Concrete walls are a passive defensive barrier used by both the GDI and Nod during the Second Tiberium War, capable of preventing most ground units from going through. Concrete was the main static defense for many bases, but they are vulnerable to explosive and cannon based attacks.
In the Second Tiberium War, laser fences and the Firestorm barriers proved to be more powerful than the old mainstay, but the fact that concrete did not need power to operate made it an attractive supplement to energy-intensive barriers. Walls could contain the spread of Tiberium somewhat, acting as a barrier to its growth on the surface. GDI and Nod have distinctive wall designs. Their construction method in this era is somewhat different as, rather than build one section at a time, they are constructed by placing two endpoints between which a segment of wall is erected. The cost associated with the construction is determined by the number of points designated, rather than the length of the wall, to a certain degree. At this time, GDI defensive structures were merged with the wall itself.
During the Third Tiberium War, GDI continued to maintain walls around their more permanent installations - most notably the defensive perimeter around the Pentagon. On the whole, however, they were phased out in favor of a newer design and more developed sonic repulsion and laser technology.