Study on fine-toned fly ash content for lightweight strain-hardening cementitious composites (LSHCC) with low fiber content

Abstract

• The lightweight strain-hardening cementitious composites (LSHCC) were developed by using a low fiber content of 1.2% by volume. • By fine-toning the fly ash content, the tensile strain capacity of LSHCC increased from 2% to 3%. • The properties of LSHCC were explained by pore structure and hydration product content determined by MIP and TGA, respectively. Fly ash content has been suspected of influencing the mechanical properties of strain-hardening cementitious composites (SHCC) by affecting the fiber–matrix interface. However, it has rarely been considered in the material design procedure. This study investigated the effect of fine-toned fly ash content on the tensile performance of lightweight strain-hardening cementitious composites (LSHCC) with fly ash cenospheres and 1.2 vol% of polyvinyl alcohol (PVA) fiber, aiming to find a proper fly ash content with which strain capacity can be improved while tensile strength can be maintained. The effect of fly ash content on the mechanical behavior and impermeability were examined by conducting compressive tests, uniaxial tests and rapid chloride permeability tests (RCPT), which were subsequently explained by the pore structure and hydration product content obtained by mercury intrusion porosimetry (MIP) and thermo-gravimetric analyses (TGA), respectively. The results showed that the tensile strain capacity of LSHCC could be efficiently improved by fine-toning the fly ash content. When the fly ash content exceed 25%, the tensile strain capacity of LSHCC increased from 2% to 3%, while the compressive and tensile strengths were maintained. Base on the desire to achieve a strength-ductility balance and the raw materials used in this study, fly ash content between 25% and 37.5% is deemed appropriate for creating sustainable LSHCC.