Influence of the design materials on the mechanical and physical properties of repair mortars of historic buildings

Historic buildings are subjected to deterioration by natural weathering or by corrosion due to polluted atmosphere and the materials more susceptible are the mortars used. This study examines the influence of the type and quantity of design materials on compressive strength, creep, water absorption and length change of repair mortars produced. The design materials used were lime, natural pozzolan, sand and brick fragments in order to obtain the compatibility required between historic and repair mortars; different quantities of Portland cement were also used in order to quantify his influence. Nine mixtures were then designed and produced considering as parameters two binder: aggregates ratios, three pozzolan: cement ratios and three sand: brick fragments ratios. The experimental measurements continued until the age of 3 years or the stabilization of the test values. The results indicate that compressive strength is strongly affected by cement content and aggregates dosage and type. It appears that the increase of cement as well as brick fragments leads to confinement of creep deformation, while the mixtures with high pozzolan and sand content experience considerably high creep values. Water absorption reaches higher values when pozzolan or aggregate dosage arises and brick is in excess. Shrinkage increases when binder or brick quantity arise and is considerably influenced by cement content.