Introduced in the early 1980s, integral water repellents have now been used in more than 20,000 concrete masonry buildings nationwide. Based on polymers, acids, or stearates, these chemical admixtures are added to the concrete used to make concrete block and to the mortar used to lay block. When added to both the units and the mortar, they help prevent efflorescence and reduce water penetration. HOW THEY WORK Most integral water repellents coat the pores of the masonry units and mortar, making them repel water. Though they coat pores, they do not bridge cracks. REDUCING WATER PENETRATION Integral water repellents normally decrease water absorption 20% to 30%, but they can decrease it by up to 50%. CONTROLLING EFFLORESCENCE Integral water repellents can be used in any type of concrete block, but one of their prime uses is in architectural concrete masonry. Because integral water repellents minimize moisture penetration, salts are not leached out of the wall to form efflorescence. DO THEY REDUCE BOND? According to NCMA tests, when integral water repellents are used in recommended dosages the bond between mortar and masonry units is adequate. ALWAYS ADD THEM TO THE MORTAR Integral water repellents must be added to both the masonry units and the mortar.