0 5 to 6 weight percent preferably from about 1 5 percent as with other cement compositions the reactivated cement composition can be treated with other conventional admixtures such as water reducing agents superplasticizers strength enhancers and the like as is well known to those skilled in this art the following examples are given for illustrative purposes only and are not meant to be a limitation on the appended claims all parts and percentages are by weight unless otherwise indicated portland cement mortar compositions were formed by mixing 20 parts of portland cement 45 parts of a standard mortar sand and 9 parts water water to cement ratio of 0 45 and 0 08 part of solid diphosphonomethyl formal formula ii wherein x 1 and z 0 hydroxy methyl phosphonic acid 2 1 wt ratio as a 30 sample a and a 50 sample b aqueous solution in addition for comparative purposes a sample of the same mortar composition was mixed without the addition of the subject admixture sample c part of each of the above prepared samples were allowed to sit in their container and observed the length of time each took to have initial set sample a took 35 hours sample b took 60 hours while sample c took only 3 5 hours after 24 hours part of each of the above samples a and b is mixed with freshly prepared mortar composition having the same ratio of cement sand and water as above the mix is in a 1 to 4 part ratio the mixture is then treated with 2 parts of calcium nitrite solid based on the calculated cement content of the mixture being treated treated sample a and sample b cured to initial set.