Question about Portland cement

[ClayEdgin]

I was recently given six 94lb bags of Portland Cement (type I, if it matters) and wondered if that would be good enough to use for stones. My 21" Slater stone mold came in Friday and I'm ITCHING to pour one, but don't want to waste my time if the cement won't work. I made a little 85lb stone out of it and it seems fine, but the white color and texture make me leery of it holding up to being dropped.

[Morgan Guthner]

It should be just fine Clay (although you may need to adjust the weight formula) - take some chicken wire and mix it up in with the pour and it'll be good and strong.

[Grant Buhr]

Don't forget -- all Sakrete is composed of is Portland cement, sand and coarse aggregate. If you toss in some sand and gravel, you should be good to go.

Proportions: 1 x cement, 2 x fine aggregate (sand) and 4 x coarse aggregate (gravel).

[Allan Heer]

Clay,

Be aware of your water/cement proportions.

Water is required to initiate the chemical reaction creating concrete, but too much water can cause a separation of cementicious materials resulting in a loss of strength.

The average store bought bag mix has an estimated compressive strength of 3,000 PSI after 28 days curing time. Mixing in additional water to create more workable or flowable concrete will greatly reduce the strength.

Just my 20 Pesos :)

[ClayEdgin]

Would just using portland cement without any sand or aggregate hold up?

[Allan Heer]

No, the sand and other coarse aggregates help bond the cement materials together, as well as increase it's compressive strength. Without an aggreagete bond, your stone will chip and crack much easier.

[ClayEdgin]

Okay, thanks for your time.

[Steve Slater]

All seems like great advice to me although I have used a 7000 psi super por rock mix a few times with no gravel or sand and it made a very smooth stone no bubble holes at all.