The role of ultra-fine supplementary cementitious materials in the durability and microstructure of airport pavement concrete

Abstract

Conventional Supplementary cementitious materials (SCMs) are indispensable constituents of high-performance concrete, despite their potential drawback of reducing the early strength of concrete. Ultra-fine supplementary cementitious materials (USCMs) have been employed to expedite the pozzolanic reaction and refine micro-scale particle gradation in airport pavement concrete. The investigation encompassed an assessment of mechanical properties, durability, phase assemblage, pore structure, morphology, and microstructure. Results showed that the incorporation of USCMs significantly enhanced the flexural and compressive strength of concrete during the early age, exhibiting respective improvements of 25.4% and 12.8%, respectively. Moreover, the freezing-thawing resistance was enhanced by a factor of 1.6, and the chloride penetration resistance was improved approximately 4 times. These enhancements can be attributed to the heightened pozzolanic and filling effects of USCMs, which resulted in the consumption of more calcium hydroxide (CH) at 7 d and facilitated the growth of additional calcium silicate hydrate (C-S-H) gel, along with lowering hydration heat and decreasing remarkably porosity. Notably, the incorporation of USCMs led to a considerable improvement in the volume fraction of harmless pores (with pore diameter ≤ 50 nm), optimizing the pore structure of the concrete and thereby augmenting its mechanical properties and durability.