Last week's answer

Question: When engineers designed the original two-lane span of the Lake Pontchartrain Causeway, building 24 miles of bridge using traditional, on-site concrete pouring methods would have taken many years. To open the bridge in just 14 months, the contractors built a dedicated, assembly-line manufacturing plant on the lakeshore. What construction method did they pioneer on a massive scale to pull this off?

Answer: Precast, prestressed hollow concrete cylindrical piles and complete deck spans that were manufactured on land and barged out to be assembled like building blocks.

Lake Pontchartrain Causeway is credited as a pioneer of using prestressed concrete. Dr. Maxwell Upson was an innovator of prestressed concrete, and saw that the material could be used to expand on how piles could be installed. He developed a 54 inch hollow cylindrical prestressed concrete pile, more than double the size of the standard solid square or circular concrete pile of 24 inches or less. These were ideal for developing the foundation of the bridge amind Louisiana's soil made up of soft clays and silts. The use of the precast material and assembly-line, mass-production methods made it possible for the bridge to be constructed in a mere 14 months. 

Sources: American Society of Civil Engineers