Page 9 - ICJ Jan 2026

TECHNICAL PAPER

ambient-curing capability, and stable slump retention-critical using these aggregates demonstrated that structural-grade
requirements for RMC operations. Laboratory investigations strength levels up to M35 can be achieved. Fresh property
confirmed strong performance across strength, modulus, assessments indicated adequate workability, while mechanical
permeability, resistivity, chloride diffusion, and corrosion testing lead to the development of various constitutive
resistance metrics, matching or exceeding OPC concrete. The relationship between properties like flexural strength [38] ,
geopolymer mix was then used to cast a single-room RGC Modulus of elasticity [39, 41-42] with the compressive strength as the
structure equipped with embedded and surface strain gauges conventional relationship between normal weight concrete does
for performance monitoring. Load testing conducted as per not stand valid for light weight concrete and same has been
[1]
IS: 456 (2000) showed deflection and strain responses well incorporated in revised IS: 9142. Durability studies revealed
within permissible limits, with substantial recovery after favorable performance with respect to permeability, shrinkage,
unloading, demonstrating reliable structural behavior. Overall, and resistance to aggressive environmental exposure. Overall,
this study successfully bridges the transition from laboratory NCCBM’s work establishes sintered fly ash lightweight concrete
development to practical field application, providing essential as a technically viable and environmentally responsible material
evidence and quality-assurance practices to support the that enables large‑scale utilization of fly ash and reduces
standardization and broader adoption of geopolymer concrete dependence on natural aggregates, contributing to resource
as a durable, high-performance, and low-carbon construction conservation and improved sustainability in the construction
material. sector.
3.6 Rheology controlled 3D printable concrete
3.5 Sintered fly ash lightweight concrete
3D-printable concrete is an emerging class of digitally placed,
Sintered fly ash lightweight concrete nowadays is getting used formwork‑free materials engineered to flow through a nozzle,
in construction industry because of its reduced dead load, retain shape upon deposition, and build structurally stable
improved durability performance, better thermal and sound layers. Unlike conventional concrete, it requires a carefully tuned
insulation along with improved fire resistance. Apart from this balance of pumpability, extrudability, and buildability governed
lower water permeability, lower chloride ion penetration and by rheology rather than slump. NCCBM’s study includes,
better corrosion resistance of lightweight concrete makes it optimization of cement, fly ash, silica fume, fine aggregate,
more durable as compared to normal concrete. NCCBM has water, and chemical admixture like PC-based superplasticizer
carried out comprehensive investigations on the production along with VMA for 3D printable concrete mixes. Various tests
and performance of sintered fly ash lightweight aggregates related to fresh properties were performed to develop a robust
as a sustainable alternative to natural coarse aggregates in 3D-printable mix. Superplasticizer demand increased with rising
concrete [37-41] . Experimental evaluation of concrete produced aggregate to binder (a/b) ratio, while increasing a/b from 0.75 to
0.90 elevated plastic viscosity by ~35 %. Flow values of 160-225
mm reflected sensitivity to material type and packing density.
Yield stress emerged as critical for structural stability, as low
yield stress caused layer collapse and inadequate buildability.
An optimum polypropylene fibre content of 0.1 % ensured
smooth extrusion with no clogging or shrinkage cracking, and
the system exhibited an open time of 12-15 minutes . Overall,
[42]
the findings underscore that precise mix design‑particularly
binder composition and admixture dosage-is essential for
achieving reliable, high-performance 3D-printable concrete.
Based upon the extensive work carried out, design guidelines
on 3D printable concrete mixes has been submitted to CED32
committee of BIS.

3.7 Plastic concrete, pervious concrete and
controlled low strength material (CLSM)
NCCBM carried out an extensive investigation into three
specialized concretes-Pervious Concrete, Plastic Concrete,
and Controlled Low Strength Material (CLSM) to develop
high‑performance, application‑specific materials using locally
available constituents. The study established clear relationships
Figure 3: Graphs for strain vs stress between mix parameters and functional properties: pervious

88 THE INDIAN CONCRETE JOURNAL | JANUARY 2026