Research on mechanical properties and sulfate erosion resistance of nano-reinforced coal gangue based geopolymer concrete

Abstract To enhance the engineering applicability of coal gangue-based geopolymer concrete (CGGC), nano-silica (NS) was used to modify CGGC, the influence of different NS dosage (0–2.5 wt%) on mechanical properties and durability of CGGC was studied. The compressive, flexural, and splitting tensile strengths were tested, the mass and strength loss of samples were analyzed under different sulfate attack ages with different NS dosages. With the increase in the dosage of NS, the mechanical strength and sulfate resistance of CGGC first increase and then decrease. When the dosage is 1%, the mechanical properties are improved most significantly, and when the dosage is 1.5%, the sulfate resistance is the strongest. Combined with scanning electron microscopy, X-ray diffraction, and pore image analysis tests, it was revealed that NS optimized the pore defects in the matrix, generated more cementitious materials, and made the microstructure of the matrix more uniform and denser, both porosity and total pore number had a good linear correlation with compressive strength and sulfate resistance. The smaller the porosity and the fewer the total pore number, the better the engineering applicability of the sample.