Effect of Grinding Treatment of Fly Ash on Compressive Strength of Hardened Geopolymers using Warm Press Method

Abstract

In this study, starting mixed wet powders were uniaxially compressed at 200 MPa for 40 min and simultaneously heated at 200°C to form hardened bodies. Three different starting slurries composed of 100 g of fly ash powders with particles of different sizes after grinding treatment, 15 g of reagent-grade sodium, and 33.3 g of fresh water were considered. In this time, the uniaxial pressure was fixed at 200 MPa. This method is called the warm press method because the heating temperature is not as high as that in the conventional hot press sintering method used for ceramics. When ground fly ash with a diameter of 6.8 μm was used, the average compressive strength of the hardened bodies reached approximately 120 MPa. As the heating temperature and duration were increased at the fixed uniaxial pressure of 200 MPa, the compressive strength of the geopolymers increased. When ground fly ash with a diameter of 6.8 μm was used and the heating temperature and duration were 280°C and 60 min, respectively, the compressive strength of the geopolymers reached approximately 150 MPa.