Concrete is a mixture of cement, water, sand, gravel, crushed rock, or other aggregates. Sometimes, one or more admixtures are added to change certain characteristics of the concrete, such as workability, durability, and time of hardening.
Top 100 Colleges by Highest Tuition. Here are the top 100 most expensive colleges by tuition for the 2008-2009 school year. The latest numbers can be found in our most expensive colleges ranking. Notes: Some colleges like Bates College, Colby College, Middlebury College, and Union College have a comprehensive fee (tuition + room/board).
4. Harvard University. Harvard University is probably the best-known university in the world, coming top in the reputation rankings most years. It was founded in 1636, and is the oldest higher education institution in the US. There are currently 20,152 students enrolled, a quarter of whom are international.