Ordinary concrete has many weaknesses. It has little resistance to

• Moisture penetration,
•  Transfer of heat,
•  Sound penetration,
•  Freeze / thaw cycles,
•  Fire,
•  and Is extremely brittle,
•  and weak in Tension.

All of these problems are a result of how concrete is made. Raw materials are mixed with water to hydrate the cement and to provide the hydraulic force necessary to properly mix the raw materials to manufacture the concrete.

Beneficially, this hydraulic force also transports the concrete to where it will be used, allows the concrete to be properly placed within its volumetric confines, and enables the concrete to enclose any necessary re-enforcing material. The concrete cures as the water content of the mixture evaporates.

Concrete when mixed and poured contains up to 20% of its volume of air and water.  During curing there is some small shrinkage, but the cured concrete basically maintains its volumetric dimensions. So when the water has evaporated and the concrete is cured, the concrete has air filled voids as approximately 20% of its volume.

It is these air filled voids that are the sole reason for all of the weaknesses in concrete.