|
Owner of data set Mannok |
Technical purpose This LCA is carried out for Mannok Aircrete blocks: Super. The constituent materials of the block comprises water, sand, cement, silt, lime, PFA, and aluminium The gross dry density of the Super block is 480 kg/m3.
These light weight and high insulating value blocks are used to improve thermal performance of buildings. They are designed for use in external walls, rising foundation walls, internal partition walls and party walls between dwellings. The blocks are manufactured and tested in accordance with BS EN 771-4:2011+A1:2015 “Specification for masonry units. Autoclaved aerated concrete masonry units”. The strength and thermal conductivity values given in this EPD are those that are reported in the BBA certificates which can be downloaded at the following pages: https://www.mannokbuild.com/aircrete-thermal-blocks/mannok-aircrete-super/
The raw materials used in production include sand, cement, lime, aluminium and water. These raw materials are poured into a mould in a slurry form. They are then transferred to the pre-cure room. The small amount of alu- minium in the slurry reacts with the water and lime and forms hydrogen gas bubbles. The liberated gas forms extremely small bubbles within the mass, causing the mixture to expand within the mould to twice its original height. Once the material has reached the correct sufficient height and hardness in the pre-curing room, it is ready for cutting. It is now referred to as a cake. The amount of expansion is variable, and cannot be precisely controlled as it is dependent on environmental factors such as ambient temperature and humidity. The cakes are trimmed to size and cut both horizontally, and vertically into the required block size, using piano wires. The cakes now cut to block size are fed into autoclaves where they are steam cured. There are six autoclaves on the site. During the autoclaving process, further reactions take place with the formation of calcium silicate hydrates, which gives strength to the blocks. After autoclaving the blocks are separated without dismantling. Colour-cod- ed straps are then placed around the pack of blocks, depending on their strength; Super, Standard and Seven. The blocks are then wrapped for delivery to site.
Cuttings from the blocks prior to blocks entering the autoclave, are recycled as “returns” and re-mixed in with the slurries. Cuttings from the blocks after the autoclave, are re-used in the nearby Mannok cement plant as minor additional constituents in the production of Portland cement. In doing so, they leave the system bound- ary of this LCA, having passed beyond the end-of-waste stage. The cuttings are now a raw material input in an external manufacturing process for another product, and have zero impact in relation to the LCA for the Mannok Aircrete blocks. |
