Study on the post-fire mechanical properties of lightweight 3D printed concrete containing expanded perlite as partial replacement of natural sand

Along with the rise in construction with 3D printing technology, 3D printed (3DP) structures also require weight reduction similar to conventional reinforcement concrete (RC) structures. In addition, the behaviour of this type of structure against fire needs to be investigated. The number of printed layers and the time gap between layers for the 3DP specimens were among the variables examined in the tests. The test results demonstrated that as the replacement percentage of natural sand (NS) with expanded perlite (EP) increased, at 25% volume of replacement the interlayer bond strength increased on average by 18.6%, while at the highest replacement level of 75%, decreased on average by 5.8%. Additionally, by incorporation of EP the compressive and flexural strengths of 3DP specimens declined averagely from 9% to 29.7%, and 39.3% to 49.3%, respectively. As the replacement level of NS increased, residual compressive and flexural strengths increased after exposure to 800 °C. Furthermore, it was demonstrated that exposure to high temperature had the least effect on interlayer bond strength, whereas it significantly reduced the compressive and flexural strength. The results showed that, increasing the time gap between layers reduced interlayer bond strength and flexural strength while negligibly affected compressive strength.