India is in a developing phase – from mass housing to mass rapid transport system, every sector is booming at the best of its capabilities. That said, with every passing year, the demands are increasing, which are turning smaller towns into tier-I, tier-2. Mass Rapid Transport System plays a vital role in increasing connectivity and aids economic development. India has developed several Metro Rail projects, which increased convenience for the citizens in terms of transportability. Kolkata is highly recognised for building the first-ever underground Metro Rail in seventies; to address the need it recently decided to expand the city Metro Rail network too. Being the key material supplier in the recent Kolkata Metro project, team ACC gained insightful information and practical hands-on experience on better building practices.
Challenges and Solution
The construction of Metro line – elevated from underground has its own challenges. Needless to say, reputed and large-scale project such as Metro Rail had stringent quality parameters; and the project team ran an extra mile to solve every challenge. The most critical aspects are key parameters, for instance, high strength, cohesive concrete having high workability/longer slump retention. Moreover, this level of supreme concrete quality needs to be achieved using available building material and in a cost-effective way too.
To our rescue came the concept of concrete rheology, and we made effective use of the same. As we know, Rheology is the “Flow Behaviour” of fresh concrete and you can play with rheology by changing water content, changing amount & type of fine particles, using chemical admixtures of changing grades of aggregates. Hence, one can produce concrete which can be de-moulded instantly as in case of precast concrete products or pump concrete to the height of buildings taller than Eiffel Tower. One can also produce roller compacted concrete as we use for hydropower dams or opt for self-compacting concrete.
In the Metro Rail project, it was a challenge to achieve workability, cohesiveness and designed strength as the locally available material were not playing to our strengths. The teams had to carry out numerous trial mixes using alternative sources of aggregates, which were locally available before they arrived at the right concrete mix. Team’ collective effort, knowledge and resilience led to successful quality check.
#Better Building Practices
- Whether it is a Metro Rail or Mansion project, good cohesiveness and desired workability of fresh concrete enables to achieve desired hardened properties
- Designing concrete for the desired rheology is an art as well as science, which requires a deeper understanding of the material called concrete
- One can play with the rheology of concrete to produce a variety of concrete for the required purpose
- Cohesive concrete can be transported without segregation
- The desired workability helps in placing and compacting concrete with ease