In short: the answer depends on whether or not the concrete has already been poured and cured.
- During the Production Process
If a new house that you’ll move into is being built, there is one thing you can do to strengthen the concrete slabs on the property. Adding steel rods, or rebar, is the best way to increase the tensile limits of concrete. Rebar has excellent tensile distribution and can bend a lot before snapping in half. By adding rebar through the concrete, whenever the slab has to withstand pressure, the energy gets released and distributed through the slab, but a lot of the tensile load is handled by the rebar itself. With rebar, concrete slabs are less likely to break from tensile pressure.
There is no material that can be mixed into the concrete in order to reinforce it. Concrete needs to be firm enough to withstand a large amount of weight. If you add anything that makes it more elastic, you run the risk of weakening its compression properties. Making structurally sound concrete is all about mixing the right amount of the right materials. Experimenting with different materials might actually be more detrimental to the health of the slab.
- After the Curing Process
Once concrete has been poured and cured, there’s nothing you can do to strengthen it. Concrete slabs strengthen on their own over time. For a small slab, it can take about a month to fully finish strengthening while large slabs can take up to a year. You may have heard that pouring water on the slab will strengthen it, but this is only true if the slab is in the curing process, not after.
If you have a slab that has cracked and settled due to pressure, there is a way to fix it and reinforce it so that it doesn’t break again. It can be lifted using polyurethane foam, which is the best material to lift settled concrete slabs. The foam creates an even foundation for the slab to rest on, so that even when pressure is applied, it doesn’t break.