he
construction sector is one of the fastest growing sectors in India
contributing to 22% of the total CO2 emission in India. India is one of
the largest cement producers in the world. The country has an installed
capacity of 300 million tonnes (2011) which is slated to rise to 600
million tonnes by 2020. Since the production of clinker relies largely
on limestone, it produces around 137 million tonnes of carbon dioxide
(as of 2010) which is approximately 7% of the total man made CO2
emissions of the country. Apart from environmental emissions, the
industry also uses quite a substantial amount of natural resources,
majority of which are in form of limestone and coal.
The resources for making cement are finite.
Increasing depletion of naturally resourced raw materials will affect
the production of cement in the future. To optimise the use of natural
resources, supplementary cementitous materials (SCM’s) are a viable
alternative. India uses a substantial amount of fly ash as SCM’s.
However, the substitution of fly ash is limited to 30%.
Limestone Calcined Clay Cement or LC3 is a
new type of composite cement based on a blend of clinker, calcined clay
and raw limestone. Clinker content is as low as 50%. LC3
technology has several advantages over Ordinary Portland Cement (OPC)
and Portland Pozzolanic Cement (PPC) such as:
• reduced emission of CO2 up to 30% compared to OPC
• lower energy consumption even with respect to PPC in some cases
• comparable strength with OPC
• improved durability
LC3 has a high chloride penetration
resistance and produces a dense microstructure with high resistivity
which makes it very suitable in corrosive atmospheres like the marine
environment. As the requirement of calcination temperature of china clay
is lower than clinkerisation by 500ºC to 600ºC, so a significant thermal
energy is saved for LC3 production compared to OPC. Even at
the locations with shortage of high quality fly ash, production of LC3
is more economical than PPC. LC3 can be produced using low
grade china clay which is in abundant quantity in India. Even in several
cases, the quality of the clay rejected by clay industries is well
accepted for LC3 production. Hence, it gives another
dimension towards utilisation of the wastes and efficient resource
management.
200 tonnes of LC3 has been produced in
India so far. A detailed study and assessment are in progress to
understand all aspects of the cement. Various building materials like
micro concrete roofing tiles, pavers, kerb stones, hollow concrete
blocks etc. have been produced in pilot scale using LC3. ■