Effect of pH and exposure duration on the deterioration of vegetation-growing concrete attacked by oxalic and acetic acid

Vegetation-growing concrete supports plant growth through interconnected pores, but root-secreted organic acids progressively degrade its cementitious matrix, threatening long-term durability. However, the coupled effects of acid type, pH, and exposure duration remain insufficiently quantified, and the distinct degradation mechanisms of oxalic and acetic acids are not well understood. This study exposed vegetation-growing concrete to oxalic and acetic acid solutions at pH 1.5, 2.5, and 3.5 for 3–56 days. Compressive strength, mass change, porosity, and water permeability were measured, and scanning electron microscope and XRD were used to characterize the microstructural and phase evolution. The results show that acid type is the dominant factor governing strength loss, followed by exposure duration and pH. Acetic acid causes more severe damage than oxalic acid. Oxalic acid induces temporary pore filling through calcium oxalate precipitation, whereas acetic acid decomposes both portlandite and the C-S-H gel. Adding 20% mineral powder reduces the strength loss rate by 45.4%. These findings clarify the distinct erosion mechanisms and support the durability design of vegetation-growing concrete.