Cementitious Polymer Modified Block Jointing Mortar BuildWell Block Jointing Mortar is a superior water resistant cement based mortar specially formulated for joining AAC blocks. It contains selected graded dry sand grey cement and imported polymers to improve workability, water retention durability and adhesion. Block Jointing Mortar contains fine graded sand it helps in laying an even strong and thin layer of joint. This is not only cost-effective but also builds even walls as this improves the leveling of walls and the plaster thickness can be reduced. This further reduces thickness of putty application thus an all-round reduction of cost can be achieved.