Performance Analysis of Cementitious Materials with AOD Slag and Silica Fume: Long-Term Strength and Durability Aspects

Argon oxygen decarburization (AOD) slag is one type of stainless steel (SS) slag, which is continuously produced in reasonably larger quantities and has very few options for reusability in the SS-making industry. The aim of the study is to use AOD slag in portland cement (PC) systems as a sustainability initiative (i.e., reduced cement and hence, reduced CO2 emissions) to check its feasibility to serve as a potential cement replacement material in PC mortars at 0%, 15%, and 25% dosages. In addition, the strategies to use heat curing and silica fume (SF) were employed in AOD slag mortar to check if enhanced performance can be achieved. Microstructural, long-term strength and durability, and sulfate resistance characteristics were assessed using scientific techniques and standard tests. The results demonstrated that, except for the threshold pore size (TPS), adding 15% AOD slag had no discernible effect on the distribution of unhydrated cement grains, porosity, strength, and most durability tests. In the sulfate resistance test, despite a modest decrease in strength and negligible strength loss, expansions were greater, and cracks were visible. At a higher AOD slag dosage of 25%, all tests revealed a poor microstructure, decreased early- and later-age strengths, poor durability features, and high expansions and microcracking brought on by sulfate attack. The incorporation of SF produced a more compact and denser microstructure with less porosity and lower pore diameters, establishing SF as a viable approach for enhancing mixtures, including AOD slag. The use of heat under stepped heat curing regimes yielded beneficial outcomes only at 15% dosage, leading to minimal strength loss at later ages. Overall, the study revealed that 15% AOD slag in the ground form can increase construction sustainability except in sulfate-rich environments. Higher AOD slag dosage might help reduce cement consumption, but performance would decline, rendering it dangerous and unsatisfactory. The incorporation of SF broadens the application of AOD slag to sulfate-rich situations as well.