Barrier, construction article and method of manufacture thereof

A barrier comprising a cured phosphate composition and a glass fibre scrim, wherein the cured phosphate composition is impregnated within the glass fibre scrim and further wherein the glass fibre scrim has a mesh size in the range of from 0.5 mm×0.5 mm to 9 mm×9 mm and further wherein the glass fibre scrim is capable of reducing the pH of demineralised water having a pH of 7 to a pH 6.3 or lower, when assessed in accordance with ISO 3071:2005, said barrier having a thickness of at least 1 mm;

• the cured phosphate composition is formed from a curable composition comprising:
• a phosphate selected from the group consisting of:
• phosphoric acid, phosphoric acid salts and combinations thereof,
• a metal oxide, a metal silicate, and water,
• where the weight ratio between the phosphate and the metal oxide is between about 3:1 and 1:1.