Understanding the thermo-mechanical behavior of Low-Cement Concrete (LCC) under fire is essential for its safe and durable use in structures. This study investigates cylindrical specimens (⌀100 × 200 mm) made with Ordinary Portland Cement (OPC)-CS1, 35% Fly Ash (FA)-CS2, and 50% Ground Granulated Blast Furnace Slag (GGBS)-CS3 preloaded to 30% of their 90-day compressive strength and exposed to peak temperatures of 400 °C and 600 °C, followed by cooling to 400 °C, 200 °C or ambient. Axial strain evolution was monitored using Digital Image Correlation (DIC), while residual compressive strength was measured post-exposure. Results show that CS1 exhibited the highest early-age strength and largest thermal expansion, whereas CS2 and CS3 showed slower expansion, earlier onset of contraction, and moderate peak strains. LCC mixes experienced delayed internal heating, reducing thermal gradients during fire exposure. Residual strength was highest for CS1 (77%), followed by CS3 (67%) and CS2 (63%). After heating to 600 °C, concretes lost on average 20-24% of their strength, while 400 °C exposure gave an average loss of 10-15%. Prolonged heating improved SCM concretes’ retention, showing that fly ash and GGBS can limit thermal deformation while maintaining long-term strength and fire resilience. • OPC gains strength rapidly, while LCC develops strength more slowly. • LCC lowers peak expansion and moderates strains under thermal loading. • LCC delays internal heating and reduces thermal gradients during exposure. • Strength loss was 20–24% at 600 °C and 10–15% at 400 °C after cooling. • 50% GGBS concrete shows better post-fire strength than 35% Fly Ash.
Rokade et al. (Sun,) studied this question.