Abstract: A modular panel of glass fiber reinforced concrete having a thickness of at least 3/8 inch, and containing four (4) to six (6) percent glass fiber and at least fifty (50) percent by weight cement, has upstanding edges forming flanges oriented normal to the plane of the panel and a thickness equal to the thickness of the panel, which flanges on contiguous panels can be joined to form a composite wall structure by bolting said flanges together. The novel panel and flange arrangement allows self-supporting wall structures to be constructed wherein only lateral loading (normal to the plane of the wall) need be carried by the adjacent framework. An elastomer gasket is used between the flanges to accommodate expansion and contraction of the individual panels in a composite wall of the panels.The invention includes composite walls of a plurality of the panels and a building structure employing such composite walls, with an adjacent framework and the interconnective arrangements between these several components.