This question is premised on a particular cement product that could be handled like clay but appeared to dry looking like poured concrete. It turns out that is not the case. So the "simplest" answer is that the question is based on bad assumptions. However, depending on actual requirements, the objective of the question could have full or partial solutions.
ShapeCrete
Start with the product that triggered the question. The example you saw on the ShapeCrete web site is easy to misinterpret. After a lot of investigation, it appears it was an anomaly, and not quite what it seemed to look like. Getting into all the details would be tangential to this answer. But if you want to exploring that example, what it appeared to be and why, the technique used, or how to reliably get readily-visible bubbles in ShapeCrete or a similar product, that would be great fodder for a separate question.
The key points are these:
- It's a cement product.
- It can be mixed to be pourable, in which case it will have the bubbles of poured concrete but not the surface texture.
- It can be mixed to handle like clay, in which case the result will look like clay.
It is no longer available. But if what it does is useful to you, yes, there are alternatives. I found an equivalent competing product: SculptCrete. There may be others. Note that neither ShapeCrete nor its competitors will dry to look like poured concrete when used like clay.
DIY Mixes
There are also DIY cement mixes that handle like clay. They typically have a surface texture like concrete rather than like clay. So a DIY mixture may be close enough for some applications, or could be a good starting point to replicate the look of poured concrete. Do a search on "diy concrete clay". You'll find videos like Making a Concrete Mix that Works Like Clay and How To Make Concrete Clay At Home. Each recipe will have different characteristics, depending on the purpose.
Concrete appearance
The characteristic appearance of poured concrete comes from two aspects:
- Surface texture (smooth and grainy)
- Surface bubbles
The surface texture comes from the component sand of a certain particle size. That can be easily replicated by using a mixture that contains sand of similar size. Clays use a much smaller particle size and result in a smoother surface. However, you can start with a concrete mix and modify it to handle more like clay (most of the DIY concrete clay mixes), or start with an air dry clay and add some sand to make the surface texture similar to concrete.
Bubbles are a characteristic of poured concrete. Pouring it into a mold results in some of those bubbles being on what will become the surface when it is demolded.
By its nature, clay-like materials do not have surface bubbles, at least of a size that looks like poured concrete. You can do things to get bubbles into the surface. On material that is wet, soft, and barely clay-like, it's easier to do and there are more ways to do it. On material that is firm, dense clay, there are limited ways to modify the surface to produce bubble pocks, but it can be done. If the material only has to look like poured concrete and doesn't have to actually be concrete, there are more options.
Basically, the requirement for handling like clay is the opposite of the requirement for surface bubbles. The more clay-like it is, the fewer options there are for getting bubble pocks into the surface. It's worth examining the requirements for a specific project in detail because there are trade-offs that can make the project a lot easier if some of the requirements aren't critical.
How to get a specific kind or type of clay-like material to look like poured concrete would be a discussion for another question.
