Its list of ingredients may give the impression that the drinkable substance Delft Green is just a new superfood trend. However, this combination of clay, seaweed extract and water, which plays a big part in the project 'A Cure for Concrete', actually improves the quality of concrete. The coating was created by professor Stephen Picken. Photographer Sujata Majumdar is now testing the substance at her minilab at the Science Centre in Delft, aiming to turn concrete walls into photographic plates. Let's find out what this coating exactly is!
Delft Green is a so-called concrete curing compound. These compounds are used to prevent the loss of moisture during the curing process of recently placed concrete, as this can lead to cracks. Moreover, Delft Green prevents moss growth, dusty floors and porous surfaces, improving the visual appearance of concrete. What makes Delft Green special compared to other curing compounds, is that it is a bio-based polymer material and is therefore completely biodegradable. Because of its natural ingredients, there is no need to work with safety goggles, face masks or gloves. Bio-based polymers became less popular with the rise of synthetic polymers, but with the current state of bioprocess technologies we should re-examine their use.
The polymers are obtained from wastewater and treatment of industrial process streams. One of the ways this can be done, is through advanced bioprocess technologies that allow rapid sedimentation by using granular sludge, and remove exopolymer containing particles without the use of chemicals. The advantages of these technologies, which involve polymerisation by nature, are that they use less energy, space, financial means and no chemicals. Moreover, the polymer properties can be optimised by including ingredients, such as natural clay, graphene(oxide) and similar high aspect ratio nanoparticles. In this way, natural materials like nacre (shells), bones and wood can be mimicked, making it possible to produce lightweight polymer materials with ultimate properties that are able to surpass those of current man-made synthetic polymers.
The final result is a batch of completely natural ‘slimy green stuff’, that is used in coatings such as Delft Green, but also in a wide array of other applications; from textile fibres to insulation foams. Professor Picken is constantly looking for new and innovative uses for his creation, and the project ‘A Cure for Concrete’ is just one example of how the creative aspect of these applications can complement and improve their practical use.
More information about Delft Green can be found on the website of Slimy Green Stuff, Picken’s TU Delft company, which is specialized in developing and applying technology for the production and use of biobased polymers.