The use of microsilica-gel bonding in no-cement (NCC) shotcreting has gained interest in the last decade with the aim of increasing the lifetime of the refractory material. Consequently, the accelerators that are conventionally used for low-cement and ultra-low cement shotcreting are not suitable. Alternatives that are currently being used for NCC shotcreting either have cost implications for installation or maintenance of equipment or performance limitations of the refractory product. This study investigates the use of different hydrogels as accelerators in NCC shotcreting, together with a binder system, SioxX®-Flow, with the aim of improving the shotcrete applying process, high temperature refractory properties, and limitations associated with current alkali-free accelerators. The evaluation consisted of two parts: 1) characterization of the hydrogels through rheology measurements, 2) evaluation of hydrogels in refractory shotcrete. The characterization of the hydrogel consisted of rheology evaluation of refractory slurry suspension that contained the hydrogel and oscillatory rheology for the pure hydrogels to determine gel strength. The evaluation of the hydrogel in the refractory shotcrete included non-destructive resonance frequency and damping analysis of samples after demoulding, drying, and firing at 1500°C. A preferred hydrogel was proposed based on the requirements for application of refractory shotcrete and results from this evaluation.

Currently, the main purpose for obtaining alternative binders for use in taphole clay is to reduce the exposure to harmful polycyclic aromatic hydrocarbons (PAH) associated with conventional coal tar (CTht) binders. Some advances have been made such as using lower-PAH alternative binder or phenolic resole resin (resin-bonded) in taphole clays. The use of non-toxic binders has become exceedingly difficult due to the versatility of CTht in taphole clay. This study investigated a combination binder system that consisted of a sugar alcohol (research-grade glycerine) and phenolic resole resin as a potential non-toxic binder for use in platinum smelting taphole clay. The binder system was characterized according to its composition through Fourier-transform infrared spectroscopy and the PAH content (16-EPA-PAH) was determine using targeted gas chromatography mass spectroscopy. Flow behaviour of the binder was determined through rotational rheology, and the volatilization and rheological thermal stability of the binders were assessed through thermogravimetric analysis and thermorheology, respectively. The effect of mixing these binder constituents on the cross-linking behaviour of the phenolic resin was evaluated using differential scanning calorimetry. The combination binder had a higher average mass loss and lower carbon yield compared to conventional CTht, but with a lower total PAH content, making it a more health-friendly alternative.