Influence of carbonation on the load dependent deformation of hydraulic lime mortars

▶ Lime mortar deformation attributed to creep and shrinkage mechanism. ▶ Deformation within lime matrix rather than the sand aggregate. ▶ Creep attributed to dissolution and precipitation of crystals in matrix. ▶ Creep most significant during the first fourteen days after loading. ▶ Deformation rate was a function of the extent of carbonation. The time dependent deformation of natural hydraulic lime mortar (NHL3.5) through creep and shrinkage under load, in the first 63 days after mixing, has been investigated. An apparatus was constructed to measure the dimensional changes of eight individual specimens simultaneously. The influence of load on deformation rate was found to decrease with time during the experiment. The rate of decrease in load dependent deformation, creep, with time was shown to be inversely proportional to the extent of carbonation. This observation supports the theory that deformation can be explained by the dissolution of calcium hydroxide crystals under stress and subsequent re-precipitation of calcite in areas free from stress.