Mechanical compatibility and adhesion between alkali-activated repair mortars and Portland cement concrete substrate: Fid-Bau Portal

Mechanical compatibility and adhesion between alkali-activated repair mortars and Portland cement concrete substrate

Nunes, Vitor A. / Borges, Paulo H.R. / Zanotti, Cristina

Highlights • Properties of AAM formulations were assessed for compatibility with PC substrate. • Adhesion and 4-point bending tests were carried out for selected formulations. • Neat MK-based alkali-activated mortars appear improper for repair applications. • High alkalinity conditions jeopardize the bond strength of MK + BFS repair mortars.

Abstract Alkali-activated materials (AAM) have been widely promoted as potential repair material for Portland-cement concrete (PCC). However, a thorough evaluation of compatibility and adhesion of AAM to PCC substrates and the correlation of these properties to the AAM composition is still required. AAMs obtained from metakaolin (MK) partially substituted (0, 20, 40, 60 and 80 wt%) with blast furnace slag (BFS) and their mechanical compatibility with a representative PCC substrate was investigated. Mortars with equivalent compressive strength and modulus of elasticity (with and without polypropylene fiber reinforcement) were applied onto the substrate and subjected to bond tests (pull-off and bending tests). Results indicate that neat MK-based mortars present excellent adhesion to PCC, but are vulnerable to delamination. The addition of 20% BFS mitigates this issue, by reducing the solution demand and drying shrinkage. Higher contents of BFS (>60%) have reduced bond strength, probably due to high alkalinity.