Precast concrete
Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels, floors, roofs, and piles.
[1] Recently lightweight expanded polystyrene foam is being used as the cores of precast wall panels, saving weight and increasing thermal insulation.
Precast concrete is employed in both interior and exterior applications, from highway, bridge, and high-rise projects to parking structures, K-12 schools, warehouses, mixed-use, and industrial building construction.
The forms used in a precast plant can be reused hundreds to thousands of times before they have to be replaced, often making it cheaper than onsite casting in terms of cost per unit of formwork.
Precast architectural panels are also used to clad all or part of a building facade or erect free-standing walls for landscaping, soundproofing, and security.
Precast concrete molds can be made of timber, steel, plastic, rubber, fiberglass, or other synthetic materials, with each giving a unique finish.
Ancient Roman builders made use of concrete and soon poured the material into moulds to build their complex network of aqueducts, culverts, and tunnels.
In Australia, The New South Wales Government Railways made extensive use of precast concrete construction for its stations and similar buildings.
Precast concrete building components and site amenities are used architecturally as fireplace mantels, cladding, trim products, accessories and curtain walls.
It is essential that each structural component be designed and tested to withstand both the tensile and compressive loads that the member will be subjected to over its lifespan.
Expanded polystyrene cores are now in precast concrete panels for structural use, making them lighter and serving as thermal insulation.
Underground vaults or mausoleums require watertight structures that withstand natural forces for extended periods of time.
When designed with heavy weight in mind, precast products counteract the buoyant forces of water significantly better than most materials.
The original double-wall design consisted of two wythes of reinforced concrete separated by an interior void, held together with embedded steel trusses.
To achieve better thermal performance, insulation was added in the void, and in many applications today the steel trusses have been replaced by composite (fibreglass, plastic, etc.)
The interior and exterior wythes of concrete are held together (through the insulation) with some form of connecting system that is able to provide the needed structural integrity.
[citation needed] Window and door openings are cast into the walls at the manufacturing plant as part of the fabrication process.
The carpenters, electricians and plumbers do need to make some slight adjustments when first becoming familiar with some of the unique aspects of the wall panels.
Besides their energy efficiency and aesthetic versatility, they also provide excellent noise attenuation, outstanding durability (resistant to rot, mold, etc.
Compared to double-walls, for example, which have to be insulated and filled with concrete on site, sandwich panels require much less labor and scaffolding.
The efficiency, durability, ease, cost effectiveness, and sustainable properties[13] of these products have brought a revolutionary shift in the time consumed in construction of any structure.
The wide range of designs, colours, and structural options that these products provide is also making it a favourable choice for its consumers.
