## 2 Materials and Methods
### Testing Procedures  
The 10 \(\times\) 50 \(\times\) 225 mm plates were assayed in all the tests carried out, except for thermogravimetry (pastes) and SEM (small pieces of plates or AR-attacked fibers).  
1. Water absorption and dry density. To determine the percentage of water absorption by immersion and dry density, the procedure described in Standard UNE-EN 1170-6: 1998 [25] was followed. Six specimens were measured for each GRC type and treatment;
2. A four-point bending test (10 \(\times\) 50 \(\times\) 225 mm specimens, load rate 0.03 \(\pm\) 0.003 mm/s) was performed in accordance with European Standard EN 1170-5 [23] to calculate the composites' modulus of rupture (see Equation (1)) and toughness (computed as the area under the load-displacement curve until the load drops to 10% of \(F_{MOR}\)). \[Modulus\ of\ rupture\ (in\ MPa)=\frac{F_{MOR}\times L}{b\times d^{2}}\] (1) where \(F_{MOR}\) the maximum load (in N), \(L\) is the major span (in mm, 200 mm in our test), \(b\) is the width (in mm, 50 mm in our test), and \(d\) is the thickness (in mm, 10 mm in our test);
3. Electronic scanning microscopy (SEM, JEOL JSM6300), equipped with energy dispersive X-ray (EDS: Link-Isis, Oxford Instruments, Oxford, UK) for microanalyses, was used to observe fiber deterioration. The acceleration voltage was 20 kV and the samples were covered with carbon. AR glass fibers were subjected to different aggressive reagents and heat treatment in aqueous medium between 28 and 70 days at 55 \({}^{\circ}\)C by immersion in saturated Ca(OH)\({}_{2}\) and 5% NaOH solutions. After exposure, fiber deterioration was analyzed by SEM.
4. Wetting-drying cycles. Specimens were subjected to wetting-drying cycles according to Standard UNE-ENV 1170-8:1997 [26], and were immersed for 24 h in either deionized water or a solution with 3.5% NaCl. Next, they were dried in a ventilated oven at 60 \({}^{\circ}\)C for 23 h. When removed from the oven, they were allowed to cool for 1 h. This cycle was repeated 10, 25, and 50 times for both the specimens saturated with water and those saturated with the NaCl solution to monitor the mass of each specimen at the end of every cycle. Six specimens were measured for each GRC type and treatment;
5. A thermogravimetric analysis (TGA 850 Mettler-Toledo, Greifensee, Switzerland) was carried out on pastes to assess the calcium hydroxide content and combined water in the cementing products. Samples were subjected to a heating ramp of 10 \({}^{\circ}\)C/min from 35 \({}^{\circ}\)C to 600 \({}^{\circ}\)C using a sealed aluminum crucible with a pinhole. The test atmosphere was nitrogen, fed at a rate of 75 mL/min;
6. Freeze-thaw cycles. Specimens were subjected to freezing-thawing according to ASTM C 1185-03, Section 12, \"Freeze-Thaw-Cladding Products\" [27]. Next, specimens were frozen at \(-\)20 \({}^{\circ}\)C for 2 h before being submitted to the thawing process at 20 \({}^{\circ}\)C for 2 h immersed in water. This cycle was repeated 50 and 100 times. A visual record and monitoring the mass of each specimen were carried out at the end of every cycle. Six specimens were measured for each GRC type and treatment;
7. Exposure to chemically aggressive agents. After specimens underwent the curing and aging processes, they were immersed in different aggressive solutions: 1 M solution of ammonium chloride (NH4 Cl) at 20 \({}^{\circ}\)C and 0.5 M of sulfuric acid (H2 SO4) at 20 \({}^{\circ}\)C. A visual record was made and the mass evolution of each specimen was recorded periodically by controlling the changes in the pH of each solution, which varied constantly as an effect of the interaction between acid solutions and alkaline composites. The NH4 Cl solution was changed when pH reached 9, as was the H2 SO4 solution when it reached 1.5. Six specimens were measured for each GRC type and treatment.