The Development of Self-Propelled Machines in Illinois for Construction of Concrete Slabs Without Forms

There have been many important developments in road building equipment in recent years; possibly the greatest progress has been made with earth-moving equipment. The size and mobility of earthmoving equipment have been developed to such an extent that pro­ duction has been increased tremendously on the average road con­ struction project. This has had a definite effect on the cost of road work as grading prices are actually lower today than in the earlier days of road building. Asphalt paving equipment has changed considerably in recent years with larger hot-mix plants and the development of several efficient asphalt finishing machines that eliminate the need of hand finishing. Concrete paving equipment has also been developed to increase production and reduce the need of so much hand labor. Among some of the modern developments are the 34-E dual drum paver, concrete spreaders, surface vibrators, and the longitudinal float. These changes have made it possible to increase production and produce smoother riding surfaces. An entirely new and different type of concrete paver or finish­ ing machine was developed in Iowa in 1949 that incorporated the use of slip forms in lieu of staked-in-place steel forms. The machine