Effect of milled pegmatite quarry wastes powders on structure, microstructure and mechanical properties of pegmatite-based geopolymers

In this investigation, mechanical activation (MA) of pegmatite quarry wastes was perform via an eccentric vibratory mill to improve the geopolymeric reactivity. The MA at miscellaneous times (0 to 90 min) resulted in different activation degrees of samples with improved the fineness of particle size and specific surface area from 2.974 to 5.311 m2.g− 1. Geopolymer binders were synthesized by partly replacing the pegmatite quarry waste with 12.5 wt% of metakaolin. The activating solution used was a mixture of 10 M NaOH and Na2SiO3 solution with a volume ratio of 1:1. Reaction kinetics, compressive strength, water absorption, chemical (FT-IR, XRD, 27Al and 29Si MAS NMR), and microstructural (SEM/EDS and TEM) analyses were done to characterize the obtained geopolymer binders. The microstructural characterization reveals that undissolved/unreacted particles decreased while the non-bridge particles increased with pegmatite milled. Under SEM/EDS and TEM, fineness of pegmatite particles is highlighted by the formation of more reaction product. As a result, the compressive strength of geopolymer binders improved from 22.3 to 51.6 MPa for 0 to 60 min of milling. From these results, there is feasibility of valorising feldspathic (pegmatite) quarry wastes as alternative aluminosilicate precursors to develop environmentally-friendly geopolymer binders. The resulting binders with high-strength and low water absorption (≤ 8.6%) associated to minimization of CO2-emissions can be used as potential candidate in structural applications. [Display omitted]