Performance and life-cycle assessment of high-volume fly ash concrete mixes containing steel slag sand

•Addition of slag sand enhanced the early age mechanical strength of high volume fly ash concrete.•The use of high volume of fly ash and slag sand improved the ductility of concrete mix.•The production cost and embodied CO2 of high-volume fly ash concrete were 21% and 42% lesser than the control mix (i.e., without any fly ash). The present study discusses the performance of high-volume fly ash concrete (HVFAC) mixes containing slag sand which is a solid waste obtained from basic oxygen steel making industry. The design of such mixes was optimized to attain sufficient strength for structural purposes and then cement and natural sand in them were replaced with fly ash and slag sand up to 50%. Other than temperature developments, their fresh and hardened properties like slump, air content, compressive and tensile strengths, elastic modulus, strain softening response under uniaxial compression, shrinkage, water permeation, sorption and absorption, chloride ions diffusion and migration, and bulk electrical resistance at different ages were also studied in detail. The impact of fly ash and slag sand on the sustainability of such mixes were assessed and their co-effects on concrete microstructure were discussed with the results of scanning electron microscopy and Mercury intrusion porosimetry. The HVFAC mixes displayed a slower strength increase at early ages, but they were found to be highly workable, durable, and temperature rise in them was comparatively lower. The strength and durability of these mixes at early ages were found to enhance in the presence of slag sand which is generally capable of strengthening the aggregate-paste interface. India is the second largest producer of cement in the world. Both the fly ash and slag sand possess a lower energy requirement and their inclusions led to the production of eco-friendly concrete which is highly desirable for Indian conditions.