I don't know why you choose cement as the product […]
I don't know why you choose cement as the product shell. Generally, you will choose plaster for crafts. How big is your product shell, what role does the product shell play, is there any crack resistance requirement, and what load it bears? I think your concern is not whether to add aggregates or not, but whether to add steel or not.
If you really want to use cementChina cement flower pots as the outer shell. According to the updated information, it is a handheld level. Then I don’t think we should add aggregates. What you want is cement, not concrete. The coarse aggregate in concrete generally uses pebbles or crushed stones, with a diameter of 4-5 cm. The aggregate itself does not shrink, so the addition of aggregate will reduce the shrinkage of concrete.
If you want to join, you can use fine gravel concrete, the maximum particle size is controlled by 1cm. In addition, aggregates will not improve the performance you need. In my experience, coarse aggregate can mainly improve the elastic modulus of concrete, that is, make concrete not easily deformed, but you don't need such an elastic modulus. As for the brittleness, it does not have much effect. Adding glass fiber or carbon fiber is a good idea. In addition, it is recommended to add an expansion agent to resist the shrinkage of the concrete. At a temperature of 300°C, concrete may crack, and aluminate cement may be better.