Use of nano-structured waste materials for improving mechanical, physical and structural properties of cement mortar

This work investigates the high-energy ball-milling process in order to develop ultra fine nanostructured mineral admixtures. Three types of waste byproduct minerals including; spent catalyst (S.C), copper slag (BFS) and cement kiln dust (CKD) were milled for 2 and 4 h in high energy planetary ball mill and then calcined at 750 °C. The prepared materials were characterized for their particle size/morphology by field emission scanning electron microscope (FESEM). X-ray diffraction (XRD) was used for crystallinity studies and phase analysis. Upon milling, nanostructured particles were obtained with dimensions less than 100 nm. The milling process led to modification of particles morphology and surface texture. XRD patterns indicated that nanostructured materials are found to be more amorphous as compared with the fresh (as received) materials. The aim of this study was also directed to investigate the effect of the prepared nanostructured materials on compressive strength and capillary water absorption (sorptivity) of mortars. For this purpose, blended mortar samples were prepared with partial replacement of cement by different amounts 5%, 10%, 15% and 20% of nanostructured S.C, BFS and CKD. The compressive strength and sorptivity tests were performed at 28 days of curing; the phase composition/decomposition was studied by (XRD) and microstructure was investigated by (FESEM). Results showed that compressive strength of nanostructured blended mortar is greater than that of plain mortar, an enhancement of about 33% was observed. The capillary water absorption generally decreases with increasing replacements of cement by nanostructured materials. A decrease of about 44% was observed at 20% of nanostructured CKD. The microstructure of blended mortar appeared quite dense and compact with great modification/improving for interfacial transition zone (ITZ) between cement paste and aggregate.