Cellulose is the most abundant material on Earth. If you take a very close look, perhaps with a magnifying glass, at some kinds of paper – for example, tissue or newsprint – you will be able to see tiny hair-like filaments. Those are pulp fibers made from cellulose. As we all learned in school, paper comes from wood, and wood is made up of tiny fibers made of cellulose that are glued together with other compounds called lignin and hemicellulose. Wood (and other cellulose-rich plants such as cotton) can be shredded into the tiny bits that contain long chains of cellulose polymers – repeating, end-to-end chains of sugar molecules that plants and trees make during the process of photosynthesis.
Clearly, because it is natural and does indeed grow on trees, cellulose is extremely abundant, renewable, and inexpensive. Plant/wood fiber have been added to cementitious materials for centuries for greater strength and durability in finished structures. Indeed, due to its many desirable features, natural cellulose fiber is still a popular and ubiquitous ingredient in the current manufacture of concrete. The advantages of natural cellulose as an additive in concrete include the ability to hold water to keep the cement hydrated during curing; uniform distribution when added to other substances; improvement in both tension resistance and compression resistance, which leads to crack resistance in the finished product; greater temperature resistance; and increased durability. However, adding whole wood or plant fibers has some disadvantages too: the alkaline cement tends to eat away the fiber surface, leading to some loss in strength over time.
The Debut of Nanocellulose
After millennia of adding plant fibers to concrete, a new and very exciting development in the history of cellulose has occurred in just the past 50 years. Cellulose fibers can be further and dramatically reduced in size to their smallest building block, nanocellulose. In its crystallized form, this substance appears as tiny rods that are about 50-300 nanometers (nm) in length and 5-20 nm wide.