Do Hydraulic Limes Contain Cement?
Products marked NHL2, NHL3.5 or NHL5 must be made according to European Norm / British Standard 459. which means they contain no cement. However, it is more complicated than that! There are also lime based products classified as NHL-Z which do contain cement, often in the form of GGBS (granulated blast furnace slag a.k.a slag cement). Unfortunately people are often sold NHL5-Z as an alternative to the much higher quality pure NHL5, with the GGBS described as a “pozzolan”. In reality, NHL-Z products are cheap, inferior limes, unsuitable for historic buildings. For a useful intoduction on GGBS and its pore blocking effect, see here. At Lime green we use St Astier Natural Hydraulic Limes which do not to contain any Portland Cement or pozzolans. A few of our products (Monosaintastier and Thermocromex) for new build with concrete blocks do contain cement . This is always clearly stated on the product information. If in doubt ask your supplier; all reputable suppliers will be up front and cl
