I am not typing the right words or phrases in the search bar. I have seen threads on here where someone was casting giant cement rocks using molds to create their layout. I have one section where I want to do this and I already have a mold I want to use. What I am wondering is what kind of mix was used to make the rocks? regular Portland cement or hydraulic cement. What sand/gravel/cement ratio? and is it stuck to a screen mesh with mortar? I’ll keep looking but hoping someone beats me to it.
Devon Sinsley said:
I am not typing the right words or phrases in the search bar. I have seen threads on here where someone was casting giant cement rocks using molds to create their layout. I have one section where I want to do this and I already have a mold I want to use. What I am wondering is what kind of mix was used to make the rocks? regular Portland cement or hydraulic cement. What sand/gravel/cement ratio? and is it stuck to a screen mesh with mortar? I’ll keep looking but hoping someone beats me to it.
First, don’t limit your search to here. (Yes, it’s a GREAT site, but it falls a bit short of encapsulating all of the knowledge in the world) At any rate, there’s lots of articles on the web ( I searched on “casting giant cement rocks using molds” and got LOTS of hits)
I didn’t use regular cement for my mill, but it ended up lasting a LONG time. (Still good, I believe - and it was built almost 20 years ago!) I used Quikrete, if I recall correctly (not very likely, but it COULD happen!) (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-foot-in-mouth.gif)
When I do rock patterns, I use mortar mix and crinkled aluminum foil. For the lake, there is a concrete sub-layer with the mortar mix on top just for the texture.
When I make “faux rocks” to cover/hide stuff (electrical boxes and sprinklers), I make a wire armature and cover it with masking tape. Then I use hydraulic cement sifted on top/bottom wetted with a spray bottle built up in layers. I do the same for structres and buildings except I use a stryofoam base structure and sift onto that.
Thanks guys. But someone on here did a very extensive write up about getting together at someones house and making a bunch of cement rocks. I have a basic knowledge of what I am doing, basically a large version of ones made with plaster for indoors.But the main things I am after is what that particular person was using to make them. Seems it was a proven method. I am sure I could do just fine. But I just recall a very specific mention of the type of cement and the ratios they used to make it.
Maybe I need to be more clear. I am wanting more of a rock wall face as opposed to stand alone rocks. I have an area I want to stand castings on edge to create an entire cliff scene. So I am am in need of big very flat cement rock faces not just big cement rocks. I am kinda wanting it to look like Dennis Rayons but I don’t think he was the one who did the write up. Even Ray Dunikan has the right look but I don’t think it was him either.
Heh, I don’t recall that one, but I have been known to be forgetful.
Instead of searching for something VERY specific, I might try searching on a single word or two; such as “rock” or “cement rock” - hoping to find SOMETHING that perhaps triggers a memory - or even hits on it directly.
If I don’t get the link to the article I think I am talking about (who knows whats actually going on in my brain) I will wing it with hydraulic cement and sand and pea gravel mortared to screen.
Devon Sinsley said:
If I don’t get the link to the article I think I am talking about (who knows whats actually going on in my brain) I will wing it with hydraulic cement and sand and pea gravel mortared to screen.
Are you searching for a forum post OR an article? I don’t think the search works across both, but I have been known to be SO wrong. Hopefully, you can get some feedback as it’s rather too easy to go ahead and wing it, only to find out that the natural life of the method you chose is 24 months…(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-foot-in-mouth.gif)
…sort of like the old and proven “Hard Shell” technique way of scenery construction, using plaster, in the smaller indoor scales. It is actually a CONCRETE mix, and “Cement” is only a part of the mix…
The mix is morter (Sp) mix…adding crushed stone adds to its strength…
But at what ratio Fred? It’s one thing when you are pouring a concrete slab. But detail structure for a railroad? I am thinking 2 parts hydraulic cement, 2 parts sand, I part pea gravel.
Sand only, as mortar is made is weak. It crumbles. Too much pea gravel and you will lose detail. I am relatively certain I could figure it out. 2 parts hydraulic cement two parts sand 1 part pea gravel I like would do it.
Just remember that the cement content is only the binder, so adding too much does not necessarily improve the strength. Experiment to get the best results for your needs, remembering that the climate in your location can, and will effect the lasting ability of the structure. Extreme swings in humidity, and heat can reduce the durability of concrete. Mortar, if properly mixed, with the edition of lime (Not the fruit) …yes they used to add it to the mix, but now is often included in the bags of “Mortar Mix” obtained at builders’ supply stores; can be good for what you are attempting. If mixed properly it doesn’t crumble. Crumbling may indicate lack of the needed cement, and possibly no lime was used, or possibly the mix was too dry.
Do a bit of research on the subject of Concrete, and Mortar mixes…it may help you succeed in your project.
Fred Mills
Thank you for correcting my spelling of “Mortar”…I just couldn’t get it correctly, for some “Aging reason”…(I suppose)
Fred Mills
Thank you for correcting my spelling of “Mortar”…I just couldn’t get it correctly, for some “Aging reason”…(I suppose)
Fred Mills
Don’t know your exact application, but for what it’s worth here is how I have done it in the past.
Used bagged mortor mix with a couple of shovels full of Portland Cement added to make it creamier and less gritty.
Over a wire frame used 1 foot square sheets of burlap dipped in a thinned batch of the mix.
Kept the burlap damp until cured, covered with wetted towels.
Painted/trowled on a second coat to strengthen the burlap, keep damp until cured.
Used krinkled foil for the forms, about hand size, filled with a dough thick mix and applied to a very wetted base.
Stripped off foil while mortor was still soft/uncured and sculped with a few basic hand tools.
I would reference some pictures but off course they are all lost in the Freight Sheds, You know, that place that you pay to store your pictures.
I use a product called “Acrylic Render” for my cliff faces.
I have used it over a wire frame covered with shade mesh for rocks in the past.
Being acrylic it expands and contracts with weather changes without cracking.
https://www.bunnings.com.au/dunlop-20kg-multipurpose-acrylic-render_p0760242
I colour it with cement oxides.
Don’t know if it is available in the US but may be worth some research.
I’ll take a look
I can’t seem to find it.
Devon, you may want to look at vinyl concrete patch. Quikrete is one manufacturer.
https://www.quikrete.com/productlines/vinylconcretepatcher.asp
Dan Hilyer said:
Devon, you may want to look at vinyl concrete patch. Quikrete is one manufacturer.
https://www.quikrete.com/productlines/vinylconcretepatcher.asp
That is a very interesting product to use. It is very fine, so it’s great for casting detail. I used it to repair a large concrete casting that didn’t de-mold well…
Devon Sinsley said:
I can’t seem to find it.
Try looking for Stucco it is very similar.