High‐performance fly ash‐reinforced engineering composites with thermosetting polyamine as matrix

Abstract Preparation of composites by combining fly ash (FA) with organic polymers is a promising approach for realizing the value‐added utilization of FA and reducing environmental pollution. However, the high content of FA generally leads to a significant decline in the mechanical strength of the composites, due to the discontinuous feature of FA particles and poor inorganic–organic interfacial compatibility. In this study, a new matrix, melamine‐hexamethylenediamine (MH) resin, was used without any modifications to the FA. The reinforcing effects of FA on heat resistance, compressive, and tensile strength of the composites were achieved. Specifically, compared to the neat MH resin, the compressive strength of the composites increased by 50%–70%, reaching up to 270 MPa with the addition of 40%–70% FA. Additionally, ~2%–10% increase in tensile strength was achieved for composites containing 10%–40% FA. Although the flexural strength of the composites decreased with the increase in FA content, the strength remained above 100 MPa when the FA content was below 40%. The obvious reinforcing effects of FA can be attributed to the good interfacial compatibility between MH and FA, allowing the addition of FA up to 40%. With excellent comprehensive performances, the composites could be promising structural materials in engineering applications. Highlights Melamine‐hexamethylenediamine (MH) resin was used for the first time as the matrix of fly ash‐reinforced composites. Significant reinforcing effects of fly ash on the composites were observed. The composites exhibited high mechanical strength and excellent environmental durability. The MH resin appeared to be a promising matrix for high‐performance fly ash‐based composites.