# Sustainable Development of Concrete through Aggregates and Innovative Materials: A Review
## 4 Organic Aggregates
### Nanocellulose  
Nanocellulose can be aggregated in concrete to improve its mechanical properties and durability [111]. Nanocellulose is the most abundant renewable polymer that could be used in the construction industry [112]. There are different types of structures such as bacterial cellulose, nanofibers and isolated nanocrystals [113]. Nanocellulose has important properties such as low cost, light weight, low health hazard, biocompatibility, low toxicity and low production costs of natural resources [114; 115]. [PERSON] et al. [116] studied the mechanical strength of microfilaments based in bacterial cellulose and regenerated bacterial cellulose, obtaining important breakthroughs in the development of various materials [116]. These bacterial celluloses have been employed to prevent microbial corrosion of concrete [117]. Furthermore, [PERSON] and [PERSON] [113] investigated the efficiency of nanocellulose as reinforcement employed as polymer, considering the properties of elastic modulus and strength. Nanocellulose can be obtained through plants, microbes, natural chemical reactions and enzymatic synthesis. On the other hand, [PERSON] et al. [118] presented information about production and cost-efficiency relation strategies of bacterial cellulose. The use of nanofibers as a reinforcement material in concrete can improve the concrete service life and mechanical strength. [PERSON] et al. [119] made concrete mixtures using nanofibers obtained from waste algae (_Cladophora sp_) and commercial cotton cellulose nanofibers. Both types of nanofibers were added in cement mixtures. For concrete specimens incorporated with 1.0 g cellulose nanofiber (generated from waste algae), the flexural strength of the specimens increased up to 5.96 MPa, which is 3.74 MPa higher than that control concrete specimen (without nanofibers). However, the concrete specimens added commercial cellulose nanofiber showed a reduction of their flexural strength compared with control specimen. These algal cellulose nanofibers are abundant in nature and can be used as reinforced materials in concrete. [PERSON] et al. [120] presented a review about various types of nanocellulose polymers that have potential application as reinforcement in concretes and tensile strength. [PERSON] et al. [121] developed a methodology for the self-repair of concrete with structural failures through a bacteria that produces calcium carbonate. This bacteria is mixed with concrete in an encapsulated form with a geopolymer (on account of the reaction of the bacteria with water). Thus, when the first crack is generated, there will be a water flow that breaks the capsule, and the bacteria kicks off the self-repairing process. Based on the strength results  
Figure 11: Coconut fibers used to improve concrete properties. Reprinted with permission from [110]. Copyright© 2017, Elsevier B.V.  
of geopolymer cubes (20 mm \(\times\) 20 mm \(\times\) 25 mm), average strength of 26.89 MPa and 28.04 MPa were measured after one and four weeks of curing, respectively. The use of nanocellulose to enhance the concrete performance leads to sustainable and environmentally friendly products. In addition, nanocellulose can have future applications as self-repairing material to solve structural problems in buildings (see Figure 12) [122]. Table 8 shows significant information on the improvement of concrete using organic aggregates, coconut fiber, bamboo and nanocellulose.