One of the primary characteristics of precast concrete structures is their factory-based production, or prefabrication. Factory-based production is a mode of manufacturing and is not synonymous with factory production. While most precast concrete components are manufactured in component factories, on-site production is also possible; the latter is commonly referred to as mobile or nomadic production.

PC factories produce prefabricated components primarily through assembly-line production, long-distance formwork casting, and fixed-mold-frame casting.

Pipeline

The pipeline production method is suitable for manufacturing simple components such as truss-reinforced composite slabs, double-sided composite slabs, and flat slabs. There are three types of pipelines: manual, semi-automatic, and fully automatic. For components with a single type and relatively simple tendon configurations, the assembly line can achieve a high level of automation and intelligent operation.

Zhang Shanfa

The long-line method is commonly used in the production of prestressed components, such as SP panels and double-T panels.

Fixed Mold Base

The fixed-formwork method can produce a wide range of components, including columns, beams, floor slabs, wall panels, staircases, bay windows, balcony slabs, and corner elements, making it highly versatile, flexible, and adaptable. It also requires relatively low initial capital investment, which is why it is currently the most widely used construction technique in China.

The production components for the fixed-mold platforms used in precast concrete element manufacturing are “laid down” during casting, while the actual molding process involves insertion into the molds. Stair assemblies are typically manufactured using a three-dimensional, stacked production approach; some factories employ this method to produce non-decorative finish-layer wall panels and column elements that have no window or door openings.

For precast construction projects located in areas without nearby PC component factories, the required precast components can be manufactured on a nearby flat site.

Prefabricated components that are heavy, have complex shapes, and vary widely in size are either difficult or impossible to transport, so a nomadic production approach is employed.

For certain projects and road sections where component transport vehicles have difficulty accessing the construction site, mobile production will also be employed.

Factory purchase or on-site prefabrication?

Component factories are highly mechanized and automated, enabling mass production of standardized components, while skilled industrial workers can produce complex components with controllable and stable quality. Compared with on-site prefabrication, factory procurement incurs additional transportation and tax costs. In the Shanghai area, most factories purchase precast concrete components.

Nomadic prefabrication requires land, and the overall packaging unit must have the requisite equipment and manpower, resulting in limited production capacity. However, it entails low investment and a short construction timeline. Short transportation distances for components minimize losses, and integrated management of component fabrication, installation, and on-site construction is feasible. Nomadic production is well-suited for projects with underdeveloped industrialization, small-scale projects, and specific specialized projects.

Concrete precast component assembly line or fixed-mold table?

The fixed-mold approach is easy to understand: it involves shifting on-site work to the factory to produce various components. However, this method suffers from low productivity and offers little room for future growth.

The production of single-panel components on precast concrete assembly lines can be automated and智能化, achieving high efficiency. However, the initial investment is substantial, requiring a larger city or market scale.

Currently, composite floor slabs and double-sided composite shear walls are highly automated and best suited for assembly-line production. The fabrication of bay windows, with their complex formwork and rebar tying requirements, is more appropriate for fixed-mold-frame production. Standard wall panels are manufactured on assembly lines, resulting in improved production efficiency.