Nowadays, the strengthening of the existing masonry buildings is still an important and required activity caused by the necessity protecting these buildings against future earthquakes. Moreover, the research regarding the preservation of the constructed heritage in the past centuries is looking for new strengthening solutions and materials. In the last century in Romania and all Eastern Europe, many masonry buildings poorly designed against earthquakes were constructed and in the present time strengthening measures are required to be taken. The paper presents a new experimental study regarding the behavior of masonry walls made of old bricks extracted from demolished buildings which were strengthened with overlays of eco-concrete prepared with silica fume and different types of fibers. The tests were carried out according to the standard ASTM E519/E519M. The plain masonry wall and the retrofitted one were subjected to the diagonal compression test and the corresponding maximum failure forces were determined, and comparisons were made. For the brittle masonry, the retrofit with overlays lead to a ductile behavior which is particularly important where the provision of tensile restraint is intended to strengthen the masonry against future seismic effects. Through this experimental investigation, comparing to the capacity of the plain masonry wall, it is shown how the capacity of the retrofitted walls was highly increased using concrete overlays containing silica fume and different types of fibers.