Rheological behaviour, hydration, and microstructure of self-compacting concrete incorporating ground ferronickel slag as partial cement replacement

Abstract

Self-compacting concrete (SCC) is a special type of concrete which has some additional requirements beyond those of traditionally vibrated concrete, such as high flowability and consolidation by self-weight without any segregation of the ingredients. In this research, the production of SCC has been investigated by utilizing a metallurgical by-product, namely ferronickel slag (FNS) to enhance the green supply chain in concrete industry. FNS at 40% replacement of natural sand, and ground ferronickel slag (GFNS) at the rates of 0%, 20%, 35%, and 50% replacement of cement was used, and the rheological, hydration, strength, and microstructural development of SCC are presented in this paper. The fresh properties were assessed by rheology, slump flow, T50, V-funnel, J ring, L-box, U-box, and visual stability index tests. The heat of hydration was determined by isothermal calorimetry, and scanning electron microscope, energy dispersive x-ray spectroscopy, and x-ray powder diffraction techniques were used for microstructural analysis. The results were evaluated against the recommendations of the European and Japanese standards for SCC. Increases in fluidity and workability and decreases in yield stress and viscosity were observed with the increase in GFNS content. Delayed hydration heat was observed with the use of GFNS. The low calcium content of GFNS is attributed to this retardation. The 28 days compressive strength decreased from 79 MPa for the control mix by 16% due to 35% cement replacement by GFNS. This is considered reasonable due to the use of low-calcium GFNS as a cement replacement. The heterogeneous and porous morphology of the microstructure of GFNS incorporated SCC is ascribed to this decrement. Considering both fresh and hardened properties, the GFNS incorporated SCC mixtures are found comparable to the control SCC mixture. Therefore, FNS can be used as a promising alternative ingredient for SCC to strengthen the eco-friendly supply chain and sustainable waste management.