What is Zemdrain?DuPont Zemdrain are form liners used in civil engineering applications like bridges, tunnels, dams, water tanks and waste water treatment plants. To be precise, it is a controlled permeability formwork liner where longer life concrete is required in a project.
Why use form liners for concrete?
What is Zemdrain made of?It comes as a sheet made up of fine polypropylene fibers with numerous pores creating an air and water permeable membrane. Both sides of the fabric exhibit their individual properties and functioning.
The filtering side holds back the cement particles giving a strong covercrete. The fine fiber bonded composition does not stick to the concrete. These are grey for Zemdrain Classic and white for Zemdrain MD. There is no release agent applicable for the product.
How exactly does it work?When lining the formwork the material in fact drains away excess water from the cover zone of the concrete. The concrete so left behind is a protective and strengthening cover for the core and reinforcement that are guarded against aggressive elements. The surface is free from blowholes as it disperses air bubbles.
The Zemdrain advantageZemdrain offers a concrete structure with superior durability without additional treatment or chemicals due to the low w/c ratio obtained in the concrete cover zone. The liner allows a regulated evacuation of excess water and air from the fresh concrete while retaining the cement particles. There is no vacuum or soaking effect as the drainage is by gravitation. The cement type, additives used and the quantity of excess water determine the time taken for the process. Some of the excess water is retained by the sheet and goes towards the curing of the concrete.
Apart from the strength advantage the concrete offers resistance enhancement towards carbonation, freeze-thaw with salt, chloride diffusion, microbiological growth and reduced permeability.
Zemdrain Classic is the first generation product that has proved its performance on over 1 million square meters of concrete surface across the globe. Zemdrain MD, the second generation product was launched in 1997 and is already in use in several hundred sites worldwide. The installation process requires tensioning around the formwork to avoid folds for Zemdrain Classic. It can be used as a curing membrane when left on the concrete prior to its stripping. Zemdrain MD, the second generation product in the line, is stiffer and easier to fix.
As compared to 20% wastage generated in using Zemdrain Classic, only 2-5% waste is generates when you use Zemdrain MD. The new product is also easier to install and uses less manpower. Plus, it can be re-used up to three times, whereas Classic is not normally used more than once.
The last wordThe panacea cure for exposed concrete structures and their related issues certainly seems to have arrived with Dupont's Zemdrain.
Zemdrain is now here in India and though it's been introduced recently, its popularity in such a short span of time is proof that this is a product that has, proverbially speaking, hit the nail right on the head.