Issue 78

C. S. Karadumpa et alii, Fracture and Structural Integrity, 78 (2026) 146-167; DOI: 10.3221/IGF-ESIS.78.09

kg/m³, w/b ratio of 0.48, and 0.4% polycarboxylate ether (PCE) superplasticizer, targeting a slump range of 100 ± 10 mm. For the nano-modified mixtures, the mix design philosophy was based on the premise that nano-reinforcement could improve the mechanical performance of concrete. Therefore, while maintaining the same target concrete grade (M30) and workability requirements, the binder content was intentionally reduced from 450 kg/m³ to 410 kg/m³. The reduction in binder content was compensated by the anticipated reinforcing effect of GO and CNTs, thereby enabling a reduction in cementitious material consumption without compromising the target performance. Corresponding adjustments were made to the aggregate proportions to maintain volumetric consistency of the concrete mixtures. The water-to-binder ratio was maintained at 0.48, and a PCE dosage of 0.4% by binder weight was used to facilitate proper nanomaterial dispersion and achieve the desired workability.

Material

Property

Specification

Composite Cement (JSW, IS 16415:2015)

Composition

OPC 55–60%; GGBS 30–35%; Class F Fly Ash 10–15% Specific gravity: 2.58; Blaine fineness: 385 m²/kg CaO 52.3; SiO ₂ 28.6; Al ₂ O ₃ 9.8; Fe ₂ O ₃ 3.2; MgO 2.9; SO ₃ 2.1 Specific gravity: 2.55; Water absorption: 1.04% Initial: 110 min; Final: 285 min LA abrasion: 22%; Crushing value: 18%; Impact value: 14% Purity >95%; Thickness 0.8–1.2 nm (2–3 layers) Lateral size: 0.5–5 μ m; Surface area >500 m²/g (BET) Oxygen content: 38–42 wt%; Functional groups: –OH, – COOH, –O– Purity >95%; Diameter: 10–20 nm; Length: 10–30 μ m Surface area: 180 m²/g; Aspect ratio >1000 Tensile strength: 50–200 GPa; Young’s modulus: ~ 1000 GPa Solid content: 40%; Specific gravity: 1.08; pH 6.5–7.5 Fineness modulus: 2.78 Specific gravity: 2.53; Water absorption: 0.5%

Physical properties

Setting times

Chemical composition (wt%) Physical properties

Fine Aggregate (River sand, Zone II)

Gradation

Coarse Aggregate (Crushed granite, 12.5 mm)

Physical properties

Mechanical properties Purity & structure Particle characteristics

Graphene Oxide (GO)

Chemical features

Multiwall Carbon Nanotubes (MWCNT)

Purity & geometry Physical properties Mechanical properties Chemical properties

Superplasticizer (PCE-based)

Dosage 0.8–1.2% by weight of cement Table 2: Properties of cement, aggregates, nanomaterials, and admixtures.

Fine aggregate (kg)

Coarse aggregate (kg)

Mix No.

Binder (kg)

GO (g)

CNT (g)

w/b ratio

Water (kg)

PCE (kg)

Mix ID

Description

SCM-based concrete (no nanomaterials) SCM-based concrete + GO -0.01% SCM-based concrete + GO -0.03% SCM-based concrete + GO -0.05% SCM-based concrete + CNT -0.1% SCM-based concrete + CNT -0.2% SCM-based concrete + CNT -0.3% SCM-based concrete + GO -0.03% + CNT - 0.1%

Mix 1

Control

450

----

----

0.48

216.0

559.04

960.80

1.80

GO 0.01% GO 0.03% GO 0.05% CNT 0.1% CNT 0.2% CNT 0.3%

Mix 2

410

41

----

0.48

196.8

605.7

1028.7

1.64

Mix 3

410

123

----

0.48

196.8

605.7

1028.7

1.64

Mix 4

410

205

----

0.48

196.8

605.7

1028.7

1.64

Mix 5

410

----

410

0.48

196.8

605.7

1028.7

1.64

Mix 6

410

----

820

0.48

196.8

605.7

1028.7

1.64

Mix 7

410

----

1230

0.48

196.8

605.7

1028.7

1.64

Mix 8

Hybrid

410

123

410

0.48

196.8

605.7

1028.7

1.64

Table 3: Mix identification and key proportions.

150