Fly ash geopolymer concrete durability to sulphate, acid and peat attack

The durability of concrete has a profound impact on the service life of structural elements. Indonesia has extensive peat soils, which provide a highly aggressive environment for concrete structures. Geopolymer concrete has demonstrated good durability when exposed to acid /sulphate conditions similar to those encountered in peat soils. This paper investigates the performance of geopolymer concretes produced using Indonesian type F fly ash under sulphate and acid chemical attack. Geopolymer concrete specimens have been exposed for 12-months in a range of solutions: 5% sodium sulphate, 5% magnesium sulphate, 1% and 3% sulphuric acid, and simulated peat solution. The mechanical and durability properties of specimens together with a control concrete have been monitored for compressive strength, change in mass, water absorption and volume of permeable voids, ultra pulse velocity, air and water permeability, pH profile, and microstructural analysis (XRD, SEM/EDS). The control immersed in water achieved 56.93 MPa at 12-months of age. Magnesium sulphate exposure had a significant deterioration impact on the compressive strength of geopolymer concrete, demonstrating an 11% reduction in strength, while those exposed to sodium sulphate had an 8.9% increase in strength. Specimens exposed to peat solution displayed a slightly increased strength and those in acid conditions a 1.2% and 4.5% decrease in 1% acid and 3% acid, respectively. In general, the geopolymer concrete displayed a high level of resistance against sodium sulphate, 1% sulphuric acid and simulated peat attack.