Phosphogypsum-fly ash-lime solidified mixtures can form strength in a short time for the mixture

but excessive phosphogypsum will result in the expansion and the loss of strength . This technical note summarizes strength-forming mechanism of phosphogypsum mixtures for subbase constructions. The experimental results indicate that excessive phosphogypsum resulted in the expansion. The loss of strength and the optimum grading of phosphogypsum and fly ash is 1 to 1. The program of reusing phosphogypsum mixtures is discussed based on it.