Synergistic enhancement of compressive strength and impact resistance in alkali-activated fiber-reinforced concrete through silica fume and hybrid fiber integration

The utilization of industrial waste is a fundamental and significant aspect of advancing technologies in the cement and concrete fields. Enhancing concrete properties with waste materials is efficient and beneficial from economic, ecological, and technological perspectives. Alkali activated concrete (AAC) with an optimized mixture of supplementary materials still requires attention particularly regarding the effects of silica and fiber content as even less quantity can significantly impact the performance of concrete. To optimize and enhance the strength and impact resistance of concrete, assessments were conducted on the effect of silica fume with the incorporation of polypropylene and steel fibers through investigations using experiments, data visualization technique (DVT) and response surface methodology (RSM). Silica fume was used as an addition to fly ash and ground granulated blast furnace slag (GGBS) in the AAC mixtures at 0 %, 5 %, 10 %, and 15 % by weight of binder content. Polypropylene fibers were used at volume fractions of 0.3 %, 0.45 %, and 0.6 %, steel fibers at 1.5 %, 2 %, and 2.5 %, and hybrid fibers at 1.5 %, 1.75 %, and 2 %, all within the total volume fraction of AAC. The results indicated that the addition of silica fume improved fiber dispersion and interaction between hybrid fibers and silica fume leads to higher impact resistance, significantly enhancing the concrete ductility, crack resistance, and energy absorption. According to the experimental research findings, a composition with 2.5 % steel fiber and 10 % silica fume exhibited the highest compressive strength (110.45 MPa). However, a combination of 2 % hybrid fibers with 10 % silica fume resulted in not only improved compressive strength but also the highest impact resistance (58.2 kN-m). Response surface methodology gave the best optimized results at 11.521 % silica and 1.893 % hybrid fibers. It is concluded that the performance of sustainable concrete was improved, and its properties were enhanced to a greater extent in the construction field.