Precast concrete construction offers several key features such as dimensional accuracy, better finishes, and faster erection which are absent when other method of concrete construction is considered. This article highlights features of precast concrete construction.
Features of precast concrete construction include:
Great dimensional accuracy and finishes
Better quality critical elements
No on-site space for moulds and reinforcement storage
Faster erection at site
1. Great dimensional accuracy and finishes
Precast concrete construction provides superior dimensional accuracies and finished concrete surfaces in comparison with cast in-situ concrete. This is largely due to the desirable environment in factories where precast concrete elements are manufactured.
Controlled production condition enables manufacturer to properly execute stringent quality control measures to meet specified or national standards during production.
For example, the quality of inside surface of moulds can be kept in good condition, raw material blending is properly controlled, great accuracy is achieved during reinforcement installation.
Fig.1:Great accuracy and quality finishes
Additionally, there is no grout loss, such as that from badly fitting formwork, which results in poor quality concrete like shown in fig.2.
Fig.2: Poor concrete quality due to bad forming
Finally, in conventional brickwork construction, it is a challenge to ensure consistency in forming openings for windows and door frames. Any excessive gaps or improper filling of such gaps may lead to water seepage at the frame and wall joints.
2. Better quality critical elements
Frequently, precasting construction method is an ideal answer to quality problems when there are difficulties in executing the particular type of work in-situ.
For example, the installation of formwork, reinforcements, and provision of openings during the construction of staircases, refuse chutes, and lift pose considerable challenges leading to grout loss, inconsistent joints, surface damages and imperfections. Using pre-cast elements for these components, such defects can be reduced.
Fig.4: Refuse chute
3. Design flexibility
Precast concrete elements can be constructed to be meet requirements of the design. Complex shapes, sizes and specific technical requirements can be easily fabricated in precast plant.
Complex designs would be difficult to construct using onsite using traditional construction. in this case, precast concrete construction offers desired solution for such construction issue.
Precasting permits greater design flexibility and repeated use of similar shapes and sizes results in better economy.
Fig.5:complex shapes can be fabricated and erected without quality compromisation
4. No on-site space for moulds and reinforcement storage
Precast components are made in a factory and delivered to site where they are lifted straight from the lorry onto the building.
Fig.6:Unloading precast members for direct installation
5. Faster erection at site
precast concrete components arrive at the job site ready to install, which can save weeks over cast-in-place construction. weather conditions at the job site will not significantly affect the construction schedule.
These lead to faster erection of precast concrete members. The difference between in-situ and precast construction is as shown in fig.7.
In both cases there is considerable amount of finishing work to be carried out. This is often less in precast than in-situ work due to the quality of the products.