Tailoring magnesium potassium phosphate cement-based adhesive for the improved bonding performance of CFRP/concrete interface

Magnesium potassium phosphate cement (MKPC) with rapid hardening and early high strength can be used as inorganic adhesive for externally bonded carbon fiber reinforced polymer (CFRP). This study aims to tailor MKPC as inorganic adhesive with good infiltration and bonding strength for CFRP-reinforced concrete. The influences of water-to-binder (w/b) ratios and particle sizes of potassium dihydrogen phosphate (PDP) on the fresh properties, hydration kinetics, pore structure, and strength development of MKPC were studied. The bonding strength of CFRP/concrete with MKPC-based adhesive was evaluated by double-shear tests. Results showed that a lower w/b ratio and a finer PDP enhanced the strength of MKPC due to a refined microstructure. The bonding strength of CFRP/concrete was dependent on the rheological characteristics and strength of MKPC. The use of a coarse PDP in MKPC was beneficial to enhance the bonding strength of CFRP/concrete. MKPC with coarse PDP and aw/ b ratio of 0.2 resulted in the greatest bonding strength, corresponding to a 20 % enhancement compared to epoxy resin. The superior bonding performance of MKPC was ascribed to its higher strength, a better infiltration for CFRP, and a larger MPC/concrete interfacial transition zone (ITZ).