Abstract: Shale ceramsite (SC), functioning as a lightweight, porous aggregate with moderate strength, serves as intentional defects in geopolymer composites to induce saturated cracking behavior within the matrix. This study designed and fabricated 9 groups of high ductility geopolymer composite (HDGC) specimens with varying SC content and particle size distributions. Uniaxial compression tests, tensile tests, scanning electron microscopy, and energy-dispersive spectroscopy analyses were conducted at different curing ages to investigate the effects of SC content and particle size distribution on HDGC’s compressive strength, tensile strength, tensile strain, crack morphology, and microstructure. Results show that there is an interface reaction between SC and the matrix, and as the SC particle size decreases, the microstructure of SC-matrix interfacet is more compact. With the increase of SC content, the tensile strength and tensile strain of HDGC initially increase and then decreast. Whereas these properties generally decrease with the increase of SC particle size. Notably, the tensile strength and ultimate tensile strain of HDGC with 40% (mass fraction) SC and particle size distribution of 0.15~<0.30 mm achieve 5.8 MPa and 9.3%, respectively. This study can provide a theoretical reference for the design and application of green high-performance geopolymer composites.

Key words: high ductility geopolymer, shale ceramsite, compressive strength, tensile strength, microstructure, interfacial transition zone