# Sustainable Development of Concrete through Aggregates and Innovative Materials: A Review
## 3 Synthetic Fibers
### Epoxy Resins  
Epoxy resins are materials that mixed with concrete can increase its compressive and tensile strength as well as the elastic modulus. These materials have workability and segregation reduction advantages. The concrete containing epoxy resin increases its ductility and reduces the permeability and contraction. Furthermore, this concrete type offers corrosion resistance [88]. Due to the adhesion properties and chemical resistance, the epoxy resins have been used as adhesive materials and corrosion resistant paints in the construction industry. [PERSON] et al. [88] measured the properties of epoxy resin mortar resistance considering different grout proportions mixed with epoxy resins (0%, 5% and 30% dosages). The highest values of compressive, flexural and tensile strength were observed in modified mortars with 30% epoxy resin dosage. The epoxy resin increased the compressive strength, splitting tensile strength and elastic modulus by up to 21%, 84% and 190%, respectively, after 28- and 90-day of curing. Furthermore, the toughness and resistance to acid erosion of epoxy resin-modified goats were significantly improved when epoxy resin dosages increased. [PERSON] et al. [89] evaluated the resistance properties of modified mortars with bisphenol A-type epoxy resin (5%, 10%, 15% and 20% dosages). These mechanical properties were measured in wet-dry and dry curing conditions. The maximum compressive strength, tensile strength and flexural strength were achieved with the epoxy resin dosage of 10%. After 28 days of curing, the highest compressive strength and flexural strength were 36  
Figure 9: Textile waste can be used to improve some properties of concrete: (**a**) waste blue-jeans and (**b**) cotton fiber from blue-jeans. Reprinted with permission from [87]. Copyright © 2018, Elsevier B.V.  
and 3 MPa, respectively. Furthermore, the water absorption decreased as the epoxy resin percentage increased. [PERSON] et al. [90] added epoxy resin in concrete employed in railway sleepers to study its physical and mechanical properties as well as reduce its costs. To conserve a suitable balance between physical and mechanical properties and cost, the mixes adding fillers from 30% to 50% could be a good option for coating of composite railway sleepers. Proportions greater than 60% substantially increased the concrete porosity. In addition, density of concrete is increased with an epoxy polymer by 33.9% using the proportions from 0.0% to 60%. [PERSON] et al. [91] studied the compressive and tensile behavior of a new polymer concrete. This concrete exhibits low shrinkage, good chemical resistance, high durability, corrosion resistance and excellent adhesion characteristics. Compressive resistance tests were carried out according to the guidelines established by the ASTM D695 (American Society for Testing and Materials, West ConshohockenCity, PA, USA). The maximum strength was two to three times greater than the control sample. The compressive and tensile strength were kept constant when the amount of epoxy resins was increased. In addition, elastic modulus improved for higher proportions of epoxy resins. Epoxy resins have been used in asphaltic concrete, displaying results with excellent strength properties, high temperature stability and fatigue resistance. [PERSON] et al. [92] measured the surface properties of asphaltic concrete with epoxy resins, obtaining a permeability of 7.7 \(\times\) 10\({}^{-5}\) mm/s. It is a very low value mainly as a result of low air voids in asphaltic concrete with epoxy resins. Epoxy resins can improve the resistance in mortars manufacture but had no effect in the construction of structural elements such as railway sleepers, where concrete resistance properties decreased. However, the epoxy resins can increase the permeability properties and fatigue resistance. Epoxy resins allow creating new concretes that improve the chemical and mechanical resistance characteristics.