Fresh and hardened state performance of self-compacting slag based alkali activated concrete using nanosilica and steel fiber

Abstract

This study investigates the fresh and hardened state performance of slag-based self-compacting alkali-activated concretes (SCAAC) reinforced with steel fibers (SF) and nano-silica (NS), cured at an ambient temperature. Two different hooked-end SF with two fiber volumes and NS were used to examine the combined effect of the SF volume ratio, SF aspect ratio, and NS on the fresh and hardened state performance of SCAAC. In extension, the influence of specimen thickness to steel fiber length (d/FL) ratio on the failure modes of the bending specimens was evaluated. The fresh state properties were evaluated via T50 value, slump flow, V-funnel, and L-Box tests, while the hardened state properties were studied through compressive strength, splitting tensile strength, modulus of elasticity, and flexural tensile strength tests. The relationship analyses were carried out among fresh and hardened state properties, and scanning electron microscopy (SEM) was also conducted to examine the microstructure. The results indicated that fresh state performance was favorably affected by NS inclusion but adversely influenced by SF content and aspect ratio. The hardened state performances enhanced with a higher amount of SF volume and an aspect ratio. Also, the NS improved the splitting tensile and flexural strength but decreased the compressive strength and elasticity modulus of the specimens. The d/FL ratio was found a significant parameter on failure modes, and the specimens having a d/FL ratio of 3.33 showed flexural cracks. In contrast, the specimens having a d/FL ratio of 1.25 exhibited inclined flexural-shear cracks, especially for 1% SF.