Slight-expansive road base course binder: Properties, hydration and performance

A new type of slight-expansive cement as road base course binder (RBCB) was prepared to compensate shrinkage of stabilized road base course. The micro calorimeter, XRD, TG-DTA and SEM were used to study the hydration process, the hydration products and the microstructure of RBCB comparing with common 32.5 grade Portland slag cement (P.S 32.5). The results indicate that the RBCB has a slight expansion ratio during hydration process, and it has a much lower dry shrinkage ratio, less hydration heat and a more stable hydration process than P.S 32.5 cement. The main hydration products of this cement are amorphous C-S-H gel and needle like AFt crystal, which interlock among the C-S-H gel and other products and contribute to the strength development of the cement paste. The generating of AFt results in a slight volume expansion, which compensates the shrinkage and contributes to the good volume stability of RBCB. The road base course stabilized by RBCB has higher mechanical properties and lessens the shrinkage crake substantially.