Natural Cement by Phil Richardson
The May CPD event at the Norwich Centre of Excellence was given by Phil Richardson from Natural Cement Distribution Ltd.
Phil introduced the material by giving the background of its history, which dates back 2,000 years and was used in the construction of the Colosseum in Rome, and in the Statue of Liberty and the Brooklyn Bridge in the USA. Closer to home, it was utilised in building the Eddystone Lighthouse and John Nash’s Terraces. More recently it has been used in the French TGV rail network.
Commercial production of the material started in 1842 in Porte de France, and it continues to be mined in the French Alps. The production method in vertical lime kilns was then described to us. The material has no Agrément Certificate or CE marking but is produced to NF P15-314, the French norm. The low embedded carbon footprint was stressed as compared with Ordinary Portland Cement (OPC).
The free lime in the product as mined is used in the kilning and mixing process and, therefore, lime burns as associated with the use of OPC are not a problem and with its lower chromium content the material is very safe to use.
Phil then went on to discuss the compressive and flexural strength of the product together with its shrinkage characteristics, speed of setting/strength gain and sulphuric acid and sea water resistance providing protection to embedded steel. It does not need potable water for mixing. The rebound when used in spraying methods is low, resulting in less clean up being required. The set material can go to ordinary landfill and the packaging is fully recyclable.
The uses of the material were then covered in detail, ranging from tanking and roadway ramps to installation of shower trays. It is particularly useful where the quick setting time and rapid strength gain is useful and has, therefore, been utilised in retaining walls and tunnel linings. It can also be used in underpinning where its minimal shrinkage obviates the need for dry packing and rapid strength gain means that a scheme can proceed much more quickly than utilising traditional OPC concrete. It has been utilised to repair bridge abutments suffering from river scour and for grouting.
In sea defence work the usual grit blast steel cleaning operation can be replaced by water jetting to remove loose rust. When utilised for screeds, these can take traffic the next day. The material can be used in temperatures ranging from -14°C to +40°C. Its use in concrete repairs was then discussed when its rapid strength gain is very advantageous, and a short clip of repair methodology was shown.
In answer to questions at the end of his presentation Phil discussed material costs and concluded by emphasising the vapour permeable nature of the product.