Q2 2018

Concrete Pavement Progress www.acpa.org 12 I O W A H I S T O R I C U S 2 0 ground. “Today, we focus on foundations that allow drainage under the pavement, but that was not done in the 1920s.” Concrete pavements were also cured differently in the 1920s. “The standard was one day wet burlap and seven days of wet earth,” he says. For the 1921 pavement, the contractor—C.F. Lytle Construction, a Sioux- City based contractor—mixed concrete onsite producing one cubic yard at a time. “One part cement, two parts sand, and three parts rock was the usual mix,” explains Hanson. “In the 1920s, it was common to use wet batch concrete, then contractors moved to dry batch. We did not really see wet batch plants again until the 1950s.” After obtaining the first contract for paving what would be designated US 20 in 1921, Lytle received several other contracts in the same county and began looking for a way to improve efficiency and speed production. He opted to move away from hauling rock and sand to the site by trucks and instead set up a “movable plant.” An article in the June-July issue of the Service Bulletin produced by the Iowa Highway Commission describes Lytle’s innovative strategy to meet the demands of handling over almost 30miles of paving between 1921 to 1924: “Mounted on wheels, from mixer to cook shack, one Iowa concrete road builder’s outfit is ready at a word to pull up stakes … and move at railroad speed to a new location.” continues on page 14 » » continued from page 11 Truck dumping aggregate in skip hoist. Placing burlap for one day of wet burlap curing. Seven day wet earth curing. All photos courtesy of Iowa DOT.