PSI - Issue 70

R. Mohanraj et al. / Procedia Structural Integrity 70 (2025) 358–364

360

mixing. Specimens were compacted using 25 tamping blows per layer in three layers, cured at 27 ± 2°C, and tested for compressive strength at 7, 28, and 56 days. The study evaluates how nano- TiO₂ incorporation and precise mix design affect concrete strength and durability. 3. Experimental Study 3.1. Compressive Strength Test To evaluate the compressive strength of flash-based cement mortar with varying percentages of nano- TiO₂, tests were conducted following ASTM C109 and IS 4031-Part 6 standards. Mortar mixes were prepared using cement, flash, nano- TiO₂, fine aggregates, and water, then poured into 50 mm cube molds in two layers and compacted. After 24 hours of setting, specimens were cured in potable water at 25 ± 2°C for 7, 28, and 56 days (Pattusamy et al. (2023)). After curing, cubes were surface dried and tested in a calibrated Compression Testing Machine (CTM) under a constant axial load. Results revealed the influence of nano- TiO₂ dosage on strength performance. 3.2. FTIR (Fourier Transform Infrared) Spectroscopy Test As per ASTM E1252, Fourier Transform Infrared (FTIR) spectroscopy was used to examine the structural changes and chemical bond formation in nano- TiO₂ modified cement mortar. After 28 days of curing, samples were extracted from each mix to confirm that the hydration processes were finished. Before being milled into a fine powder, the collected specimens were dried in an oven set to 105°C for 24 hours to eliminate any remaining moisture. After that, potassium bromide (KBr) was added to the powdered samples, and they were crushed into clear pellets for FTIR examination. An infrared beam was sent through the produced pellets in the FTIR spectrometer, scanning the sample throughout a wavelength range of 4000 cm⁻ ¹ to 400 cm⁻ ¹. The absorption peaks in the resultant spectra were indicative of several chemical linkages found in the mortar. To determine how nano- TiO₂ affects the composition of the material, notable peaks associated with calcium silicate hydrate (C-S-H), Ti-O bonds, and other cement hydration products were examined. The FTIR results gave important details on phase changes and chemical interactions, which helped to clarify the molecular effects of nano- TiO₂ on cement mortar. 4. Results and Discussion 4.1. Compressive Strength Test The findings indicate that adding nano-TiO 2 has a significant impact on the compressive strength of cement mortar (Fig. 1). In particular, a specific optimal percentage of nano-TiO 2 substitution for cement resulted in a marked improvement in compressive strength at both early and later curing durations compared to the control mix (0% nano-TiO 2 ). This enhancement is linked to the ability of the nano-particles to serve as effective nucleation sites, which speeds up the hydration process and leads to a denser, more refined microstructure with lower porosity. Additionally, the nano-TiO 2 particles helped fill the gaps within the cement matrix, further contributing to increased density and strength. However, the data indicate that exceeding this optimal dosage of nano-TiO 2 resulted in a decrease in compressive strength. This decline is likely due to the agglomeration of nanoparticles at higher concentrations, creating localized weak zones within the mortar. Furthermore, the increased surface area of excessive nano-TiO 2 might have led to higher water demand, potentially increasing the water-cement ratio and negatively impacting strength development. However, the data clearly shows that surpassing the optimal dosage of nano-TiO 2 leads to a reduction in compressive strength. This decrease is probably a result of the clumping of nanoparticles at elevated concentrations, forming localized weak points within the mortar. Additionally, the greater surface area of the excessive nano-TiO2 may have caused an increased water demand, which could raise the water cement ratio and adversely affect strength development.