what causes concrete/cement to fall apart?

per my other thread, I've noticed something with the increased melt we've got. the rough, unfinished concrete on either side of my trench drain is basically dissolving into concrete coloured sand!!! I can take my bare finger and poke into it.
what causes this??? it is literally vapourizing and completely disentigrated! basically well formed mounds of sand now....same goes for the forming that held the rails in place. I can scrape it away with a pain scraper!!
any thoughts on what caused this, and ideas on how to prevent MY repair from doing the same in 1 season??
b
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This may have been too much sand and too little concrete. Since strength wasn't the objective the installer may have saved money by not using sufficient cement.
RB
Hamilton Audio wrote:

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A real crappy - cheap mix, you got ripped
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Hamilton Audio wrote:

Poor mix. I assume it was commercially mixed so too little or improper mixing is unlikely. Sand, gravel, cement, water ratio wasn't correct. I personally wouldn't use anything but 6 sack cement (6 sacks per cubic yard) for anything around my house, and yours may have been as little as 2-1/2 sack. Contractors often skimp for very little savings. For the home owner, nothing less than 5 sack should be used and the cost of another sack to make it 6 sack is minimal. Or, too much water was used. Workers sometimes add a lot of water to make working the mixture easier. A stiff mixture will be much stronger. Then, the curing may have been wrong. The mix may have frozen or it may have dried very quickly. Most likely it was a combination of too much water and failure to cure properly.
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rock salt
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