Texture, morphology and strength performance of self-compacting alkali-activated concrete: role of fly ash as GBSF replacement

Abstract

The improvement of the rheology, morphology and strength performance of the self-compacting alkali-activated concretes (SCAACs) incorporated with fly ash (FA) as ground blast furnace slag (GBFS) replacement remains challenging. To meet this need, five mixtures were prepared with different amounts of FA (30, 40, 50, 60 and 70, weight %) as the GBFS substitute. The prepared specimens were thoroughly characterized to examine their textures, microstructures and strength properties. Various characteristics of the obtained SCAACs were compared with the control mixture containing 100% of GBFS. The achieved SCAACs prepared with 40, 50 and 60% of FA displayed enhanced workability performance (plastic viscosity, passing ability and filling, segregation resistance). In addition, the compressive strength, splitting tensile and flexural strengths of the SCAACs were dropped with the increase in FA contents. The concrete prepared with 70% of FA content showed poor structure due to the formation of less hydration products. The observed reduction in the drying shrinkage of the proposed SCAACs was mainly attributed to the addition of the higher amount of FA in the mixture. It is established that the substitution of GBFS by FA may be prospective for the production of the cement-free self-compaction sustainable concretes beneficial towards the building sectors.