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TECHNICAL PAPER

carbonation resistance, and corrosion performance . For PLC,
[14]
assessment of eight concrete mixes showed that limestone
fineness ≥ 600 m²/kg and overall cement fineness ≥ 425 m²/
kg ensure performance parity with OPC at limestone contents
up to 15 % [26,27] . Investigations on HVFAC demonstrated that
blends incorporating 40 % fly ash with a Blaine fineness of
400-410 m²/kg achieve carbonation and corrosion performance
comparable to PPC containing 35 % fly ash at 300 m²/kg
[16]
fineness . In fly ash‑limestone composite cements (24 mixes),
optimal performance was achieved with minimum OPC content
of 65 % (clinker ≥ 60 %), fly ash 15‑30 %, and limestone 5‑10 %
for achieving durability and mechanical properties equivalent or
superior to PPC [23-27] . Based upon the mechanical and durability
study carried out on concrete designed at various combinations,
following proportions were suggested and drafts were prepared
that are submitted to Bureau of Indian standards for discussion
as well as deliberations.

The findings of the study will support the development of new
Figure 2: RCC samples in field environment for durability study cement standards that promote sustainability and achieve a
significantly lower carbon footprint‑approximately 30‑60 %
chloride ingress values below 1,000 coulombs in RCPT tests. lower than that of ordinary Portland cement. Furthermore,
Reinforcement corrosion studies confirmed passive behavior in the research confirms that low‑carbon cementitious systems
moderate exposure environments when mix design and curing offer a dual advantage: they not only ensure the durability
were adequately controlled. These results demonstrated that and long-term performance of concrete but also contribute
substantial clinker reduction is feasible without compromising substantially to both national and global decarbonization goals.
durability, provided performance-based criteria are applied. To promote indigenous cementitious materials as potential
The generated data have contributed to durability-linked replacements for imported additives such as silica fume,
provisions and clinker substitution limits in the ongoing revision comprehensive studies have been undertaken on the use of
of IS: 456 and draft low-carbon cement standards, supporting a ultrafine cementitious materials specifically ultrafine fly ash and
transition from prescriptive cement composition requirements to ultrafine GGBS in concrete production. These materials have
exposure‑based performance specifications. now been standardized in terms of their physical and chemical
characteristics through IS: 19058 (Ultrafine Fly Ash) and IS: 16715
The extensive evaluations on various composite cement
systems‑including fly ash‑slag composite cement, Portland (Ultrafine GGBS). Additionally, ongoing research is exploring the
application of ultrafine and nanomaterials, including nanosilica
limestone cement (PLC), high‑volume fly ash cement (HVFAC), and graphene, for the development of high-performance and
fly ash‑limestone composite cement, helps to establish
ultra-high-performance concrete.
optimal blend proportions ensuring mechanical and durability
performance comparable to or exceeding that of PPC [8, 13-17, 23-27] . 3.3 High performance concrete (HPC) and ultra
Studies on fly ash‑slag composites, comprising 20 mortar and high performance concrete (UHPC)
72 concrete mixes, indicated that maintaining a minimum OPC
content of 50 % (or clinker ≥ 45 %), fly ash between 10‑25 %, Fundamental studies on high-performance concrete (HPC)
and GGBS between 25-40 % yields favourable strength, and ultra-high performance concrete (UHPC) addressed

Table 2: Low carbon cementitious systems
TYPE OF LOW CARBON MINIMUM CLINKER TYPE OF SCM OR ALTERNATIVE MATERIALS, PERCENT
CEMENTITIOUS SYSTEM CONTENT, PERCENT
FLY ASH GGBS LIMESTONE LD SLAG
Fly ash - slag composite cement 45 10-25 25-40 - -
Portland limestone cement (PLC) 80 - - 10-15 -
LD slag-based Portland slag cement 40 - 51 - ≤ 9
Fly ash-limestone composite 60 15-30 - 10-15 -
High volume fly ash cement 55 40-45

86 THE INDIAN CONCRETE JOURNAL | JANUARY 2026