AAC Joint Mortar is a Portland cement based powder mix which is polymer modified. The formulation includes selected high quality graded sands, special shrinkage compensating components plus powerful plasticizing agents which produce a workable thixotropic mortar at a low water content. The resulting mix enables thin joints between thermal blocks to be made. Horizontal and vertical joints are formed down to 3mm in thickness. These thin joints contribute to the maintenance of built wall U-values. Joint Mortar is supplied ready for onsite use requiring only the addition of measured mixing water. The mixed mortar will remain workable for two hours.