Precast Concrete: Uses, Development, and Qualities
Precast concrete is a construction material that manufacturers produce by pouring concrete into molds and then transporting the finished product to the building site. Precast concrete components have revolutionized the building industry because they are a way that builders can have an efficient and versatile product that is also consistent and precise. From towering skyscrapers and arching bridges to residential homes, precast concrete is a popular choice that allows builders to reduce building times, enhance durability, and provide design flexibility.
What is Precast Concrete?
Precast concrete is a molded concrete form that is made in advance and then transported to the construction site. The process of creating precast concrete forms involves several steps. These include the creation of the mold according to specific dimensions, pouring the concrete, drying and curing of the form in a controlled environment, and then transportation of the finished product.
Precast concrete is available in a variety of forms ranging from simple to complex. These forms include walls, beams, columns, slabs, bunker silos, feed troughs, girders, stairs, catch basins, manholes, floating docks, and building facades.
Development of Precast Concrete in the Building Industry
The Romans were the first to engineer precast concrete elements for their varied building projects, but it wasn’t until the 20th century that there was the widespread adoption of precasting concrete in the building industry. The rapid growth of cities after WWII led to the need for quick and cost-effective construction techniques led to this and many other innovations in concrete technology.
During the 1950s and 1960s, the adoption of precast concrete in all areas of construction became more prevalent. The possibilities of precast concrete expanded with new innovations in using high-strength concrete as well as prestressed techniques. Innovations in transportation also expanded the reach of precast elements.
Precast concrete technology continues to advance today. New materials such as fiber-reinforced concrete have improved the performance and durability of precast concrete elements. The introduction of computer-aided design (CAD) and Building Information Modeling (BIM) has enhanced the efficiency and precision of precast concrete production. Precast concrete is embraced throughout all segments of the building industry as a reliable and efficient solution for modern construction.
Components in Precast Concrete
Precast concrete contains certain standard elements, but some precast elements might be specialized for particular purposes and unique designs.
- Cement – In most cases, ordinary Portland cement is the primary component of precast concrete, though some manufacturers use OPC in combination with other cementitious materials like fly ash or slag if they are creating precast forms for harsh weather environments.
- Aggregates – Aggregates are inert granular material that provides strength, stability, and volume to the concrete. Common aggregates in precast concrete are gravel, crushed stone, and sand. Lightweight aggregates like expanded shale or slag are common to reduce the weight of precast forms. Recycled materials like crushed concrete or asphalt help to reduce the environmental impact of precast forms.
- Water – Water is required for the hydration of the cement. Precast concrete manufacturers carefully control the amount of water to achieve the optimal level of strength and workability.
- Admixture – Manufacturers include a variety of admixtures to enhance the properties of the precast forms. These include additives like waterproofing mixtures and iron oxides for coloring.
- Reinforcement – In some precast forms, extra strength is required. Manufacturers add different types and levels of reinforcement to the forms. These strengthening components include steel bars, steel mesh, steel and polymeric fibers, and steel tendons.
Qualities of Precast Concrete
Precast concrete has distinct qualities which means that it works well for some projects but not for others.
Strength and Durability
Among building experts, precast concrete is known for its exceptional strength and durability. The controlled manufacturing process helps to ensure consistent and uniform strength throughout the components.
Quality Control
Concrete manufacturers produce precast concrete in a highly controlled environment. This setting allows for rigorous control measures that ensure that the precast elements meet specific standards and specifications. These manufacturers use standardized molds, reinforcements, and concrete mixtures that contribute to this reproducible quality.
Design Flexibility
Precast concrete allows architects and engineers to create customized components for specific purposes and designs. They can introduce complex architectural details, textures, and patterns into precast elements to enhance their design appeal.
At the same time, because the concrete companies manufacture these components off-site, there is little possibility of modification after production. This means that late changes are difficult if not impossible. This can limit design flexibility on-site.
Speed of Construction
Precast elements allow for a faster speed of construction because so much of the work can take place off-site and then be transported already complete to the building site. This means that builders can save time and labor costs and minimize disruption to the surrounding environment.
Sustainability
Precast concrete allows for more sustainability in construction practices. This process creates more efficient use of materials so excess waste is minimized. In addition, precast concrete can be dismantled and reused which helps to minimize construction waste.
Precise Quality and Finishes
The controlled manufacturing environment allows for accurate dimensions, tight tolerances, and consistent surface textures. This precision allows for easier on-site finishing.
Costs
Because these elements are premade, there is greater cost-efficiency overall because of saved labor costs and quicker project completion. Yet, there is a greater initial cost as the manufacturers pass on the cost to cover their specialized equipment and processes. Transportation costs will also increase the initial cost.
Handling and Installation
Handling and installing precast concrete requires specialized knowledge and equipment. The failure to follow correct procedures, especially in important areas like joints, can lead to damage, misalignment, or reduced structural performance.
Sourcing Precast Concrete
Precast concrete is a popular option that you can find at various places, including both national and local suppliers and manufacturers. In the United States, you can find suppliers listed at the National Precast Concrete Association (NPCA). Their website provides a searchable directory that lists specific precast manufacturers in different states and regions. Many states also have directories for precast concrete makers. Online directories for precast concrete companies can be found at The Blue Book Construction & Building Network and Thomasnet.
When you are looking for a precast concrete manufacturer, be sure to consider their expertise and experience by looking at their history and considering references. Inquire about their quality control process to be sure that their products will meet specified requirements. Consider also their customization capabilities, customer service support, and transportation methods.