A technique for early age strength determination of hollowcore slab, enabling partial replacement with slag: Field and laboratory investigations

•A novel technique for early age strength determination of zero slump concrete.•Investigations with 0% & 50% GGBS-concrete mix for hollowcore slabs.•A novel chloride free admixture demonstrating strength enhancement of GGBS-concrete.•Developed mix, along with admixture and thermal activation.•Achieved necessary and sufficient strength at early age for hollowcore slabs.•Study in perspective of precast industry.