Evaluation of Spreading and Effectiveness of Injection Products against Rising Damp in Mortar/Brick Combinations

Abstract

Rising damp is one of the most recurrent and well-known hazards to existing buildings and monuments. Several types of intervention exist to tackle the problem. Among these, the creation of a damp-proof course against capillary rise by means of injection of chemical products is one of the most diffused methods, thanks to the relatively easy and cheap application. Despite positive results when applied under controlled conditions in laboratory, these interventions do not always deliver the desired result in practice. Several studies have shown varying degrees of success. Various factors, like the lack of homogeneity of the substrate and a high moisture and salt content may affect the effectiveness of treatments. Moreover, the type of substrate and the combination of materials with different pore size distribution influence the spreading and the effectiveness of chemical products. Since rising damp is a problem that is mainly manifested in masonry, that is usually composed of at least two materials, the last factor may be of great importance.The current paper reports the results of a research on the transport of chemical injection products in relatively small mortar/brick combinations. Since no easy to perform test method for small combined specimens, giving results within a short time, was available, a special test method was developed.The effect of the interface between brick and mortar on the transport of the products was studied by the application of several injection products and creams. The tested products include pore filling and water repellent products and products in water as well as in organic solvent.The obtained results show clear differences in spreading and effectiveness in the different substrates and between products in organic solvent and water based ones, as well as between creams and liquid products. The results show that water based products can easily be transported through the mortar joint, differently from what occurs with products in an organic solvent. This is the consequence of the different transport mechanisms of water based products and products in organic solvent in water filled pores.