Abstract: This invention relates to apparatus for producing and delivering a rapidly setting composition and method of delivering a rapid setting cementitious grout. The rapidly setting composition comprises a first interactive component and a second interactive component. The first component comprises a retarded cementitious grout and the second is a gelling agent therefor, the rate of addition of the gelling agent being selected so as to control the rate of set of the deliverable composition. The particular apparatus includes means for supplying the gelling agent through an auxiliary pipeline to the main supply pipeline and means for monitoring the flow rate of the first component through the main supply line, means for monitoring the flow rate of the gelling agent through the auxiliary supply line, and means for adjusting the flow rate of the gelling agent to reduce difference between the monitored value and a reference value.