# Surface Modification of Glass Textile for the Reinforcement of a Cement-Based Composite: A Review
## 4 Modification Techniques of Glass Fibers
### Organic Coatings  
The application of organic coatings is a widespread and well-established manufacturing technique, employed for the modification of fibers surface and finishing of textiles [48; 49]. Both short fibers and AR glass fabric modified with organic coating are already available on the market [50]. Because of the great variety of organic polymers available, this modification technique theoretically offers an extended array of products, whose characteristics can be adjusted to meet specific needs by varying the chemical formulation of the coatings. The use of organic coatings for the modification of AR-glass fibers was first introduced in order to improve their alkali-resistance, but more recently the impregnation of multi-filaments fabric and textile has been proposed on both laboratory and commercial scale, also for the improvement of the stress transfer between the filaments. Despite the great variety of polymers available on the market, the majority of studies conducted on the improvement of glass fibers fabric reinforced concrete are basically based on epoxy resin and styrene-butadiene copolymer. Epoxy resins have been successfully employed in different studies to improve the load bearing capacity of FRCM systems [51; 52; 53; 54; 55; 56; 57; 58; 59; 60]. [PERSON] et al., report that by impregnating the AR-glass fabric with epoxy resin, the maximum tensile strength of the composite could be triplicated [57]. [PERSON] et al., obtained an improvement of the 70% in the load-bearing capacity of epoxy impregnated AR-glass fabric compared to the uncoated system [59]. [PERSON] et al., report an increase in the tensile strength of FRCM composites, reinforced with epoxy coated fabrics [51]. The increased mechanical performance observed for coated systems, compared to the dry one, is attributed to the ability of the resin to penetrate into the yarn, increasing the stress transfer between the single filaments (Figure 4). Figure 4: Schematic representation of (a) uncoated and (b) coated yarn embedded in a cementitious matrix. As a consequence, a larger load-bearing cross-section can be activated in the yarn, leading to an improvement in the efficiency of the mechanical properties of the reinforcement. [PERSON] et al., compared the utilization of the reinforcement for dry and epoxy impregnated systems, defined as the ratio between the maximal tensile strength, obtained by a uniaxial tensile test conducted on dog-bone shaped specimens, and the theoretical maximum tensile strength, calculated out of the tensile strength of one single filament and the number of filaments used in one yarn [53]. The reinforcement utilization for the dry fabric was only 43%, while employing an epoxy-coated fabric it increased to 75%. Of course, in order to maximize the number of filaments engaged in the stress transfer, it is necessary that the epoxy coating fully penetrates in the fabric yarn. Epoxies have a good wetting behavior, however, the efficiency of the coating process also depends on the rheological properties of the coating employed. [PERSON] et al., demonstrated that by diluting the epoxy resin used for impregnation of AR-glass fabric with acetone, superior tensile strength of the composite can be obtained [55]. The authors correlated the viscosity of the coating with the tensile strength obtained for the composite and found out that the optimal coating formulation was achieved by a dilution degree of 75% (75 g acetone, 28 g epoxy resin). Although the dilution degree looks high, it should be noted that the solid content of polymeric water-based dispersion, employed for textile coatings, are often reported to be lower than 50% [45; 56; 61]. Indeed, although the great majority of the epoxy employed in experimental studies for the modification of reinforcement fabric are standard bi-component epoxy resins, some studies also reported the use of water-based epoxy coatings [28; 56; 61; 62].