Research on design and optimization for compositions of ultra-high-performance geopolymer concrete

Ultra-high-performance geopolymer concrete (UHPGC) has been developed as a building material that fulfills the demands for ultra-high strength, environmental sustainability, and durability. This paper investigated the influence of material composition on the performance of UHPGC through flowability and compressive strength tests. The optimal mix ratio was identified, and the UHPGC microstructure was analyzed. The enhanced strength of the material was analyzed considering the pozzolanic activity of the iron tailings sand (ITS). UHPGC with a water-to-binder ratio of 0.26, binder-to-sand ratio of 1.4, NaOH concentration of 8 mol/L, water glass modulus of 2.25, and silica fume content of 25 % exhibited excellent flowability and mechanical property. And the UHPGC with the optimal mix ratio achieved the maximum flowability of 257 mm and 28 d compressive strength of 118.0 MPa. Water-to-binder ratio and water glass modulus had the greatest influence on UHPGC flowability and 28 d compressive strength, respectively. The UHPGC prepared with the optimal mix ratio exhibited complete internal gel connections and a dense structure, with the most probable pore size and cumulative pore volume of UHPGC being as small as 3.8 nm and 0.22 mL/g, respectively. The widths of the interfacial transition zones in the UHPGC samples prepared with the river sand (RS) and ITS were 3.7 and 3.0 mu m, respectively. The compressive strength of the UHPGC prepared with ITS was 11.4 % higher than that of UHPGC prepared with RS. Our findings provide a basis to evaluate the performance and design of UHPGCs.