated - - -

I have constructed a dozen steel pan concrete decks and swear by the process
The steel pan is supported by decay resistant i.e.pressure treated framing built with a border and center girder if needed No joists The steel pan has 1/4 inch rebar and good to go
Very careful to keep wet as the concrete cures extreme heat actually very hot to the touch is created because of the steel pan I recommend constant soaking for 24hrs