To study the deterioration of alkali-excited fly ash concrete under sulfate environment

this paper studies the variations in mass loss

ultrasonic wave velocity loss

and compressive strength loss of fly ash concrete

by examining the specimens of different alkali admixtures (0%

5%

8%

and 10%) under the coupling of freeze-thaw cycling and different sulfate contents. We determine deterioration patterns through experimental tests using electron microscopy

EDS energy spectroscopy

and XRD diffraction

and develop an artificial neural network prediction model of deterioration patterns based on the test data. The results show adding alkaline exciters improves the durability of fly ash concrete significantly at the optimal alkali admixture of 8%. The deterioration of the specimens shows a linear positive correlation with the number of freeze-thaw cycles. In terms of mass loss

the specimens with different dosages show two stages

smooth declining and accelerated declining; the latter stage appears earlier for the specimens without the alkali exciter. In terms of the loss of ultrasonic wave velocity and the loss of compressive strength

the specimens doped with alkali exciters show only a steady declining stage. Microscopic analysis reveals that the intensified deterioration of alkali-excited fly ash concrete is caused by gradual generation of gypsum and calcovanadate

and our artificial neural network prediction model has high accuracy.