Conventional concrete production that uses ordinary Portland cement (OPC) as a binder seems unsustainable due to its high energy consumption, natural resource exhaustion and huge carbon dioxide (CO₂) emissions. To transform the conventional process of concrete production to a more sustainable process, the replacement of high energy-consumptive PC with new binders such as fly ash and alkali-activated slag (AAS) from available industrial by-products has been recognized as an alternative. This paper investigates the effect of curing conditions and steel fiber inclusion on the compressive and flexural performance of AAS concrete with a specified compressive strength of 40 MPa to evaluate the feasibility of AAS concrete as an alternative to normal concrete for CO₂ emission reduction in the concrete industry. Their performances are compared with reference concrete produced using OPC. The eco-efficiency of AAS use for concrete production was also evaluated by binder intensity and CO₂ intensity based on the test results and literature data. Test results show that it is possible to produce AAS concrete with compressive and flexural performances comparable to conventional concrete. Wet-curing and steel fiber inclusion improve the mechanical performance of AAS concrete. Also, the utilization of AAS as a sustainable binder can lead to significant CO₂ emissions reduction and resources and energy conservation in the concrete industry.

Specially processed steel cord (SC) macrofibres, each consisting of five twisted steel fibres, are used to improve the post-cracking behaviour of cementitious composites. The long steel cords have a large diameter, and are characterised by high tensile strength, frictional bond strength and flexural rigidity. In addition to these steel cord macrofibres, microfibres are used to enhance the snubbing strength and total tensile behaviour of the composite. The two specific hybrid fibre blends studied in the present paper are SC and polyethylene (PE), as well as SC and polyvinyl alcohol (PVA) fibres. The objectives of the current study are to explore the mechanisms by which fibres interact with the composite matrix, and to provide a rigorous characterisation of the performance achievable with hybrid-fibre-reinforced cementitious composites (HFRCCs). Cement-based composites containing large volume fractions (1·0∼2·3%) of various hybrid fibres were compared in terms of flow and fibre dispersion, as well as compressive, splitting tensile, flexural and uniaxial tensile properties. The workability of HFRCCs is governed by the high surface area of the microfibres. The results confirm that the flexural strength, tensile strength and ductility (pseudo-strain-hardening) of HFRCCs are tremendously improved in comparison with mortar or monofibre systems. Furthermore, there is a synergy effect in the microfibre and macrofibre hybrid systems.