Lime, clay and silica are 3 main ingredients of cement
Do you mean concrete, that holds things together or for roads and bridges? It can be confusing because many call concrete cement. Concrete that is being mixed in the drum truck is made of cement (a dust), rock, sand, water, air. For some projects they will add flyash or other lighter weight additives and lower the actual amount of cement included.
This Site Might Help You. RE: What are the ingredients of cement? Portland cement
I hate to link to Wikipedia, but a proper answer is rather complex and the article there is actually rather complete and accurate.
