Sustainable Refractories with Recycled Content

The Challenge

Andalusite-based refractories are valued for thermal shock resistance and volume stability, but resource scarcity and environmental concerns drive interest in recycled alternatives. Recycled andalusite presents challenges due to impurities and variable grain decomposition into mullite, factors that create higher concentrations of amorphous phase in the refractory composition, reducing refractoriness and lowering softening temperatures.

The Solution

This research examined thermomechanical performance of shaped refractory products with varying ratios of unrecycled and recycled andalusite. The GrindoSonic MK7 coupled with a high-temperature furnace enabled E-modulus measurement up to 1500°C, tracking the evolution of elastic properties through heating and cooling cycles. Combined with refractoriness under load testing and hot modulus of rupture measurements, this provided comprehensive thermomechanical characterization across compositions.

Key takeaway: High-temperature E-modulus tracking via IET revealed that selectively replacing only the coarse fraction with recycled andalusite preserves thermomechanical performance nearly identical to virgin material.

Results

A selective approach proved effective: replacing only the coarse fraction with recycled andalusite while retaining fine unrecycled andalusite limits the concentration of amorphous phase and preserves thermomechanical performance close to reference material. The D59R61 composition displayed E-modulus profiles almost identical to unreycled reference samples, demonstrating that sustainability and high performance can be combined through strategic particle size selection.