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As steam, and later electricity and gasoline power, became increasingly available, manufacturers of concrete mixing equipment no longer had to rely on human or animal-powered operation. More power meant that the existing technology could be augmented to facilitate better quality of production. Early steam powered mixers included: The Ransome mixer, which consisted of a hollow drum on a horizontal axis; The Gilbreth rotary mixer, which had an opening large enough for a wheelbarrow to fit inside; The International mixer, which was comparable to the Ransome, but was more highly mechanized and designed for larger operations; and the Smith-Chicago mixer, a self-contained mixing plant mounted on a steel truck for mobility. Gasoline powered mixers were also manufactured by Ransome Concrete Machinery Co. and the Smith Co. Both machines served as self-contained plants. The Ransome mixer featured a fixed-batch hopper and did its mixing with scoops, and the Smith mixer had a self-powered charging bucket. The Municipal Engineering and Contracting Co. of Chicago manufactured a self-propelled mixing and spreading machine for laying pavement. The machine loaded ingredients and distributed the concrete itself, supplied its own water, and propelled itself all under the power of a 16-hp gasoline engine.