Analyzing rice husk ash-based silica in Thuathienhue for ultra-high quanlity concrete

Abstract

In comparison to conventional Portland cement concrete, Ultra-High Performance Concrete (UHPC) utilizes significantly higher amounts of binders, potentially reaching up to 1000 kg/m3, and active mineral admixtures such as silica fume, which can be as high as 250 kg/m3. This has led to increased costs for UHPC and posed challenges in the supply of these mineral admixtures in the manufacturing of UHPC, especially in developing countries like Vietnam. Finding alternative mineral admixtures with equivalent functionality to silica fume to partially replace cement in UHPC is essential. Among the active mineral admixtures used for UHPC, thermally treated rice husk ash under stringent conditions is considered a promising supply source for UHPC production. This study proposes an industrially controlled continuous pyrolysis model with an automated pyrolysis regime for producing silica-enriched amorphous rice husk ash. The experiment surveyed common rice husk sources in the Thua Thien Hue province under optimal pyrolysis conditions at 700°C, with a residence time of 1 hour in the pyrolysis chamber and a continuous production mode. XRD and SEM analysis results indicate that rice husk ash can be a substitute for part of the cement and industrial mineral admixtures in UHPC production, with potential for developing an industrial-scale model to achieve dual objectives of economic and environmental efficiency.

Key words: Rice husk ash; amorphous silica; pyrolysis model; mineral admixture; UHPC.