Over the last few years, the United States has experienced a shortage of fly ash and slag that consequently created a need for an alternative material that is locally available, sustainable, and provides desirable concrete properties. Recent studies have shown that Ground Glass Pozzolan (GGP) offers favorable attributes as a supplementary cementitious material (SCM) for concrete. However, there are limited studies demonstrating freeze-thaw (FT) resistance of concrete with GGP, as well as assessing the FT resistance in relation with the air-void system of GGP mixtures. In response, this study aimed to evaluate both macro- and micro-level behavior of GGP on FT resistance, and characterize mixtures with different contents of GGP. Six concrete mixtures were evaluated: three mixtures with 20, 30, and 40% GGP as cement replacements and three other reference mixtures with 30% fly ash and 40% slag and 100% Ordinary Portland cement (OPC). Following ASTM standards, concrete beam samples were tested for accelerated FT resistance and dynamic modulus of elasticity up to 1000 cycles. All concretes showed high FT resistance with a durability factor over 90% and, consequently, minimal deterioration and scaling. Core samples extracted from the FT conditioned beams were scanned with the X-ray micro-tomography (CTscan) to identify air-void parameters. Through image analysis a quantification of air-void parameters was obtained, and their relationship to FT resistance was established. Using CT scan analysis, we demonstrated that concretes with the highest cement replacement with GGP and slag developed the most desirable spacing factor and specific surface for FT resistance.@en

Recent studies have shown promising potential for using Glass Pozzolan (GP) as an alternative supplementary cementitious material (SCM) due to the scarcity of fly ash and slag in the United States. However, comprehensive studies on the freeze-thaw (FT) resistance and air void system of mixtures containing GP are lacking. Therefore, this study aimed to evaluate GP’s effect on FT resistance and characterize mixtures with different GP contents, both macro- and microscopically. In this study, six concrete mixes were considered: Three mixes with 20%, 30% and 40% GP as cement replacements and two other comparable mixes with 30% fly ash and 40% slag, as well as a mix with 100% Ordinary Portland cement (OPC) as a reference. Concrete samples were prepared, cured and tested according to the ASTM standards for accelerated FT resistance for 1000 cycles and corresponding dynamic modulus of elasticity (Ed). All the samples showed minimal deterioration and scaling and high F/T resistance with a durability factor of over 90%. The relationships among FT resistance parameters, air-pressured method measurements of fresh concretes and air void analysis parameters of hardened concretes were examined in this study. X-ray micro-tomography (micro-CT scan) was used to evaluate micro-cracks development after 1000 freeze-thaw cycles and to determine spatial parameters of air voids in the concretes. Pore structure properties obtained from mercury intrusion porosimetry (MIP) and N2 adsorption method showed refined pore structure for higher cement replacement with GP, indicating more gel formation (C-S-H) which was verified by thermogravimetric analysis (TGA).

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