RESEARCH ON THE DAMAGE OF GEOPOLYMER CONCRETE UNDER THE ACTION OF SALTWATER AND FREEZE-THAW

Geopolymer concrete was prepared with a mixture of high-activity metakaolin excited by fly ash with sodium waterglass (Na₂O·mSiO₂). The damage degree of geopolymer concrete immersed in the saline solution (3.5% NaCl solution, 3.5% Na₂SO₄ solution, 3.5% Na₂SO₄ +3.5% NaCl solution and tap water) after being subjected to freeze-thaw cycles was studied. The changes in the apparent morphology, mass loss rate and relative dynamic elastic modulus of the specimens in each freezing-thawing cycle were analyzed. The results showed that, under the action of salt erosion, with the increase of freezing-thawing times, the phenomenon of slurry spalling on the surface of specimen became more and more obvious, and the loss of mass and relative dynamic elastic modulus was more serious. According to the curve of mass loss rate and relative dynamic modulus of elasticity, it could be seen that the freeze-thaw damage of geopolymer concrete under the same freeze-thaw times in the four kinds of solutions from strong to weak was as follows:compound salt freeze, chloride freeze, water freeze and sulfate freeze. It was indicated that the composite salt environment was the most unfavorable to the frost resistance of geopolymer concrete. The research results can provide some theoretical references for the design of geopolymer concrete structures in saltwater and freeze-thaw environment.