Influence of mixture design parameters on the static and dynamic compressive properties of slag-based geopolymer concrete

This study investigated the influences of water-to-binder mass ratio (0.44, 0.47, and 0.50), and waterglass (8%, 12% and 16%) and fly ash (0%, 25% and 50%) contents on the slump, cubic compressive strength, and static and dynamic compressive behaviors of slag-based geopolymer concrete (GC). Static compressive tests were carried out by using an electro-hydraulic servo-controlled compressive test system, and dynamic ones were performed by using a split Hopkinson pressure bar (SHPB) apparatus. The specimens with a wide range of the compressive strength (from 50 MPa to 80 MPa) were prepared. The results show that the workability of fresh slag-based GC increased with increasing water-to-binder ratio, and waterglass and fly ash contents. The cubic compressive strength increased with the decreases of water-to-binder ratio and fly ash content, and the increase of the waterglass content. Increasing waterglass content contributed to the improvement of the static compressive behavior of slag-based GC, such as elastic modulus and peak stress, while it led to the rise of the brittleness. Slag-based GC with different water-to-binder mass ratios, and waterglass and fly ash contents showed a strong strain-rate dependency. However, the inclusion of 50% fly ash induced a sharp increase of the dynamic compressive strength and dynamic increase factor (DIF) at a high strain rate. Moreover, both the two formulations for fitting static compressive stress-strain curve and DIF with higher accuracy were proposed in this study