For the repair and strengthening of historical masonry structures, high penetrability injection grouts which use lime, natural pozzolan, portland cement and some with silica fume have been developed. The type, morphology and evolution of the microstructure and hydration products as evidenced by mercury intrusion porosimetry and X-ray diffraction are presented. Furthermore, the evolution of the insoluble residue and soluble silica contents is also presented. The results of mechanical and bonding tests are presented. Grout mixtures at different ages up to 180 days are compared. The results indicate that ternary blends of the type lime-natural pozzolan-normal portland cement with or without addition of silica fume are highly sensitive to curing conditions. If appropriate curing and quality control are applied, the grout mixtures developed very good mechanical properties and address both durability and economy issues.