Determination of mechanical and microstructural properties of engineered cementitious composite incorporating different types of SCM, filler, and PVA fiber

Engineered cementitious composite (ECC) is a particular class of fiber-reinforced cementitious composite due to its unique ability to perform stain-hardening and attain high deflection capacity through multiple microcrack formations. In this experimental examination program, natural zeolite powder (NZP) and natural perlite powder (NPP) were used as supplementary cementitious materials (SCMs) in addition to two types of polyvinyl alcohol (PVA) fiber, oiled PVA and non-oiled PVA fibers with 2 percent of volume fraction. In order to reduce the reliance of ECC production on silica sand, natural perlite sand (NPS) was used as a partial replacement for silica sand at (0, 25, 50, 75, and 100 percent). The ECC specimens' mechanical properties and microstructural characteristics were examined at 7- and 28-days' age. In general, ECC containing NZP obtained better load-deflection performance and flexural strength and revealed a higher deflection capacity than ECC containing NPP. However, the opposite was observed in the compressive strength results. In particular, ECC specimens with oiled PVA fiber resulted in higher deflection capacity than ECC specimens containing non-oiled PVA fiber, while compressive and flexural strengths slightly dropped due to the use of oiled PVA fiber. Furthermore, the partial replacement of silica with perlite sand adversely affected the deflection capacity. Moreover, it can be noted from the scanning electron microscope (SEM) images that the high amount of NPS resulted in a premature failure of the PVA fiber. The NZP was most effective in reducing the molecular bonding strength of non-oiled PVA fiber and cementitious composite. Thus, pulled-out fibers were more than the ruptured end PVA fiber in ECC containing NZP as an SCM. An X-ray diffraction test was also conducted to assess ECC's microstructural properties and pozzolanic reactivity containing SCMs like NPP and NZP.