Geopolymer cement composed of porcelain polishing residue submitted to accelerated degradation by acid attack

Geopolymers are widely recognized for their exceptional chemical resistance; their reactions occur in strongly alkaline environments and, if exposed to acidic conditions, the dissolution process is reduced compared to conventional cementitious systems. As a consequence, their mechanical performance demonstrates stability over time. However, the performance of residue-containing systems has not been studied thoroughly under similar conditions. In this work, the durability of metakaolin-based geopolymeric cements subjected to the action of sulfuric acid was studied, and the effect of replacing metakaolin with a porcelain polishing residue (PPR) was investigated. The experimental methodology consisted of the continuous immersion of the compositions in a solution of 1 wt% sulfuric acid, and the mechanical and microstructural properties were evaluated. As results, samples with 15%PPR content achieved similar compressive strength to the reference sample. On the other hand, samples with 45% PPR showed a 24.3% reduction in the same parameter after 28 days. However, this reduction decrease to 12.7% after 45 days of immersion for the same group. The experimental analyses allowed us to conclude that the acid attack is characterized by the ion exchange between the sodium of the matrix and the hydrogen of the acid, compromising the Si–O–Al bonds and deteriorating the geopolymerization product. The incorporation of PPR provides, through partial susbtituition, resilience to acid attacks. • Geopolymer systems may undergo leaching of free Na + ions during acid attack, which can buffer the pH reduction. • Porcelain polishing residue can act as sacrificial components, mitigating degradation during acid exposure. • The PONCKS methodology can be adapted for use in amorphous systems containing crystalline phases. • Even after acid exposure, some systems exhibit relatively low mass loss, compare with the reference group.