Tips For Casting Concrete - Use A Slurry
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- Опубліковано 8 вер 2024
- A slurry is a mixture of cement powder and water (sometimes with glue or other admixtures also) which is mixed to the consistency of something like cake batter or warm butter. With a slurry paste, you can paint the inside of your mold before you cast your concrete or mortar. The slurry adds a layer of fine detail because of how dense the cement is. You do not want your slurry layer to be thick but more like a skim or skin coating. Once you have painted your slurry in place, it is very important to add your concrete into the mold before the slurry begins to dry.
If the slurry dries before you add your concrete to the mold, reapply another wet layer of slurry and then add your concrete. You should still vibrate the mold but the addition of a slurry layer should help to minimize or even prevent honeycombing or voids left in the concrete.
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#CreatingConcrete #concretecastings #diyconcrete
I really love your channel. Thank you for being so 'concrete' out there for us 😁. Following.
Btw: one of the best fiber is Lesser Bulrush (Typha angustifolia) for both concrete and clay. The tiny fluffy fibers of the flowers make the concrete (clay) titanium hard and long lasting. I made some trials for thin wall structures - works like charm, especially with light concretes. Don't tell anyone my secret - the big construction guys will go after me 😅. Blessings.
that seams very obvious but I just couldn't figure out the honeycomb problem. Thank you for this. Subscribed!!!!!!!
I am happy this information was helpful for you. Cheers.
Cool, love the palm sander idea. I'm starting to make decorative stone to refinish my basement. Dying it a Pennsylvania Blue Stone. I always called your slurry, painting with Portland. I also freshen up my Lions of Venice every year with painting with Portland. You have nailed everything I have learned. I prefer the damp sponge method.
I learned concrete working from Italians and the term they use for slurry is "Boo-yaka" not sure about the spelling...but I always thought it was a funny thing to hear these old guys all yelling.
Best advice for concrete casting ever
just discovered your channel, ive just ordered my first molds today. looking forward to building along with you
Just found this channel, great content. I want to make CLC roof panels. Have some innovative ideas for low cost, lightweight structural reenforcement to add strength & rigidity.
Great info! Enjoy your day!
I hope to see more of your videos, and maybe a little longer / more detail? Good instruction, and thanks.
How did you get your concrete, so smooth, did you put sand in it. Your slurry was perfect. My concrete (not slurry) never come out creamy, I even sift before hand.
You mentioned to only use the slurry for coating the inside of the mold, and not to let it get too thick. What would happen if you used slurry (Portland cement and water) only, to fill an entire mold? I am thinking about a ‘life’ casting of hands. I love the smoothness of the slurry cement when dried, but wasn’t sure if it would work. Thanks for the informative videos!!
It would yield poor results. The ultra smooth effect can be accomplished with water reducers and using some finer grade sands for aggregates. a 1:1 or 2:1 sand to cement would be the range I was working in. Many people looking for this finished quality look towards bagged products that are modified heavily with polymers and water reducer already. A product called cement-all is the most commonly used. The only drawback is price is high versus sand and cement and admixtures that you add and mix on your own. But a high quality 2:1 mix with water reducer and 10% acrylic latex, which you then vibrate thoroughly in your mold should produce results like you are seeking. Good luck!
@@creatingconcrete Thanks Steve! Ironically, I picked up Cement-all over the weekend and used it for my project which turned out great! I was worried about strength in using the Portland Cement and water only. I appreciate your detailed response and I love your videos!
Is there such a thing as dry-casting of concrete? What I have in mind is to mix the dry ingredients thoroughly, place into mould & vibrate, then introduce water from the bottom (possibly with additives to reduce viscosity & surface tension), perhaps through a membrane or filter so as not to wash out any cement, and apply a slight vacuum to the top to draw water through whole mix. If the process could be made to work, it would have advantages like ease of manipulation, no heavy mixing, less wastage, less cleanup, no voids or bubbles.
It does not sound like it will work. I do not think you can get an adequate mix or even hydration doing something like this. Additionally you would have air pockets.
Thanks buddy. You're a lekkaaah brainy dude!!! You're very helpful.
Glad you found these videos helpful!
this is so helpful
Can I make the slurry a little bit thinner and "paint or drizzle" it on top of my wet concrete RIGHT after I've poured and smoothed out my wet concrete in my stepping stone frame? I'm wanting to add color to stepping stones that I am making out of Quikkrete ready mix.
Digging your videos!
Thank you. I am so happy you are enjoying them
Thanks for answering me back so fast!! Will the slurry help with cutting down on the amount of pin holes in the finished item? I unmolded a
turtle this morning and I used a release agent. Is the release agent what cases the air or pin holes?
A lot of times it is just poor consolidation of the concrete (not enough vibrating) that causes the pin holes. A release agent can sometimes contribute if there is too much and / or there are tiny air bubbles left, so wiping away excess with a clean cloth or paper towel before you apply the slurry helps. But a slurry can really help cut down, if not eliminate, pin holes in the finished product.
@@creatingconcrete Great information!! Thanks. I think I needed to vibrate the mold more than I did. I used Quikrete Mortar Mix type - N to make the stepping stone, do you think this material is strong enough to be used for stepping stones?
@@robertferguson558 Yes regular mortar (just add water) would be suitable for this.
Thank you for these usefull tips :)
Glad it was helpful!
Thank you
Do you still use a release agent before applying the slurry?
Absolutely. A release agent should always be used when casting concrete to have a cleaner demolding process and less chance to break your finished product because it was stuck in the mold.
You're my unofficial concrete mentor. I've been trying to make concrete tiles, and notice your mortar here looks extra smooth. What sort of concrete mix do you use to achieve this smooth mortar? I currently am using Quikrete High Strength and it feels very aggregate heavy. Any suggestions you have I'd be all ears. My first three pours are on my channel, if that helps troubleshoot at all. Thanks again for sharing all your knowledge here!
Make your own mix with porland cement type general use and graded, clean washed sand. 1 cement and 2 sand. This will give yo ua more creamy, smooth mortar mix
@@creatingconcrete thank you! After this video I saw your 1 part cement, 2 parts sand video. Many thanks, and greatly appreciate all the video advice!
So, how would you slurry the inside of a mold that you can't get a paint brush inside?
You possibly could pour in a wet slurry paste and rotate the mold and then pour out any excess. In some cases a slurry might not be possible. Molding and casting is pretty dynamic and there are a lot of different methods and variations.
@@creatingconcrete I agree. I’m still new to the hobby and so far I’m strictly small items like mini planters and candle jars with silicone molds. The slurry technique might be very impractical for such deep molds. But I’ll definitely try this when I make my own molds when I need pavers for my yard and making abstract industrial sculptures with welded steel and concrete blocks.
Thanks! Question: about 3rd vibration step of this process:
In making stepping stones in molds, for the outdoors, & decided to try a $5+ bag pre-mix crack resistant concrete, only for stepping stones projects...It has fibers + some mystery ingredients + air entrainer, to be mixed w/ a motor, for freeze thaw protection & to reduce shrinkage. They advise you can add your own acrylic reinforcer). Can you still use the slurry process for a smooth top layer when using such a mix? (I’m thinking maybe do the slurry, then a thin vibration layer, & then finish with the crack resistant). Is it mutually contradictory to want a smooth top layer, using a slurry, while using such a crack resistant concrete?
The slurry would only be for the parts of the block that are touching your mold. The top, if it is exposed, is finsihed by hand / trowel. I would be hesitant to add any admixtres to an already modified mix as you could have conflicts with the other ingredients, especially the air entrainer which I believe conflicts with the acrylic additive.
I appreciate every single one of your cautions. Concrete has so many surprises. @@creatingconcrete
I think we are talking 'top' of the actual stepping stone vs 'top' surface of the mold from different viewpoints. I was thinking 'top' of the actual stepping stone which I realize would be bottom of the mold. ha ha.
I saw this bizarre pdf tech sheet online after asking this question, that went into detail of extreme problems you can have if you try to do smooth finishing on an air entrained concrete... but I think it was more finicky for construction jobs. They can't glue disasters back together like I can as an artist :)@@creatingconcrete