DO NOT USE FOR ANYTHING THAT HOLDS WATER!
this will hold up outside and resembles the other fast setting cement mixes that are available.It is also less than half the price.Adding 1/10 of a portion of limestone will help to achieve a whiter colour."

I haven't tried this as yet,so no comment as to what it's like.Pricewise,this sounds a good deal!
Cheers from here

I've mixed up a couple recipes using POP in them and find they absorb a lot of water when you get them wet.

There are a ton of materials in the tiles section of the hardware store that might make Portland more claylike when hand shaping but you would have to wait a couple years to see how they handle the weather.

It's easy to see why it's impossible to duplicate some of the old Faux Bois finishes from the masters. They could have added almost ANYTHING to their recipes.

anotherchris

If you make a mixture like that it certain WILL be soft and easy to break!
Portland cement when used to make concrete can be mixed 1 part Portland to 2 parts sand, adding more Portland does not make it stronger and in fact can make it weaker and cause increased shrinkage.

Portland is the GLUE, it's a binder for the sand, so Portland with no sand is very weak.
Conversely, Portland with too much sand is weak.

Portland cement works best and is the strongest with the absolute minimum of water, the only water needed is enough to dampen the material, more than that, especially to make it pour like plaster causes WEAK concrete, the key to strong concrete is less water.

Less water unfortunately makes it difficult to work with when it's trowel consistancy, but concrete comes out best, liquifies a bit and air bubble leave when you WORK IT, don't just dump it in a form or mold and walk away.

Warm water will cause a faster set, COLD water will delay it a little.

As far as gardencast goes, if you look at the MSDS sheets on laguna clay's site, it, like hydocal, hydrostone, FGR 95, drystone etc are all plaster of paris with various amounts of portland cement and <5% crystalline silica, in fact, Gardencast's specs say it is 50% plaster of paris and 40% Portland cement as I recall, and you add the sand- 1 part to 1 part Gardencast. Once you add the sand the ratio would be approx 25% plaster, 20% Portland and 50% sand.
Plaster is NOT an exterior material no matter what anyone says or what you add to it or apply onto it, so what happens is, because the mixture is 25% plaster, over time that plaster will degrade but the Portland and sand will stay, so probably as the plaster dissolves out it will leave pits and holes and an eroded surface in the statue.

The fact that gardencast is mixed with only 12.5 parts of water to 100# of material i s another interesting one, because less water is stronger, but this small amount of water leaves the mix extremely thick- almost like thinset mortar used in setting ceramic time, it is STIFF and not easy to pour.
My test with this product today I wound up adding 50% more water just to get it liquid enough TO pour, it was more like wall paste at the ratio they state 1-1/2 gals to 50# Garden cast and 50# sand

I took 1 qt water 8.3 # of sand and 8.3# of gardencast as I didnt want to mix the entire bag

If you make a mixture like that it certain WILL be soft and easy to break!
Portland cement when used to make concrete can be mixed 1 part Portland to 2 parts sand, adding more Portland does not make it stronger and in fact can make it weaker and cause increased shrinkage.

Portland is the GLUE, it's a binder for the sand, so Portland with no sand is very weak.
Conversely, Portland with too much sand is weak.

Portland cement works best and is the strongest with the absolute minimum of water, the only water needed is enough to dampen the material, more than that, especially to make it pour like plaster causes WEAK concrete, the key to strong concrete is less water.

Less water unfortunately makes it difficult to work with when it's trowel consistancy, but concrete comes out best, liquifies a bit and air bubble leave when you WORK IT, don't just dump it in a form or mold and walk away.

Warm water will cause a faster set, COLD water will delay it a little.

As far as gardencast goes, if you look at the MSDS sheets on laguna clay's site, it, like hydocal, hydrostone, FGR 95, drystone etc are all plaster of paris with various amounts of portland cement and <5% crystalline silica, in fact, Gardencast's specs say it is 50% plaster of paris and 40% Portland cement as I recall, and you add the sand- 1 part to 1 part Gardencast. Once you add the sand the ratio would be approx 25% plaster, 20% Portland and 50% sand.
Plaster is NOT an exterior material no matter what anyone says or what you add to it or apply onto it, so what happens is, because the mixture is 25% plaster, over time that plaster will degrade but the Portland and sand will stay, so probably as the plaster dissolves out it will leave pits and holes and an eroded surface in the statue.

The fact that gardencast is mixed with only 12.5 parts of water to 100# of material i s another interesting one, because less water is stronger, but this small amount of water leaves the mix extremely thick- almost like thinset mortar used in setting ceramic time, it is STIFF and not easy to pour.
My test with this product today I wound up adding 50% more water just to get it liquid enough TO pour, it was more like wall paste at the ratio they state 1-1/2 gals to 50# Garden cast and 50# sand

I took 1 qt water 8.3 # of sand and 8.3# of gardencast as I didnt want to mix the entire bag

None of my mixes have been as strong as Gardencast. I can get the surface hardness, but the castings are brittle."

Sounds like you are adding too much water to make it pourable, at the correct ratio of 12.5 parts of water, it is not pourable, it's more like wallpaper paste, and since it uses so little water, adding a little more would be real easy to had added way too much water.

OLD material that has been sitting around, even if not lumpy will harden up faster.

As an aside for another comment; if your Portland cement has lumps and rocks in it throw it OUT- the lumps and rocks are calcined, in other words the material has absorbed moisture and some has set slightly, once Portland starts to set the chemical reaction is used up. What happens if you screen out the lumps or crush them into powder, is you will get weak concrete.

General rule is- if you can EASILY powder SMALL lumps between your fingertips, use it, but use it UP FAST, once you have a bag whose outer half inch against the paper bag is lumpy and rocky you'll never get decent concrete even if you screen that crud out- toss it.

I have a pallet of some 50, 50# bags I have to to throw away- only a year and a half old carefully stored in a dry basement with a dehumidifier and covered with plastic because they have a lot of lumps and rocks, the stuff didn't want to set well or harden well.

I bought a new 94# bag at Menards and it set over night, got quite warm and was rock hard, so if you compare the two you would find that difference as well.