Effect of Crushed Aggregates on Strength and Durability of Concrete Containing Metakaolin and Air entrace Subjected to Freezing and Thawing Cycles

Document Type : Original Article

Authors

Faculty of Civil Engineering، Semnan University، Semnan, Iran.

Abstract

Concrete is one of the most widely used construction materials, and aggregates play an important role in its strength and durability. The quality of aggregates affects the compressive strength and permeability of concrete. This research has investigated the effect of aggregate grading, metakaolin, and air entrace on the compressive strength and durability of concrete. Concrete samples were prepared with two types of aggregate grading, including single fine gravel and fine-coarse gravel combination, with different sand-to-gravel ratios, and their compressive strength was tested at 7 and 28 days of age. It is worth noting that these aggregates originate from the sand and gravel mines in Darband, Semnan. In addition, the samples were subjected to 300 freeze-thaw cycles to assess the durability of the concrete under cold conditions. The results indicated that the use of 12.5% metakaolin helped to increase strength and reduce permeability, but the application 5% air entrace reduced the minor strength amount but increased the durability subjected to freezing and thawing cycles. Overall, the highest strength and internal density were observed in samples with fine gravel (5-10 mm) aggregate only, a gravel-to-sand ratio of 60:40, and 12.5% metakaolin. The simultaneous use of metakaolin and air entrace creates a good balance between the strength and durability of concrete, and a reduction of cement by about 18-23%.

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Articles in Press, Accepted Manuscript
Available Online from 06 August 2026

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