Causes of damage to masonry after restoration

The article provides the analysis of the causes of damage in the masonry of historical buildings after their restoration. It has been established that the use of mortars of an increased grade and, accordingly, stiffness during repairs of historical masonry leads to an increase in tensile stresses in bricks under temperature and humidity effects. The reasoning behind the use of such mortars is to increase the strength and durability of the restored areas of historical masonry. The results of numerical simulation show that the masonry mortar must be sufficiently strong in compression and, at the same time, sufficiently plastic. It is shown that the use of hard mortars based on a cement binder, compared with plastic mortars based on a lime binder, on average doubles the value of normal tensile stresses at a temperature difference ΔТ=+100С.. This effect is much higher when stones swell due to their moisture. According to the results, for restoration work with brickwork, one should use mortars in accordance with the technology corresponding to this historical period, i.e., lime with additives that were identified during laboratory tests of samples taken from historical masonry. Low-grade mineral solutions with a low modulus of elasticity are preferable. It increases the crack resistance of the masonry under temperature and humidity effects. The article also shows that improper jointing of masonry joints facilitates the destruction of masonry. It happens when areas of accumulation of rainwater are formed, leading to increased wetting of stones in areas of direct impact of rainfall.

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