This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs) to Portland cement (C) ratio (SCM/C) on the flexural fatigue performance of engineered cementitious composites (ECCs). ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand), type of SCMs (fly ash “FA” or slag), SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag) exhibited strain hardening behavior (under static loading) with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag) in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.

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 study evaluated the self-healing capability of engineered cementitious composite (ECC) produced with 5% MgO expansive agent (MEA) compared with standard ECC counterparts. The efficiency of the proposed ECC-MgO self-healing system was studied based on the rapid chloride ion permeability (RCP) and sorptivity behaviors of the virgin and cracked specimens when exposed to water, natural, and autoclave curing conditions for different durations. Test results indicated better resistance to chloride ion penetration in addition to significant reduction in sorptivity indexes (considered as measures of self-healing capability) for water- and natural-cured preloaded cracked ECC-MgO specimens compared with their ECC counterparts. The higher self-healing ability of ECC-MgO system was attributed to the formation of healing compounds within the crack walls due to the delayed MEA hydration, as confirmed from microstructural characterization based on scanning electron microscopic (SEM) analyses. The study revealed the potential of using the self-healing ECC-MgO system as sustainable and durable material for infrastructure applications.