Transport properties of kaolin limestone blend and hybrid slag blend high-strength self-compacting concrete

ABSTRACT

This study aims to develop a high-strength, high-performance self-compacting concrete through sustainable cement replacement using tailor-made supplementary cementitious materials. Two blends were formed: a hybrid slag blend consisting of ultrafine slag and ground granulated blast furnace slag in a 2:1 ratio with 1.5% gypsum, and a kaolinite-limestone blend combining calcined kaolin and limestone powder with different origins in a 2:1 ratio with 1% gypsum. Material selection was based on the chemical compatibility with the cement to ensure synergistic behavior. Durability characteristics were evaluated through water absorption, porosity, sorptivity, and rapid chloride penetration tests, while microstructural characteristics were analysed using SEM, XRD, and FTIR analyses. The HSB mix, at 30% replacement, significantly improved durability by reducing water absorption and porosity, and enhancing chloride resistance. The KLB mixes exhibited superior performance up to 50% replacement, with the volume of permeable voids decreasing from 2.71% to 1.35% at 28 days and from 2.62% to 1.05% at 90 days, respectively. The sorptivity index followed a similar declining trend, and chloride penetration in KLB at 50% mix remained negligible across all curing periods. XRD analysis confirmed a reduction of clinker phases, while FTIR revealed the formation of stable carboaluminate phases in KLB mixes, enhanced durability.

Keywords:
Sorptivity; porosity; water absorption; rapid chloride penetration test; gypsum