Adhesion characterization of tungsten mine waste geopolymeric binder. Influence of OPC concrete substrate surface treatment

Tungsten mine waste mud (TMWM) was investigated for its potential use as repair material of ordinary portland cement (OPC) concrete. Bond strength between OPC concrete substrate and three repair materials was analysed. TMWM geopolymeric binder and two commercial repair products were used as repair materials. Bond strength behaviour was assessed from slant shear tests. A total of 128 slant shear specimens were made in order to evaluate bond strength at 1, 3, 7 and 28 days curing. Four kinds of concrete substrate surface treatment were used, as cast against metallic formwork, as cast against wood formwork, saw cut and acid etching. This study indicates that TMWM geopolymeric binders possess very high bond strength even at early ages and that behaviour is not affected by low surface treatment roughness. Commercial repair products on the other hand show very low bond strength and are very dependent on surface treatment roughness. Scanning electron micrographs reveal that TMWM geopolymeric binders chemically bond to the concrete substrate, while cost comparisons show this geopolymeric repair solution is by far the most cost efficient.