Calcined clays for shotcrete
Isabel Galan, Haochuan Wang, Augusto Cezar Maciel Soares, Marjorie Pons Pineyro, Rudolf Röck, Florian Steindl, Joachim Juhart, Florian MittermayrAbstract
This study evaluates the feasibility of using calcined clays as clinker‐replacing constituents in wet‐mix shotcrete while maintaining pumpability, sprayability, early strength, and durability‐related indicators. Four clays with different mineralogy and calcination temperatures were assessed through laboratory screening and full‐scale spraying trials. Binders combined 55‐65% of CEM I 52.5 R with ground granulated blast‐furnace slag, ultrafine limestone, and clays at a total binder content of 420 kg/m 3 . An alkali‐free, Al 2 (SO 4 ) 3 ‐based accelerator was used at 7% by mass of binder. Early strength at 6 h ranged between 5 and 9 MPa; at 1 day, strengths were 16‐17 MPa. The leaching/sintering potential, expressed as calcium leached per mass of shotcrete, was lower for mixtures containing the more reactive clay, calcined at 400 and 600 °C. These results indicate that properly selected and processed calcined clays can partially replace clinker in shotcrete binders without compromising early performance, while potentially improving durability‐related indicators.