Development of sustainable cementitious adhesives for tile installation systems

This study develops sustainable, high-performance cementitious tile adhesives (CTA) by redesigning the binder system to enhance early mechanical strength while reducing environmental impact. Three ordinary Portland cements (OPC) and four ground-granulated blast-furnace slags (GGBS) sourced from Italy, India, Turkey, and Singapore were evaluated. OPC reactivity was found to correlate with specific surface area, with the finer Italian cement showing faster hydration and superior early strength. In contrast, GGBS reactivity was governed mainly by chemical composition, particularly Al₂O₃ content. Binders incorporating 40–70% GGBS as OPC replacement were investigated to optimize early reactivity and mechanical properties. A 50% GGBS blend provided the best balance between sustainability and strength development. This optimized binder was formulated into a CTA designed to meet the C2TE classification of EN 12004-2:2017, targeting a 24-h tensile adhesion strength of 1 MPa. Rheological performance was optimized by adjusting the cellulose ether system; a 6000 mPa·s viscosity grade combined with 0.05% rheology modifier achieved suitable workability, water retention, and open time. The final adhesive attained >1 MPa tensile adhesion strength at 24 h and vertical slip ≤0.5 mm, satisfying C2TE requirements. In parallel, jute fibers were surface-treated using NaOH, laboratory concrete wash water (LCWW), and batching concrete wash water (BCWW). Treatments improved tensile strength by approximately 20–25%. Durability testing in simulated pore solutions (pH 13, 12, and 10) at 50 °C for 28 days showed that BCWW-treated fibers retained the highest tensile strength. This performance is attributed to a thin protective mineral layer formed by the multiionic composition of BCWW (Ca²⁺, K⁺, Na⁺). Pull-out tests confirmed superior interfacial bonding and highest pull-out energy for BCWW-treated fibers, demonstrating a sustainable alternative to conventional alkaline treatments