Investigation of paperboard tubes as formwork for concrete bridge decks

Abstract

The objective of the research reported in this paper was to investigate the use of short arc-length segments and semi-circular segments of paperboard (also known as cardboard) tubes as formwork in bridge deck applications for either long-span [20–50m (60–160ft)] steel or prestressed concrete bridges or short-span [6–20m (20–60ft)] “Beam-in-Slab” bridges. In both these types of structures conventional plywood and light framing lumber formwork can be expensive and time consuming to install. For over 30years, paperboard tubes have been used throughout the world to form round, reinforced concrete columns or occasionally voided slabs. These tubes (also know as Sonotubes) are produced throughout the world, and are preferred to conventional steel, plywood, or even fiber reinforced plastic (FRP) formwork because they are economical, disposable and recyclable. Due to their tubular shapes they have not been considered for use in “flat” elements such as slabs and walls. This paper presents results of a series of laboratory tests conducted at the University of Wisconsin – Madison that demonstrate that paperboard tube segments can be used as formwork for certain types of slabs, particularly for bridge decks and a variety of other types of construction where a flat surface is not essential. The testing, which was intended to simulated construction site loading conditions, included ultimate and service load tests, as well as impact loading. Tests were also conducted to investigate how moisture content affects the structural performance of the tubes. Results showed that commercially produced large diameter paperboard tubes may well be viable economical and recyclable materials for forming concrete elements, particularly those used in bridge decks when wide-flange prestressed girders are used.