Page 1 - Open Access - Feb 2020

TECHNICAL PAPER

PersPectives on Blended

cementitious systems

with calcined clay-

limestone comBination

for sustainaBle low

carBon cement

transition Yuvaraj DhanDapani,
Manu SanthanaM, ravinDra Gettu,
raDhakriShna G. pillai

Abstract including – improving the energy efficiency of kilns and pre-
calciners, alternative fuels, alternative raw materials, new
This paper presents a summary of the major findings from the alternative clinkers, improving grinding efficiency, carbon
studies conducted at Indian Institute of Technology (IIT), Madras capture and storage, and substituting clinker with supplementary
on Limestone Calcined Clay Cement (LC3), in comparison cementitious materials (denoted as SCM hereafter) [1,2] . In a
with plain portland cement and fly ash-based binder. The technology roadmap by World Business Council for Sustainable
study attempts to delineate the chemical and physical effects Development (WBCSD) and International Energy Agency (IEA),
of binder components in LC3 on hydration and hardening,
property development, binder chemistry and durability clinker substitution was identified as one of the major solutions
indicators to evolve fundamental understanding on the for a sustainable transition to a controlled 2ºC rise in temperature
[3]
performance of such low clinker binders. Such an assessment scenario in cement industry . The production of clinker, which is
can drive the practical adoption and extend the applicability the essence of cement, has a severe impact on the raw material
of such binders in various domains of cement-based materials. reserves. It is widely accepted that the path forward for the
The experimental strategy involved the assessment of the pore production of sustainable concrete involves the reduction of the
structure evolution and electrical properties on cementitious clinker factor in the binder, which is made possible by the use
[2,4]
pastes, along with measurement of the durability parameters of suitable alternative binding materials or SCMs . Availability
on concrete for resistance to ingress of moisture by absorption, of potential substitute materials and environmental concerns
and chloride ions by migration and diffusion mechanisms. related to clinker production have powered the use of SCM
The synergistic interactions of the blend of calcined clay and over the last few decades. With the low availability of good
limestone impact the physical structure positively at early ages quality fly ash and slag and the uncertainty of tapping into the
as opposed to fly ash systems, which require prolonged curing natural pozzolan sources, calcined clay has emerged as the most
to realise their potential. The study reveals a combination of promising alternative for the extender in blended cement [5,6] .
calcined clay and limestone can be a potential combination for Another development over the last two decades has been the
producing high-performance concrete, more specifically in a increased use of ground limestone as an additive in the binder,
chloride laden environment, along with the beneficial alternative either up to 5% as a performance improver or up to 15% in
resource utilisation and sustainability prospects. Portland Limestone Cement (PLC) formulations [7,8] . More recent
literature has indicated the synergistic effects of using limestone
Keywords: Calcined clay, Formation factor, Limestone, in combination with other SCMs a part of a ternary binder system
Microstructure, Ternary Blends. with portland cement [9–13] .

2. BACKGROUND ON TERNARY CEMENT
1. INTRODUCTION
COMPOSITE WITH LIMESTONE AND
Cement consumption is projected to quadruple in the next
few decades in India to meet the growing infrastructure, CALCINED CLAY
economic and social advances. Many strategies have been The requirement for SCMs is expected to reach 500 million
[5]
suggested for reducing the CO 2 emission in cement production tons as per estimates presented in to meet the demand

The IndIan ConCreTe Journal | FeBruarY 2020 31