# Surface Modification of Glass Textile for the Reinforcement of a Cement-Based Composite: A Review
## 4 Modification Techniques of Glass Fibers
### Organic Coatings
[PERSON] et al., suggest that waterborne epoxy coatings are particularly promising for the fresh on fresh coating application method, in which the polymer impregnated textile is embedded in the cementitious matrix directly after application of the liquid resin [56]. Indeed, according to the authors, hardened epoxy resin has no interaction with the cementitious matrix, as could be proved from EDX analysis at the fiber-matrix interface-zone. As a consequence, the improvement in the load-bearing capacity of the composite is not attributed to a stronger chemical interaction between the epoxy resin and the inorganic matrix, but rather to the high friction that can be transmitted via shear bond, thanks to the close contact between the matrix and the reinforcement. Because of the absence of good chemical interaction and therefore of good adhesion between the epoxy resin and concrete, the coated reinforcement can act as a separating layer, resulting in delamination failure, as reported in some studies [14; 51]. On the contrary, fresh waterborne epoxy coating can improve the interaction of the reinforcement with the matrix by homogenization of the interface-zone. [PERSON] et al. performed tensile tests on dog-bone-shaped specimens reinforced with water-born epoxy impregnated AR-glass fabric, using both the fresh to hard (f/h) and fresh to fresh (f/f) methods, and observed that in the sample prepared with the f/f technique, the unh hardened epoxy was able to admix and interact with the fresh concrete, forming a homogenized interfacial zone, while on f/h application method a clear-cut interface between concrete and reinforcement is formed [59]. Improvement of the mechanical properties of the composite by f/f method has been reported also by [PERSON] and [PERSON] for styrene-acrylic polymer [63]. However, in the same work, the authors also report that, although the wet process lead to an improvement of the initial mechanical properties of the composite, specimens subjected to accelerated aging experience a lower decrease of the tensile strength when realized with the fresh-to-hard method, since precuring the polymeric coating allows a polymeric film to be formed around the fiber bundle, which protects the glass filaments from alkali degradation. A promising alternative to epoxy resin are styrene-butadiene coatings,which have been reported to improve the interaction at the fiber-matrix interface [45; 47; 64]. [PERSON] et al., investigated the effect of different styrene-butadiene coating formulations on the mechanical properties and durability of two types of commercial AR-glass fibers [45]. In order to evaluate the impact of the coatings on the interface and the consequence of surface modification on the overall mechanical properties of the composite, the authors compared the results of the single fiber pull-out test, yarn pull-out test and tensile test performedon concrete specimens reinforced with continuous rovings. The authors calculated both the adhesion strength and interfacial friction for the coated and uncoated fibers, and report that the selected styrene-butadiene coating provide a superior adhesion with the cementitious matrix. Interestingly they found out that by employing the selected coatings on two different commercial AR-glass yarns, although both coated yarns displayed improved tensile strength, the overall mechanical properties of the composite were not always increased. Similar results have been reported by [PERSON] et al. [47], which were attributed to the superior compatibility between sizing and coatings. Interestingly the authors demonstrated that by tailoring the compatibility of coatings and sizing, rovings characterized by a lower initial tensile strength lead to composite with superior performances. Styrene-butadiene coatings also have been employed to increase the durability of glass fibers to alkali attack.