Crack width control and mechanical properties of low carbon engineered cementitious composites (ECC)

Abstract

• An ECC with LC3 binder reinforced with polypropylene fiber designed for tight crack width (less than 50 µm at 1% tensile strain) has been developed. • Crumb rubber at 50% replacement level of fly ash was found to be optimal in balancing tight crack width and compressive strength loss. • Compared with PVA-ECC, the embodied carbon of the PP-ECC was reduced by 40–50%. Engineered Cementitious Composites (ECC) have superior properties with high tensile ductility and tight crack width compared to conventional concrete. The properties of ECC are significantly influenced by the material composition which can be tailored to enhance the sustainability of ECC. Towards this goal, recycled crumb rubber (CR) and silica fume (SF) were used to tailor the properties of a polypropylene-fiber reinforced ECC with a low carbon binder based on limestone calcined clay cement (LC3) in this study. Crumb rubber was found to be effective in enhancing strain-hardening performance and reducing the width of the multiple microcracks. However, a loss of compressive strength was accompanied by an increasing amount of CR. While silica fume or lower w/b ratio enhanced the compressive strength, the crack width of ECC increased at higher SF content or lower w/b. The underlying mechanisms of these trends were traced to the alteration of the matrix fracture toughness and fiber/matrix interfacial bond. Rubber particle bridging was found to contribute to crack width control. The combined use of the LC3 green binder and CR led to a lowering of the embodied and operational carbon footprint of ECC.