Corrosion and deterioration mechanism of water-rich filling materials in acid solution

To study the impact of acid environment on the water-rich filling materials, experimental methods including intensity detection, scanning electron microscopy and X-ray diffraction were used to analyze the macro and micro changes of water-rich filling materials in acid environment and to discuss the corrosion and deterioration mechanism. After soaking for 180 d in hydrochloric solu-tions of pH 1 and pH 3, the compressive strength of the materials decreases by 88.8% and 58%, respectively, compared with that of standard curing for 28 d. After soaking in a sulfuric acid solution of pH 3, the compressive strength decreases by 68%. When the ma-terials were soaked in a sulfuric acid solution of pH 1, the compressive strength is zero. Microscopic tests show that dihydrate gypsum is generated in the materials with the prolongation of immersion time in the sulfuric acid solution. In the hydrochloric acid solution, di-hydrate gypsum is produced only in the solution of pH 1 after soaking for 180 d. The corrosion of the hydrochloric acid solution on the materials is mainly the dissolution corrosion of hardened structure with the neutralization effect of H⁺. The corrosion of the sulfuric acid solution on the materials is the dissolution corrosion of hardened structure with the neutralization effect of H⁺ and the expansion corrosion of dihydrate gypsum. The corrosive action of the sulfuric acid solution on the materials is stronger than that of the hydrochlo-ric acid solution.