Issue with concrete
#1
04-08-22, 06:27 AM
Issue with concrete
I poured some concrete in my basement. Used bags, Menards brand, when mixing and using the amount of water called for, was not even close to something pourable, had to add more water. When done, had it finished off nice with a smooth surface, left it for a few days. I noticed when walking on it if you drag or shuffled you feet it just kind of f took the top layer off. just rubbing with your fingers would do it as well, if you kept rubbing in 1 spot the more it would remove. It's been over a year now since it was poured, it still will do that of you rub anywhere on the slab. I'm thinking of putting some epoxy coating over it, but concerned it will just come off with the way the concrete is. I've used bagged concrete before, never had an issue like this. Anyone have an idea what night have happened?
#2
04-08-22, 07:06 AM
Group Moderator
Anytime you mix concrete with so much water that it is "pourable" you really weaken the mix, so it's not surprising that the surface is chalky.
Here are a few quotes from a site by overland concrete:
-"Never add unnecessary water to concrete for ease of placement.* Increasing the water/cement ratio of the concrete leads to low compressive strength, plastic shrinkage cracks, excess bleed water*, lower freeze/thaw resistance and scaling* of the surface!"
-"Never finish concrete while * bleed water is present and don't throw water on to the slab in the finishing process. Increasing the water/cement ratio at the surface of the slab is the surest way to guarantee surface * scaling of the slab."
-"Never overwork or over finish the surface of any exposed concrete slab. This brings too much fine material to the surface, works out the designed air entrainment*, and will weaken the surface of the slab leaving the top of slab more vulnerable to freeze/thaw damage and sheet scaling."
About all you could do at this point to control the dust is apply a sealer, assuming that was never done.
Here are a few quotes from a site by overland concrete:
-"Never add unnecessary water to concrete for ease of placement.* Increasing the water/cement ratio of the concrete leads to low compressive strength, plastic shrinkage cracks, excess bleed water*, lower freeze/thaw resistance and scaling* of the surface!"
-"Never finish concrete while * bleed water is present and don't throw water on to the slab in the finishing process. Increasing the water/cement ratio at the surface of the slab is the surest way to guarantee surface * scaling of the slab."
-"Never overwork or over finish the surface of any exposed concrete slab. This brings too much fine material to the surface, works out the designed air entrainment*, and will weaken the surface of the slab leaving the top of slab more vulnerable to freeze/thaw damage and sheet scaling."
About all you could do at this point to control the dust is apply a sealer, assuming that was never done.
Pilot Dane
voted this post useful.
#3
04-08-22, 08:21 AM
I only mixed enough water till it was to the consistency that I've seen off the ready mix truck. When adding the amount of water they recommended, dust was still coming out of the mixer. I'm kind of chalking it up to you get what you pay for. The next section I pour I'll use Quikcrete brand.
#4
04-08-22, 02:53 PM
Group Moderator
I'm sorry but if there were directions and you did not follow them, I think you should be looking at something other than the product for blame.
#5
04-08-22, 03:16 PM
Group Moderator
... chalk it up... a little unintentional humor, I see. 
Various Menards cement products: https://www.mmconcrete.com/ConcreteW...Comparison.pdf
If you used their cheapest concrete mix, they don't even advertise what psi it is (Red flag) when mixed according to the instructions on the bag... (which specifies adding more water can be added as needed to make a workable but "stiff" consistancy). You went beyond that.
Your mix likely had a very low percentage of portland, which is why I said it's not surprising it got chalky when you added more water. Imagine adding extra water to your glass of milk or to your pancake batter. More water is not better, no matter what you think.
Concrete mix from a truck might be wet, but it also likely has WAY more portland cement than your dry bag of redi mix did. It's the percentage of portland that adds to the cost, quality, and ultimate psi of the concrete.
Various Menards cement products: https://www.mmconcrete.com/ConcreteW...Comparison.pdf
If you used their cheapest concrete mix, they don't even advertise what psi it is (Red flag) when mixed according to the instructions on the bag... (which specifies adding more water can be added as needed to make a workable but "stiff" consistancy). You went beyond that.
Your mix likely had a very low percentage of portland, which is why I said it's not surprising it got chalky when you added more water. Imagine adding extra water to your glass of milk or to your pancake batter. More water is not better, no matter what you think.
Concrete mix from a truck might be wet, but it also likely has WAY more portland cement than your dry bag of redi mix did. It's the percentage of portland that adds to the cost, quality, and ultimate psi of the concrete.
#6
04-08-22, 03:20 PM
Not my first time mixing concrete, add the bag to the mixer and the amount of water it says, not too difficult. What do you do when it's a bunch of dusty clumps??? Checked and re read bag, what adding exactly what it said, but thanks for your 2 cents!
