The Cassair Connector Project, a 100-million-dollar upgrade from arterial city street to freeway, made use of both precast and site-cast concrete in several different structures. The largest concrete structure in the project is a 2,394-foot-long reinforced concrete twin-arch tunnel. The tunnel has 35 double-barreled segments, each about 68 feet long, 49 feet wide, and 16 feet high. The tunnel's heavily reinforced slabs serve as both structural slabs and finished pavement for the tunnel. Eighteen months were allowed for construction, with only 10 months available for actually pouring the tunnel segments.
Artist Kathy Goodhue, Dublin, Ireland, switched to concrete as a sculpting material after experiencing dissatisfaction with using metal and wood. She found that concrete was less costly and allowed her greater creativity with her color and texture needs. Despite the large scale of most of her concrete sculptures, Goodhue needs only a few simple hand tools to create them. First, she makes a small scale model of the piece in plaster, then she builds a full-scale armature using the model as a guide.
The thin-shell concrete dome topping the Sundome in Yakima, Washington, has 24 wedge-shaped segments arranged in a radial pattern like the pieces of a pie. But only six wood forms were needed to cast the 24 segments because of an innovative rotating forming and shoring system. The Sundome roof has a rise of 40 feet and a maximum clear height above the floor of 80 feet. Its 24 identical wedge-shaped segments arch to a compression ring at the crown of the roof and their bases are stabilized by a post-tensioned concrete tension ring supported on 24 reinforced concrete columns. Each segment is doubly curved like a saddle to increase the stability of the dome.
A formwork system moved by forklift rather than by crane was used to build the upper ramp of a two-level, 1,250-car cast-in-place concrete parking garage in Milwaukee. Because of the large area covered by the post-tensioned, slab-and-beam ramp, the contractor had to find an efficient way to transport formwork to the jobsite. The forming system he used consisted of beam and deck forms that can be stripped, moved, and reset using only forklifts and dollies. The main element of the system is a 60-foot-long steel beam form that rests on 18-kp support frames having hinged, height-adjustable legs. Because the beam and its framework support the deck panels, shoring is usually unnecessary.
Controlled low-strength material (CLSM) is a backfill product that flows as easily as thick pancake batter and is self-leveling. Its consistency is like that of a slurry or lean grout, yet several hours after placement the material is hard enough to support traffic loads without settling. Typical 28-day compressive strengths range from 50 to 200 psi. Because CLSM flows and needs no compacting, it is ideal for use in tight or restricted-access areas where placing and compacting soil or granular fill is difficult or impossible. Although CLSM costs more per cubic yard than most soil or granular backfill materials, its many advantages result in lower in-place costs.