Dr.L.R.Manjunatha Chairman, Indian Concrete Institute, Bangalore, & GM, JSW Cement
It is very important for us to have a greener, faster and sustainable approach towards the construction of buildings and infrastructure in order to meet the ever-increasing demands of the construction industry. One such method is the precast/prefab technology. Though this construction practice has been in use for over eight decades, it is the least understood in developing countries, and only a few countries in North America, Europe, Australia, Japan and some parts of South East Asia have explored precast construction to the fullest.
In precast concrete construction, the structural elements are casted and cured in a factory environment and post the curing period, they are transported and assembled at the place of construction. This technique helps the user save energy and time, reduce pollution, and make the construction process more efficient. However, it is also one of the most complicated construction techniques. It involves a huge amount of investment initially and availability of skilled labor for erecting the casted structures is also difficult. If there is repeated shuttering it may lead to a lot of honeycombing and undulations on the structural element casted.
Use of secondary cementitious material (SCM’s) like GGBS, fly ash, ultra-fine GGBS in the production of the concrete reduce carbon-dioxide emissions, reduce water demand, and increase the durability and serviceability of the concrete. It is also observed that by using SCM’s one can also achieve cost reduction in precast concrete production for the project. According to research, millions of trees can be saved in a year by using SCM’s in concrete production with an estimate of about 100 kgs CO2 reduction per cum of concrete if ground granulated blast furnace slag (GGBS) is used in concrete making.
Due to the increased fineness of the SCM when compared to OPC, it helps in providing an improved surface finish and also enhances the aesthetic look of the structure, apart from bringing increased resistance to permeability, sulphate attack and chloride attack, and improved compressive strength, flexural strength and tensile strength.
Benefits of precast/prefab technology:
- Reduction in the construction time.
- Reduction in the construction cost.
- Improved balance between environment and construction activities.
- Enhanced buildability of structure with increased repetitions of the same plan.
- Can reduce problems at site with minimal staging, increasing safety etc.
- Solution for quality, surface finish and durability of structure.
- Constructions are sustainable with reduced use of natural resources.