A method of primary cementing well is provided utilizing a cement and cement activator cementing composition, in which one of the components is first placed in the annulus of the well. Next, the other component is placed in the annulus above the first placed component. Densities of the components have been selected such that the density of the second placed component is sufficiently higher then the density of the first placed component to facilitate gravity mixing of the two components as the second placed component moves through the first placed component and in the process activation occurs.