Geothermal Nano-SiO 2 Waste as a Supplementary Cementitious Material for Concrete Exposed at High Critical Temperatures

• Published in: Materials 2024-09, Vol.17 (17)
• Main Authors: López-Perales, Jesús Fernando, Alonso-Alonso, María Cruz, Vázquez-Rodríguez, Francisco Javier, Guzmán-Hernández, Ana María, Gómez-Zamorano, Lauren Yolanda, Rodríguez-Castellanos, Edén Amaral, Puente-Ornelas, Rodrigo
• Format: Article
• Language: English
• ISSN: 1996-1944; 1996-1944

The partial replacement effect of Portland cement by geothermal nano-SiO waste (GNSW) for sustainable Portland-cement-based concrete was investigated to improve the properties of concrete exposed at high critical temperatures. Portland cement was partially replaced by 20 and 30 wt.% of GNSW. The partial replacement effect on Portland-cement-based concrete subjected to 350, 550, and 750 °C was evaluated by measuring the weight changes, ultrasonic pulse velocity, thermogravimetric and differential thermal analysis, X-ray diffraction, surface inspection, and scanning electron microscopy under residual conditions. The ultrasonic pulse velocity results showed that the GNSW specimens maintained suitable stability after being heated to 350 °C. The SEM analysis revealed a denser microstructure for the 20 wt.% of partial replacement of Portland cement by GNSW specimen compared to the reference concrete when exposed to temperatures up to 400 °C, maintaining stability in its microstructure. The weight losses were higher for the specimens with partial replacements of GNSW than the reference concrete at 550 °C, which can be attributed to the pozzolanic activity presented by the GNSW, which increases the amounts of CSH gel, leading to a much denser cementitious matrix, causing a higher weight loss compared to the reference concrete. GNSW is a viable supplementary cementitious material, enhancing thermal properties up to 400 °C due to its high pozzolanic activity and filler effect while offering environmental benefits by reducing industrial waste.