PSI - Issue 70

Suresh Kumar Verma et al. / Procedia Structural Integrity 70 (2025) 327–334

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• Microstructural Analysis To understand how nanomaterials influence the internal structure and hydration mechanisms, the following advanced characterization techniques were employed: Scanning Electron Microscopy (SEM): Used to study the surface morphology, pore structure, and distribution of hydration products at high resolution. SEM images provided visual evidence of densification and reduced voids due to nano-additions. 3. Results and Discussion 3.1. Workability The addition of nanoparticles to cementitious mixes affects the workability primarily due to the high specific surface area of these materials and their tendency to agglomerate. Nanoparticles, due to their extremely small size and high surface energy, tend to form clusters or agglomerates when not properly dispersed. This leads to higher friction between particles, which can reduce the flowability of the mix. Consequently, workability becomes a key concern when incorporating nanomaterials into concrete. The flow table test was conducted to assess the spread of the cement paste for each mix, with results showing the variation in flow due to different nanoparticle contents. The Table 2 summarizes the results of the flow table test for each mix: As seen from the table, the control mix (without nanoparticles) had the largest spread diameter (~155 mm), signifying the highest workability. As the percentage of nano-silica (NS5) increased to 5%, the spread diameter decreased significantly, showing a notable loss in workability (~120 mm). In contrast, the inclusion of nano-alumina (NA5) and nano-calcium carbonate (NCC5) showed more moderate reductions in flow, indicating their relatively lesser impact on workability. This data clearly highlights the importance of optimizing the dosage of superplasticizer when using nanoparticles in concrete mixes. The findings also underline the need to balance the benefits of nanomaterials in improving strength and durability with the challenge of maintaining workability for practical handling and casting.

Table 2. Flow Table Results for All Mixes

Mix ID

Mix Composition

Flow (Spread Diameter)

Reduction in Flow (compared to Control)

Control

100% OPC

155 mm 150 mm 140 mm 120 mm 150 mm 145 mm 130 mm 150 mm 140 mm 135 mm

-

NS1 NS3 NS5 NA1 NA3 NA5

1% Nano-Silica (NS) + 99% OPC 3% Nano-Silica (NS) + 97% OPC 5% Nano-Silica (NS) + 95% OPC 1% Nano-Alumina (NA) + 99% OPC 3% Nano-Alumina (NA) + 97% OPC 5% Nano-Alumina (NA) + 95% OPC

3%

10% 25%

3% 6%

15%

NCC1 NCC3 NCC5

1% Nano-Calcium Carbonate (NCC) + 99% OPC 3% Nano-Calcium Carbonate (NCC) + 97% OPC 5% Nano-Calcium Carbonate (NCC) + 95% OPC

3%

10% 12%

3.2. Compressive Strength Compressive strength is a primary indicator of the structural performance of cementitious composites. This study evaluated compressive strength at three different curing ages — 3, 7, and 28 days — according to IS 516:1959 using 70.6 mm cube specimens. The incorporation of nanoparticles (nano-silica, nano-alumina, and nano-calcium carbonate) at 1%, 3%, and 5% replacement levels of OPC was assessed to understand their influence on strength development as shown in Table 3.