Abstract: A fly ash-slag-based geopolymer concrete was prepared, and the influence mechanism of active magnesia content, sodium silicate modulus, alkali equivalent and slag content on the compressive strength and drying shrinkage was explored and analyzed through 28 d compressive strength and drying shrinkage tests. The results show that with an increase of the active magnesia content, the 28 d compressive strength of the geopolymer concrete decreases, while the drying shrinkage deformation significantly diminishes. Compared with concrete specimen with 0% (mass fraction, the same bellow) active magnesium oxide content, concrete specimens with 3%, 6% and 9% magnesium oxide show a decrease of 8.0%, 8.2% and 18.2% in 28 d compressive strength, and a decrease of 21.5%, 26.4% and 38.2% in drying shrinkage, respectively. In addition, when the content of active magnesium oxide is 3% and 6%, it not only effectively compensates for drying shrinkage, but also reduces the loss of compressive strength. As the sodium silicate modulus increases, the 28 d compressive strength and drying shrinkage deformation of the geopolymer concrete increase. With higher alkali equivalent, the 28 d compressive strength of the geopolymer concrete decreases while the drying shrinkage deformation increases. With an increase in slag content, the 28 d compressive strength of the geopolymer concrete increases, and the drying shrinkage deformation decreases. Taking into consideration the requirements for both compressive strength and shrinkage, it is recommended that in practical applications, highly active magnesia be chosen with a content range of 3% to 6%.

Key words: geopolymer concrete, fly ash-slag-based, active magnesium oxide, drying shrinkage, compressive strength