From the Merriam-Webster Online Dictionary the definitions for Cement and Concrete are as follows
"...a powder of alumina, silica, lime, iron oxide, and magnesium oxide burned together in a kiln and finely pulverized and used as an ingredient of mortar and concrete."
"...a hard strong building material made by mixing a cementing material (as portland cement) and a mineral aggregate (as sand and gravel) with sufficient water to cause the cement to set and bind the entire mass."
A very easy way to understand this: Concrete is a MIX of portland cement, sand and water.
Since you will constantly see the term "Portland cement" used as a primary ingredient in hypertufa recipes, I'll add it, also:
"...a type of hydraulic cement made by heating a limestone and clay mixture in a kiln and pulverizing the resulting material."
Now that we've got this issue cleared up, please investigate my hypertufa and concrete projects. I know you'll find something that will catch your eye!