Development and Recycling of Tilt-up Concrete

Simplicity is the key to tilt-up concrete construction. Panels are cast as near to their final position as possible-the most convenient casting base is most often the concrete floor slab of the building. Wood or steel edge forms are prepared and positioned on the casting base. Reinforcing steel, vapor seal, insulation, door and window frames, electric conduit, and outlet boxes are then positioned. Wall panels are cast on the horizontal base, cured, tilted into a vertical position and moved into place with a mobile crane.

It is believed to have been developed in the early 1900s. Records indicate that Robert Aiken, an Illinois contractor, used tilt-up methods to build retaining walls and buildings in the Midwest before 1910. However, tilt-up construction did not increase significantly until after World War Two when contractors recognized that it provides a quick, efficient method of meeting the demand for buildings despite a shortage of labor and materials.

This kind of concrete material is an economically viable method for building individually designed reinforced concrete structures. The process requires few forms and makes efficient use of modern mechanical equipment like . Ready mixed concrete for tilt-up is locally available and special labor skills are not required. Panels are formed and cast on the jobsite, and can be quickly tilted, lifted, set in place, and braced with the aid of high capacity mobile cranes.

This process readily lends itself to mass production-panel lengths and heights are easily changed and adapted to meet any individually designed building. It also can be colored, textured, and shaped to meet almost any architectural demand using techniques such as paint, brick facing, curved surfaces, and exposed aggregate.

Tilt-up construction is most frequently used for one-story commercial buildings such as warehouses or office buildings, though two, three and four-story office buildings are becoming commonplace. Condominiums and hotels as tall as ten stories have been constructed with tilt-up concrete. However, it is no longer limited to use in industrial and commercial buildings. In 1993, tilt-up concrete panels were used to construct trickling filter tanks using at a wastewater treatment plant.

Concrete pavements are made by mixing cement with water, sand, and 'virgin aggregates' obtained from rock quarries located in the proximity of the construction site. In Indiana most of these aggregates are quarried limestone.

If you are going to pave, you may have to remove the old concrete and break it into pieces anyway, so recycling makes sense. The researchers are testing concrete mixtures that contain varying percentages of recycled concrete. They also are developing cost-analysis software that will enable the state and construction contractors to estimate how much they could save by using recycled concrete. Crushing old concrete pavements into aggregate that can be recycled in new concrete can potentially reduce materials costs by 10 percent to 20 percent, depending on whether any quarries are located near construction sites.