Fabric Formwork — An Alternative Concrete Construction System

Abstract

SUMMARY The use of fabric as a concrete formwork material has been in practice for many years. As of late, geotextile fabrics are relatively readily available and cost effective as a result of their widespread acceptance and use in traditional site backfill applications. In order to employ the durable, functional, and aesthetic qualities of a concrete structural system in locations where site logistics might be prohibitive or experienced labor less locally available, alternative lightweight fabric forming systems may prove viable. The overall economy on formwork material and construction operations is consistent with the sustainable practices of using less material and energy in construction. When compared with traditional rigid wood or steel panel formwork, less material by weight is required on site for casting, with the possibility of less ensuing waste. The fabric formwork systems can take advantage of designing formwork tie and support systems for lessened pressures at greater heights. In practice, the height of the fluid concrete can be tactilely monitored on the form surface, which can allow for fewer stages of concrete construction on site. Other sustainable advantages inherent in the system are increased durability and the use of less material to form out-of-plane, curved features. In this paper, two recent residential projects in rural Vermont are presented to illustrate the sustainable advantages of geotextile fabric as part of formwork system. The fabric formwork was used for walls, columns, and elevated slab soffits, resulting in savings in formwork material weight of at least 35% compared to a standard wood panel system. This also translates to reduced energy use for material transport, less waste, fewer pour operations, and the use of socalled local labor that is not dependent on larger scale concrete operations experience. Once stripped, the fabric has the potential to be reused on-site as subgrade stabilization. OVERVIEW The use of fabrics for formwork pre-dates the currently available Geotextiles [Malone, 1999]. Here, geotextiles concrete formwork is defined as woven polyester or polypropylene fabric used primarily for earth stabilization measures that allow for the filtered passage of water. Other fabrics are used and are available. From a sustainable aspect: • A fabric formed concrete surface is found to be more durable than those formed with rigid impermeable forms in general [West, 2003], although this is not recognized by the codes to date. However, if concrete is sought for durability aspects, it can enhance that advantage. • Fabric formwork systems use less weight in material than rigid panel systems, especially in the creating of curvilinear shapes. This can translate into less energy used for on-site forming operations.