Title:
Effect of Aggressive Environments on the Durability and Mechanical Properties of Fly Ash-Based Geopolymer Concrete (Prepublished)
Author(s):
Amir H. Shokouhy, Alireza Javid, Vahab Toufigh, and Mohsen Ghaemian
Publication:
Materials Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
acid resistance; alkali resistance; durability; concrete; fly ash; geopolymer; marine resistance; ultrasonic
DOI:
10.14359/51750606
Date:
3/19/2026
Abstract:
Geopolymer concrete offers a lower-carbon alternative to OPC concrete, but long-term durability under aggressive exposure remains critical for field adoption. This study evaluated low-calcium fly ash geopolymer concretes with 0%, 10%, and 20% OPC replacement (denoted GPC100C0, GPC90C10, and GPC80C20) after immersion in tap water, seawater (pH ≈ 7.25), an alkaline solution (pH ≈ 12.5), and an acidic solution (pH ≈ 2.5). Compressive strength and ultrasonic pulse velocity (UPV) were measured at 1, 3, 6, 9, and 12 months. Across all conditions, net mass change remained below 3%. In tap water, 12-month reference compressive strengths were approximately 22 MPa (GPC100C0), 40 MPa (GPC90C10), and 43 MPa (GPC80C20). After 12 months, compressive-strength loss was clearly dependent on the exposure medium. In seawater, losses ranged from about 20% (GPC80C20) to 30% (GPC90C10). In alkaline solution, losses were about 5% (GPC100C0), 20% (GPC90C10), and 33% (GPC80C20). In acidic solution, GPC80C20 showed the lowest loss (about 8%), whereas GPC90C10 showed the highest loss (about 30%). UPV in tap water was approximately 3.2 to 3.9 km/s, and UPV–strength relationships were mixture- and exposure-specific (best-fit R² ≈ 0.84). These results provide practical guidance for durability-oriented mix selection and UPV-based in-service condition assessment.