Alkali activation of rock wool furnace slag: Effects of water glass modulus, Na2O content, and nano-TiO2

Rock wool, as an external wall insulation material, is crucial in improving the energy efficiency of structures. However, a large amount of rock wool furnace slag (RWFS) generated during the production of rock wool panels manufacturing causes environmental problems. To address these issues, this study focuses on the use of waste RWFS as a precursor in alkali-activated cementitious materials. In addition, the effect of anatase nano-TiO 2 (ANT) and rutile nano-TiO 2 (RNT) as an additive to the alkali-activated rock wool furnace slag cementitious materials (AARWFSCMs) was evaluated and quantified. Scanning Electronic Microscope (SEM), Isothermal Conduction Calorimetry (ICC), Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD) analysis were used to identify the effects of modulus 1.0–1.8 water glass modulus (Ms; SiO 2 /Na 2 O), 3%–7% Na 2 O content on AARWFSCMs. Experimental tests was conducted to quantify the properties such as the setting time, the fluidity, the compressive strength of AARWFSCMs after hardening. Results found that the optimal content of Ms, Na 2 O content in preparing AARWFSCM were 1.4, 5 % for obtaining 28-d compressive strength of 96.36 MPa. The atomic percentage of Ca/Si of the hydration products in the AARWFSCMs fluctuated within 0.94–1.50. The hydration products were a mixture of C–S–H and C–A–S–H. Moreover, the experimental results illustrated that the nano-TiO 2 , which highly beneficial in improving the compressive strength of AARWFSCMs. The additions of 0.50 % ANT and 0.75 % RNT resulted in increments of 5.9 % and 12.8 % in the 28-d compressive strength of AARWFSCMs, respectively. The obtained results provide a new method of utilization of RWFS and improving the sustainability of the construction industry.