Drying Shrinkage and Microstructural Properties of Geopolymers Including Steel and Iron Particles

Geopolymer mortars show significantly higher shrinkage than normal Portland cement mortars. So, one of the most important disadvantages of these promising alternative binding materials for their wider applications is the cracking occurring by shrinkage. Different inserts and fibers are used in fresh mixtures in order to control drying shrinkage cracks and to provide mechanical capacity. The aim of this study is to investigate the effectiveness of using both metal particles (iron particles) and metallic fibers (steel particles) in geopolymer composites to reduce drying shrinkage. In addition, microstructural properties of composites were determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses and causes of shrinkage were investigated in detail. Mixtures containing 20% ​​silica fume have 38.4% lower drying shrinkage than slag-based mixtures. In slag-based composites, decreases in drying shrinkage were found as 18.8% and 49.1% when adding 10% iron particles or 10% steel particles compared to metal-free composites.