Development of recycled strain-hardening cement-based composite (SHCC) for sustainable infrastructures

This paper presents the experimental results of an attempt to develop sustainable strain-hardening cement-based composite (SHCC) using recycled materials. SHCC exhibits desirable mechanical properties, including strain hardening and ductility. However, SHCC is composed of silica sand and a high volume of cement, which makes it more energy intensive than conventional concrete. The aim of this study is to promote SHCC sustainability in infrastructure design through the use of recycled materials. Alternative recycled materials – sand, fly ash, and polyethylene terephthalate (PET) fibers – are used to partially replace silica sand, cement, and polyvinyl alcohol (PVA) fibers, respectively, in SHCC specimens. The effects of the recycled materials on the mechanical behavior of the SHCC specimens are examined by conducting compressive tests, four-point bending (flexural) tests, and uniaxial tensile tests. Fundamental information is then used in the constitutive model to analyze and design infrastructures using SHCC with recycled materials. Test results indicate that fly ash improves both the bending and uniaxial tensile performance of SHCC due to an increase in chemical bond strength at the interface between the PVA fibers and cement matrices. However, SHCC that contains PET fibers does not perform well in the bending and uniaxial tensile tests due to the inferior material properties of the PET fibers, although its compressive behavior is similar to that of the PVA2.0 specimen. Also, it is noted that recycled sand increases the elastic modulus value of SHCC due to its larger grain size compared to that of silica sand. Based on the desire to maintain well-performing SHCC, a replacement ratio below 20% for fly ash or below 50% for recycled sand is deemed appropriate for creating sustainable SHCC, as concluded from this study.