Geopolymers have gained traction as suitable alternate cementitious materials for oil and gas cementing operations. However, its bonding properties are limited because of shrinkage. Meanwhile, there is an enormous amount of waste glass in our immediate environment, an urgent concern for the environment and human health, which could be reutilized or recycled. This study investigates the potential use of waste glass as an expansive agent controller to improve the performance of the geopolymers. The waste glass was attached to the CaO to create a composite expansive agent to control the geopolymers' expansion rate. The synthesised agents were evaluated for their impact on linear expansion, compressive strength, shear bond strength, and hydraulic sealability. The synthesised agents were tested for their impact on linear expansion, compressive strength, shear bond strength, and hydraulic sealability. The results revealed that the incorporation of 30%–70% waste glass in the expansive formulation significantly enhances the linear expansion of geopolymers by 15%–20% while improving the compressive strength in the long term by 10%–15%. These improvements are crucial for maintaining geopolymers' mechanical integrity preventing issues related to uncontrolled expansion. This study confirms that the waste glass can effectively be valorised as an expansive agent controller, offering a green and cost-effective solution for enhancing well integrity and promoting the development of more environmentally sustainable practices in the oil and gas industry.