The influence of contents of fly-ash and gypsum on the hydration of special purpose cement for road base was studied with a non-contact electrical resistivity measurement device,the relation between electrical resistivity and the setting time of this cement was investigated compared with Portland slag cement.The results indicate that the special purpose cement has a long setting time and its setting time increases with the increase in the content of gypsum and fly-ash,the effect of the content of fly ash is...