Efficiency of geopolymer vs. high-strength grout as repairing material for reinforced cementitious elements

Abstract

Geopolymer cementitious system represents an eco-friendly innovative construction material made without cement as a binder. Hence, the current study is devoted to investigate geopolymer’s characterization as repairing material for reinforced cementitious concrete elements in comparison with commercial high-strength grout. The adhesion performance of the geopolymer mortar using bonding agents based on styrene butadiene rubber (SBR) and epoxy resin were evaluated using slant shear test and pull-off test. In addition, the pull-out test was performed in order to evaluate the bond strength between steel reinforcing bars and different surrounding thicknesses of geopolymer mortar (GPM), namely; 3, 5, 11, 7.5, and 11.5 mm. Besides, the flexural performance of polypropylene fiber reinforced geopolymer mortar (FRGPM) was also evaluated. Moreover, the accelerated corrosion and half-cell potential tests were performed in order to investigate the effect of GPM thickness around steel reinforcing bars (2, 5, and 8.5 mm) as a corrosion protective layer. Test results showed that GPM had good bond strength to the cementitious concrete. In addition, epoxy resin-based bonding agent enabled the geopolymer repair mortar to achieve higher bond strength than that developed by SBR-based bonding agent. The results of rebar pull-out tests showed that using GPM mortar for anchorage of steel reinforcing bars should be implemented with minimum thickness of 5 mm in order to have sufficient bond strength. Moreover, the application of FRGPM as a tension layer enabled the repaired beam to outperform its flexural performance from the viewpoints of ultimate capacity, toughness and crack control. Furthermore, it was found that using GPM as corrosion protective layer of 2 mm thickness or more had the ability and efficiency to delay and control the chloride ions diffusivity.