Pozzolanic Analysis of GFRP Powder from Retired Wind Turbine Blades as Supplementary Cementitious Material

The increasing demand in renewable wind energy has led to more retired wind turbine blades which are mainly made by glass fiber reinforced polymer (GFRP) composite. However, the recycling methods of these waste blades are limited so the blades have to be landfilled. This paper proposes a new recycling method which is developing the GFRP powder as a supplementary cementitious material (SCM), because the glass fibers in the powder are rich in silica and may have pozzolanic reactivity. This paper presents a comprehensive pozzolanic analysis of the GFRP powder and compares with reference SCMs of blast furnace slag (BFS) and fly ash (FA). The calcium oxide content in GFRP (12.56 wt.%) is significantly lower than in BFS (39.96 wt.%). Similarly, the aluminum oxide content in GFRP (10.54 wt.%) is lower compared to BFS (15.38 wt.%) and FA (33.17 wt.%). The particle size of GFRP is also larger than BFS and FA, and the glass fibers are covered by organic resin. The pozzolanic reactivity was analyzed by hydration heat, thermogravimetric (TG), scanning electron microscope (SEM), compressive strength test and mercury intrusion porosimeter (MIP). It was found that the resin in the GFRP powder reacts in alkaline environment and generates gas which increases the mortar porosity and reduces compressive strength. GFRP powder has longer induction period and generates fewer hydration products. The lower pozzolanic reactivity of the GFRP powder is mainly due to the presence of the resin and its coating on the glass fibers. Therefore, it is essential to remove the resin to increase the pozzolanic reactivity of the GFRP powder which has the potential to be developed as a new SCM.