I don't see anything abnormal for a slab that was wet-cured this long. By now, I'm willing to bet that it's all pretty much whited-out. Even if there was minor marking/color change later where the wheels ran, I wouldn't let it bother me, as it would make me think of when my daughter was younger, having fun.
Concrete Slab Can anyone explain this?
- Thread starter JayJones
- Start date
No rain for a while, so I've been busy laying the blocks the last few days, will post a picture tomorrow. It has continued to lighten in color and the white blotches have all spread into each other, and it's almost all uniform in color now. Except where I had a sheet of OSB laying on it 
Still a couple of dark spots, but looking much more uniform than before. Now I'm curious to see what it looks like when it rains again.
Still a couple of dark spots, but looking much more uniform than before. Now I'm curious to see what it looks like when it rains again.
MikeF2316
Well-known member
Looks good. You must be getting excited, the next step sees the space defined.
Had to take a class on the mechanics of concrete and this topic came up. I looked up 'laitence' and it most likely explains what happened...after finish troweling of the slab, a uniform 'layer' of fines and cement formed on the surface. When your daughter rode her bicycle on the slab, she disturbed this surface layer. Should have no effect on the structural performance of the of the slab.
Here's the article:
PROBLEM CLINIC
MEANING OF "LAITANCE"
By Concrete Construction Staff
In the article on sealing joints of tilt-up panels ( April 1974, page 171) the word "laitance" is used. This word has frequently appeared in our concrete specifications over the years but we have never been able to find it in our dictionary. What is a good definition?
Webster's Third New International Dictionary, Unabridged says that laitance is derived from the French word lait meaning milk plus -ance, which in this instance perhaps means quality. It defines laitance as "an accumulation of fine particles on the surface of freshly placed concrete occurring when there is an upward movement of water through the concrete due to the presence of too much mixing water, to excessive tamping, or to vibration of the concrete." The book "Cement and Concrete Terminology," American Concrete Institute Publication SP-19, defines laitance as "a layer of weak and nondurable material containing cement and fines from aggregates, brought by bleeding to the top of overwet concrete, the amount of which is generally increased by overworking or overmanipulating concrete at the surface, by improper finishing or by job traffic." In general the word laitance is used to identify a thin, flaky layer of hardened but weak hydrated cement and fine sand which began life as a milky scum on the top surface of concrete.
Here's the article:
PROBLEM CLINIC
MEANING OF "LAITANCE"
By Concrete Construction Staff
In the article on sealing joints of tilt-up panels ( April 1974, page 171) the word "laitance" is used. This word has frequently appeared in our concrete specifications over the years but we have never been able to find it in our dictionary. What is a good definition?
Webster's Third New International Dictionary, Unabridged says that laitance is derived from the French word lait meaning milk plus -ance, which in this instance perhaps means quality. It defines laitance as "an accumulation of fine particles on the surface of freshly placed concrete occurring when there is an upward movement of water through the concrete due to the presence of too much mixing water, to excessive tamping, or to vibration of the concrete." The book "Cement and Concrete Terminology," American Concrete Institute Publication SP-19, defines laitance as "a layer of weak and nondurable material containing cement and fines from aggregates, brought by bleeding to the top of overwet concrete, the amount of which is generally increased by overworking or overmanipulating concrete at the surface, by improper finishing or by job traffic." In general the word laitance is used to identify a thin, flaky layer of hardened but weak hydrated cement and fine sand which began life as a milky scum on the top surface of concrete.
wssix99
Well-known member
This could be the case, but per the definition - if it is the case, then the top layer would be very weak and should scale or dust off.