ACI 549R

Abstract

INTRODUCTION: The construction of ferrocement can be divided into four phases: <br>1. fabricating the steel rods to form a skeletal framing system; <br>2. tying or fastening rods and mesh to the skeletal framing; <br>3. plastering; and <br>4. curing. <br>Note that relatively low level technical skills are required for Phases 1 and 3, while Phase 2 is very labor-intensive. This is a shortcoming for industrially developed countries but an advantage for countries where unskilled labor is relatively abundant. In developed countries where labor is relatively expensive, shotcreting (as shown in Fig. 1.1), mechanized fabrication of reinforcement cages,¹ or laminating techniques similar to those developed for marine structures can reduce the labor cost.^2,3 Experience has shown that the quality of mortar and its application to the mesh are the most critical phases. Mortar can be applied by hand or by shotcreting. Since formwork is usually not required, in contrast to conventionally reinforced concrete construction, ferrocement is especially suitable for structures with curved surfaces, such as shells and free-form shapes. In some instances, its use as a permanent form for a reinforced concrete structure can be economically justified.⁴ <br>Ferrocement has a very high tensile strength-to-weight ratio and superior cracking behavior in comparison to conventional reinforced concrete. This means that thin ferrocement structures can be made relatively light and watertight. Hence, ferrocement is an attractive material for the construction of boats, barges, prefabricated housing units, and other portable structures. However, even though for these applications ferrocement is more efficient on a weight basis, it is frequently more economical to build with conventionally reinforced concrete. This is especially true in developed countries where, due to higher material cost and the labor-intensive nature of ferrocement, its use is limited to specialized applications such as domes, wind tunnels, roof shells, mobile homes, modular housing parts (Fig. 1.2), tanks, and swimming pools. <br>While construction with ferrocement may not be costeffective in many applications, this material competes favorably with fiberglass laminates or steel used in special structures. Two feasibility studies have shown ferrocement costs to be less than those of steel or fiberglass in the construction of wind tunnels⁵ or hot water storage tanks.⁶ It is believed that the development of new mesh reinforcing systems and more efficient production techniques will make ferrocement competitive in a wide range of applications requiring thin structural elements.