The durability of manufactured sand with mineral admixture concrete in the Hexi Corridor region, northwest China

As a green alternative to natural river sand, manufactured sand is increasingly being utilized in concrete production. However, the Hexi Corridor region in Gansu Province, northwest China, faces challenging environmental conditions, including high altitude, desertification, wind-blown sand, and saline soil. Transportation infrastructure projects in this area are prone to damage caused by freeze-thaw cycles, salt erosion, and wind-blown sand abrasion. To address these issues, this study investigates the improvement of durability for manufactured sand concrete through the design of mineral admixtures with varying dosages. The results indicate that: (1) When preparing concrete with 100% river sand, the optimal compressive strength and durability are achieved with 5% fly ash, 10% slag powder, and 2% silica fume; (2) When manufactured sand replaces river sand, the compressive strength and durability of concrete are maximized when the fly ash content is 15%, and slag powder content is 10%; (3) In the early stage, the addition of single fly ash tends to generate a large number of SiO₂ spheres, which hinder the hydration reaction, reduce hydration heat, lower the frictional resistance between concrete gels, and consequently weaken the strength and wear resistance; (4) The incorporation of mineral admixtures can fill the pores in concrete and significantly reduce the number of small pores. The combined use of fly ash and mineral powder can promote early hydration and improve early strength.