Ferrocement is a versatile form of reinforced concrete and has wire meshes uniformly distributed throughout the cross-section and cement mortar. It possesses unique qualities of strength and serviceability, which remain unmatched by other thin construction materials.
Ferrocement was invented in 1848 by Joseph Louis and is known to be one of the earliest applications of reinforced concrete. The method was not very prevalent during the 19th century due to inefficient production technology. But today, it is being widely adopted with easy accessibility to the right tools and techniques.
In this article, we discuss the different methods used for the construction of ferrocement.
Methods for Construction of Ferrocement
The fabrication process of ferrocement depends on factors such as the nature of the application of ferrocement, availability of machinery for mixing, handling and placing, skill, and overall cost of labor. It can also be prepared using molds.
During the production of ferrocement, it should be ensured that there are high-level control criteria to attain appropriate encapsulation of several layers of the wire mesh reinforcement with mortar or concrete matrix. The mortar should be compacted in such a way that there is minimum presence of air voids in the matrix. The construction methods for ferrocement are outlined as follows.
1. Skeletal armature method
In the skeletal armature method, several layers of wire mesh are tied on either side of the reinforcing bars (skeleton steel). This entire framework is then welded to attain the desired shape. Following which, the mortar is applied from one side by forcing it to penetrate through the mesh layers until the excess mortar appears on the other side. This excess quantity is then pressed back, and the remaining mortar is struck off to give a good finish.
The skeletal steel is placed at the center of the section in both directions. It simply acts as spacer rods and does not contribute to the strength but adds to the dead weight of the structure. The size of the structure determines the diameter of the steel bars of the skeletal steel. It has to be cut to the required length, bent as per the profile, and tied in a sequence.
2. Closed mold method
In the closed mold method, the layers of wire mesh are either tied or stapled together and held up in position against the closed mold’s surface, i.e., a female mold or a male mold. The mortar is then applied from one side. Though it isn’t mandatory to separate the mold from the ferrocement structure, but, if needed, can be removed using release agents and other treatment agents.
The closed mold method permits the use of mesh reinforcement, eliminating the use of bars or rods, and requires plastering only from one side.
3. Integral Mold Method
As the name suggests, the mold acts as an integral part of the structure to be made. The integral mold, also known as the core, consists of a semi-rigid framework having few layers of mesh or a rigid foam of insulating materials such as polyurethane or polystyrene. The mortar can be applied from one or both sides. After it sets, the quality of ferrocement can be enhanced by adding more layers of mesh with the application of mortar on both sides. Precautions need to be taken to attain a firm bond between the mold and the layer added later on to get an integral structural unit.
4. Open Mold Method
The open mold method is partially similar to the closed mold method. Initially, the mortar is applied through one side of the mesh layers and rods to the open mold. The mold is a lattice of wooden strips. The form is then coated with a release agent or covered entirely with a polyethylene sheeting. Thus, a close but non-rigid and transparent mold would be formed. This facilitates the easy removal of the mold and allows the observation and repair of any glitches during the process of mortar application.
Ferrocement is a versatile form of reinforced concrete and has wire meshes uniformly distributed throughout the cross-section and cement mortar.
The factors that affect the construction process of ferrocement are the nature of application of ferrocement, availability of machinery for mixing, handling and placing, the skill and overall cost of labour.
The construction methods of ferrocement are skeletal armature method, closed mold method, integral mold method, and open mold method.