How is precast concrete manufactured?
The production process of precast concrete typically consists of six key stages:
1. Design and engineering
The process begins with the creation of detailed designs using advanced 3D computer-aided design tools. These designs specify the structural requirements and dimensions of the precast components. It’s at this stage where our design team can help our clients save money by choosing the most efficient way to manufacture the precast units.
2. Rebar cage assembly and form preparation
Steel reinforcement bars are cut, bent, and assembled to form the rebar cage, which is essential for structural strength. At Poundfield Precast, we use both wooden moulds and those made of steel, depending on how many units are going to be cast. For small runs, moulds made from wood will be more cost-effective, but steel moulds are preferred where multiple units are required as they can be used numerous times without getting damaged or distorted. This ensures that each unit is exactly the same as previous ones.
Cover spacing clips are used to ensure that the correct cover of concrete over the reinforcement is achieved.
Prior to the rebar being placed in the mould, release agents are sprayed onto the mould to ensure easy demoulding when the concrete has set.
The rebar is installed, along with lifters which are designed by engineers to be placed in specific positions so that the units can subsequently handled and moved safely once the concrete is set.
3. Mixing and placement
Before the concrete is poured into the mould, the quality control team carry out a precheck to ensure everything is correct, and signs the unit off as ready to pour. This then allows the mix to be prepared and high-quality raw materials, including cement, aggregates, and water, are mixed to meet specific design requirements. Once the mix has been tested for compliance by means of a slump/flow test, cubes are taken for compression testing and the batch of concrete is then poured into the mould, ensuring it flows around the reinforcement. For the majority of our projects we use self-compacting concrete which eliminates the need to use vibrating tools to remove trapped air and move residual water to the surface of the concrete. The use of SCC results in a much better surface finish with less surface voids.
4. Curing and monitoring
The concrete undergoes a controlled curing process and this stage is crucial for achieving the desired strength and durability. Cube tests are carried out where a sample of the concrete used is placed into a cube, allowed to cure and then measured for its compressive strength at 7 and 28 days. The results are compared against the specific specification of the job.
5. Demoulding and quality assurance
After curing, the concrete is carefully demoulded. Each piece undergoes rigorous quality checks to ensure it meets all the specified standards before it is released from production and marked as being ready for delivery to the customer. Each unit is labelled to ensure a fully traceable process.
6. Transportation and installation
Once the units have passed quality control, the precast components are transported to the construction site and installed by the customer or by our installation teams.
