This study aims to investigate the feasibility of utilizing waste rubber as a partial replacement for silica sand in the development of self-consolidating engineered cementitious composite (SCECC). The effects of the percentage of rubber (0–50%), rubber size [crumb rubber (CR) and powder rubber (PR)], and supplementary cementing materials (SCMs) (fly ash, ground-granulated blast-furnace slag, silica fume, and metakaolin) on the fresh and hardened properties of SCECC were studied. The results indicated that both CR and PR had promising potentials to be more economical and environmentally friendly alternative aggregates to develop sustainable SCECC with higher ductility. Although the inclusion of CR negatively affected the fresh and mechanical properties of SCECC, a number of successful mixtures with up to 30% CR could be developed with strengths greater than 40 MPa. The addition of PR showed a better performance in terms of fresh and mechanical properties compared with CR, allowing up to 40% replacement of rubber to be safely used. The inclusion of CR appeared to continuously increase the deformation capacity of SCECC up to 20% replacement level, while PR continued to improve the deformation capacity up to 50% replacement. Combining PR and different SCMs, especially metakaolin, allowed higher percentages of rubber to be used, achieving semi-lightweight concrete with adequate mechanical properties for multiple structural applications.

This paper outlines attempts to characterise a green engineered cementitious composite (ECC) with a matrix containing waste recycled glass sand (GS) as a replacement for the silica sand (SS) commonly used in ECCs. To assess self-healing rate in GS-ECCs, specimens were pre-cracked up to 60% of their original flexure deformations and left to heal under moist curing. Alkali–silica reaction expansion, compressive and flexural strength, mid-span beam deflection capacity, crack development, rapid chloride penetration and resistivity were tested to assess the performance of different sound and preloaded ECC specimens. In addition, results of scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy of healed cracks were evaluated. Mechanical and physical results of GS-ECCs showed performances that were better than or comparable to the corresponding SS-ECC. This study also reveals an acceleration and improvement in self-healing rate with GS replacement level. A C–(N,A)–S–H (calcium-(sodium, aluminium)-silicate-hydrate) with low calcium/silicon ratio was confirmed to be the main outcome in the self-healing products of GS-ECCs.