Development of high-performance geopolymer cement using industrial marble waste for integrity of geothermal wells

Geothermal well cementing demands materials capable of withstanding extreme downhole conditions including temperatures exceeding 150 °C, corrosive brines, and severe thermal cycling. This study develops a novel advanced geopolymer composite (GGDPU) utilizing marble waste as a primary precursor for sustainable geothermal cementing applications. The optimized formulation consists of 60 wt.% marble waste, 25 wt.% Class F fly ash, 13 wt.%. Clinoptilolite, and 2 wt.% Opalinus clay, activated with 1 M NaOH under hydrothermal conditions (200 °C, 2000 kPa, 2 h). Comprehensive characterization using XRD, SEM-EDX, and FTIR revealed the formation of zeolite phases (NaP1 and analcime) within a dense geopolymer matrix, contributing to exceptional mechanical and thermal properties. The developed GGDPU achieved compressive strength of 50 MPa and demonstrated outstanding thermal shock resistance up to 800 °C with weight loss below 8%. Rheological testing confirmed maintained workability at elevated temperatures (25–75 °C), essential for geothermal drilling operations. In addition, the Si/K ratio of GGDPU provides late setting and supports the preservation of geothermal well integrity. The hydrothermal synthesis successfully transformed industrial marble waste, typically 500–650 tons per 1000 m³ of marble production, into high performance cementing material while reducing CO₂ emissions by 72.2% compared to conventional Portland cement. This research demonstrates a viable pathway for waste valorization in geothermal energy infrastructure, addressing both environmental sustainability and technical performance requirements.