There are new advancements in the construction field across the world everyday. One such innovative technology in RCC construction is the evolution of ferrocement as a building material. Ferrocement has a wide range of applications in the AEC (Architecture, Engineering and Construction) industry and offers numerous structural, functional and aesthetic benefits that make it a sought-after material. Read on to learn all about what ferrocement is, its components, applications, benefits, limitations and process of preparation.
What is Ferrocement?
Ferrocement is a mixture of ferro (iron) and cement. It is a type of RCC construction in which the steel reinforcement used is in the form of meshes and/or rods with very small diameters. Believed to have been developed in the Netherlands and France in the 1840s, it was first used to make boats with streamlined shapes. Although most commonly used in the construction industry presently, ferrocement can also be used for making boats, pots, sculptures and other forms of artwork.
Components of Ferrocement
Ferrocement typically has three major components:
Mesh
The steel mesh used in ferrocement can be of the following types:
- Fine Wire Mesh: Commonly called chicken mesh, this type of mesh has hexagonal, square or rectangular openings with opening sizes ranging between 13-25mm.
- Weldmesh: This mesh consists of a grid of wires welded together perpendicularly to form square openings of sizes 25-150mm.
- Crimped Wire Mesh: This is a three-dimensional mesh formed by crimped creeper wires that intersect perpendicularly with straight wires.
- Expanded Metal: Thin gauged steel sheets are slit and expanded to form a grid with diamond shaped openings.
Skeletal Frame
Steel rods with diameters ranging between 4mm to 10mm form the frame for ferrocement structures. These rods are placed with a maximum spacing of around 500mm from each other, depending on the structural requirements and design specifications. Structural steel in the form of pipes or angles can also be used as a substitute for or along with rods.
Cement Mortar
OPC- Ordinary Portland Cement grades of 43 or 53 are generally used to prepare the mortar mix for ferrocement. Natural sand or manufactured sand (m-sand) forms the fine aggregate along with admixtures if required. The general mix proportions for cement mortar in ferrocement range between 1:1.5 and 1:4 (cement:sand) by volume.
Ferrocement Preparation
Preparation of ferrocement concrete typically follows the below steps:
- Mesh and Frame Fixing: The steel mesh and frame are bent, welded and fabricated to the desired shape as per the structural and architectural designs. The area of steel must not exceed 50% of the cross-sectional area of ferrocement.
- Casting: The cement mortar is filled between the mesh and framework by press-filling or press-spraying. This mortar is generally compacted by using a wood orbital sander, as the needle vibrator commonly used for compacting RCC is too big to be efficient for the thin-sectioned ferrocement.
- Curing: A minimum curing period of 21 days is required for the ferrocrete to properly develop strength. During this time, the structure must be kept wet constantly to avoid development of cracks.
Advantages of Ferrocement
The extensive use of ferrocement in construction can be attributed to the following benefits that it offers:
- Strength to Weight Ratio: Ferrocement concrete can be cast in very thin sections while maintaining high strength. A decrease in the general weight and size of structural components leads to an increase in effective usable area.
- Construction Time: The lack of requirement for shuttering and the ease of construction mean that ferrocement structures can be erected much faster than normal RCC structures, significantly reducing construction timelines.
- Flexibility and Versatility: Ferrocement can be moulded to almost any desired shape, including complex organic forms, thus enhancing design freedom and resulting in innovative projects.
- Sustainability: Ferrocement structures require a lower amount of steel and cement, making them more sustainable than regular RCC components.
Applications of Ferrocement
Ferrocement has diverse applications in construction and some of the major ones are:
Structural Components
- Ferrocement Slab: A ferroslab is much thinner than a regular RCC slab, thus maximising floor-to-floor heights.
- Roof: A ferrocement roof can incorporate innovative designs and shapes like domes, vaults, cylinders, pyramids and parabolic and hyperbolic curves.
- Walls: Loadbearing as well as partition walls can be made with ferrocement and these may have cavities with double layers, be soundproofed and thermally insulated and water proofed as required.
- Staircases: Staircases made of ferrocement are much thinner than regular RCC stairs. Freeform curves and organic shapes are also possible.
Water Retaining Structures
Due to its waterproof quality, ferrocrete can be used to make water-retaining structures like storage tanks, rainwater harvesting tanks and septic tanks in different shapes like squares, cylinders and spheres. Water conveyance systems like drains, culverts and canals can also be made of ferrocement. The material is often utilised for creating an additional waterproofing layer for existing structures.
Underground Structures
Ferrocrete has high tensile and compressive strength, giving it the ability to resist soil pressures underground. It can thus be used for building structures like retaining walls, tunnels and underground drainage systems. However, this requires precise structural design with increased material strength to ensure stability.
Building Add-Ons
Building elements like chajjas, lintels, canopies, louvers and other elevational features can be made with ferrocement, where its ability to take on diverse shapes is a major advantage. When existing RCC elements like beams and columns undergo concrete corrosion, they are often jacketed with ferrocement to increase strength and maintain stability.
Limitations of Ferrocement
Despite its numerous advantages, the use of ferrocement has certain drawbacks that limit its usage:
- Corrosion: Due to the thin layer of concrete that covers the metal mesh and reinforcement, ferrocrete can be more easily corroded than normal RCC. Aggressive environmental conditions can especially corrode the outer concrete surfaces rapidly and cause rusting.
- Cost: Although quicker to construct, ferrocement work is labour-intensive, especially when complex organic shapes are involved. This makes the ferrocement price much higher than regular RCC structures.
- Interior Damages: When used in residential or commercial construction, ferrocement walls and surfaces can get damaged by simple tasks like hammering nails or screws. This kind of damage can cause punctures that lead to water seepage, moisture accumulation and mould-growth issues and eventually result in risks to the building’s structural integrity.
Using Ferrocement in Your Project
Ferrocement work requires careful design, precise structural calculations and accurate execution to ensure the desired results. Brick & Bolt, a leading construction company in India, is the right agency to guarantee all these aspects in the construction of your home. With 7000+ completed homes and absolute transparency assured in all projects, the company provides the most trustworthy end-to-end construction services. For building ferrocement structures with premium quality, contact Brick & Bolt today!
Hemali Patel