PSI - Issue 70

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

331

• Water Potable tap water free from oils, acids, alkalis, salts, or organic matter was used for both mixing and curing, as specified in IS 456:2000. The water's pH and total dissolved solids (TDS) were tested to confirm its suitability. Consistent water quality is essential to avoid variations in hydration and long-term durability performance. 2.2. Mix Design Control and nano-modified cement pastes were designed with w/c = 0.4. Nanoparticles replaced OPC at 1%, 3%, and 5% by weight. Table 1 summarizes the mix compositions.

Table 1. Mix Proportions

Mix ID

Nano Type

Replacement (%)

OPC (%)

Water (%)

Nano (%)

C

-

0 1 3 5 1 3 5 1 3 5

100

40 40 40 40 40 40 40 40 40 40

0 1 3 5 1 3 5 1 3 5

NS1 NS3 NS5 NA1 NA3 NA5

SiO 2 SiO 2 SiO 2

99 97 95 99 97 95 99 97 95

Al 2 O 3 Al 2 O 3 Al 2 O 3

NCC1 NCC3 NCC5

CaCO 3 CaCO 3 CaCO 3

2.3. Testing Standards To evaluate the performance of cementitious composites modified with nano-materials, a series of standardized tests were conducted. These tests assessed fresh properties, mechanical strength, durability, and microstructural characteristics using Indian and international standards for accuracy, comparability, and reproducibility. • Workability Workability was measured using the flow table test, in accordance with IS 1199:1959 . This method is suitable for evaluating the consistency and flowability of mortar mixes containing nano-materials. The paste was placed on a standard flow table, spread using a standard cone, and then dropped 25 times in 15 seconds. The resulting spread diameter was measured in two perpendicular directions, and the average was recorded. Since nanomaterials typically reduce workability due to high surface area and water demand, this test helped assess the effectiveness of polycarboxylate-based superplasticizer in maintaining flow. • Compressive Strength Compressive strength was tested on 70.6 mm cube specimens, following the procedures outlined in IS 516:1959 . Cubes were cast for each mix variation and tested at 3, 7, and 28 days using a calibrated compression testing machine (CTM). The test results provided insight into early-age strength development (due to nucleation effects) and long-term strength gains (from pozzolanic reactions and microstructural refinement). Each result was the average of at least three specimens to ensure accuracy and minimize variability. • Water Absorption Water absorption was evaluated based on the 24-hour immersion method, as per IS 2185 (Part 1) . Oven-dried specimens were weighed (W₁), immersed in water for 24 hours, surface - dried, and reweighed (W₂). Then, the percentage water absorption was calculated: This test is crucial for assessing the permeability and pore connectivity of the matrix, especially relevant when nanomaterials are introduced to refine the pore structure.