Portland Cement

Portland cement is the most common type of cement on Earth. When mixed with sand, gravel and water it forms concrete.

It is made by heating limestone (CaCO3) and clay minerals in a kiln to form clinker (small pebble like accretions) which are then ground into a powder.

The European standard for Portland cement is:

"Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates, (3 CaO·SiO2, and 2 CaO·SiO2), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO2 shall not be less than 2.0. The magnesium oxide content (MgO) shall not exceed 5.0% by mass."

Limestone is a mineral created by life on Earth, and is unlikely to be found in any large amounts on Mars. Since 2/3 of the mass of Portland cement is limestone this will make it more expensive than on Earth. However, Calcium Carbonate (CaCO3) has been found formed by non-biological processes at 3 to 5% concentrations in polar soils by the Mars Phoenix Lander, so we may be able to find local deposits.

Sorel Cement will likely be cheaper on Mars, as well as being stronger. However, it erodes when exposed to water.