# Construction of Geosynthetic-Reinforced Pavements and Evaluation of Their Impacts
## 2 Field Construction
### Geosynthetics Installation
#### 2.2.2 Fibreglass Geogrid in Asphalt Binder Course (SP 19)  
In this study, a biaxial fibreglass geogrid was used. This product is made of high-modulus glass filaments with a polymeric coating; the coated filaments are then bonded to an engineered polymeric membrane (EPM). The fibreglass geogrid has an opening of 25.4 mm \(\times\) 25.4 mm, while the elastic modulus is 73,000 MPa and the ultimate tensile strength is 100 kN/m in both directions. During placement, the polymer-coated grids are placed directly on the asphalt surface after a tack coat is applied. As the EPM is designed to melt at elevated temperatures (around 80 \({}^{\circ}\)C), it provides more adhesion between the grids and asphalt overlays [33]. The product is stable mechanically, chemically, and biologically. This product is particularly engineered for asphalt reinforcement, where it can resist high temperatures with the polymer coating melting at temperatures \(>\)400 \({}^{\circ}\)C and the glass melting at 820 \({}^{\circ}\)C [33]  
As shown in Figure 3, the first 75 mm lift of SP 19 was placed on the unreinforced graded base layer. A tack coat was placed on the first lift after one hour when the first lift had hardened and cooled down sufficiently. Due to the short length of this trial section, the tack coat was placed using hand rollers as shown in Figure 3 (left). The tack coat used in this study is Clean Bond Coat (CBC), which is a slow-setting asphalt emulsion and cures fast. It was diluted in a ratio of 50/50 with water. With the calculated one-lane pavement area of 50 m\({}^{2}\), approximately 50 L of diluted tack coat was applied on one lane using hand rollers to ensure even application. This process was repeated twice until the lane was fully coated. After the tack coat was applied, it was allowed time to cure as indicated by a colour change from brown to black as depicted in Figure 3 (middle). For the proper installation of the fibreglass geogrid, it is important to not disturb the surface during curing; workers stepping and vehicles driving on tack-coated surfaces should be avoided. As such, the fibreglass geogrid was rolled out on the sidewalk first to minimize the potential loss of the tack coat during curing. After the tack coat was cured, the fibreglass geogrid was placed; several people held the edges of the geogrid to reduce wrinkles during placement as shown in Figure 3[34]. Wrinkle removal is also critical to ensure the bonding between the geogrid and the underlying asphalt. Several measures were taken including a drum roller running on the entire length (Figure 4), a small hand roller rolling on the wrinkle (Figure 4), as well as cutting from the middle of the wrinkle. After the placement, the second binder course lift was paved. Figure 3: Installation of fibreglass geogrid in the asphalt. The paper and other heavy equipment must be driven to the starting point of the paving direction before the tack coat application to prevent loss of the tack coat by the tires. Another challenge that occurred during the paving of the second lift overlying the geogrid was that, due to insufficient adhesion, the geogrid was lifted and picked up by the paver, which may be attributed to the tack coat not being fully cured before paving. Placing some loose asphalt mix in advance on the longitudinal and transverse edges of the geogrid, as shown in Figure 4, was found to improve the paving process. Using the same asphalt cement, as was used in the asphalt mixtures, as a tack coat could perform better than emulsions and provide better adhesion [33]. In the future, this method could be compared to the type of tack coat used in this study. As per the manufacturer's recommendation, adjacent geogrids had at least 25 mm overlap. In this study, due to the width of the geogrid (i.e., 1.5 m), three sheets of the geogrid were needed on one lane, with two sheets at full width and one sheet of 0.9 m width. When placing the geogrid on the first lane, the geogrids were placed one after another, with the narrower one placed last, closest to the centreline.