Corrosion of ordinary Portland cement and metakaolin-based geopolymer immersed in nitric acid solution

Abstract

Corrosion of cementitious materials of concrete in acid environment is crucial for the safety and durability of infrastructures. This work prepares two groups of specimens of ordinary Portland cement (OPC) and metakaolin-based geopolymer (MKG) to investigate their corrosion in 1 mol/L nitric acid solution. Changes of morphology, mass, compressive strength, pH, chemical elements, crystal phases, pores are compared and analysed. Results show the surfaces of ordinary Portland cement are corroded into petaloid grooves due to the relatively severe reaction between the calcium hydrated products and nitric acid solution. The porosity of OPC specimens increases greater than that of MKG specimens whose main compositions react relatively mildly with the nitric acid solution. However, large quantities of fragments are peeled away from the MKG specimens, and their losses of mass and compressive strength are also greater than those of OPC specimens. But the porosities of MKG specimens change little. And the strength loss of MKG specimens is mainly due to the broken matrix structure and the newly formed porous silicious framework.