Crack Resistance of Concrete Using Granulated BlastFurnace Slag Sand under Flexural Stress

Granulated blast‐furnace slag sand (BFS) has the potential to be used as an alternative to fine aggregates in concrete production. The interface between the cement paste and the aggregate in concrete is densified when BFS is used, due to the hydrates that are generated by its latent hydraulicity. This fact suggests that the crack resistance of concrete, which is closely related to the conditions at the aggregate interface, would be enhanced by the use of BFS. The fracture energy (G_F) of concrete under flexural stress is here measured to evaluate the crack resistance of concrete made using BFS. BFS samples from three different steel mills in Japan are used as the fine aggregates for concrete production, and mountain sand is used as a natural sand for comparison. Compressive strength, static modulus of elasticity, and fracture energy tests are conducted at the material ages of 28 and 91 days. The G_F of the BFS concretes increase with increasing compressive strength; on the other hand, the G_F of the concrete made using mountain sand decrease. Thus, it is concluded that BFS concrete has superior properties to concrete made using natural sand in terms of the crack resistance under flexural stress, especially in high‐strength regions for large material ages.