Regular concrete is a mix of Portland cement & aggregates like sand and pebbles.

If you add extra aggregates like peat moss, Perlite, Vermiculite & so on to it, it may weaken it because the proportion of Portland cement in it then gets smaller.

Most hypertufa enmthusiasts like to buy the pure Portland cement because they then have control over the kind of aggregates & the proportions of them. No matter what aggregates I use, I like to have a mix that's 20% to 25% Portland.

What Herb said. It is harder to get much detail with some of the premix stuff because of the size of aggregate. For stepping stones and such it might work ok.
I put my portland and supplies in 5 gallon buckets. Maybe you could take them with and break it down in them. Lighter and easier to carry.
Paws

Dijoy,

Good day. A couple of comments regarding responses already posted.
Once you get done with your now existing concrete mix you can begin to carry a couple of dry buckets with tight fitting lids in the car to down size portland cement or to be ready for broken bags that are considerably less (.50) at home depot. Of course check for newness and viability of those broken bags, NO to chunky stuff, especially at the store. Chunks larger than a marble that can not be squished between your thumb and forefinger, is going to damage the overall mix.
Premixes of concrete, according to a supply company I have gotten stuff from is usually 3parts pea gravel(or combo of larger aggregates,2parts sand, and 1part cement. So as Herb said if you add ingredients you are lessening the concentration of cement overall. Premixes of some mortar mixes are 2 1/2 sand, 1 cement, 1/2 lime, other mortar mix is 3sand,1cement.
Portland Cement is a 'dry glue' and all of the other dry ingredients have to be coated with the cement to bond everything together when you add your liquid. It is very important to mix your dry ingredients thoroughly.
BUT the good news in my book is that the bags of concrete pre-mix can be used successfully and you can get great detail if wanted.
In the FAQs (top of this page) there are a couple of mixes using premix.
If you plan to add ingredients you really have to make sure your current bag has not settled. Cement and Concrete soak up water even through those bags they come in, if there are chunks already or hard spots that you can not break with minimal force, you may just have a couple of concrete bolsters. So roll it around a bit, or better yet put it into two buckets with lids (dry) and roll it around. Wait for the dust to settle, then for hypertufa mixes you can use a part (measuring container) of the premix, and say a 1/4 part of your additions of peat moss, perlite, vermiculite. I want to stress that this medium is mostly forgiving (unless you are building a bridge or highrise structure!!!)
Now about detail; you can use premixes very successfully for leaf stepping stones, mosaic stones, concrete tiles, leaves, etc. A little more information about what you want to use it for will help identify how to help insure that the detail is gotten either on the indirect side (say your design is on the bottom of the form) or the direct side (where you want detail on top of the form after you have set things up and put your mix in)....
I know sometimes it sounds like I am foaming at the mouth.
This medium is so awesome to work in and has so many possibilities I WANT people to try, and if it doesn't work you have learned from it and can semi inexpensively make alterations to your design or recipe.
Happy casting and forming,
Dena

Dena.....

You are amazing.

Thank you

Your instructions are always so clear and "do-able"!

Jean

Dena, you are most definitely NOT foaming at the mouth! The information you gave (as well as the other responses) is exactly the type of info I was looking for.

I plan to start with some large planters. In particular I want something I can plant a medium size Sago palm in.

I'm also interested in making some stepping stones.

I suppose I could sift the larger pebbles/aggregate out of what I have on hand before I start.

Thanks.

dijoy if you are planning large containers then I suggest you avoid the recipes in the FAQ. Most are pretty weak recipes.
Making tufa from Readimix is also a bad idea. It doesn't contain enough cement to allow for the addition of peat and or perlite. You can do it but your tufa will be lack strength.
But you can add extra Portlands to the Readimix to make it stronger. The other problem with Redimix and premixes from Big Box stores is they can be old and have lost considerable strength.
And sifting readimix is NEVER a good idea even outdoors. The dust will be really nasty. It can even kill some plants.

Try here for some great no nonsense advice.
Unfortunately it appears Mag's ripped off Mabeldingeldine without her permission.
Here is Mabeldingeldine site where the great recipes and advice originated.
http://abacus.bates.edu/~aelliott/hypertufaprep.html

Here is a link that might be useful: Good advice, great recipes.

So Tufaenough if you are not buying your ingredients at a big box store where are you getting them from?
Some only have that to work with.

It may be clear to those who have done some work with either the mixes or the ingredients that you want fresh, but to those who are thinking "could I use the ingredients I already have" I think it is worth a try. And isn't it great that each has their own outlook on what will work and what won't.

I think it is equally important to know that some people have access to only the big box stores, and YES you can (In my opinion), use a pre mix (sakrete, quickrete) concrete mix successfully, and it is helpful to learn your way around one of the big box stores to know where other elements can easily be gotten, and important to check the bags of cement or concrete mix b4 you buy. If it seems hard ask the person to go get another or find a different big box store.
Happy casting, experimenting, planning and succeeding,
Dena

Dena I buy from the same place the bricklayers buy from, but if I had to buy from the Box stores I would use a strong recipe.
I think at different times of the year the Box stores could have old product. I think everyone should be prepared to add a quart of Portlands to Redimix just to be safe. It certainly won't hurt and it could be the difference between success and failure. Better safe than sorry.

Dijoy wants to make BIG planters so my advice related to that use for Redimix. Using Redimix they will be very heavy so there will be the urge to add so much peat and perlite that the final tufa will be weak.

It would be a real shame to go to all that effort and end up with broken planters when just adding a quart or two of Portlands to the recipe could make them strong.

A few fibers and Elmers glue would make a big difference as well.:)

I bought a fountain from a guy who makes concrete lawn & garden statuary. I noticed that this year it is all coming apart. Has lots of aggregate in big chunks and the whole thing is breaking apart like a cookie where the aggregate is. I would hate to see this happen in my tufa projects. This item is only 5 years old at the most. I really think the large aggregate is the main problem. I would love to know what he used in his mix.

Jo

Jo it's not the size of the aggregate, big aggregate about 1/3 the size related to the thickness is a good thing.
But there has to be a good mix of finer aggs as well.
Was this fountain painted?
Generally it recommended to reseal concrete after a year or two.

Well, y'all have given me much to think about. I appreciate all the advice.

Elmer's glue, huh? That's interesting.

Thanks.

Adding additional portland cement may be fine with the pre-mix, but I would like to make sure that those trying this idea really INCORPORATE your DRY ingredients FIRST!!! A quart of cement to a 60-80lb, might be ok.

Then add your liquid (a little at a time) and mix to a not very wet mix, you really should be able to pick up a handful and squeeze with very little displacement of water, then let the whole shabang sit for 10 minutes to "gel", then mix again and add a LITTLE water is necessary!

I would also like to mention that in my opinion adding more cement does not necessarily make a stronger over all product. There are houses that STAY together with
5-7 aggregate:1 cement.:)

That said, Dijoy I hope you will take notes on your process even if it is just for you. There is a lot to learn about cement and concrete, and variations of mixes and what the uses are.
Happy casting!
Dena

Dena are those houses made out of tufa and do people want to move them around in their yard?;-)

Here is a site that I am sure you could argue til the cows came home Tufaenough,just hope they are not 'flying cows' :). But it might also be of interest to you and to others on this forum to see what is possible.
Dream Big, there are such awesome ideas outthere, and right here at this forum.
This site has been posted manytimes, always good I think to refresh/review.
nufsaid, Dena

Here is a link that might be useful: Flying concrete

hi all i am so new here but i love it . I use a concrete mixer . for my molds . i dont see anyone useing one ( why)?

KatyB2,
I have a mixer and have used it only occasionally, when I am making something fairly large.
I have found that mixing in a bowl for most of the things I do is easier, and allows for me to get the feel of the mix, I can mix up very small batches or pretty large batches.
If I were doing many say stepping stone forms, or a leaf walkway, or columns I would likely use a mixer. Even when I give a class I have students learn how to mix in the bowl. Mostly so they are not as intimidated by the stuff and to see that you really can 'take it on vacation' with you, or create during an insomniatic night, without disturbing the whole household.
What kind of mixer do you have? And what kind of molds are you doing?
Welcome and happy casting,
dena

Befor I really got into the tufa thingy, I used reguler crete for a couple of projects, and they are still pretty healthy lookin, but I don't use it any more, I like the portland and stucco much better. I have a leaf that I sanded a bit after removing the leaf and a bunch of people have told me they liked the look, but I like the smooth look. The leaf is weathered and growing moss now, it's about 2 years old. I also have a large elephant ear about 3 foot long, and it's still in tact, but very heavy!
bonnie

Here is a link that might be useful: crete

Dena ~ thanks for the Flying Concrete link.
Their work is amazing!