Making Durable, Lower-Carbon Concrete with Unwashed Salty Sand and Blast-Furnace Slag

What is it about?

The growing demand for concrete places increasing pressure on natural sand resources and contributes to carbon emissions from cement production. Salty sand offers an alternative, but its use in concrete is challenging because the salt it contains can accelerate the corrosion of steel reinforcement and reduce long-term durability. This study investigates whether untreated salty sand can be used to produce strong, durable, and lower-carbon concrete by replacing part of the cement with blast-furnace slag, an industrial by-product of steel production. The results show that the developed concrete achieved high strength, reduced water absorption, and improved resistance to chloride penetration and sulfate exposure. Computer-based assessments also indicated that mixtures containing more slag could delay the predicted onset of steel corrosion under standardized conditions. The mixture with the highest slag content reduced estimated carbon emissions by 34.2%, while an intermediate slag content provided the best overall balance of performance. These findings highlight a promising approach to using locally available salty sand more efficiently while reducing the environmental impact of concrete production.

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Photo by Karim Elmalhy on Unsplash

Photo by Karim Elmalhy on Unsplash

Why is it important?

This study addresses two important challenges in sustainable construction: reducing dependence on conventional sand resources and lowering carbon emissions from concrete production. Its distinctive contribution lies in evaluating untreated chloride-contaminated saline sand in fine-grained concrete incorporating fly ash and blast-furnace slag, while integrating mechanical performance, durability, scenario-based corrosion assessment, and environmental efficiency. Unlike studies focusing primarily on strength or individual durability properties, this research examines the trade-offs among chloride resistance, sulfate resistance, corrosion-related performance, and embodied carbon emissions. The results show that increasing slag content improves resistance to chloride transport, while a 30% slag replacement provides the most balanced overall performance. A 40% replacement reduces estimated carbon emissions by 34.2%. These findings are particularly timely as the construction industry seeks lower-carbon materials and alternatives to conventional aggregates. The study provides useful evidence for developing more resource-efficient concrete and selecting suitable mixtures for further durability assessment and practical application, particularly in regions where saline sand is readily available.

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