Cement serves as a binder for holding other materials together. There are many different types of cement, but the most common is lime-based Portland cement, a subtype of hydraulic cement, and it is based on calcium carbonate and clay. However, there are other cements , both hydraulic and non-hydraulic, that are based on polymers, sulfur , gypsum, asphalt, bauxite or Pozzolana instead. Concrete has many different forms, is very cheap (due to being based on two very common components - normally lime and clay, as well as an aggregate) and very versatile: The Pantheon is over two millennia old yet still stands, and pervious concrete shows great promise for environmentally-friendly pavements  while concrete's high-strength and low cost make it a prime choice for the efficiencies of prefabricated construction and mass-production.  One of the materials that demand the most amount of energy during producing, transport and construction. The amount of CO2 emitted by the cement industry is nearly 900 kg of CO2 for every 1000 kg of cement produced.
Nowadays plenty of experiments have been carried out to mix in different organic binding materials. The aims of doing this is to reduce the amount of cement needed in concrete structures and to make it lighter or stronger so it can be designed differently and cheaper. Some examples are horse hair, hemp fibres, old and shredded card board and paper, old crushed glass.
There are some companies that market concrete building blocks under different trademarks like: