Can someone with expertise in concrete construction clear up an issue for me? I would think this type of construction was not safe because concrete needs some

Can someone with expertise in concrete construction clear up an issue for me? I would think this type of construction was not safe because concrete needs some sort of reinforcement to make up for its low tensile strength. The wikipedia page on rebar (http://en.wikipedia.org/wiki/Rebar http://en.wikipedia.org/wiki/Rebar) seems to support my concerns, so my question is am I missing something? Is it possible to make up for a lack of steel reinforcement using special concrete mixtures, or is it perhaps unnecessary for small scale construction?