Wondering what happened to a bag of pre-mixed concrete that has been stored for 2-3 years dry in the utility room. Took this bag, mixed it with the right amount of water, and cast a large birdbath directly on site on plastic-covered ground. Unfortunately, it didn't turn into a birdbath as the mixture hasn't cured after 2 days under the plastic and crumbles in the hand like wet soil??? What happened? Is there an expiration date for dry-mixed concrete in a bag? gaia
It's not that it got cold in the evening, so the concrete didn't have time to set? You shouldn't pour without cold weather additives in the mix below 5 degrees Celsius.
The 6-month rule is probably because a chromate reducer stops working, and the risk of contact allergy increases...or something like that.
See the following PDF:
http://www.finjabetong.se/aktuell/pdfny/3325.pdf
The 6-month rule is probably because a chromate reducer stops working, and the risk of contact allergy increases...or something like that.
See the following PDF:
http://www.finjabetong.se/aktuell/pdfny/3325.pdf
But if the product is chromate-reduced, doesn't that mean there are fewer chromates in it from the start? That can hardly change over time, can it? I was completely convinced that the six months was because the concrete started to cure in the bag in normal humidity. And I've experienced the same thing with concrete that's around one to one and a half years old and has been kept dry, it simply doesn't become very strong.
Edit: My mistake, I just found what you said, that the chromate-reducing agent was effective for six months.
Edit: My mistake, I just found what you said, that the chromate-reducing agent was effective for six months.
I'm not saying I'm right, but even Cementa writes that the storage maximum of 6 months is because the effect of chromate reduction diminishes over time see:
http://www.heidelbergcement.com/NR/...1-4A59-BA96-E9793F9CA7CD/0/Produktbl_Bygg.pdf
http://www.heidelbergcement.com/NR/...1-4A59-BA96-E9793F9CA7CD/0/Produktbl_Bygg.pdf
Okay, but the question then is whether you can use old cement if you take precautions regarding chromium allergy.
Then I am quite curious about how gaia was with the outside temperature at the time of casting.
Then I am quite curious about how gaia was with the outside temperature at the time of casting.
The outside temperature this afternoon at the end of April was about 18 degrees and around 5-8 degrees at the lowest during a few morning hours the night after (Skåne). It was at least 12 hours until the temperature dropped, so it should have set before then. There was no ground frost, though. Everything was loosely covered with plastic.Fasting65 said:
Not even two grains of sand are bonded in this casting. The material seems rather too loose, and the thoughts drift to a sandcastle...
.We used about 2.5 liters of municipal water to mix this bag.
I've experienced an old bag turning into a concrete block but never where the dry concrete doesn't set at all...
We cast a foundation for our accumulator tanks and boiler about 2 years ago, and it was a leftover bag. The tanks are still in their place, but now one starts to wonder...
...and it would be useful to know what went wrong this time...
Could an embedded galvanized chicken wire cause disruptions in this casting?
gaia
I would be satisfied if it ended up not being particularly strong, but my casting has a strength equal to zero. It feels like gritty soil, and the only positive thing is that you can rake it out and forget about it. The concrete looked normal in a dry state and there were only a few slightly firmer small lumps closest to the outer side of the bag that could be mixed out. The color was also correct, so it wasn't just gravel in the bag, but still, it didn't become a birdbath. What went wrong? gaiajon_h said: