Though precast construction is in use for almost 80 years, it continues to be the least understood construction method in developing countries. Only a limited number of countries in North America, Europe, Australia, Japan and some parts of South East Asia have explored the method of precast construction. As the construction industry revolutionized usage of equipment, high grade concrete and steel, there has been substantial development in the precast concrete industry. Recent examples of precast concrete components used in architectural and structural applications have resulted in high quality buildings.
Precast concrete is a concrete which has been cast and cured in a location other than its final destination. The distance travelled from the casting yard to the site may be a few meters or hundreds of kilometers away. Precast concrete beams for very large crude carrier jetties for Jurong Island in Singapore were produced 40 km away from the site and transported to the site (Figure 1). Figure 2 shows architectural facades with window openings and structural walls that were produced about 5 km from the site.
Figure 3 shows a residential apartment building in Singapore under construction. The Housing and Development Board (HDB) in Singapore is responsible for building all public housing in Singapore, which make up around 80% of the island’s housing. These are built using almost 70-80% precast elements including façade walls, columns, load bearing walls, pre-stressed precast planks, staircases, lift walls etc. The key to success using precast concrete is to be able to offer the client, architect and consulting engineer a solution that is, buildable, economical and faster to build. (Ref. 1,2,3).
Precast frames offer advantages of simplicity in design and production with flexibility of application, permitting a wide range of facade treatments. Façade elements like precast bay windows (Figure 2) with protruding ledges is a classic example of a wide range of surface features provided to the designer with a bagful of options. The precasting operation transfers the manufacturing and storage content of the project away from site, thereby eliminating many of the problems which a contractor may face when executing conventional construction such as wet weather; lack of site space; noise; and waste disposal.
Figure 4 shows various precasting operations such as mould preparation, concreting, curing, demoulding and storage during production of a precast façade element. Precast concrete façade elements can be produced to extremely high levels of accuracy because of the controlled factory environment and use of quality steel forms or moulds; all of which provide quick, easy erection and connection.