Mechanical properties and energy absorption performance of foamed geopolymer under quasi-static and dynamic compression

To assess the potential for substituting foam concrete with low-carbon foamed geopolymer (FG) in the field of structural protection, a series of quasi-static and dynamic compression tests were conducted. These tests aimed to examine the mechanical performance and energy absorption of FG while considering the factors of FG density, granulated blast furnace slag (GBFS) replacement rate, and water–solid ratio. Additionally, supplementary investigations involving XRD analysis, indentation tests, X-CT scanning, and 3D reconstruction techniques were conducted to explore the influence of GBFS replacement rate on the energy absorption of FG in terms of base material properties and internal pore structure. The results of the quasi-static compressive tests showed that increasing the FG density and reducing the water–solid ratio had a positive effect on energy absorption, however, it also resulted in a notable increase in peak strength. Increasing the GBFS replacement rate not only enhanced the load-bearing capacity but also increased the extent of spalling damage, thus FG with a moderate GBFS replacement rate of 20% demonstrated superior performance in terms of energy absorption and load transfer. Under dynamic compression, all specimens predominantly experienced vertical splitting failure. However, with increasing loading velocity, crushing failure emerged at the two ends of the specimens, particularly in the case of low-density specimens. As the loading velocity increased, the specimen exhibited a significant increase in peak strength, demonstrating a notable strain rate effect, however, the energy absorption of the specimen remained relatively stable without significant alterations. In addition, a simplified DIF was proposed to predict the peak strength of FG with varying densities and two distinct GBFS replacement rates under different strain rates. It provided some valuable insights into the potential application of FG in the field of structural protection.