High calcium fly ash geopolymer mortar containing Portland cement for use as repair material

• FA geopolymer mortars (GPM) containing PC could be used as alternative repair material (RM).
• GPM gave sufficiently high slant bond and bending strengths compared with RM.
• The interface zone of concrete and GPM was more homogeneous and denser than that of concrete and RM.

This article investigated the utilization of high calcium fly ash geopolymer mortars (GPM) containing ordinary Portland cement (PC) for use as Portland cement concrete (PCC) repair material. The shear bond strength of PCC substrate and repair binder and bending strength of notched concrete beam filled with repair binder were used to evaluate the performances of GPM and commercial repair binders (RM). Test results indicated that the use of GPM gave sufficiently high shear bond and bending strengths compared with the use of RM suggesting that it could be used as an alternative product for concrete repair works. In addition, the results from scanning electron microscopy of fracture surfaces indicated that the interface zone of concrete and GPM was more homogeneous and denser than that of concrete and RM. The GPM with 14 M NaOH solution and 10% PC was the optimum mixture for improving the shear bond and bending strengths.