There has been a rapid increase in the demand for aggregates used in construction activities, in which, natural aggregate is the most common one. However, the exploitation of natural aggregates caused the depletion of natural resources and environmental pollution. Therefore, this study aims to investigate the feasibility of manufacturing artificial coarse and fine aggregates by alkaline activation of fly ash-slag blends. In this study, a mixture of 50% fly ash and 50% slag was activated by an alkaline solution including NaOH 10M and Na2SiO3. The effects of different alkali equivalent (AE) and alkali modulus (Ms) on the characteristics of the produced aggregates. Characteristics of the 28-day-old artificial aggregates (AA), including grain size distribution, density, water absorption, and crushing strength were then tested according to the TCVN 7572-2006 Vietnamese standard. A comparison between the characteristics of artificial and natural aggregates was also performed in this study. Experimental results pointed out that the grain size distribution of the AAs was adjustable simply by the crusher. Both AE and Ms slightly affected the AAs’ properties. The strength of the AAs developed rapidly as increasing AE from 5 to 9% and rising Ms from 0.6 to 0.8 had an advantageous impact on the aggregates’ strength. However, the strength value dropped as the Ms increased further. However, the crushing strength of the AAs was comparable to that of the natural aggregate. The values of density and water absorption of the AAs ranged from 2291–2474 kg/m3 and 14.1–19.2%, respectively. This study found that the AAs prepared with the AE of 9% and Ms of 0.8 exhibited a better performance among the samples and the proposed AAs can be applied successfully in the construction activities.