The first brick is the hardest, because once you have one you can knock it on someone's head so that he cries and bleeds even more.<p>Jokes aside, I think you need clay and limestone to create cement. Clay has been found Limestone is probably not available on Mars, although I believe there were reports of some carbonates in tiny quantities. The lack of ubiquitous carbonate is seen as evidence that Mars never really had a denser atmosphere with fluid water.