Sustainable development of eco-friendly ultra-high performance concrete (UHPC): Cost, carbon emission, and structural ductility

•Ultra-high performance concrete (UHPC) is a high-tech concrete composite that swiftly grown in popularity worldwide.•The 2% steel fibers used in UHPC design accounts about 30% and 40% of material cost and carbon emissions.•UHPC requires higher initial materials cost than NSC due to its high OPC content, steel fiber, and lack of design regulations.•This paper systematically reviews the cost of raw materials, carbon emission, and ductility performance of UHPC.•This review can help to improve current design efficiency and standards for the cost-effective, and viable UHPC recipe.•More attentions are required to standardize curing, improve structural ductility, and set cost design guidelines for UHPC. Ultra-high performance concrete (UHPC) is a cutting-edge pozzolan composite material composed of a high proportion of discontinuous internal reinforcing fibers, a water-to-binder material ratio of no more than 0.25, and an optimal gradient of granular particles. Despite various potential concrete applications, UHPC is only utilized on occasion because of a lack of widely accepted design standards, rigid design requirements, high starting costs, and a lack of contractor experience. The creation and widespread adoption of UHPC design code requirements would motivate industry participants to implement large-scale applications. With the recent efforts of institutes (such as ACI) that identified the use of high-strength steel fibers in concrete as a significant research priority, it becomes highly relevant. According to sources, existing UHPC materials comprise 2% or more steel fibers, accounting for around 30% and 40% of material prices and 40% of carbon emissions, respectively. Moreover, it is discovered that UHPC mostly exhibits a lower structural ductility than conventional concrete applications and frequently collapses early after crack localization. Regarding the sustainability aspect, the technological use of cementitious materials in the design of UHPC supports the concept of sustainable development, enabling slender sections, thereby using less concrete (less cement) that leads to lower embodied energy and CO2 emissions compared to conventional concrete. Therefore, the need to evaluate the major findings of previous researches and exhibit the potential approaches that could lead to lowering fiber volume (to reduce cost) and improve the structural ductility of structural applications of UHPC is urgently required. However, this paper systematically reviews the